JP2006086420A - Semiconductor optical sensor and information device therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor optical sensor (illuminance sensor) that produces a linear output with a high precision in a range from low illumination (a few lux) to high illumination (tens of thousands of lux) by providing multiple low and high illumination sensors independently and switching them appropriately, and to provide a mobile phone with this illuminance sensor. <P>SOLUTION: This semiconductor optical sensor comprises multiple photo diodes 1A and 2B with different illuminance-output characteristics, a switch 8 that selects any of multiple photo diodes, an amplifier 9 connected to the output of the photo diode selected by the switch and an output section (OUT) connecting to the amplifier 9. Switching takes place among multiple photo diodes with different illuminance-output characteristics, depending on the illuminance of irradiation by the photo diode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor optical sensor device for an illuminance sensor, and more particularly to a semiconductor optical sensor device capable of detecting illuminance over a wide range from several lux to several tens of thousands of lux.

A semiconductor optical sensor device (illuminance sensor) is an optical sensor that outputs a linear output in accordance with the ambient illuminance (brightness), and is mainly used in mobile phones in accordance with the ambient illuminance (brightness). It is used for ON / OFF control of LEDs (Light Emitting Diodes) of a backlight and an operation unit (key unit). For example, it is used as a sensor that suppresses unnecessary power consumption by turning off the backlight or the light emitting diode of the key unit when the surroundings are bright, and turning on or adjusting the brightness when the surroundings are dark.
In a cellular phone, on / off of the light emitting diode in the key unit is controlled in a low illuminance range of about several lux to 100 lux. Since the conventional illuminance sensor has been used only for on / off control of the light emitting diode of the key portion, it is designed to output a linear output in a low illuminance range of several lux to 100 lux.

  However, at present, power consumption is increased due to the full color of the liquid crystal in addition to turning on and off the light emitting diode of the key part, and control of the backlight of the liquid crystal screen is also required. In the case of a transmissive liquid crystal screen, the backlight on the back of the screen is used as a light source, the saturation is high, and it is easy to see in a dark room, but the screen becomes dark in a bright outdoors. For this reason, it is difficult to see the screen unless the backlight is adjusted according to the ambient brightness. However, there is a limit to the brightness of the backlight. Under high illuminance of tens of thousands of lux, the backlight of the liquid crystal screen is turned off on the mobile phone system. Thus, in order to adjust the brightness of the liquid crystal screen, it is necessary to detect illuminance up to tens of thousands of lux.

The high-illuminance photodiode part has low sensitivity even when low-light intensity light is input, and low-light intensity light is difficult to detect. The low-illuminance photodiode part is too sensitive and high-illuminance light is input. Saturates. That is, for example, when a conventional illuminance sensor optimized to have a linear characteristic in a low illuminance range of several lux to several hundred lux is used for on / off control of a light emitting diode of a key part of a mobile phone, Lux high illumination cannot be detected. In addition, when an illuminance sensor having a photodiode unit for high illuminance is used to detect high illuminance of tens of thousands of lux like a liquid crystal screen of a mobile phone or the like, detection at low illuminance, which is the control illuminance of the key unit, is possible. There was a problem that it would be difficult.
The prior art describes a photoelectric switch circuit having two amplifiers having different gains and a comparator (binarization circuit) as shown in Patent Document 1. According to the purpose, two amplifiers are provided.
JP-A-6-294874

  The present invention provides a semiconductor photosensor device (illuminance sensor) that provides a linear output with high accuracy at low illuminance of several lux to high illuminance of tens of thousands of lux, and a mobile phone incorporating this illuminance sensor. .

One aspect of the semiconductor optical sensor device of the present invention includes a plurality of photodiode portions having different illuminance-output characteristics, a switch for selecting one of the plurality of photodiode portions, and an output portion connected to the switch And switching between selection / non-selection of the plurality of photodiode units based on the illuminance of incident light applied to the photodiode units.
The semiconductor optical sensor device according to the present invention includes a photodiode unit, a plurality of amplifiers connected to the photodiode unit, having the outputs of the photodiodes as inputs and having different gains, and the plurality of amplifiers. And a switch that selects and outputs one of the plurality of amplifiers based on the illuminance of incident light irradiated on the photodiode unit.

