JP2011089966A - Optical pulse detector and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pulse detector in which a trimming process for minimum reception sensitivity is easily performed with high accuracy and reproducibility. <P>SOLUTION: A reception unit 100 has a first trimming circuit 112 and a second trimming circuit 125. The second trimming circuit 125 includes at least a test signal generating circuit 119 which generates a pulse signal, whose amplitude is determined based on a result of trimming by the first trimming circuit 112, to input it as the test signal 122 into an amplifier circuit 102. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a receiver (receiver circuit) that is a main component of a small-sized and low-power-consumption object detection device that is mounted on a portable device such as a mobile phone.

  2. Description of the Related Art Conventionally, a detection device that detects the presence or absence of an object by projecting a light pulse and detecting reflected light from the object toward an automatic door, an automatic cleaning device for sanitary equipment, or an amusement device is well known. An example of a specific configuration is that disclosed in Patent Document 1 (not shown).

  On the other hand, portable devices such as mobile phones and media players that are becoming increasingly multifunctional, miniaturized, or thinner are equipped with sensors that detect the presence or absence of nearby objects (hereinafter referred to as “proximity sensors”). is doing. There are the following examples as the application.

  The first example is ON / OFF control of a display screen backlight in a portable device having a telephone function and a display screen. For example, when an approach of human skin is detected during a call, the backlight of the liquid crystal screen is turned off, and when a change to a non-proximity state is detected, the backlight is turned on again. This will reduce the power consumption of the entire system.

  The second example is ON / OFF control of a touch panel function in a portable device having a telephone function and a touch panel function. For example, the touch panel function is turned off when making a call or inserting a device into a pocket. This prevents system malfunction.

  The third example is a touchless switch in a portable device having a wireless communication function. For example, when an operator brings a finger or hand close to a wireless mouse, a wireless keyboard, a game console controller, or the like by wireless communication, it starts and sleeps when the operator moves it away. This will reduce the power consumption of the equipment.

  Proximity sensors for portable device applications such as those mentioned above have higher tolerances to ambient light such as sunlight and fluorescent lamps, as well as the desired sensing distance and response time compared to conventional photosensor technology. It is desired that the sensing characteristics are realized with an extremely small mounting area, and the proximity sensor itself has extremely low power consumption and low cost. Among these demands, in particular, there is a strong demand for suppressing variations in detection distance due to individual differences in proximity sensors.

  The object to be detected in the application of the proximity sensor has a significant variation in reflectance due to individual differences and individual differences such as the human body, particularly skin and hair. On the other hand, there are not a few individual variations in each characteristic of the detection device itself such as a light emitting element, a light receiving element, or a receiving unit.

  However, the value of existence of an object detection device such as the proximity sensor is that it can be used for a wide range of purposes at a low cost without limiting the target object and without using a special and expensive dedicated element. As a result, the requirements for uniformity or stability in mass production rather than absolute values of the detection characteristics of the sensor itself, in particular the detection distance, are extremely strict.

  In order to achieve this object, it is well known that means for individually adjusting detection sensitivity, for example, can be incorporated in the manufacturing process of the object detection apparatus. As a conventional technique, for example, a trimming technique in a manufacturing process of an integrated circuit as in Patent Document 2 is known. Specifically, in the manufacturing process of an IC (Integrated Circuit) chip in which a photodiode and a preamplifier circuit are integrated, in order to correct the sensitivity of the individually measured photodiode, In order to trim the gain (resistance value), a previously integrated fuse (wiring material that can be cut by applying power) is cut (cut). As another conventional technique, as disclosed in Patent Document 3, a resistor to be cut apart from the integrated circuit is mounted on the same package substrate, and then trimmed so as to obtain a desired characteristic. A technique of trimming so that desired characteristics can be obtained after a resistor or fuse to be cut in advance and a cutting circuit and a control circuit are integrated and mounted on a package as a final product is also well known.

  In the present application, “trimming” means a process of adjusting a desired characteristic by repeatedly changing some characteristic of the target device within a predetermined fluctuation range. In particular, in the present application, “trimming of minimum reception sensitivity” means processing for adjusting the minimum reception sensitivity of a target apparatus to a desired sensitivity by repeatedly changing the minimum reception sensitivity within a predetermined fluctuation range.

Japanese Utility Model Publication No. 6-018983 (published on March 11, 1994) JP 63-108808 (published May 13, 1988) Japanese Utility Model Publication No. 5-043624 (released on June 11, 1993)

  As a phenomenon generally seen in a receiving unit that amplifies a current input signal generated when a light pulse enters a photodiode and binarizes it into a digital signal (pulse), the delay amount of the binarized pulse It can be mentioned that the change greatly depends on the level of the input signal. For example, even if the receiving unit has a simple configuration without a continuous AGC (Automatic Gain Control) function, when the level of the input signal approaches the minimum receiving sensitivity of the optical pulse detector, The output signal will have a significant time delay with respect to the input signal.

  Here, the minimum reception sensitivity is the minimum input signal level that the optical pulse detector can satisfy the specification. Further, the signal level at an arbitrary position in the optical pulse detection device is a signal difference corresponding to a difference between on and off states of pulse emission to be received, that is, a signal amplitude on the time axis. . That is, the minimum receiving sensitivity in this specification is the amplitude of the incident optical pulse, and a photodiode is generated accordingly, and as a result of reproducing the current signal input to the receiving unit as a digital pulse, the proximity sensor If it is, it is determined that detection (with a reflecting object) is made at a desired distance, and if it is an optical communication device, it is a minimum input signal amplitude that satisfies a desired bit error rate.

  In addition, as in the case of the proximity sensor described above, in a receiving unit that applies a synchronization gate so as to determine the presence or absence of a reflector depending on whether or not a received pulse exists within a period corresponding to the light pulse projected by itself, the waveform distortion Although the deviation of the width of the reception pulse with respect to the light emission pulse is not strictly limited, the minimum reception sensitivity is determined not only by the noise level but also by the delay amount itself. This situation is shown in FIG. At the analog output node of the comparison circuit (comparator) for the optical input signal sa of two strengths in the vicinity of the minimum input level, that is, in the case of the minimum level (solid line) and the level slightly higher than the minimum level (one-dotted line) The voltage-time waveforms sb and sd, the voltage-time waveforms sc and se digitized in the next stage, and the synchronous reception gate signal sf for determining the presence or absence of a reception signal synchronized with the input pulse are shown. . For sb and sd, the output level at no signal and the output conversion level of the comparator threshold are also indicated by dotted lines. Note that the difference between sb and sd and similarly the difference between sc and se correspond to the case where the response characteristics of the entire receiving system are moderate and slow, respectively. Relatively high. As apparent from FIG. 8, when the amplified signal is delayed beyond the range of the gate signal, even if there is a sufficient signal amplitude, it is not detected as reflected light.

  As can be seen from the above description, when attempting to trim the minimum reception sensitivity in the optical pulse detection device, the determination based on simple DC level measurement (for example, whether or not the DC gain is within the allowable range), the optical pulse detection device. As a result, it is difficult to obtain the desired uniformity of operating characteristics. This is because, with respect to the signal amplitude of the threshold value of the comparison circuit near the minimum receiving sensitivity, whether the output is inverted at the end of the gate period due to variations in the time constant at the output node of the comparison circuit that normally has a high impedance. This is because it directly affects whether or not. Therefore, unless the trimming success / failure is determined based on the result of detecting whether or not the output of the comparator is inverted at a specific timing using an input signal in the vicinity of the minimum sensitivity at which the above problem becomes apparent, The minimum receiver sensitivity is not trimmed under the conditions in which the device is used. This is the same as long as the binarization process has a finite time constant even during the operation of a comparison circuit that performs only level slices without using a synchronization gate, such as a general optical pulse receiving circuit for communication. Therefore, this is one of the dominant factors in which the minimum sensitivity varies for each receiver of the optical pulse detector. On the other hand, the noise level in the circuit is a main factor that determines the absolute value of the sensitivity limit, but does not directly affect the sensitivity variation of each receiver.

  In response to the above problems, for example, in a pre-shipment inspection in a wafer manufacturing process, an attempt can be made to use a pulse signal as a test signal input to the chip from the outside. However, the signal input from the test device should be accurately controlled and input to the level of the minimum reception sensitivity, whether or not it has been actually achieved, or externally mixed noise to the above signal level. It is difficult to suppress sufficiently, especially in the mass production process. Furthermore, when trimming the sensitivity of the receiver with respect to the input of the minimum reception sensitivity level, the output of the comparator is stochastic due to the influence of circuit internal noise in the process until the probable condition is extracted. Behaves differently (results change with each measurement). For this reason, it is essential to perform some statistical processing and eliminate ambiguity due to the influence.

  As described above, the optical pulse detection device according to the related art has a problem that trimming of the minimum reception sensitivity is very difficult.

  The present invention is an invention made in view of the above problems, and an object of the present invention is to easily perform trimming of minimum reception sensitivity with high accuracy and high reproducibility, and to this optical pulse detection device. An object of the present invention is to provide an electronic device including an optical pulse detection device.

  That is, the present invention discloses means for performing the trimming of the minimum receiving sensitivity in the wafer manufacturing process of the integrated circuit including at least the optical pulse receiving circuit with extremely high accuracy and high reproducibility with respect to the above problems. . That is, a test signal to be used for trimming of the minimum reception sensitivity is stably generated inside the circuit to be inspected and is input to the circuit to be inspected. Means for extracting the trimming conditions are disclosed. In particular, the object is to realize trimming of minimum reception sensitivity with high accuracy and high reproducibility in a space-saving manner and at a low cost. Based on the extracted trimming execution conditions, it can be arbitrarily selected whether actual trimming (application of power for cutting the fuse) is performed inside the circuit under test or from outside the circuit under test. In addition, some means for solving the problems disclosed by the present application, in particular, means for solving the problem of how to complete the extraction of the trimming condition based on the output of the comparator showing the stochastic behavior It can be easily understood by those skilled in the art through the following description that the present invention can be applied to trimming including correction of an optical system performed after completion of packaging as a product of an optical pulse detection device.

  In order to solve the above problem, an optical pulse detection device of the present invention compares a light receiving element, an amplifying means for amplifying the output signal of the light receiving element, and an amplitude of the output signal of the amplifying means by comparing with a threshold value. Comparing means for quantifying and outputting, at least, an optical pulse detection device comprising: a first trimming means for performing first fuse trimming on the optical pulse detection device; and a first trimming device on the optical pulse detection device. A second trimming means for performing two-fuse trimming, wherein the second trimming means is based on a signal whose absolute value is controlled by the first fuse trimming by the first trimming means. It includes at least inspection signal generation means for generating a pulse signal having a known amplitude and inputting it as an inspection signal to the amplification means. That.

  According to the above configuration, the inspection signal generation means, which is a component of the second trimming means, uses the result of performing the first fuse trimming by the first trimming means to generate the inspection signal, so that it is known. It is possible to input the inspection signal controlled to a specific level with high accuracy to the amplification means. In particular, the comparison means is configured to operate with respect to the current threshold, and the current controlled with high accuracy by the first fuse trimming by the first trimming means is used directly and as the current threshold, and the second trimming means. It is desirable to generate an inspection signal used for the second fuse trimming according to. According to this configuration, the inspection signal generation means can generate a current signal convenient as an inspection signal for the optical pulse detection device with known accuracy. Further, since it is only necessary to set the output to 0 during the OFF period, it can be easily shaped into a pulse waveform while maintaining the signal amplitude accuracy and an appropriate time constant. Therefore, it is possible to use the inspection signal as a current pulse in the optical pulse detection device after accurately and reliably controlling the amplitude of the inspection signal used for trimming the minimum reception sensitivity at a level equivalent to the actual use condition. it can. In addition, after the inspection signal is input to the amplification means, the control signal used for amplitude control of the inspection signal can be reused by switching to another purpose, that is, threshold control of the comparison means. In this way, high-accuracy trimming with minimum reception sensitivity in the optical pulse detection device can be realized with reduced space and cost.