  A semiconductor optical sensor device (illuminance sensor) that provides a linear output with high accuracy in a wide range of illuminance from low illuminance of several lux to high illuminance of tens of thousands of lux can be provided. Further, by using such an illuminance sensor, it is possible to provide a mobile phone capable of both turning on and off the light emitting diode of the key unit controlled with low illuminance and controlling the brightness of the liquid crystal screen controlled with high illuminance.

  Hereinafter, embodiments of the invention will be described with reference to examples.

First, Embodiment 1 will be described with reference to FIGS.
FIG. 1 is a circuit block diagram of an illuminance sensor of this embodiment formed on one semiconductor chip, FIG. 2A is a circuit diagram showing an example of a photodiode section described in this embodiment, and FIG. b) is a partial cross-sectional view of the semiconductor substrate showing the photodiode structure of this circuit diagram, and FIG. 3 is a circuit diagram of another example of the photodiode portion described in this embodiment and the photodiode structure of this circuit diagram. 4 is a partial cross-sectional view of a semiconductor substrate, FIG. 4 is a schematic plan view of a photodiode showing a method for changing the illuminance characteristics of the photodiode (PD) portion of this embodiment, and FIG. 5 is an illuminance-output of the illuminance sensor of this embodiment. FIG. 6 is a characteristic diagram showing characteristics and a characteristic diagram showing illuminance-mode output characteristics.

  As shown in FIG. 1, the illuminance sensor includes, in a light receiving portion, a low-illuminance photodiode portion (PD portion) 1A and a high-illuminance photodiode portion (PD portion) 1B having the same spectral characteristics. A first amplifier 9 is connected to the output side of the photodiode unit 1, and a switch (SW) 8 for selecting either the low illuminance photodiode unit 1A or the high illuminance photodiode unit 1B is inserted therebetween. Has been. The first amplifier 9 composed of at least one amplifier is connected to a second amplifier 10 composed of at least one amplifier, and the second amplifier 10 is connected to the output part (OUT) of the illuminance sensor. The illuminance sensor further includes a reference voltage generation circuit 5 and a mode detection circuit 6. The mode detection circuit 6 inputs the output of the first amplifier 9 and the output of the reference voltage generation circuit 5, and compares them. Based on this output, the switch 8 controls which photodiode portion is selected. The mode detection circuit 6 is further provided with a mode output unit (mode OUT) that can detect the output state (mode) from the outside. From the mode OUT, mode information indicating which photodiode is used is output. The second amplifier 10 is used as an output circuit.

Next, the operation of the illuminance sensor will be described with reference to FIG.
5A, the horizontal axis indicates the illuminance of light input to the illuminance sensor, the vertical axis indicates the output of the illuminance sensor, and in FIG. 5B, the horizontal axis indicates the illuminance, and the vertical axis indicates the mode. The mode output of the detection circuit is shown.
As shown in FIG. 1, in the initial state, the switch (SW) 8 is turned on (ON) toward the low-illuminance photodiode portion 1A (the state shown in FIG. 1). In this state, when light having a certain illuminance is irradiated onto the illuminance sensor, the illuminance is detected by the low-illuminance photodiode unit 1A and the first amplifier 9, and the output is detected by the mode detection circuit 6 and the reference voltage generation circuit 5 Compare with the voltage.

At this time, when the illuminance of light entering the photodiode portion of the light receiving portion, that is, the input of the mode detection circuit 6 is lower than the set threshold value (generated by the reference voltage generation circuit 5) of the mode detection circuit 6, the switch 8 Is not switched, and the output signal of the first amplifier 9 is output from the output section (OUT) while the photodiode section 1A for low illuminance remains connected to the first amplifier 9. However, when the input of the mode detection circuit 6 is higher than the set threshold value of the mode detection circuit 6, the switch 8 is switched to connect the high-illuminance photodiode unit 1B to the first amplifier 9, and the output unit (OUT) To output an output signal of the first amplifier 9. In the case of this embodiment, as an example, the set threshold value of the mode detection circuit 6 is set to the illuminance EV1 of the input light. When the input of the mode detection circuit 6 is lower than the set threshold value (EV1), the output of the mode detection circuit 6 is set to mode 1 (output 0), and the illuminance sensor operates as a low-illuminance photodiode unit (PD unit). When 1A is used and is higher than the set threshold value (EV1), the high-illuminance photodiode part (PD part) 1B is used as mode 2. In FIG. 5, EV1 is a value somewhat lower than 1000 lux, but this is an example, and it is necessary to set the EV1 value to an arbitrary value depending on the type of equipment using the illuminance sensor.
According to this example, the low illuminance photodiode portion and the high illuminance photodiode portion can be switched and used, so that the linearity is accurate in a wide range from low illuminance of several lux to high illuminance of tens of thousands of lux. Output can be produced.

The photodiode unit for low illuminance has linear illuminance-output characteristics from several lux to several hundred lux. The photodiode unit for high illuminance has linear illuminance-output characteristics from several hundred lux to tens of thousands of lux. Photodiodes are not suitable for detecting the illuminance because the output is saturated with respect to the illuminance outside the linear region. The switching illuminance EV1 is set within an illuminance range having linear illuminance-output characteristics between the low illuminance photodiode portion and the high illuminance photodiode portion. In consideration of hysteresis, when switching illuminance EV2 is further set to switch from the high illuminance photodiode part to the low illuminance photodiode part and from the low illuminance photodiode part to the high illuminance photodiode part The switching illuminance may be changed.
The structures of the low illuminance photodiode portion 1A and the high illuminance photodiode portion 1B are, for example, as shown in FIG. 2 or FIG.

  In the case of FIG. 2, FIG. 2A is a circuit diagram showing a circuit configuration of the photodiode portion. The pnp transistors Q1 and Q2 constitute a current mirror for detecting the total photocurrent of the two photodiodes PD1 and PD2. The transistor Q1 has a base and a collector connected to the common cathode terminal A of the two photodiodes PD1 and PD2, and an emitter connected to the power supply terminal (Vcc). The output pnp transistor Q2 has a base connected to the base of the transistor Q1, an emitter connected to the power supply terminal (Vcc), and a collector connected to the output terminal (OUT). The npn transistors Q3 and Q4 constitute a current mirror for detecting the photocurrent of the photodiode PD1. The transistor Q3 has a base and a collector connected to the anode terminal B of the photodiode PD1, an emitter connected to the ground terminal (GND), and a collector connected to the output terminal (OUT). The anode terminal C of the photodiode PD2 is grounded. The area ratio of the transistors Q1 and Q2 and the emitter area ratio of the transistors Q3 and Q4 are optimally set so as to obtain a desired spectral sensitivity output according to the spectral sensitivity characteristics of the two photodiodes PD1 and PD2. For example, the emitter area of the transistor Q2 is set to n times (n is a positive number) that of the transistor Q1, and the emitter area of the transistor Q4 is set to m times (M is a positive number) that of the transistor Q3. To do. When light is incident on the light receiving portion of FIG. 2B, the output current IOUT is IOUT = I2−I1 where the collector current of the transistor Q2 is I1 and the collector current of the transistor Q4 is I2. The collector current I1 is I1 = n (Ip1 + Ip2) with respect to the photocurrents Ip1 and Ip2 of the two photodiodes PD1 and PD2. The collector current I2 of the transistor Q4 is I2 = m · Ip1. Therefore, the output current IOUT is IOUT = m · Ip1-n (Ip1 + Ip2) = (mn) [Ip− {n / (mn)} Ip2]. The illuminance sensor detects illuminance in a state where unnecessary infrared components are removed.

  Each of the photodiode portions 1A and 1B is mainly composed of the photodiodes PD1 and PD2 shown in FIG. 2A, and the photodiodes PD1 and PD2 share a cathode electrode in an element formation region on a semiconductor substrate such as silicon. Are formed vertically (FIG. 2B). FIG. 2B is a partial cross-sectional view of the silicon semiconductor substrate on which the photodiode portion is formed. The semiconductor substrate is composed of a P-type semiconductor substrate 15 and an N-type epitaxial layer 16 formed thereon. A P-type impurity diffusion region 17 is formed in the surface region of the N-type epitaxial layer 16. An anode electrode 13 is formed on the surface of the N-type epitaxial layer 16, and a cathode electrode 14 is formed on the surface of the P-type impurity diffusion region 17. The N-type epitaxial layer 16 and the P-type impurity diffusion region 17 of the semiconductor substrate constitute the photodiode PD1 of FIG. 2A, and the P-type semiconductor substrate 15 and the N-type epitaxial layer 16 of FIG. The diode PD2 is configured, the anode electrode 13 is connected to the photodiode PD1, and the cathode electrode 14 is shared by the photodiodes PD1 and PD2.