  In the optical pulse detector of the present invention, the first trimming means adjusts the threshold value of the comparison means, and the second trimming means adjusts the amplification factor of the amplification means. It is characterized by being.

  According to the above configuration, high-accuracy trimming with minimum reception sensitivity in the optical pulse detection device can be easily realized with low space and low cost.

  In the optical pulse detector of the present invention, the first trimming means performs a first adjustment of a threshold value of the comparison means, and the second trimming means is a second threshold value of the comparison means. It is characterized by adjustment.

  Also with the above configuration, high-accuracy trimming with minimum reception sensitivity in the optical pulse detection device can be easily realized in a small space and at a low cost. In particular, by adjusting the threshold value of the comparison means in both the first fuse trimming by the first trimming means and the second fuse trimming by the second trimming means, it is possible to minimize the bandwidth and noise amount of the optical pulse detection device. It is possible to avoid a secondary change in a parameter that has an essential influence on the reception sensitivity. As a result, the difficulty of design due to the interaction of each characteristic of the analog circuit and the necessity of redundant design to overcome it are eliminated, and the desired trimming accuracy can be easily ensured at low cost and space saving. Is possible.

  In the optical pulse detector of the present invention, the second trimming means further counts whether or not the output of the comparing means exists within a gate period generated based on the pulse of the inspection signal. And trimming control means for judging success or failure of the second fuse trimming by the second trimming means.

  According to the above configuration, in the trimming control means that is a component of the second trimming means, it is counted whether or not the output of the comparison means exists within the gate period generated based on the pulse of the inspection signal. Thus, by determining the success or failure of the second fuse trimming, the influence of in-circuit noise can be greatly reduced. For example, the trimming control means controls the number of pulses of the inspection signal to be generated, counts the output by multiplying the logic output of the comparison means in accordance with the ON period of the pulse, and matches the number of inspection pulses generated. It can be determined whether or not. By using a test signal of multiple pulses and determining that reception sensitivity has been achieved (trimming success) only when the count number matches the pulse number, errors that can occur stochastically at the output of the comparison means due to the effects of circuit noise This makes it possible to clearly determine the boundary of the gain trimming success or failure.

  In the optical pulse detector of the present invention, the second trimming means further counts whether or not the output of the comparing means exists within a gate period generated based on the pulse of the inspection signal. In addition to the gate period, trimming control means for monitoring the output of the comparison means and determining the success or failure of the second fuse trimming by the second trimming means is provided.

  In this way, in the trimming control means, which is a component of the second trimming means, counts whether or not the output of the comparison means exists within the gate period generated based on the pulse of the inspection signal, In addition to the gate period, the influence of in-circuit noise can be further reduced by monitoring the output of the comparison means and determining the success or failure of the second fuse trimming. For example, the trimming control means controls the number of pulses of the inspection signal to be generated (or the pulse repetition period and pulse width), and gates the logical output of the comparison means in accordance with the pulse ON period of the inspection signal. In addition to counting the output, the logic output of the comparison means is gated to the noise output other than the pulse ON period of the inspection signal (eg, any period in the OFF period from immediately after the pulse is turned on until the next pulse is turned on). Can be counted. For example, the number of events that can be obtained as a pair with a logical output in the ON period of the inspection signal (received a synchronized signal) and no logical output in the OFF period (no noise output uncorrelated with the inspection signal) By determining that reception sensitivity is achieved (trimming success) only when it matches the number of pulses in the generated inspection signal, the influence of errors that can occur probabilistically at the output of the comparison means due to the influence of circuit noise is made even more apparent. Thus, it is possible to more clearly determine whether the gain trimming has succeeded or not.

  Further, in the optical pulse detection device of the present invention, the trimming control means counts whether or not the output of the comparison means exists at least within a gate period generated based on the pulse of the inspection signal. The success or failure of the second fuse trimming by the second trimming means is determined based on the frequency of occurrence.

  According to the above configuration, by counting the number of outputs of the comparison means within the gate period and determining the success or failure of the second fuse trimming by the second trimming means, the digital signal is influenced by the influence of circuit noise. An error that may occur can be made more apparent, and success or failure can be determined more clearly.

  The optical pulse detection apparatus of the present invention controls a hold unit for holding a signal at a desired portion in the amplification unit to which the inspection signal is input at a desired timing, and controls the inspection signal generation unit and the hold unit. Trimming control means for judging the success or failure of the second fuse trimming by the second trimming means from the binarized output of the comparing means obtained in this way.

  According to the above configuration, even if the voltage gain or signal delay as the comparison circuit varies, it is possible to extract the optimum execution condition of the second fuse trimming for the specific hold timing. Moreover, according to said structure, since the complicated signal processing is not accompanied by the evaluation of the inspection signal with respect to each setting, it is possible to significantly reduce the time required for the total inspection process. For example, once the signal level is held, it is not necessary to set, for example, a register used for correcting the sensitivity of the light receiving element when generating the inspection signal. The held signal level is maintained only for a finite time, and there are error factors such as droop due to leakage current around the hold circuit, but the level can be designed to be sufficiently negligible. As a result, the time margin given to the trimming control means is significantly increased as compared with the embodiments described so far. Since the threshold value of the comparison circuit can be set at an arbitrary timing, the entire inspection mode can be designed very easily.

  The adjustment means in the second trimming means of the optical pulse detection device of the present invention includes a temporary adjustment means that can be repeatedly executed and a main adjustment means that cannot be changed after the execution, and the second trimming means. The trimming control means in the means determines the success or failure of temporary trimming for each of at least some of the settings included in the adjustable range of the temporary adjustment means, and extracts the most probable implementation condition for the main adjustment means. Then, the adjustment means is implemented on the basis of the implementation condition obtained by outputting to the outside and reading out the output.

  More preferably, the setting ranges of both the adjusting means are overlapped with each other, and the second trimming condition is tried in advance using the temporary adjusting means for each of at least a part of the settings of the temporary adjusting means. To do.

  With such a configuration, as described above, the output of the comparison means is gated to count the number of logical outputs corresponding to the inspection signal, or the hold means is used to hold at a specific timing. The feature disclosed by the present application for improving the trimming accuracy of the minimum reception sensitivity, such as confirming the logic output corresponding to the inspection signal, can be repeatedly performed any number of times for any setting. Therefore, even when it is significantly affected by internal noise, it is possible to collect statistically sufficient information and reliably extract the most probable conditions for carrying out the adjustment means. . Further, the extracted execution condition is output to the outside of the apparatus, and the adjustment unit is executed based on the output, thereby reducing the inspection time to the minimum necessary and the second trimming unit performs the second operation. Fuse trimming can be performed reliably.

  The optical pulse detection device of the present invention is characterized in that the light receiving element is integrated together with the amplifying means, the comparing means, the first trimming means, and the second trimming means.

  The amplification means, the comparison means, the first trimming means, and the second trimming means are configured as described above, and further provided separately to correct the sensitivity of the light receiving element by integrating the light receiving elements. By using the adjustment function (for example, register setting is switched by an external control signal), the amplitude of the inspection signal can be additionally corrected to generate a more desirable inspection signal. In particular, when the inspection signal is input to the amplification means, the control signal can be reused for other purposes, that is, threshold control of the comparison means. Therefore, high-accuracy trimming with minimum reception sensitivity in the pulsed light detection device can be realized with reduced space and cost.

  In addition, an electronic apparatus according to the present invention includes any one of the above-described optical pulse detection devices, and controls its own operation based on a detection result of the optical pulse detection device.

  In other words, the optical pulse detection device of the present invention is mounted on an electronic device as a proximity sensor that detects the proximity state of a reflector, and the electronic device performs its own operation control based on the detection result of the optical pulse detection device. Features. By mounting the optical pulse detection device of the present invention as a proximity sensor in an electronic device, the individual variation is sufficiently suppressed while being highly sensitive, and a uniform detection distance characteristic is provided at a low cost. The reflectance of the measurement object is allowed and can be used in various applications.

  By the way, even if the above-mentioned problems are overcome and the minimum receiving sensitivity of the circuit part can be reliably adjusted to the desired range at the wafer test stage, the reflected light intensity of the light pulse is compared with a threshold value to determine the presence or absence of a reflecting object. However, in the proximity sensor, the following important problem remains. That is, there is a problem of erroneous detection due to reflection of the housing window. An electronic device in which the proximity sensor is mounted needs an optical “window” for projecting a light pulse from the proximity sensor to the outside and receiving the reflected light from the measurement object. However, this “window” is not conspicuous for the design and color scheme of the housing from the viewpoint of design, and as a result, a housing window with high transmittance that is more ideal for proximity sensors is expected to be adopted. There is almost no. Usually, it is necessary to assume a reflectance of several percent to several tens percent. Actually, the sensitivity setting of the proximity sensor whenever the optical characteristics of the window, the distance from the proximity sensor to the housing window, and the housing design of the electronic device such as the partition plate inserted between the light emitting and receiving parts are changed. Alternatively, it is necessary to adjust the pulse emission amount.

  Therefore, an electronic apparatus according to the present invention is an electronic apparatus that is equipped with the above-described optical pulse detection device and controls its own operation based on the detection result of the optical pulse detection device. In order to avoid erroneous detection by the reflected pulse light being reflected by the casing window of the electronic device, the optical pulse detection device uses the temporary adjustment means of the second trimming means to use the minimum reception to be used. It has at least a function of automatically adjusting sensitivity, and the automatic adjustment function is activated by an instruction from the outside of the optical pulse detection device.

  As a result, the optimum sensitivity setting in the final mounting state can be automatically extracted and stored in the prototype stage of the electronic device, and the operation setting condition of the final product can be easily and reliably determined. Further, even in a scene that is actually used by an end user, a more advanced malfunction prevention function can be realized by appropriately starting the automatic extraction function of the optimum sensitivity setting from the electronic device side.

  As described above, the optical pulse detection device of the present invention includes a light receiving element, an amplifying unit that amplifies the output signal of the light receiving element, and a comparison that binarizes and outputs the amplitude of the output signal of the amplifying unit with a threshold value. A first pulse trimming unit for performing the first fuse trimming on the optical pulse detection device, and a second fuse trimming on the optical pulse detection device. A second trimming means, and the second trimming means has a known amplitude based on a signal whose absolute value is controlled by the first fuse trimming by the first trimming means. It includes at least inspection signal generation means for generating a pulse signal and inputting it as an inspection signal to the amplification means.

  Therefore, there is an effect that it is easy to perform trimming of the minimum reception sensitivity with high accuracy and high reproducibility.

It is a circuit block diagram which shows the structure of the receiving part in the 1st Embodiment of this invention. 2A is a circuit diagram showing the configuration of the test signal generation circuit according to the present invention, and FIG. 2B is a timing chart showing the operation of the test signal generation circuit shown in FIG. . It is a timing chart which shows operation | movement of the trimming control means in the 1st Embodiment of this invention. It is a circuit block diagram which shows the structure of the receiving part in the 2nd and 4th embodiment of this invention. It is a timing chart which shows operation | movement of the trimming control means in the 2nd and 4th embodiment of this invention. It is a circuit block diagram which shows the structure of the receiving part in the 3rd Embodiment of this invention. It is a figure explaining a mode that the amplifier circuit shown in FIG. 6 is changed from a track mode to a hold mode. It is a figure explaining a mode that the pulse position and pulse width of a binarization output are fluctuate | varied with the delay characteristic of a receiving part. It is a figure which shows each part signal waveform of the amplifier circuit which concerns on this invention, and the waveform operation which concerns on the threshold value of a comparison circuit in detail. FIG. 3 is a circuit block diagram showing in detail a configuration of a control circuit including trimming control means in the first embodiment of the present invention. It is the circuit diagram which showed the circuit part of the programmable current source in the 1st Embodiment of this invention in detail. It is a circuit block diagram which shows in detail the structure of the control circuit provided with the trimming control means in the 2nd and 4th embodiment of this invention. It is the circuit diagram which showed the circuit part of the programmable current source in the 2nd and 4th embodiment of this invention in detail.