  In the case of FIG. 3, FIG. 3A is a circuit diagram showing a circuit configuration of the photodiode portion. The transistor Q2 has a collector connected to the anode terminal of the photodiode PD1, an emitter connected to the ground terminal (GND), and a collector connected to the output terminal (OUT). The transistors Q1 and Q2 constitute a current mirror for detecting the photocurrent of the photodiode PD1. The transistor Q1 has a base and a collector connected to the anode terminal of the photodiode PD2, and an emitter connected to the ground terminal (GND). When light is incident on the light receiving portion in FIG. 3B, the output current IOUT is IOUT = Ip1−Ip2 with respect to the photocurrents Ip1 and Ip2 of the two photodiodes PD1 and PD2. The illuminance sensor detects illuminance in a state where unnecessary infrared components are removed by the photodiode PD2.

The photodiode PD1 shown in the circuit diagram of FIG. 3A is shown on the semiconductor substrate of FIG. The semiconductor substrate is composed of a P-type semiconductor substrate 15 and an N-type epitaxial layer 16 formed thereon. A P-type impurity diffusion region 17 is formed in the surface region of the N-type epitaxial layer 16. The N-type epitaxial layer 16 and the P-type impurity diffusion region 17 of the semiconductor substrate constitute the photodiode PD1 shown in FIG. A part of the P-type impurity diffusion region 17 is shielded by a visible light region cut filter (light shielding filter) 21 to adjust the sensitivity-output characteristics of the photodiode portion. The photodiode PD2 is also formed on the semiconductor substrate in the same manner as the photodiode PD1.
As a method of forming the low illuminance photodiode portion and the high illuminance photodiode portion in this embodiment, a method of appropriately setting the element formation size (area) of the photodiode, a wiring electrode layer or the like as a light shielding plate For example, a method of changing the light receiving area by using it may be used.

  FIG. 4A shows an example in which the illuminance characteristics of the photodiode (PD) portion are changed depending on the area. The high illuminance photodiode portion has a smaller area than the low illuminance photodiode portion. As described above, the illuminance sensor uses a low-sensitivity element because it receives a large amount of light when detecting high illuminance. When detecting low illuminance, the illuminance sensor needs to use a high-sensitivity element because the amount of received light is small. The amount of received light is proportional to the area, the high illuminance photodiode portion increases the area, and the low illuminance photodiode portion decreases the area. Further, in this figure, the high-illuminance photodiode portion and the low-illuminance photodiode portion are arranged close to each other for the purpose of making the light receiving environment as uniform as possible. Even with the same semiconductor substrate, the light receiving characteristics may change depending on the location, such as the peripheral part and the central part. In order to avoid it, both are arranged close to each other. The shape of the photodiode portion is rectangular in the figure, but is not limited to this shape, and may be circular, for example. The area ratio of the high-illuminance photodiode portion / low-photodiode portion can be appropriately changed according to the application. However, it is difficult to change after patterning.

FIG. 4B shows a method of arranging a plurality of photodiodes having the same area and the same light receiving characteristics, and switching the number of photodiodes to be used according to the illuminance characteristics of the photodiode portion. A switch is attached to each photodiode (PD), and the switch is turned on and off to obtain a predetermined illuminance characteristic. The high-illuminance photodiode section has a smaller number of photodiodes than the low-illuminance photodiode section. The area ratio of the high-illuminance photodiode portion / low-photodiode portion can be appropriately changed by a switch operation depending on the application. Since this change is possible even after the photodiode is formed, the illuminance sensor can be easily formed.
In the case of FIG. 4C, an element having the same area and structure is used for the photodiode of the photodiode section, and a neutral density filter is formed on a part of the photodiode (PD) of the photodiode section for high illuminance. This is a method of changing the illuminance characteristics. In the above two examples, a photodiode for high illuminance or low illuminance is selected by changing the light receiving area, but in this example, it is used for a photodiode having the same characteristics, and the light receiving performance is lowered to an appropriate diode in the diode. The use of the diode is divided by changing the diode characteristics using a neutral density filter. A photodiode (PD) using a neutral density filter is used for a high-illuminance photodiode portion, and other elements are used for a low-illuminance photodiode portion. Also, in this figure, as in FIG. 4A, the high illuminance photodiode portion and the low illuminance photodiode portion are arranged close to each other, in order to make the light receiving environment as uniform as possible. is there.

  According to this embodiment, a photodiode unit for low illuminance and high illuminance are provided independently, and these are switched in accordance with incident light, so that from low illuminance of several lux to high illuminance of tens of thousands of lux. In the illuminance, an illuminance sensor that provides a linear output with high accuracy can be obtained.

Next, Embodiment 2 will be described with reference to FIG.
This embodiment is composed of three or more n photodiode portions, whereas the first embodiment has a photodiode portion composed of two photodiode portions selected by a switch. It is characterized by having a photodiode portion.
FIG. 6 is a circuit block diagram of the illuminance sensor of this embodiment formed on one semiconductor chip. As shown in FIG. 6, the illuminance sensor has a plurality of photodiode parts (PD part 1, PD part 2,..., PD part n) having the same spectral characteristics in the light receiving part and having different illuminance-output characteristics. 1 is provided. A first amplifier 9 is connected to the output side of the photodiode section 1, and a switch (SW) 8 for selecting a predetermined photodiode section from the plurality of photodiode sections 1 is inserted between them. The first amplifier 9 is connected to the second amplifier 10, and the second amplifier 10 is connected to the output part (OUT) of the illuminance sensor. The illuminance sensor further includes a reference voltage generation circuit 5 and a mode detection circuit 6. The mode detection circuit 6 inputs the output of the first amplifier 9 and the output of the reference voltage generation circuit 5, and compares them. Then, the switch 8 is driven to select which photodiode portion is selected based on this output. The mode detection circuit 6 is further provided with a mode output unit (mode OUT) that can detect the output state (mode) from the outside.

In the initial state, the switch (SW) 8 is turned on (ON) toward the low-illuminance photodiode section, such as the photodiode section (PD section 1), for example (the state shown in FIG. 6). . In this state, when light of a certain illuminance is irradiated to the illuminance sensor, the illuminance is detected by the photodiode unit (PD unit 1) and the first amplifier 9, and the output is detected by the mode detection circuit 6 as a reference voltage generation circuit. Compare with 5 voltage.
At this time, when the illuminance of light entering the photodiode portion of the light receiving portion, that is, the input of the mode detection circuit 6 is lower than the set threshold value of the mode detection circuit 6, the switch 8 is not switched and the photodiode portion (PD portion 1) Is connected to the first amplifier 9 and the output signal of the first amplifier 9 is output from the output section (OUT). However, when the input of the mode detection circuit 6 is higher than the set threshold value of the mode detection circuit 6, the switch 8 is switched to connect, for example, the photodiode unit (PD unit n) to the first amplifier 9 and output. The output signal of the first amplifier 9 is output from the section (OUT). In the first embodiment, one setting threshold value of the mode detection circuit 6 is provided, for example, EV1, but if two setting threshold values are set, this is made effective by preparing three selection photodiode portions. Can be used.

In this embodiment, n photodiode portions for selection are prepared. Therefore, by preparing (n−1) set threshold values for the mode detection circuit 6, n photodiode portions can be used effectively. One set threshold is required to switch between two photodiode sections. The structure of the photodiode portion 1 is, for example, as shown in FIG. 2 or FIG. The method for forming the photodiode portion 1 in this embodiment is the same as that in the first embodiment.
As described above, according to this embodiment, by separately providing a plurality of photodiode portions having different illuminance-output characteristics, and switching them, the illuminance from a low illuminance of several lux to a high illuminance of tens of thousands of lux, An illuminance sensor that produces a linear output with high accuracy can be obtained.
In the first embodiment, the initial state is set for low illuminance, but if light with high illuminance suddenly enters, the output of the illuminance sensor is output until the mode is set by the mode detection circuit 6. The saturation value of the low illuminance amplifier is output to the section (OUT).
Until the mode is set by the mode detection circuit 6, the output unit (OUT) is fixed to the ground potential, and after the mode is set, if control is performed so that an output signal is output from the output unit (OUT). Can be prevented.

  In the first embodiment, the case of having two detection units (in this embodiment, a photodiode unit) for low illuminance and high illuminance has been described, but in this embodiment, three or more different illuminance-output characteristics are provided. By setting a necessary number of potentials in the reference voltage generation circuit for the photodiode portion as well, detection up to high illuminance and detection with high accuracy are possible. For example, the present invention can be applied to an illuminance sensor corresponding to an information device having a center of a detection unit in an illuminance region of 10 lux or less or an illuminance region of 100,000 lux or more as shown in FIG.