[First Embodiment]
First, referring to FIG. 1, a configuration example of a receiving unit (a part of a circuit function block constituting an optical pulse detection device) 100 according to the first embodiment, which is the most typical of the present invention, and normal sensor operation Will be described along with the role of each functional block along the signal path.

  When a light pulse is incident on the photodiode (light receiving element) 101, the photodiode 101 generates a current signal, and the current signal is input to an amplifier circuit (amplifying unit) 102. The capacitor 1011 functions as a dummy capacitor of the photodiode 101, and is provided for the purpose of removing in-phase electrical noise mixed from the outside or a power supply line. The amplification circuit 102 in FIG. 1 includes a transimpedance amplifier and a voltage amplification circuit connected via capacitive coupling, and the voltage amplification circuit can change the amplification factor stepwise by digital operation, so-called PGA (Programmable). Gain Amplifier). In FIG. 1, in the amplifier circuit 102, the current signal output from the photodiode 101 is converted into a voltage signal by a transimpedance amplifier, and further voltage amplification is performed by PGA. If a sufficient signal amplitude is obtained, the amplifier circuit 102 omits the voltage amplification stage (PGA in FIG. 1), and simultaneously with the conversion to the voltage signal by the transimpedance amplifier, the transimpedance amplifier It can also be designed to act as The output signal of the amplifier circuit 102 is further input to the comparison circuit (comparison means) 103 as differential signals 1041 and 1042 via capacitive coupling. The comparison circuit 103 compares the amplitude relationship between the amplitude of the differential output signal (output signal) from the amplifier circuit 102 and a set threshold value according to the result of comparing the magnitude level with the H level (for example, the power supply voltage Vdd) or the L level (for example). For example, the digital output signal 106 having two values (GND level) is generated.

  Further, in FIG. 1, the following circuit configuration is taken as a specific example of the comparison circuit 103. The comparison circuit 103 combines an output current of an OTA (Operational Trans-conductance Amplifier) 104 and a threshold current 108 that is an output current of the threshold generation circuit 105 to generate an analog output of the high impedance node 107 (the comparison circuit (comparator) described above). (Corresponding to a node) is further charged and discharged, and further binarized as a rail-to-rail digital output signal 106 by a two-stage inverter. Here, the OTA 104 is a general operational amplifier circuit that push-pulls a current proportional to the input voltage difference between the differential signals 1041 and 1042 to the high impedance node 107.

  Further, a current waveform operation is applied to a DC current 114a (details will be described later) input to the threshold generation circuit 105 based on the fed back digital output signal 106 as shown in FIG. In the circuit 105, a threshold current 108 is generated. Thereby, hysteresis is provided in the input / output characteristics of the entire comparison circuit 103. As described above, the incident light pulse is stably reproduced as the digital output signal 106.

  Here, during normal reception operation, the digital output signal 106 of the comparison circuit 103 is subjected to further signal processing (determination processing) as data to be output to the outside of the reception unit 100 by the control circuit 109. obtain. For example, when outputting the presence or absence of light pulse input (reflection of light emission pulse from the light emitting element driven by the light pulse detection device) in association with the presence or absence of a reflective object, such as a proximity sensor, The basis of the above determination can be obtained by counting whether or not the reception and reproduction pulses synchronized with them are obtained the same number of times.

  The details of the overall configuration and operation sequence of the control circuit 109, particularly the operation sequence during trimming control, will be described in detail later with reference mainly to FIG. 10 or FIG. The important point to be emphasized here is that the normal sensing operation as a sensor and the success / failure determination in the trimming of the minimum reception sensitivity in the receiving unit 100 are completely the same or very similar, that is, the same. By implementing the circuit block (the control circuit 109), the trimming of the minimum reception sensitivity is performed under the condition that is equal to or very close to the actual sensor operation, and the object of the present invention is achieved. is there.

Now, the data to be output to the outside (here, the sensing result of the presence or absence of a reflecting object) obtained in this way is an external interface such as an I ² C bus interface, for example, as is often done in a general sensor device. The data is read from the outside via 111. Conversely, a register (not shown) in the interface circuit 110 or the control circuit 109 is switched via the external interface 111 in order to switch the operation mode as the optical pulse detection device or adjust the characteristics of the receiving unit 100. ) May also be performed. In the interface circuit 110, parallel-serial or serial-parallel conversion is performed in accordance with a specific protocol, and the sensing result and data input / output for control are performed via a buffer.

  Note that the present invention does not impose any preconditions on the specific configuration method of each block described so far, and covers all receiving units that reproduce optical pulses as digital pulse signals. For example, in each of the analog circuit blocks of the photodiode 101, the amplifier circuit 102, and the comparison circuit 103, a fully differential circuit and capacitive coupling are not essential, and a coupling capacitance bias circuit is omitted. Further, the number of stages of the amplifier circuit can be arbitrarily changed within a range in which a desired sensitivity level can be realized. Alternatively, an offset cancel circuit and a DC cancel circuit not shown here may be included. The configuration of the comparison circuit 103 and the method of providing hysteresis are not limited to the configuration according to FIG. 1, and any configuration desired by those skilled in the art can be applied. As for the external input / output unit, it is of course possible to directly output the digital output signal 106 of the comparison circuit 103 as a buffer without passing through the control circuit 109 or the interface circuit 110, as in a more general optical receiver circuit. It is.

  In FIG. 1, there are usually common blocks such as a light emitting element drive signal generation unit and a drive circuit unit that are integrated with the reception unit 100, as well as a bias current / voltage generation circuit and an oscillation circuit for generating an internal clock signal. All are omitted. In addition to these functional blocks, an analog / digital mixed integrated circuit in which all the digital signal processing units are integrated is used to constitute the optical pulse detection device of the present invention, so that the total size and cost of the device are most effectively reduced. Can be reduced. FIG. 1 shows a part of functional blocks of such an IC chip.

  Therefore, the control circuit 109 that performs digital signal processing includes clock signal frequency division and multiplication, or a transmission signal generation and timing control function based on this, as well as registers or memories required for operation settings. At least it can be included. However, even when the entire optical pulse detection device is configured by combining individual IC chips and components for each partial functional block, if the requirements disclosed by the present application are satisfied, the effect can be fully enjoyed. It will become apparent by the following detailed description.

  Next, FIG. 10 shows a more detailed configuration example of the entire control circuit 109 in the first embodiment of the present invention, which is abbreviated in FIG. Note that the control circuit 109 is added to the trimming control unit and the trimming success / failure determination / control unit, or the operation mode setting and switching control unit of each unit of the receiving unit 100 to be trimmed. Thus, it is possible to include all control functions including circuits that do not need to be described in detail, for example, a control unit of a drive circuit of a light emitting element and an input / output control unit of a communication interface with the outside of the apparatus. In the following, description will be given of control related to setting and switching of the operation modes of the trimming control unit, the trimming success / failure determination / control unit, and each part of the receiving unit to be trimmed.

  First, in FIG. 10, a control signal generation unit 1097 for generating the inspection signal 122 of FIG. 1 is provided. The control signal generation unit 1097 uses a clock signal 1091 that is an output of the oscillator 1090 and various counters, so that a control signal having an arbitrary period and pulse width can be generated at an arbitrary timing with the period of the clock signal 1091 as a unit. It can be generated or stopped (a well-known technique and details are not shown). In the control signal generation unit 1097, the control signal 123 or a signal (not shown) for driving the light emitting element, and a synchronous reception gate signal 1093 used for driving the latch circuit (RSFF) in synchronization with these signals. The reset signal 1095 of the latch circuit generated in the same cycle as these signals, the control signal 116 of the selector 115, and various setting controls such as operation start and stop of the amplifier circuit 102 not shown in detail. And a control signal for performing (see FIG. 3 for a specific example).

  Here, the control signal 123 and the light emitting element drive signal are used exclusively in the receiving unit 100, and when one signal is generated, the other signal is not generated. Further, only when the control signal generation unit 1097 generates the control signal 123 used only in the wafer test trimming process, the control signal generation unit 1097 also generates the control signal 116 of the selector 115 corresponding thereto. Whether the entire receiving unit 100 performs a normal sensor operation or an operation in a trimming process in a wafer test is instructed through the interface 111 from the outside. Of course, in addition to this, general control such as the operation of the receiving unit 100 by an activation command from the outside is necessary. In FIG. 10, the determination / control unit 1096 performs this control.

  Next, the determination / control unit 1096 used as a means for determining the success or failure of trimming in the reception unit 100 will be described. The main actual state of the determination / control unit 1096 is a so-called well-known state machine that monitors various conditions and realizes a desired operation algorithm from the combination thereof (like the control signal generation unit 1097, Details are not shown). Here, in the control circuit 109 illustrated in FIG. 10, a signal processing unit 1092 is provided between the comparison circuit 103 and the determination / control unit 1096. Here, the operation of the signal processing unit 1092 will be described first.

  During normal operation, for example, when operating as a proximity sensor, the light pulse reflected by the reflector is converted into a current signal by the photodiode 101, and the current signal is input to and amplified by the amplifier circuit 102. The digital output signal 106 binarized at 103 is provided to the signal processing unit 1092 as a material for determining the presence or absence of a reflecting object. On the other hand, in the second (minimum receiving sensitivity) trimming step according to the present invention, a test signal 122 (current pulse) having a known amplitude generated based on the result of the first trimming (first fuse trimming). Signal) is input to the amplification circuit 102 and amplified, and the digital output signal 106 binarized by the comparison circuit 103 is supplied to the signal processing unit 1092 as a material for determining the success or failure of the second trimming (second fuse trimming). The

  Therefore, these two operation modes, that is, an operation as a normal proximity sensor and a trimming operation (wafer test mode) are switched from the external interface 111 through the determination / control unit 1096, thereby detecting / non-detecting the optical pulse input. And the detection / non-detection determination for the inspection signal input can be performed by the same signal processing and determination standard (operation algorithm).

  As described above, either the case where the presence / absence of the light pulse input is determined in association with the presence / absence of the reflecting object during the normal operation, or the case where the sensitivity of the receiving unit 100 with respect to the input of the inspection signal in the trimming process is determined However, the above determination may be based on whether or not the same number of digital signal pulses received and reproduced in synchronization (with substantially the same timing) are obtained for a plurality of input pulse signals. it can.

  In FIG. 10, the above-described series of operations is realized by the control signal generation unit 1097 and the signal processing unit 1092. The outline is as follows (refer to FIG. 3 for a specific example).

  In the signal processing unit 1092, first, using the synchronous reception gate signal 1093, a negative logical product of the digital output signal 106 of the comparison circuit 103 and the synchronous reception gate signal 1093 is obtained (NAND in FIG. 10), and the negative logical product is obtained. The output is latched (RSFF in FIG. 10). If the synchronous reception output 1094 obtained in this way is at the H level (detection) immediately before the end of the repetition period of the synchronous reception gate signal 1093, the signal processing unit 1092 increases the count number. The latch circuit RSFF is reset by a reset signal 1095 at the end of the repetition period of the synchronous reception gate signal 1093. In this way, the determination / control unit 1096 selects the next operation (implementing a desired operation algorithm) based on whether or not the number of times the synchronous reception output 1094 has occurred reaches a predetermined count number N. be able to.

  The outline of the operation has been described along with the role of each functional block along the signal path over the entire configuration example of the reception unit 100 according to the first embodiment of the present invention with reference to FIGS. 1 and 10.

  2A and 10 shown so far show a more detailed internal configuration for a specific block inside the receiving unit 100 of FIG. 1 so that those skilled in the art can easily understand. is there. On the other hand, FIG. 1 is shown in order to see the whole structure of these functional blocks. Therefore, as a matter of course, a wide range of functional blocks in FIG. 1 cannot be illustrated in their entirety in FIG. 2 or FIG. In this sense, it is not possible to take a perfect one-to-one correspondence for all elements between FIG. 2 (a) or FIG. 10 and FIG. Their correspondence can be judged. Further, constituent elements (for example, 1184 and 124) of the present invention not described in FIG. 10 will be described later with reference to FIG. Thus, the optical pulse detection device of the present invention should be construed to be realized based on the overall configuration of the receiving unit 100 shown in FIG.