Next, Embodiment 3 will be described with reference to FIGS.
This embodiment has two photodiodes selected by the switch, while the first and second embodiments have a photodiode part composed of two or more photodiode parts selected by the switch. It is characterized by having the amplifier comprised from these.
FIG. 7 is a circuit block diagram of the illuminance sensor of this embodiment formed on one semiconductor chip, and FIG. 8 is a characteristic diagram showing illuminance-output characteristics and illuminance-mode output characteristics of the illuminance sensor of this embodiment. FIG.
As shown in FIG. 7, the illuminance sensor includes a photodiode unit (PD unit) 1 in the light receiving unit. The photodiode unit 1 may be the one used in the first and second embodiments, or may be other ones having different characteristics, and the photodiode unit is not limited. The first amplifier 2 is connected to the output side of the photodiode section. The first amplifier 2 is connected to a plurality of second amplifiers 3 (18, 19) having mutually different characteristics such as amplification (see FIG. 8A), and the second amplifier 3 is an output of the illuminance sensor. The unit (OUT) is connected via a switch (SW) 7.

The simplest configuration of the second amplifier 18 for low illuminance and the second amplifier 19 for high illuminance can be realized by an amplifier having the same circuit configuration and changing only the gain (gain). The low illuminance amplifier has linear input / output characteristics from several lux to several hundred lux by converting the input photocurrent into illuminance. Further, the high illumination amplifier has linear input / output characteristics from several hundred lux to several tens of thousands of lux. The output is constant with respect to the input outside the linear range. The switching illuminance is set within the range where the linear input / output characteristics of the low illuminance amplifier and high illuminance amplifier overlap. In consideration of hysteresis, the switching illuminance EV2 is further set to change the switching illuminance between when switching from the high illuminance amplifier to the low illuminance amplifier and when switching from the low illuminance amplifier to the high illuminance amplifier. Also good.
The method for forming the photodiode portion 1 in this embodiment is the same as that in the first embodiment.

  The switch 7 selects one of the low illuminance amplifier 18 and the high illuminance amplifier 19 constituting the plurality of second amplifiers 3 having different characteristics such as an amplifier. The illuminance sensor further includes a reference voltage generation circuit 5 and a mode detection circuit 6. The mode detection circuit 6 inputs the output of the first amplifier 2 and the output of the reference voltage generation circuit 5 and compares them. Then, the switch 7 is driven to select which amplifier is selected based on this output. The mode detection circuit 6 is further provided with a mode output section (mode OUT) that can detect the output state (mode) (see FIG. 8B) from the outside.

Next, the illuminance sensor of this embodiment will be described with reference to FIG.
8A, the horizontal axis indicates the illuminance of light input to the illuminance sensor, the vertical axis indicates the output of the illuminance sensor, and in FIG. 8B, the horizontal axis indicates the illuminance, and the vertical axis indicates the mode. The mode output of the detection circuit is shown.
In the initial state, the switch 7 is on (ON) to the low-illuminance amplifier 18 side (the state shown in FIG. 7). When light having a certain illuminance is applied to the photodiode unit (PD unit) 1, the first amplifier 2 converts the light into an output corresponding to the illuminance. The output of the first amplifier 2 is input to the second amplifier 18 for low illuminance, the second amplifier 19 for high illuminance, and the mode detection circuit 6. The mode detection circuit 6 compares this output with the threshold value (EV1) set by the reference voltage generation circuit 5, and switches the switch 7.
When the output of the first amplifier 2 is lower than the set threshold value (EV1), the switch 7 outputs the output of the second amplifier 18 for low illuminance to the output unit (OUT), and the set threshold value If it is higher than (EV1), it is switched by the switch 7 and the output of the second amplifier 19 for high illuminance is output to the output section (OUT).

When the plurality of amplifiers 3 include a first amplifier and a second amplifier, the first amplifier receives a photocurrent for incident light with an illuminance y of c ≦ y ≦ EV1. In addition, the second amplifier has a linear input / output characteristic when a photocurrent for incident light with an illuminance y of EV1 <y ≦ d is input. The switch for switching between them selects the first amplifier when the illuminance of incident light incident on the photodiode portion satisfies y ≦ EV1, and the illuminance of incident light incident on the photodiode portion is EV1. The second amplifier may be selected when <y.
As described above, in this embodiment, a low illuminance amplifier and a high illuminance amplifier (second amplifier shown in FIG. 7) are provided independently, and by switching these, a low illuminance of several lux to a high illuminance of tens of thousands of lux It is possible to obtain an illuminance sensor that outputs a linear output with high accuracy up to illuminance.