  Hereinafter, in the same manner as described above, the adjustment function of each circuit block in the receiving unit 100 will be described with reference to FIG. The adjustment function mentioned here includes, for example, a function for switching analog circuit constants or a variable function that can be set with a digital value from the control circuit 109, as well as a function related to trimming, which is the subject of the present invention.

  As described above, the threshold current 108 input to the high impedance node 107 of the comparison circuit 103 in FIG. 1 is generated by the threshold generation circuit 105 based on the DC current 114a. In the example of FIG. 1, the value of the output current 114 is set from the determination / control unit 1096 of the control circuit 109 based on a command from the first trimming circuit (first trimming means) 112 or the external interface 111. A control signal 8181 for giving an instruction is given to the programmable current source 113. The output current 114 of the programmable current source 113 is switched to one of the paths of the DC current 114a, the DC current 114b, and the DC current 114c by the selector 115 by the control signal 116 from the control signal generation unit 1097 of the control circuit 109.

  The DC current 114 a is supplied to the threshold value generation circuit 105. The threshold generation circuit 105 generates the threshold current 108 of the comparison circuit 103 by performing the waveform operation shown in FIG. 9 on the supplied DC current 114 a and supplies the threshold current 108 to the OTA 104.

  The DC current 114b is subjected to the first trimming by cutting four fuses shown in the first trimming circuit 112 in the wafer test process which is the final stage of the IC chip wafer manufacturing of FIG. This is used as a monitor current when the current source 113 is programmed). For example, in the example of FIG. 1, the receiving unit 100 is trimmed so that the measured value is closest to the target value in a state where the DC current 114a itself is output from the terminal 117 to the outside as the DC current 114b by switching the transmission gate. Is done. Of course, the DC output 114b and / or the DC current 114c may be separately generated by a current mirror or a current memory, instead of switching and reusing the same output current 114 at the transmission gate on the time axis. In that case, the accuracy of the current value is slightly lowered due to mismatch of elements in the circuit and charge injection, but it is sufficiently possible to be within an allowable range by circuit design.

  In this way, in the first trimming according to FIG. 1, the output current 114 of the programmable current source 113 measures the value of the DC current 114b output from the terminal 117 as a result of the path being switched by the selector 115. Meanwhile, the four fuses provided in the first trimming circuit 112 are appropriately cut as necessary. By this disconnection, the output current 114 of the programmable current source 113, whose absolute value is controlled by the first trimming circuit 112, is further switched by the selector 115 and supplied to the comparison circuit 103 as the DC current 114a. Thereby, the absolute value of the threshold value of the comparison circuit 103, that is, the amplitude of the threshold current after the waveform operation of FIG. 9 is directly determined with known accuracy.

  Next, operations of the decoder 124 and the control circuit 109 when the first trimming is performed will be described. Although it has already been shown that the control circuit 109 in the receiving unit 100 of FIG. 1 can be configured as shown in FIG. 10, in the following, as the simplest specific configuration example of the first trimming circuit 112, a related programmable An example in which the circuit portion of the current source 113 is described in more detail is shown in FIG. That is, in FIG. 11, a portion related to the second trimming circuit (second trimming means) 125 is not shown. For this reason, the broken line indicating the sense circuit 1184 for detecting the connection form of the trimming fuse and the decoder 124 for decoding the sense result and controlling the programmable current source 113 and / or PGA is a portion related to the second trimming means. (The second trimming will be separately described later).

  The programmable current source 113 shown in FIG. 11 has an internal configuration in which a current generated using an operational amplifier is divided into a p-channel metal oxide semiconductor transistor (hereinafter referred to as PMOS) side and an n-channel metal oxide semiconductor transistor (hereinafter referred to as PMOS). Basically, two current mirrors are folded back on the side called NMOS. Among these, the current mirror on the PMOS side is configured such that the current value flowing into the current mirror on the NMOS side can be set and the final output current 114 can be adjusted to a desired value by opening and closing the switch by the control signal 8181. .

  A plurality of fuses (trimming fuses) to be cut in the first trimming circuit 112 shown in FIG. 11 are not shown for convenience in FIG. 10 on the source side of the NMOS whose gate voltage is controlled by the negative feedback of the operational amplifier. In addition, the fuses are connected in parallel with each other and the fuses are connected in series with each other and used directly as variable resistance elements in the analog circuit. Therefore, in the example of FIG. 11, a sense circuit (a portion corresponding to the first trimming means in 1184 in FIG. 10) of the connection form of the first trimming fuse included in the first trimming circuit 112 is illustrated. As described above, the decoder 124 which is substantially merely a wiring and is connected to the first trimming fuse is also realized as a part of the analog circuit (variable resistance element) as described above.

  However, the connection of the trimming fuse, the configuration of the sense circuit, and the configuration of the decoder can be arbitrarily changed. For example, also in FIGS. 1 and 10, in the second trimming circuit 125, unlike the first trimming circuit 112, a plurality of fuses are connected in parallel. Also, in the detection (sense) of the connection state of the fuse, which can be generally included in the decoder 124, any modification can be made using the known sense circuit 1184. For example, in the second trimming circuit 125 of FIG. 10, the power supply voltage Vdd level is applied to one end of all the fuses, and trimming bit information is reproduced by sensing the voltage at the other end. As another modification of the fuse connection and sense circuit 1184, the voltage of each part of the resistance ladder composed of a fuse and a resistance element is compared with a predetermined reference voltage in the decoder 124, and predetermined trimming bit information is determined according to the comparison result. It is also possible to design such that is reproduced and decoded as various control signals. The details of the trimming fuse connection mode and the implementation method of the decoder 124 do not limit the gist of the present invention.

  The programmable current source 113, the decoder 124, and the determination / control unit 1096 of the control circuit 109 can adjust the value of the output current 114 of the programmable current source 113 even after the first trimming is performed. be able to. This can be realized by making the adjustment setting (programming) of the programmable current source 113 by the first trimming circuit 112 and the control signal 818 independent from each other, as can be easily understood with reference to FIGS. This makes it possible to make additional corrections that are useful in performing the second trimming. In the examples of FIGS. 10 and 11, the control signal 818 is supplied as the control signal 8181 via the simple buffer 818a. However, the buffer 818a is composed of various logic circuits to provide a more desirable trimming means. It can also be configured. Examples of these modifications will be described later with reference to FIGS. 4, 12, and 13.

  On the other hand, the first trimming circuit 112 performs trimming of the reception sensitivity of the receiving unit 100 based on the output current 114 of the programmable current source 113 whose absolute value is controlled for each IC chip. The second trimming is performed to adjust the amplification factor of the voltage amplifier circuit PGA. In this case, for example, the output current 114 itself switches the path to the inspection signal generation circuit (inspection signal generation means) 119, which is one of the components of the second trimming circuit, as the DC current 114c by the selector 115. Entered. The inspection signal generation circuit 119 accurately outputs the DC current 114c obtained as a result of the first trimming with an accuracy of 2.00 μA−3% to 2.00 μA + 3% (3σ) by the internal minute current generation circuit 120, for example. 1/50 times, a minute DC current corresponding to the minimum receiving sensitivity of the receiving unit 100 is generated. The magnification of 1/50 is typically determined from the set value of the total current gain from the input section of the amplifier circuit 102 to the output of the OTA 104 in the comparison circuit 103. A value obtained by dividing the current value of the threshold current 108 set during actual circuit operation by the total current gain is a measure of the minimum output current value of the photodiode 101 that can be reproduced as a pulse by the receiving unit 100. Determine the minimum receiving sensitivity.

  The minute current generation circuit 120 used here preferably has a configuration in which an error is compressed by negative feedback by an error amplifier 200 as shown in FIG. 2A, for example, rather than a current mirror circuit. In FIG. 2A, elements already described in FIG. 1 are denoted by the same reference numerals as those in FIG.

  A DC current 114b (2.00 μA) and a small current to be generated for each of the resistor R and the resistor 50R (resistance value 50 times the resistor R) carefully laid out so that the ratio of the resistance values is accurately 1:50 When (40.0 nA) flows, the gate voltage of the NMOS is controlled by the error amplifier 200 so that the voltage drops are equal to each other.

  The enable signal φEN is supplied as part of the control signal 123 from the control signal generator 1097 (see FIG. 10) in the control circuit 109 to the error amplifier 200 and the current source in FIG. The error amplifier 200 and the current source are activated or stopped depending on whether the enable signal φEN is at the H level or the L level. In addition, the opening / closing control of each switch including the transmission gate (also simply referred to as a switch) 121 is a part of the control signal 123 (control signal φA, control signal φB1, control signal φB2, control signal) supplied from the control signal generator 1097. Signal φC). Hereinafter, each switch of the inspection signal generation circuit 119 is configured to be closed when the control signal becomes H level and open (H active) when the control signal becomes L level.

  FIG. 2B shows a timing chart of each signal of the control signal 123 for the inspection signal generation circuit 119. Since the inspection signal generation circuit 119 is used only when the second trimming is performed, the control signal generation unit 1097 of the control circuit 109 receives the enable signal φEN as the control signal, that is, the enable signal during the activation. = H level is transmitted. 2B, during the subsequent active period of the control signal φA, that is, the H level transmission period, the voltage drop due to the current flowing through the resistor 50R is caused only by the bias current source flowing through the resistor R. The NMOS gate voltage in the feedback path to which the control signal φA is supplied is driven by the error amplifier 200 so as to be equal to the voltage drop. At this time, the adverse effect of the finite offset of the error amplifier 200 is accumulated in the feedback path on the control signal φA side.

  Next, as shown in the period pb of FIG. 2B, when the control signal φB1 becomes H level, the DC current 114a flows into the resistor R in addition to the bias current. Subsequently, when the control signal φB2 becomes H level, the gate voltage of the NMOS in the feedback path to which the control signal φB2 is supplied is an error so as to cancel the increment of the voltage drop at the resistor R due to the addition of the DC current 114a. It is driven by the amplifier 200. At the end of each of these current generation periods (the control signal φA or the control signal φB2 returns from the H level to the L level), it is held in each capacitor provided in the test signal generation circuit 119 shown in FIG. Further, the gate voltage of each NMOS is disconnected from the loop, and each output current is stored as a current memory. In order to suppress an error caused by the electric charge generated at the time of switching, a certain time difference is provided at each switching timing between the H level of the control signal φB1 and the H level of the control signal φB2. It is also desirable to reduce errors using a dummy switch (not shown).

  Thereafter, as shown in the period pc of FIG. 2B, the switch 121 is closed during the active period of the control signal φC, and a current pulse is output as the inspection signal 122 from the current memory. Mainly in view of the slew rate determined by the OFF-state leakage current of the switch 121 and the holding capacity value, the inspection signal 122 can be repeatedly output within a period in which the accuracy of the current memory can be ensured. In FIG. 2B, as shown in the period pd, after the generation / retention of the minute current, the control signal φC becomes active three times, and three current pulses having an amplitude of 50 nA are generated. As described above, the control signal generation unit 1097 of the control circuit 109 generates the control signal 123 in FIG. 1 as trimming control means in the second trimming circuit 125, and efficiently generates, holds, and outputs a high-precision minute current. By switching frequently, the inspection signal 122, which is a pulse signal having a known amplitude, is generated.

In the above example, the output current 114 itself obtained as a result of performing the first trimming is switched by the selector 115 as the DC current 114c for the inspection signal generation circuit 119 and as the DC current 114a for the threshold generation circuit 105. The configuration to be input has been described. However, if an inspection signal that directly corresponds to the amplitude setting value of the actual threshold current 108 and the setting value of the total current gain is to be generated, the output current of the minute current generation circuit 120 becomes extremely small, and the circuit does not operate stably. There may be concerns. In such a case,
1) The threshold current 108 used in the inspection process for determining the success or failure of the second trimming is set to a constant ratio larger than the set amplitude of the threshold current 108 used during normal operation, and the magnification of the minute current generation Is the reciprocal of the total current gain, and the amplitude of the inspection signal 122 is increased by a certain ratio.
Or
2) The threshold current 108 used in the inspection process for determining the success or failure of the second trimming after taking a means for reducing the total current gain by a certain ratio in either the amplifier circuit 102 or the comparison circuit 103 is normally The amplitude of the inspection signal 122 is increased by a certain ratio while maintaining the same set amplitude as that during operation.
Thus, it is possible to design a minute current value to be generated as a larger value. In particular, the DC current 114b monitored by the first trimming and the DC current 114c input to the minute current generation circuit 120 are set to a large value by the same constant ratio, thereby preventing a decrease in accuracy when generating the minute current. . For example, for the DC current 114a input to the threshold value generation circuit 105, a desired setting value is obtained by adding a current mirror circuit in which the mirror ratio is reduced by a certain ratio from the value of the DC current 114b monitored in the first trimming. be able to. According to such a configuration, even if the absolute setting accuracy of the threshold current 108 is slightly lowered and the target value is shifted, the inspection means is uniformly applied to reduce the variation in individual minimum reception sensitivity. The purpose of adjustment can be achieved with sufficient accuracy, and in the actual operation, uniform correction is made to the threshold setting conditions specified from the outside, and the final minimum reception sensitivity is set as the target. This is possible and will not cause any trouble.

  As is clear from the above description, one of the basic components of the present invention is the first trimming, and the threshold current 108 of the comparison circuit 103 is directly and highly accurately controlled (with known accuracy). At the same time, based on the result of the implementation, the optical pulse detection device is to generate a current signal convenient as its own inspection signal with known accuracy. In particular, this is preferably realized by configuring the comparison circuit 103 to operate with respect to the current threshold as shown in FIG. That is, with respect to the minute DC current generated based on the first trimming execution result, the transmission signal is simply turned ON / OFF so that the amplitude is zero during the inspection signal pulse OFF period. It can be easily shaped into a pulse waveform while maintaining current amplitude accuracy and a reasonable time constant. Of course, the threshold value of the comparison circuit 103 can be a voltage signal, and the input of the inspection signal to the amplifier circuit 102 can be a voltage signal. In this case, however, a separate reference voltage generation, impedance conversion, or AC coupling is possible. And the circuit scale increases, and it is difficult to directly use the result of the first trimming for the second trimming.

  Here, as shown in FIG. 2B, each signal of the control signal 123 is complementarily switched on the time axis, so that when the inspection signal 122 is actually input to the amplifier circuit 102, the programmable current source It is also possible to reuse the control signal 818 of 113 for other purposes, that is, adjustment of the threshold current 108 of the comparison circuit 103. That is, as shown in FIG. 11, by making the adjustment setting (programming) of the programmable current source 113 by the first trimming circuit 112 and the control signal 818 independent from each other, a programmable circuit that tends to have a relatively large circuit scale. The circuit scale can be reduced by reusing the current source 113. In particular, in the manufacturing process of the IC chip in which the light receiving element (photodiode 101) is integrated, the second trimming can be performed while easily correcting the sensitivity of the photodiode 101.

  For example, based on the sensitivity measurement result (ratio with respect to the standard value) of the photodiode 101 performed separately from the first or second trimming, the value of the DC current 114c used for generating the minute current is multiplied by the sensitivity ratio. The inspection signal 122 can be generated after the setting of the control signal 818 is designated from the outside so as to be closest to the measured value. Alternatively, the setting of the control signal 818 can be designated from the outside so that the value of the DC current 114a used for generating the threshold current 108 is closest to the value obtained by multiplying the sensitivity ratio.

  In this manner, a current pulse waveform is generated based on the high-accuracy DC current generated by the first trimming, and the second trimming is performed based on the result of observing the response of the receiving unit 100 to the current pulse waveform. . Hereinafter, the details of the second trimming, that is, the gain trimming of the amplifier circuit 102 in FIG. 1 will be described with reference to FIG.

  The constituent elements of the second trimming circuit according to the present invention include, firstly, an inspection signal generation circuit 119 that generates an inspection signal based on the result of the first trimming as described above. As a second requirement, for example, the amplification factor of the amplifier circuit 102 including PGA can be adjusted by the second trimming circuit 125. In general, it can be said that a voltage amplifier circuit such as the above PGA is a circuit block that can easily realize an adjustment function based on the ratio of the passive element size as compared with the transimpedance amplifier in the previous stage and the comparison circuit in the subsequent stage. Therefore, by configuring the second trimming circuit in this way, it is possible to most easily realize high-precision trimming with the minimum reception sensitivity, which is the object of the present application. In the example of FIG. 1, the connection state of the three fuses shown in the second trimming circuit 125 is reflected in the gain switching control signal of the amplifier circuit by the decoder 124, and is amplified from the control circuit 109. The rate switching setting is not performed (see FIG. 10).

  Further, as a third constituent requirement, the control circuit 109 functions as trimming control means in the second trimming as follows. The control circuit 109 adjusts the timing of the inspection signal 122 by the control signal generation unit 1097, generates the synchronous reception gate signal 1093 in synchronization with the timing, and outputs the digital output of the comparison circuit 103 based on the synchronous reception gate signal 1093 by the signal processing unit 1092. A series of inspection sequences including at least acquisition of the signal 106, counting of the synchronous reception output 1094 by the determination / control unit 1096, determination of success or failure of the second trimming based on the count result, and output of the determination result to the outside carry out.

  From here, the above-described series of sequences will be specifically described with reference to FIG. The adjustment of the pulse timing of the inspection signal 122 by the control signal generator 1097 corresponds to the generation of the control signal φC in the control signal 123 in the timing chart shown in FIG. The control signal φC includes at least an H level pulse width W, a pulse repetition period T, and a total number N of pulses (N = 3 in FIG. 3) as control parameters.

  The chart qa in FIG. 3 shows the waveform of the control signal φC that opens and closes the transmission gate 121 in order to generate the inspection signal 122, and corresponds to the drive waveform of the transmitter (not shown) in actual operation. A chart qb in FIG. 3 is a waveform example of the digital output signal 106 output from the comparison circuit 103. In the waveform of the digital output signal 106 shown in the chart qb of FIG. 3, the pulse width and / or the delay amount varies from pulse to pulse with respect to the waveform of the control signal φC shown in the chart qa of FIG.

  The chart qc in FIG. 3 shows the synchronous reception gate signal 1093. The synchronous reception gate signal 1093 has exactly the same H and L level output timing as the inspection signal 122, and is completely the same as the inspection signal 122. It is generated as a synchronized signal. The synchronous reception gate signal 1093 may be a signal that is substantially synchronized with the inspection signal 122 by giving a fixed delay time to either or both of rising and falling edges. By such a delay time giving operation, a synchronization gate can be applied in consideration of a so-called group delay in the amplifier circuit 102, but on the other hand, a new variation factor can be brought about in the minimum receiving sensitivity of the receiving unit 100. Therefore, caution is necessary.

  The digital output signal 106 output from the comparison circuit 103 is captured by the signal processing unit 1092 as follows. The signal processing unit 1092 obtains a logical product of the digital output signal 106 of the chart qb in FIG. 3 and the synchronous reception gate signal 1093 in the chart qc of FIG. 3, and is determined by the synchronous reception gate signal 1093. That is, the result of determining (latching) the presence or absence of the digital output signal 106 in the synchronous reception gate period in which the synchronous reception gate signal 1093 is at the H level, that is, the synchronous reception output 1094 is output (chart in FIG. 3). qe). The synchronous reception output 1094 is reset to L level when the reset signal 1095 (chart qd in FIG. 3) becomes H level immediately before the end of the repetition period T of the inspection signal 122 (chart qe in FIG. 3). The synchronous reception output 1094 is input to a counter (not shown) provided in the determination / control unit 1096, and the number of occurrences of leading edges (rising edges) from the L level to the H level is counted.

  When the count number matches the total number N of pulses in the inspection signal 122, the determination / control unit 1096 reproduces all the pulses of the inspection signal 122 normally in the comparison circuit 103 in a series of inspection sequences. That is, it is determined that the second trimming has been successful (a sufficient amplification factor has been obtained). On the other hand, if the count number does not coincide with the total number N of pulses in the inspection signal 122, the determination / control unit 1096 has failed to set the second trimming condition (in the process of increasing the amplification factor). , The amplification factor is still insufficient). However, the success or failure of the fuse cutting operation itself should be detected separately and does not affect the success or failure determination of the second trimming here.

  As described above, when the second trimming is performed together with the sensitivity correction of the photodiode in the configuration of FIG. 1, the operation mode in which the second trimming is performed on the receiving unit 100 from the outside via the control circuit 109. (That is, when an instruction to start the series of inspection sequences is given to the control circuit 109 from the outside), the setting of the threshold value of the comparison circuit 103 and the setting of the amplitude of the inspection signal 122 if necessary Conditions are specified, and these set values must be held in the register 1102 as illustrated in FIG. 10 and supplied to the control circuit 109. Alternatively, it is also necessary to reset the contents of the register 1102 to a known initial value when the power is turned on, in case the setting condition is not specified. The control circuit 109 including the trimming control unit configured as described above, together with the programmable current source 113 and the selector 115, switches the above setting conditions at the pulse timing as shown in FIG. The inspection signal generation circuit 119 is appropriately controlled.

  The actual second trimming is performed as follows, for example. First trimming (and separately measuring the sensitivity of the photodiode if necessary) is performed. At the time of completion of the wafer manufacturing process, the trimming fuses included in the second trimming circuit 125 are all electrically short-circuited, and are designed to give the minimum amplification factor within the adjustable range of the amplifier circuit 102. ing.

  First, in this state, an instruction is given from the outside through the external interface 111 to execute the above-described series of inspection sequences. Then, it is confirmed that the second trimming is determined to be unsuccessful, that is, the test signal is not successfully received (pulse regeneration) for N consecutive times. Naturally, such an adjustment range of the amplification factor must be built in the amplifier circuit 102 in advance.

  If it is determined that the second trimming has failed as described above, the amplification factor of the PGA (corresponding to the connection state of each trimming fuse included in the second trimming circuit 125) set at the time of the failure is set to 1LSB. The determination / control unit 1096 of the control circuit 109 is instructed from the outside to increase (Least Significant Bit) and to execute the above-described series of inspection sequences shown in FIG. When these steps are repeated and it is confirmed that the second trimming is determined to be successful for the first time (the inspection signal 122 has been reproduced N times consecutively), the setting of the amplification factor is confirmed, and the second Trimming is complete.

  As described above, in the second trimming, based on the signal whose absolute value is controlled by the first trimming means, a pulse signal having a known amplitude is input to the amplifying means by the second trimming means as an inspection signal. As a result, cutting of each fuse that is also a part of the second trimming means, that is, second fuse trimming is performed, and the receiver 100 provided as a main component of the optical pulse detection device of the present invention. The reception sensitivity is trimmed.

  Here, in order to output the determination results of the case of failure and the case of success to the outside, the following device is required. That is, it is necessary to know from the outside through the external interface 111 whether or not the circuit to be inspected (the receiving unit 100) has entered the second trimming inspection operation, and then whether the circuit has been determined to have failed or succeeded. This can be realized by the output unit 1103 (and the output terminal 1104) provided for the above purpose in the interface circuit 110 shown in FIG. 10 as follows. The output terminal 1104 outputs an H level when the trimming inspection operation is not started (no instruction is given from the outside), and an L level is output when the trimming inspection operation is started. Once the control circuit 109 determines that the trimming has failed, the output terminal 1104 returns to the H level again. When the control circuit 109 determines that the trimming has failed, the output terminal 1104 has the oscillator 1090 of the circuit under test. The control circuit 109 drives the output unit 1103 so that the clock signal 1091 is output. According to such a configuration, the above-described object can be achieved by adding only one output terminal, and the above-mentioned four output states can be easily distinguished even if a very general tester is used during wafer testing. . Of course, other variations can be easily implemented.