Next, Example 4 will be described with reference to FIG.
In this embodiment, the first and second embodiments have a photodiode portion composed of two or more photodiode portions selected by a switch, whereas three or more selected by a switch. It is characterized by having the amplifier comprised from these amplifiers.
FIG. 9 is a circuit block diagram of the illuminance sensor of this embodiment formed on one semiconductor chip. As shown in FIG. 9, the illuminance sensor includes a plurality of second amplifiers (amplifier 1, amplifier 2,..., Amplifier n) 1 having different characteristics such as amplification degree in the light receiving unit. A first amplifier 2 is connected to the output side of the photodiode unit 1. The first amplifier 2 is connected to the second amplifier 3, and the second amplifier 3 is connected to the output unit (OUT) via the switch (SW) 7. The photodiode portion used in this embodiment may be the same as or different from that used in the first and second embodiments. The illuminance sensor further includes a reference voltage generation circuit 5 and a mode detection circuit 6. The mode detection circuit 6 inputs the output of the first amplifier 2 and the output of the reference voltage generation circuit 5 and compares them. Then, the switch 7 is driven to select which second amplifier is selected based on this output. The mode detection circuit 6 is further provided with a mode output unit (mode OUT) that can detect the output state (mode) from the outside.

In the initial state, the switch 7 is turned on (ON) to the second amplifier for low illuminance like the second amplifier (amplifier 1) (in the state shown in FIG. 9). In this state, when light having a certain illuminance is applied to the illuminance sensor, the illuminance is detected by the output of the first amplifier 2, and the output is compared with the voltage of the reference voltage generation circuit 5 by the mode detection circuit 6.
At this time, if the illuminance of light entering the photodiode portion of the light receiving portion, that is, the input of the mode detection circuit 6 is lower than the set threshold value of the mode detection circuit 6, the switch 7 is not switched and the second amplifier (amplifier 1) Is connected to the first amplifier 2 and the output signal of the first amplifier 2 is output from the output section (OUT). However, when the input of the mode detection circuit 6 is higher than the set threshold value of the mode detection circuit 6, the switch 7 is switched to connect, for example, the second amplifier (amplifier unit n) to the first amplifier 2, The output signal of the first amplifier 2 is output from the output section (OUT). In the third embodiment, one threshold value set by the reference voltage setting circuit 5 is provided, for example, EV1, but if two setting threshold values are set, three amplifiers for selection are prepared. It can be used effectively. In this embodiment, n amplifiers (second amplifiers) for selection are prepared. Accordingly, by preparing (n−1) set threshold values, n amplifiers for selection can be used effectively.

The structure of the photodiode portion 1 is, for example, as shown in FIG. 2 or FIG. The method for forming the photodiode portion in this embodiment is the same as that in the first embodiment.
As described above, according to this embodiment, a plurality of second amplifiers having different characteristics such as amplification factors are provided independently, and by switching these, the illuminance from a low illuminance of several lux to a high illuminance of tens of thousands of lux In this case, an illuminance sensor that provides an accurate output can be obtained.
In the first embodiment, the initial state is set to a mode for low illuminance, but when light with high illuminance suddenly enters, the output of the illuminance sensor is output until the mode is set by the mode detection circuit 5. The saturation value of the low illuminance amplifier is output to the section (OUT). Until the mode is set by the mode detection circuit 6, the output unit (OUT) is fixed to the ground potential, and after the mode is set, if control is performed so that an output signal is output from the output unit (OUT). Can be prevented.

Next, Example 5 will be described with reference to FIG.
FIG. 10 is a schematic plan view of the mobile phone. A mobile phone is composed of an operation surface (key part) that is separated from the liquid crystal screen. The brightness of the liquid crystal screen and the key part is controlled so that any part can cope with the external environment. Therefore, the illuminance sensor described in these embodiments, which are one embodiment of the present invention, is incorporated in such a mobile phone.
The operation unit needs to switch on / off the light of the operation unit with low illuminance, and the LCD screen needs to suppress the brightness of the LCD screen to reduce power consumption when the surrounding environment is high illuminance. is there. By incorporating the illuminance sensor of the present invention, it is possible to detect from low illuminance to high illuminance with high accuracy, so that the operation unit and the liquid crystal screen can be controlled. By incorporating this illuminance sensor, both the on / off of the light emitting diode of the key part controlled by low illuminance and the brightness control of the liquid crystal screen controlled by high illuminance are both formed in one chip shape. It can be effectively performed by a device (illuminance sensor).