By determining whether or not the second trimming is successful as described above, it is possible to reduce the influence of in-circuit noise that becomes a problem near the minimum reception sensitivity. If the success of N consecutive receptions is a condition for the end of the second trimming, the occurrence probability is represented by (1-p) ^N, where p is the reception error occurrence probability per test signal pulse, and N As long as p is not lowered to some extent in accordance with the set value of, the success probability does not approach 100%. Accordingly, it is possible to clearly determine the trimming success / failure boundary without being affected by noise as N is increased. Actually, N is about 3 to 7, and the effect can be sufficiently obtained without setting the value so large.

  In addition, a state where a reception error occurrence probability is relatively high (low detection success probability) for one pulse reception, such as a proximity sensor, defines a detection distance (that is, an event with a low occurrence probability). In an optical pulse detection device whose characteristics are determined), it is necessary to more reliably reduce the influence of noise and perform trimming with high accuracy and reproducibility. For this purpose, the following procedure can be adopted. That is, the observation (inspection) is continued until it can be confirmed that the event of successful reception of N consecutive test pulses occurs at a certain rate. As described above, if the occurrence of the event of successful N-th consecutive pulse reception is immediately the condition for the end of the second trimming, the event only occurs once, and before the event occurs Since the concept of the time required, that is, the frequency of occurrence, is not included, the extraction of the trimming condition itself is directly affected by the probability event. To avoid this problem, observe for a longer period of time and observe that the event of successful reception of N consecutive pulses occurs M times within an attempt to repeat the generation of N consecutive pulse trains L times. Then, the trimming condition can be extracted so that the ratio (that is, the occurrence frequency M / L) falls within a desired range or is closest to a desired value. Although this is a trade-off with the total time required for the inspection, observing the occurrence frequency of events as described above is essentially important for the purpose of aligning the minimum reception sensitivity. A means for solving this trade-off will be separately described later.

  As described in detail above, by configuring the first and second trimming circuits of the present invention, all characteristics within individual ICs are reflected in high-precision trimming with minimum reception sensitivity in the optical pulse detector. In addition to inspection, it has become possible to achieve this at a low cost and at a low cost.

[Second Embodiment]
Up to this point, as a first embodiment of the present invention, a functional block configuration example of a typical receiving unit 100 (FIG. 1), a configuration and operation of a test signal generation circuit 119 (FIGS. 2A and 2B). The operation of the trimming control means (FIG. 3) has been described.

  Hereinafter, as a second embodiment of the present invention, the functional block configuration of another typical receiving unit 500 will be described in detail with reference to FIGS. 4, 12, and 13. 4 is a block diagram of the entire receiving unit 500, FIG. 12 is a more specific configuration example of the first and second trimming means, and FIG. 13 is applied with the first and second trimmings. The details of the circuit configuration example of the programmable current source are shown.

  12 and 13 show a more detailed internal configuration for a specific block in the receiving unit 500 of FIG. 4 so that those skilled in the art can easily understand, like FIGS. 10 and 11 with respect to FIG. It is a thing. Therefore, as a matter of course, in some cases, all the functional blocks described in FIG. 4 cannot be entirely illustrated within FIG. In this sense, it is not possible to take a perfect one-to-one correspondence for all the elements between FIG. 12 and FIG. 13 and FIG. Can be judged. The components of the present invention that are not described in FIG. 12 will be described later with reference to FIG. Thus, the optical pulse detection device of the present invention should be construed to be realized based on the overall configuration of the receiving unit 500 shown in FIG. For this reason, the resistance element ladder shown in FIG. 13 is not shown in FIG. 12 for convenience.

  The differences in configuration between the receiving unit 100 and the receiving unit 500 are listed as follows.

  For the output current 114 of the programmable current source 113, the selector 115 and its control signal 116 provided in FIG. As described above, this is a modification example in which DC currents 114a to 114c may be arranged in parallel as shown in FIG.

  In particular, the first trimming circuit 112 and the second trimming circuit 125 are both configured to operate independently of the DC current 114a supplied to the threshold value generation circuit 105. On the other hand, in FIG. 1, the amplification factor of the PGA in the amplifier circuit 102 is an adjustment target of the second trimming circuit 125.

  The internal configuration of the programmable current source 113 is basically two current mirrors that fold back the current generated using the operational amplifier on the PMOS side and the NMOS side. This is common to FIGS. 11 and 13. It has a configuration. Note that the number of fuses in the first trimming circuit 112 is four in both FIG. 1 and FIG. 4, but the number of fuses in the second trimming circuit 125 in FIG. 4 is changed from three to four in FIG. It has increased.

  Further, as is apparent from FIG. 12, the signal processing unit 1092 of the control circuit 109 including the trimming control unit is coupled with the synchronous signal processing unit 1092a (same configuration as the signal processing unit 1092 shown in FIG. 10) and asynchronous signal processing. Part 1092b. Further, as can be seen from FIG. 12, the path from the control circuit 109 is added to the path for setting the current value of the programmable current source 113 in addition to the path from the first and second trimming means (control). Signals 400 and 401 and buffer 418b). The path composed of the control signals 400 and 401 and the buffer 418b can be controlled by the control circuit 109 independently of the decoder 124 provided for the first and second trimming means. The control signal 400 has the same function as the control signal 818 (see FIG. 1), the buffer 418b has the same function as the buffer 818a (see FIG. 1), and the control signal 401 has the same function as the control signal 8181 (see FIG. 1). Can be interpreted.

  The largest difference between the receiving unit 500 in FIG. 4 and the receiving unit 100 in FIG. 1 is that the first trimming circuit 112 and the second trimming circuit 125 each independently control the output current of the programmable current source 113. That is.

  That is, the receiving unit 500 determines the basic threshold current value (DC current 114a) of the comparison circuit 103 while monitoring the DC current 114b by the first trimming as in the case of FIG. (DC current 114c) is used to generate the inspection signal 122. Further, based on the response of the receiving unit 500 to the inspection signal 122, the value of the threshold current 108 of the comparison circuit 103 is adjusted again by the second trimming circuit 125 so as to obtain a desired sensitivity.

  In FIG. 13, the second trimming circuit 125 shown in FIG. 4 is a second trimming circuit that is a component of the second trimming circuit 125 excluding the control circuit 109 in order to illustrate the concept so that those skilled in the art can easily understand. The circuit is divided into circuits 125 ′. The correspondence between the members with “′” and the members without “′” can be easily recognized with reference to FIGS. 4 and 13.

  As in the case of FIG. 11, the four fuses in the first trimming circuit 112 shown in FIG. 13 are configured as a part of a variable resistor in the analog circuit as a composite with a resistance element (FIG. 13). A first trimming circuit 112). Therefore, the sense circuit of the connection form of the first trimming fuse (the portion corresponding to the first trimming means in 1184 in FIG. 12) is substantially merely a wiring as shown in the figure, and the sense circuit of the first trimming fuse As described above, the connection type decoder 124 is also realized as a part of the analog circuit (variable resistance element). The connection of the trimming fuse, the configuration of the sense circuit, and the configuration of the decoder can be arbitrarily changed as described with reference to FIGS.

  On the other hand, the four fuses in the second trimming circuit 125 shown in FIG. 13 are provided for reproduction as a digital signal by the sense circuit 1184 in the decoder 124. Further, the control signal 118 from the determination / control unit 1096 of the control circuit 109 shown in FIG. 12 includes a control signal 1183 that indicates a setting condition of the programmable current source 113. Further, the control signal 118 shown in FIGS. 12 and 13 includes another control signal 1182, and two controls for setting the values of the DC currents 114 a to 114 c output from the programmable current source 113. One of the signals is selected by the selector 418a in accordance with the control signal 1182 and is output from the decoder 124 as the final control signal 1181, and the connection of the PMOS current mirror of the programmable current source 113 is changed.

  Here, as described above, in the receiving unit 500, either the setting condition based on the result of sensing the connection state of the fuse or the setting condition written to the register 1102 from the external interface 111 is exclusive. The second trimming circuit 125 can be configured so as to be selected and acted on, to be switched by the control signal 1182 so that one setting always works effectively, or to perform calculation from both setting conditions. . The details of the techniques for realizing these trimming fuses and decoders do not limit the gist of the present invention.

  Now, in the receiving unit 500, one of the most important advantages of adjusting the threshold value of the comparison circuit 103 in both the first and second trimmings as described above is the reception as in the first embodiment. By trimming the amplification factor of the unit, it is possible to avoid a situation in which a parameter that has an essential influence on the minimum reception sensitivity such as the bandwidth and the amount of noise of the receiving unit unintentionally changes in a secondary manner. For example, when trimming the gain of the amplifier circuit 102 as in the first embodiment, it may be necessary to increase or decrease the value of the resistor that determines the gain by several tens of percent. Such a large change in the analog circuit constant usually has a wide range of influences on the bandwidth of the receiver, the high-frequency response characteristics, and the noise level input to the comparator. For this reason, the minimum to maximum gain setting range that should be built in the circuit in advance in order to perform trimming with high accuracy often converges to an appropriate one only after repeated trials and evaluations. That is, it is extremely difficult to completely determine the range in which the characteristics of the actually produced device vary from the design stage. On the contrary, if a wide trimming pull-in range that can absorb the characteristic variation with a sufficient margin is created in advance, the width of the minimum unit that can be finally compressed by trimming is widened. Therefore, after all, the number of surplus elements and the number of trimming bits to be built in the IC chip increases, and the chip size and manufacturing cost increase. However, in the case of the sensitivity adjustment by performing the trimming of the threshold values illustrated in FIGS. 4, 12, and 13, in order to overcome the difficulty of design due to the interaction of the analog characteristics as described above. The need for redundant design is eliminated, and desired trimming accuracy can be relatively easily ensured at low cost and in a small space.

  Alternatively, as shown in FIGS. 4, 12, and 13, the current output reflecting only the first trimming result can be obtained at the same time as adjusting the threshold value of the comparison circuit 103 in both the first and second trimmings. By configuring the programmable current source 113 as described above, the following advantages can be obtained. That is, the accuracy of the absolute value of the current obtained by the first trimming is required separately from the current value for generating the inspection signal including the correction of the individual photodiode sensitivity, which is originally targeted for the second trimming. It can be supplied to the circuit block.

  In the following, with reference to FIG. 5, a more desirable trimming control means as a second embodiment of the present invention will be described.

  In the trimming control unit according to FIG. 3, based on the pulse generated as the inspection signal 122, whether or not the digital output signal 106 is at the H level within the synchronization gate period in which the synchronization reception gate signal 1093 is at the H level. The determination / control unit 1096 only counts the synchronization reception output 1094 of the synchronization signal processing unit 1092a to be obtained, thereby determining the success or failure of the second trimming.

  On the other hand, the trimming control means according to FIG. 5 further determines whether the digital output signal 106 is at the H level or not during the period other than the synchronous reception gate period, that is, the period during which the input signal to the amplifier circuit 102 cannot originally occur. In order to monitor whether the signal is at the level, the asynchronous signal processing unit 1092b performs asynchronous signal processing using the asynchronous reception gate signal 1098 generated by the control signal generation unit 1097.

  The waveforms of the chart ra and chart re in FIG. 5, that is, the inspection signal 122 (control signal φC) and the reset signal 1095 are the same waveforms as the chart qa and the chart qe in FIG. Omit. 5 is an example of the waveform of the digital output signal 106 of the comparison circuit 103, but the waveform shown in the chart rb in FIG. 5 is irrelevant to the inspection signal 122 compared to the waveform shown in the chart qb in FIG. An unnecessary pulse is generated. Further, the waveform of the synchronous reception gate signal 1093 shown in the chart rc in FIG. 5 is compared with the waveform of the synchronous reception gate signal 1093 shown in the chart qc in FIG. 122 pulse width) is added, and the pulse width is doubled. In the chart re of FIG. 5, as in the chart qe of FIG. 3, the determination / control unit 1096 obtains the negative logical product of the digital output signal 106 and the synchronous reception gate signal 1093, and the digital output signal 106 within the synchronous gate period The result of determining (latching) the presence or absence is output.