Thus, an illuminance sensor is mounted on an information device having a portion that detects and controls incident light with low illuminance and a portion that detects and controls incident light with high illuminance. Each control target in the portable device can be controlled based on the incident light detected by the illuminance sensor that is formed on one chip and can detect the illuminance in a wide illuminance range. Can be reduced.
Although the embodiments of the invention have been described with reference to the examples, a combination of these examples can also be used as examples of the present invention. For example, it is also possible to provide a switch for each of the photodiode unit and the amplifier to be selected by the switch.
In the above embodiments, a case where a plurality of photodiode portions having different illuminance characteristics are independently provided and switched, and a case where two amplifiers having different amplification degrees are independently provided and switched are described. Since the area of the amplifier is larger than that of the photodiode, the former case is advantageous in terms of downsizing the semiconductor device.

The circuit block diagram of the illumination intensity sensor formed on one semiconductor chip of Example 1 which is one Example of this invention. The circuit diagram which shows an example of the photodiode part of FIG. 1, and the fragmentary sectional view of the semiconductor substrate which shows the photodiode structure of this circuit diagram. The circuit diagram of the other example of the photodiode part of FIG. 1, and the fragmentary sectional view of the semiconductor substrate which shows the photodiode structure of this circuit diagram. FIG. 2 is a schematic plan view of a photodiode showing a method for changing the illuminance characteristics of the photodiode (PD) portion of FIG. 1. The characteristic figure which shows the illumination intensity-output characteristic of the illumination intensity sensor of Example 1 which is one Example of this invention, and the characteristic figure which shows illumination intensity-mode output characteristic. The circuit block diagram of the illumination intensity sensor formed on one semiconductor chip of Example 2 which is one Example of this invention. The circuit block diagram of the illumination intensity sensor formed on one semiconductor chip of Example 3 which is one Example of this invention. The characteristic view which shows the illumination intensity output characteristic of the illumination intensity sensor of FIG. 7, and the characteristic figure which shows illumination intensity-mode output characteristic. The circuit block diagram of the illumination intensity sensor formed on one semiconductor chip of Example 4 which is one Example of this invention. The schematic plan view of the mobile telephone explaining Example 5 which is one Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photodiode part 5 ... Reference voltage generation circuit 1A ... Photodiode part for low illuminance 6 ... Mode detection circuit 1B ... Photodiode part for high illuminance 7, 8 ... Switch 2 3, 9, 10 ... Amplifier 18 ... Low illuminance amplifier 5 ... Reference voltage generator 19 ... High illuminance amplifier

Claims (5)

A plurality of photodiode sections having different illuminance-output characteristics;
A switch for selecting one of the plurality of photodiode portions;
An output connected to the switch;
A semiconductor optical sensor device, wherein selection / non-selection of the plurality of photodiode units is switched based on illuminance of incident light irradiated on the photodiode units. The plurality of photodiode portions include a first photodiode portion and a second photodiode portion, and the first photodiode portion has a linear illuminance-output characteristic at an illuminance x of a ≦ x ≦ EV1. 3. The semiconductor photosensor device according to claim 2, wherein the second photodiode section has linear illuminance-output characteristics at an illuminance x of EV1 <x ≦ b. The switch selects the first photodiode portion when the illuminance of incident light incident on the photodiode portion is x ≦ EV1, and the illuminance of incident light incident on the photodiode portion is EV1. 3. The semiconductor photosensor device according to claim 2, wherein the second photodiode portion is selected when <x. A photodiode section;
A plurality of amplifiers each connected to the photodiode section, having the output of the photodiode as an input, and having different gains;
A switch that selects and outputs one of the plurality of amplifiers;
A semiconductor optical sensor device, wherein the plurality of amplifiers are switched based on an illuminance of incident light applied to the photodiode portion. 5. An information device, wherein the semiconductor optical sensor semiconductor device according to claim 1 is incorporated.

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