  The chart rf in FIG. 5 shows an asynchronous reception gate signal 1098, a period in which the pulse of the inspection signal 122 is L level and the digital output signal 106 is valid, that is, the inspection signal in the chart ra in FIG. In the period from when the control signal φC for generating 122 becomes L level to when the reset signal 1095 generated at the end of the cycle becomes H level, it can be made active for an arbitrary period.

  The determination / control unit 1096 determines (latches) whether or not there is an unnecessary pulse included in the digital output signal 106 within the asynchronous gate period by obtaining a negative logical product of the digital output signal 106 and the asynchronous reception gate signal 1098. Asynchronous reception output 1099 is output. The asynchronous reception output 1099 is reset to the L level by the reset signal 1095 together with the synchronous reception output 1094 (chart re and chart rg in FIG. 5). In this way, the determination / control unit 1096 can count noise outputs that have no correlation with the input inspection signal 122. Note that the details of the technique for embodying each signal processing of synchronous reception and asynchronous reception as described so far do not limit the gist of the present invention.

  The determination / control unit 1096 is obtained by using each of the above signals as a pair with the output of the comparison circuit (with synchronous reception) during the ON period of the inspection signal 122 and without the output of the comparison circuit (without asynchronous reception) during the OFF period. Can count. In the chart rb and the chart rf in FIG. 5, the asynchronous reception uncorrelated with the inspection signal 122 between the second and third inspection signal pulses (the asynchronous reception output 1099 of the chart rg in FIG. 5 and the asynchronous reception in the chart rb). An unnecessary pulse generated at the same timing as the reception output 1099 is detected).

  In this way, the second trimming control in which the determination / control unit 1096 shown in FIG. 12 determines that reception sensitivity is achieved (trimming success) when the count number of the pair state matches the number of pulses of the inspection signal. By configuring as a means, it is possible to make the influence of errors that can occur stochastically in the output of the comparison circuit due to the influence of in-circuit noise even more obvious, and to determine the success or failure of the second trimming more clearly. become. Therefore, high-accuracy trimming with minimum reception sensitivity in the pulsed light detection device can be realized with reduced space and cost.

  Similarly to the example of FIG. 3, in the example of FIG. 5 as well, the trimming condition is satisfied when N pairs of successful events of the presence of synchronous reception and the absence of asynchronous reception continue N times for the generation of N test pulse trains. By completing the extraction, it is possible to clearly determine the trimming success / failure boundary without being affected by in-circuit noise as N is increased. Actually, even if the value of N = 3 to 7 is not so large, the effect can be sufficiently obtained. Further, in the same manner as described in the example of FIG. 3, N pulse train generations are repeated L times, and the occurrence frequency M / L of the number M of occurrences of counter events with N consecutive synchronous receptions and no asynchronous receptions is Extracting the trimming condition so as to be within the desired range or closest to the desired value is essential for the purpose of aligning the minimum reception sensitivity and is a more desirable method.

[Third Embodiment]
In the following, a third embodiment of the present invention will be described. The embodiments described in detail so far have focused on making trimming of the minimum reception sensitivity as close to the same state as in actual reception operation as much as possible. Here, conversely, hold means is provided as a component of the second trimming circuit, and the amplifier circuit is shifted from the track mode to the hold mode at a specific timing generated based on the trailing edge of the inspection signal. This is shown in FIG. For the sake of convenience, the receiving unit 600 shown in FIG. 6 shows only a circuit block that is functionally particularly closely related to a holding circuit (holding unit) 1251 described later with respect to the receiving unit 100 shown in FIG. Although the illustration of the circuit block is omitted, this omitted part has the same configuration as that of the receiving unit 100. In addition, the code | symbol description was partially omitted about the component which is the same as that of FIG. 1 and does not require description.

  In the receiving unit 600 illustrated in FIG. 6, a hold circuit 1251 including a transmission gate and a differentially arranged capacitor is provided immediately before the input terminal unit of the OTA 104 in the comparison circuit 103.

  Each of the transmission gates constituting the hold circuit 1251 is opened / closed by a control signal 1252 generated by the control signal generation unit 1097 of the control circuit 109, similarly to the other transmission gates described so far. At the end of the H level period of the transmitter drive signal or test signal 122, the differential signal 1041 and 1042 are represented by the signals 1043 and 1044 in FIG. As shown, the DC level at the transition timing is held.

  In the case of the configuration of the hold circuit 1251 in FIG. 6, a circuit block (programmable) that can be set from the external interface 111 (see FIG. 1, etc.) existing in the signal path after the hold means, that is, the implementation described so far By changing the setting of the output current of the programmable current source 113 in the embodiment, the following advantages can be obtained. In this case, the waveform operation shown in FIG. 10 is not performed for the threshold current 108, and the threshold value generation circuit 105 needs to be changed so as to obtain a DC level output, similarly to the held signals 1043 and 1044. It is.

  In the case of a general reception operation including a general pulse reception unit that does not use a gate signal, when it is desired to obtain a total minimum reception sensitivity from the photodiode 101 and the amplification circuit 102 to the comparison circuit 103 at a desired timing, By holding the signal of each part after the hold circuit 1251 at the transition timing of the control signal 1252 used only at the time of the inspection, the differential input signal of the comparison circuit 103 is held at the difference between the signal 1043 and the signal 1044. (See FIG. 7).

  In this state, a DC current signal proportional to the DC amplitude when the differential input signal is held charges the high impedance node 107 of the comparison circuit 103. On the other hand, the high impedance node 107 is discharged by the threshold current 108. Therefore, the voltage of the high impedance node 107 becomes H level or L level depending on the relationship between the large and small of these two current components.

  Therefore, in the hold state shown in FIG. 7, the level detection of the digital output signal 106 of the comparison circuit 103 for each threshold setting is repeated while sequentially scanning the set value of the threshold current 108 within the adjustable range. This makes it possible to know in advance whether or not the second trimming (in this example, the setting of the threshold current 108) has been successful, as described in the above embodiments.

  That is, even if the output impedance at the high impedance node 107 of the comparison circuit 103 varies from one chip to another and as a result, the voltage gain and signal delay as the comparison circuit 103 vary, It is possible to extract the optimum execution conditions for the second trimming.

  Further, according to the above configuration, since the evaluation of the inspection signal 122 for each setting does not involve signal processing as in the embodiments described so far, the time required for the total inspection process is greatly reduced. It becomes possible to do. For example, once the signal level is held, it is not necessary to set the register used for correcting the sensitivity of the photodiode when the inspection signal 122 is generated. The held signal level is maintained only for a finite time, and there are error factors such as droop due to leakage current around the hold circuit, but the level can be designed to be sufficiently negligible. As a result, the time margin given to the control circuit 109 is significantly increased as compared with the embodiments described so far. Since the threshold value of the comparison circuit can be set at an arbitrary timing, the entire inspection mode can be designed very easily.

  These advantages are maximized in combination with the second trimming means in the fourth embodiment by the temporary adjustment means that can be repeatedly executed and the adjustment means that cannot be changed after the execution, which will be described below. Demonstrate the effect.

  However, since the in-circuit noise level is also held as a signal level together with the above hold operation, as described in the description of the minute current generation circuit 120 with reference to FIG. It may be desirable to scale up each amplitude of the signal 122 within a range where the amplifier circuit 102 does not saturate to ensure a signal-to-noise ratio.

  Here, the hold circuit 1251 shown in FIG. 6 is a conceptual diagram, and any circuit that can realize the various features disclosed in the present application can be freely modified into a known circuit. For example, a source follower is inserted into a node corresponding to the differential input portion of the comparison circuit 103 and the hold circuit 1251 in FIG. 6, and the gate voltage of the source follower is held by a capacitor added to the gate. Thus, it can be realized by inserting a switch opened / closed by the control signal 1252 in series at the position of the hold circuit 1251 in FIG.

[Fourth Embodiment]
Hereinafter, the fourth embodiment of the present invention will be described with reference to FIG. 4 again. In both the first and second embodiments, in the second trimming, the trimming bit is changed one by one, the reception sensitivity is inspected, and this is repeated to determine success or failure. . However, as mentioned in the third embodiment, if the trimming and the measurement (inspection) are repeated alternately, the total inspection time becomes long and means for shortening it is necessary.

  Further, as is apparent from the description of the actual second trimming process described with reference to FIG. 3, the sensitivity of the optical pulse detection device is only improved in one direction, either in the direction of improvement or in the direction of deterioration. It cannot be adjusted. That is, since the second trimming is performed by cutting each fuse, it is a matter of course that once these fuses are cut, the setting conditions before cutting cannot be restored.

  In order to cope with these problems, the adjustment of the threshold current 108 of the comparison circuit 103 by the second trimming circuit 125, which is an example of a component of the second trimming circuit in the optical pulse detection device of the present invention, is repeatedly performed. An example of a configuration that includes a possible temporary adjustment means and a main adjustment means that cannot be changed after implementation will be described with reference to FIG.

  Here, this adjustment means refers to a path in which the output current of the programmable current source 113 is determined by the connection / cut-off state of the four fuses shown in the second trimming circuit 125. The temporary adjustment means refers to a path that is written and specified in the register 1102 from the external interface 111 and the output current of the programmable current source 113 is determined by the control signal 118 from the control circuit 109.

  That is, the temporary adjustment means is provided for adjusting each value of the DC currents 114a to 114c, which are output currents of the programmable current source 113, regardless of the connection / cut-off state of the fuse included in the second trimming means. It is realized by the configuration of the control signal 118 generated by the control signal generation unit 1097 of the control circuit 109 and the decoder 124. As already described, the control signal 118 in FIG. 13 includes the control signal 1182. When setting the output value of the programmable current source 113, which setting condition of the temporary adjustment means and this adjustment means is selected and output from the decoder 124 (control signal 1181) and given to the programmable current source 113, The control circuit 109 can be configured so that it can be selectively output from the selector 418a in accordance with the control signal 1182 (starting up in the wafer test mode or the trimming mode).

  Here, according to the configuration of FIG. 13, m = n, assuming that the setting by this adjustment means (fuse connection state) is m bits and the setting by the temporary adjustment means (instruction from the external interface) is n bits. This is not always necessary. Normally, it is desirable that m <n, the adjustment range of the temporary adjustment unit is wide, and the setting conditions by the temporary adjustment unit completely include the setting conditions by this adjustment unit. In that case, only the common m-bit setting is instructed to be used by the control signal 1182, and the corresponding part of the control signal 1183 is applied to the remaining (mn) bits. For example, a modification in which an initial value is forcibly applied to (mn) bits is possible.

  Furthermore, the control circuit 109 as the trimming control means in the second trimming circuit 125 performs a series of inspections as described above for each of at least some of the settings included in the adjustable range of the temporary adjustment means. A sequence is executed to determine the success or failure of each temporary trimming. In this way, the highest sensitivity setting that can be realized by the circuit to be inspected with respect to the inspection signal 122 having a known amplitude and accuracy by the first trimming, that is, the second trimming success already described is determined. The second trimming control circuit 109 can be configured so that the circuit under test itself automatically searches for and extracts the minimum threshold setting (or the highest amplification setting).

  Next, the most probable setting condition of the temporary adjustment means extracted as described above is output to the external interface 111 through the interface circuit 110. Here, in the same manner as described in the actual second trimming process in the first embodiment, the dedicated output terminal 1104 shown in FIG. 12 is provided, and the completion of the condition extraction is output to the outside. . At this time, the original sensitivity (threshold value) setting register in the interface circuit 110 holds the register setting when the condition extraction is completed, and is read out from the outside through the external interface 111.

  In the fourth embodiment, when the external interface 111 instructs the circuit under test (receiving unit 500) to perform a trimming operation (wafer test mode) instead of a normal sensor operation, up to here. A series of operations in the second trimming described is executed by the circuit under test itself.

  Based on the most probable setting condition of the temporary adjustment means obtained in this way, trimming by the main adjustment means in the second trimming is performed. In other words, the configuration of the second trimming means including the control circuit 109, the decoder 124, and the programmable current source 113 as shown in FIGS. 4, 12, and 13 is the same as the setting condition of the temporary adjustment means. The fuse connection form guaranteed to produce the result (adjustment result of the minimum reception sensitivity) can be reliably realized as the main adjustment means in the second trimming.

  Here, the example in which the second trimming is performed on the threshold current 108 of the comparison circuit 103 has been described with reference to FIGS. 4, 12, and 13. However, as illustrated in FIG. It will be apparent from the description so far that the present invention can be applied to the amplification factor.

  Also, by providing the provisional adjustment means, the output of the comparison circuit is multiplied by a synchronization gate to count the number of logic outputs corresponding to the inspection signal, or the hold level is used to hold the signal level at a specific timing. The characteristics disclosed in this application for improving the trimming accuracy of the minimum reception sensitivity, such as confirming the output of the comparison circuit corresponding to the state, are tried repeatedly for any sensitivity setting, and a specific event occurs. The frequency can be accurately evaluated. Therefore, it is possible to collect statistically sufficiently reliable information even under a situation where the influence of the circuit internal noise is remarkably received.

  Alternatively, after holding the signal level of an arbitrary node in the amplifier circuit 102 by a hold circuit at a specific timing with respect to the inspection signal, various adjustable circuit settings existing in the signal path after the hold circuit are scanned. be able to. The most preferred embodiment of this combination is a case where the setting condition of the temporary adjustment means in the second trimming is scanned. As a result, the total time required for extracting the most probable second trimming condition can be greatly reduced.

  Apart from that, the following control operations are also possible. For example, with respect to the register for setting the bias current of the amplifier circuit and the frequency of the internal oscillator, the above-mentioned most probable temporary adjustment of the second trimming is performed for each setting while changing the setting within the adjustable range. The setting conditions of means are extracted. In this way, whether or not a desired trimming result can be obtained even under more severe circuit operation conditions is examined in advance, and the quality of the circuit to be inspected can be improved while greatly reducing the inspection time. In this way, high-precision adjustment of the minimum reception sensitivity in the pulsed light detection device can be realized with a small space and a low cost.

  As described in order, the trimming circuits of various optical pulse detection devices disclosed in the present application can stably realize high-precision trimming with minimum reception sensitivity. In particular, since most of the components are realized by diverting or switching circuit blocks or functions used during actual operation as an optical pulse detector, this application can save space and cost without increasing the analog circuit scale. The object of the invention can be achieved. In addition, the pulse light detection algorithm in actual operation and the trimming success / failure judgment algorithm in the wafer test can be shared, so the minimum in a more realistic state without increasing the circuit scale of the digital signal processing part Receiving sensitivity can be trimmed.

  As described above, by mounting the optical pulse detection device of the present invention as a proximity sensor in an electronic device, individual variation is sufficiently suppressed while being highly sensitive, and uniform detection distance characteristics are provided at low cost. Therefore, it can be used for a wide range of applications without limiting the reflectance of the measurement object. As a result, the electronic device can provide fine power saving operation and a more sophisticated user interface.

  Also, a method for solving the problem of erroneous detection due to reflection of a housing window portion of an electronic device in a state where a proximity sensor module mounted with an IC chip subjected to trimming disclosed in the present application is mounted on the final electronic device Will be described.

  As can be easily imagined, the distance between the housing window and the light receiving and emitting surface of the proximity sensor is the same as the distance between the light emitting and receiving parts of the proximity sensor, for example, with a gap of several mm or more. If it is mounted on, the proximity sensor makes it very difficult to distinguish between the housing window and the actual measurement object outside.

  To solve this problem, temporary adjustment means in the second trimming is used. As described with reference to FIG. 13, the sensitivity can be set independently regardless of the fuse connection state of the second trimming means (the result of the second trimming performed by the adjusting means). Moreover, since it is a temporary adjustment means, if it is the setting within the setting range, it can be used.

  Therefore, after creating a state where there is actually no reflective object to be detected, that is, a state where only the reflected light from the housing window exists, the proximity sensor is realized within the range that does not reliably perform “false detection output”. If the highest sensitivity setting to be obtained is extracted, this will be the minimum feasible reception sensitivity specific to the implementation of the electronic device. Although the optimum sensitivity setting as the final product can vary greatly depending on the design of each part of the electronic device, the extraction method itself is the same number of synchronizations as the test pulse train as described in detail for the second trimming so far. This is very similar to the method of counting receptions.

  That is, here, as a final product (proximity sensor) instead of a test pulse, the optical pulse is actually output N times, and a minimum threshold value setting that can maintain a state where there is no synchronous reception at least N times, Alternatively, an optimum sensitivity search operation mode (or product operation check mode) for searching and extracting the maximum gain setting is provided. Thus, the extracted result (sensitivity setting condition) is output to the outside through the interface circuit 110. Further, at this time, a dedicated output terminal different from the interface circuit 110 may be provided so that a trigger (interrupt) is output from the inspected product side to the outside.

  As described above, in the present embodiment, the external interface 111 instructs the circuit under test (receiver 110) not to perform a normal sensor operation but to perform an optimum sensitivity search operation (product operation check mode). Then, the control circuit 109 is configured so that the series of minimum sensitivity search operations described above are executed by the circuit under test itself.

  In this way, at the prototype stage of electronic equipment, by accumulating data that automatically extracts the optimum sensitivity setting in the final mounting state, it is possible to easily and reliably determine the sensitivity condition to be set for the final product. become able to. Alternatively, even after the final product has been shipped, in the scene where the end user actually uses the electronic device, the above-described automatic sensitivity setting automatic extraction function is activated at an appropriate timing from the electronic device side. It is possible to obtain an effect of preventing malfunction.

  The present invention discloses a means for performing trimming of minimum receiving sensitivity in a wafer manufacturing process of an integrated circuit including at least an optical pulse receiving circuit with extremely high accuracy and good reproducibility. That is, in the present invention, a test signal to be used for trimming of the minimum reception sensitivity is stably generated inside the circuit to be inspected and input to the circuit to be inspected, and based on the response of the circuit to be inspected to the test signal, A means for the circuit itself to extract the trimming execution condition is disclosed. In particular, an object of the present invention is to realize trimming of minimum reception sensitivity with high accuracy and high reproducibility in a space-saving and low cost manner. In the present invention, whether the actual trimming (application of power for cutting the fuse) is performed inside the circuit under test or from outside the circuit under test is arbitrary based on the extracted trimming execution conditions. Can be selected. In addition, some means for solving the problems disclosed by the present application, in particular, means for solving the problem of how to complete the extraction of the trimming condition based on the output of the comparator showing the stochastic behavior Can also be applied to trimming including correction of the optical system performed after completing the packaging as a product of the optical pulse detection device.

  The photodiode 101, the amplifier circuit 102, the comparison circuit 103, the first trimming circuit 112, and the second trimming circuit 125 are preferably integrated in the same IC. Thereby, in the optical pulse detection apparatus of this invention, space saving and cost reduction are possible.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention is suitable for a receiving unit for detecting a light pulse, in particular, a receiving unit of a small and low power consumption object detecting device for mounting on a portable device such as a mobile phone.

100, 500, 600
Receiver (part of the circuit functional blocks that make up the optical pulse detector)
101 Photodiode (light receiving element)
102 Amplification circuit (amplification means)
103 Comparison circuit (comparison means)
106 Digital output signal (binarized output)
109 Control circuit (trimming control means)
1092 Signal processing unit (trimming control means)
1092a Synchronous signal processing unit 1092b Asynchronous signal processing unit 1093 Synchronous reception gate signal 1094 Synchronous reception output 1095 Reset signal 1096 Determination / control unit (trimming control means)
1097 Control signal generator (trimming control means)
1098 Asynchronous reception gate signal (trimming control means)
1099 Asynchronous reception output 112 First trimming circuit (first trimming means)
114c DC current (signal whose absolute value is controlled by the first trimming means)
119 Inspection signal generation circuit (inspection signal generation means)
122 Inspection signal 125 Second trimming circuit (second trimming means)
1251 Hold circuit (hold means)

Claims (11)

An optical pulse detection device comprising at least a light receiving element, an amplifying means for amplifying an output signal of the light receiving element, and a comparing means for comparing the amplitude of the output signal of the amplifying means with a threshold value to output a binary signal. And
First trimming means for performing first fuse trimming on the optical pulse detector;
Second trimming means for performing second fuse trimming on the optical pulse detection device,
The second trimming means generates a pulse signal having a known amplitude based on the signal whose absolute value is controlled by the first fuse trimming by the first trimming means, and inputs the pulse signal as an inspection signal to the amplification means. An optical pulse detection device comprising at least inspection signal generation means for performing the inspection. The first trimming means adjusts the threshold value of the comparison means,
2. The optical pulse detection device according to claim 1, wherein the second trimming means adjusts an amplification factor of the amplification means. The first trimming means performs a first adjustment of the threshold value of the comparison means,
2. The optical pulse detection device according to claim 1, wherein the second trimming means performs a second adjustment of a threshold value of the comparison means.   The second trimming means further counts whether or not the output of the comparison means exists within a gate period generated based on the pulse of the inspection signal, and the second fuse by the second trimming means. The optical pulse detection device according to claim 1, further comprising a trimming control unit that determines whether the trimming is successful.   The second trimming means further counts whether or not the output of the comparison means is present within a gate period generated based on the pulse of the inspection signal, and other than the gate period, the second trimming means 2. The optical pulse detection device according to claim 1, further comprising trimming control means for monitoring the output and determining success or failure of the second fuse trimming by the second trimming means.   The trimming control unit counts whether or not the output of the comparison unit exists within at least a gate period generated based on the pulse of the inspection signal, and based on the occurrence frequency of the count, the second trimming unit 6. The optical pulse detection device according to claim 4, wherein the success or failure of the second fuse trimming is determined.   Binarization of a holding means for holding a signal of a desired part in the amplification means to which the inspection signal is inputted at a desired timing, and the comparison means obtained by controlling the inspection signal generating means and the holding means. 2. The optical pulse detection device according to claim 1, further comprising trimming control means for judging the success or failure of the second fuse trimming by the second trimming means from the output. The adjustment means in the second trimming means includes a temporary adjustment means that can be repeatedly executed and a main adjustment means that cannot be changed after the execution.
The trimming control means in the second trimming means determines the success or failure of provisional trimming for each of at least a part of the settings included in the adjustable range of the temporary adjustment means, and for the most probable main adjustment means. 4. The optical pulse detection according to claim 2, wherein the adjustment unit is implemented based on the execution condition obtained by extracting the output condition and outputting the output to the outside and reading out the output. 5. apparatus.   9. The light according to claim 1, wherein the light receiving element is integrated together with the amplifying means, the comparing means, the first trimming means, and the second trimming means. Pulse detector.   An electronic apparatus comprising the optical pulse detection device according to any one of claims 1 to 9 and controlling its own operation based on a detection result of the optical pulse detection device. An electronic device equipped with the optical pulse detection device according to claim 8 and controlling its own operation based on a detection result of the optical pulse detection device,
In order to avoid erroneous detection of the pulsed light projected by the optical pulse detection device being reflected by the housing window of the electronic device, the optical pulse detection device uses a temporary adjustment unit of the second trimming unit. And an electronic device having at least a function of automatically adjusting the minimum reception sensitivity to be used, the automatic adjustment function being activated by an instruction from the outside of the optical pulse detection device.

Images