JP2004165726A - Control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized low-cost control circuit having high versatility. <P>SOLUTION: A D/A converter 102 capable of switching an output voltage based on a set value held in a register 105, an operational amplifier 109 having two input terminals and one output terminal, and a switch 108 for selectively inputting the output of the D/A converter 102 to one of the two input terminals of the operational amplifier, are formed on the same chip. The input terminal not selected by the switch 108 and the output terminal of the operational amplifier are connectable to an external circuit. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement in a control circuit such as a one-chip microcomputer having an analog circuit formed on the same chip.
[0002]
[Prior art]
A control circuit (microcomputer) equipped with an analog circuit provided with, for example, an operational amplifier (op-amp) on the same chip, in addition to an arithmetic control unit that performs digital arithmetic, is widely used in various fields. The present applicant has also proposed a microcomputer having a built-in analog circuit dedicated to a camera, for example, in Patent Document 1.
[0003]
Such microcomputers are also used in consumer products such as various electric products and portable devices. This makes it possible to easily perform complicated calculations and sequence control based on the operation input by the user and the detection result by the sensor, and further control the display device and the actuator according to a predetermined program.
[0004]
Recently, in addition to a timer and a pulse generator, a microcomputer that efficiently controls a display device (for example, an LCD) and peripheral circuits such as an A / D conversion circuit and a D / A conversion circuit are built in the chip. There is also. Since such a microcomputer can be used in a completely different product in the same manner, cost reduction is progressing due to mass production effects. For example, chips used in cameras as described above are used for remote controllers and home appliances.
[0005]
In such a flow, miniaturization of circuits is being promoted by improving semiconductor manufacturing processes, and CPU manufacturers are intensely competing for cost while achieving reduction in chip area.
[0006]
Regarding the improvement of the above-described operational amplifier, Japanese Patent Application Laid-Open No. H11-163873 and the like have proposed a technique of providing a switch switching function in an input section of the operational amplifier to perform offset correction.
[0007]
[Patent Document 1]
JP-A-11-142722
[0008]
[Patent Document 2]
JP-A-6-260851
[0009]
[Problems to be solved by the invention]
What is important in the manufacture of microcomputers, as described above, is the versatility that the same microcomputer can be used for as many circuits as possible. If one kind can be adopted for only one kind of product, the development cost of the microcomputer is all added to the cost of the product, which hinders cost reduction. In particular, if the peripheral circuit is incorrectly selected, the functions related to the peripheral circuit cannot be used. That is, the area and terminals of the peripheral circuits are wasted, and as a result, such circuits are avoided by many users.
[0010]
Also in Patent Document 1, since the analog circuit section includes many circuits dedicated to the camera, the application area of the product is limited, although the chip area is increased and the cost is increased. As a result, cost reduction due to mass production is unlikely.
[0011]
Further, analog circuits such as operational amplifiers are easy to increase in size despite being basic circuits. In other words, an operational amplifier requires two terminals and one output terminal, for a total of three terminals, and is rarely generalized as a peripheral circuit.
[0012]
The present invention has been made in view of the above circumstances, and has as its object to provide a small, low-cost, highly versatile control circuit.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, a control circuit according to the present invention provides a D / A converter capable of switching an output voltage based on a set value held in a register, and an operation having two input terminals and one output terminal. An amplifier and switching means for selectively inputting the output of the D / A converter to one of the two input terminals of the operational amplifier are configured on the same chip, and are not selected by the switching means. A control circuit wherein the input terminal and the output terminal of the operational amplifier are connectable to an external circuit.
[0014]
In order to achieve the above object, a control circuit according to the present invention includes an external terminal for connecting to an external circuit, an operational amplifier, a D / A converter, a + input terminal of the operational amplifier, A first switch that selects two terminals of the three terminals, an input terminal on the negative side of the amplifier and an output terminal of the operational amplifier, and switches to connect to the external terminal; and a first switch that is selected by the first switch. And a second switch for switching the remaining one terminal to be connected to the output of the D / A converter or the selected terminal.
[0015]
In order to achieve the above object, a control circuit according to the present invention is a control circuit having an operational amplifier circuit on the same chip, wherein the first external connection connects an output of the operational amplifier circuit to an external circuit. A second external connection terminal for connecting one of the two inputs of the operational amplifier circuit to an external circuit; an internal circuit connectable to another input of the operational amplifier circuit; Setting means for setting a connection between each input of the circuit, the second external connection terminal and the internal circuit; switching means for switching connection of each input of the operational amplifier circuit according to the setting of the setting means; It is characterized by having.
[0016]
Further, in order to achieve the above object, a control circuit according to the present invention is a control circuit having a plurality of operational amplifier circuits on the same chip, wherein each output of the operational amplifier circuits is connected to an external circuit. A first external connection terminal group, a second external connection terminal group for connecting one of the two inputs of the plurality of operational amplifier circuits to an external circuit, and the plurality of operational amplifier circuits, respectively. An internal circuit connectable to each of the other inputs, an input of each of the plurality of operational amplifier circuits, and setting means for independently setting a connection between the second external connection terminal and the internal circuit; Switching means for switching the connection of each input of the plurality of operational amplifier circuits in accordance with the setting of the setting means.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is an electric circuit diagram showing an example of the control circuit according to the first embodiment of the present invention.
The microcomputer (hereinafter, referred to as a control CPU) 101 is an integrated circuit (IC) including a core CPU 101a, an input / output (I / O) circuit 118, an internal bus 120, and a ROM 121. For example, when a signal is input to the control CPU 101 from the input terminal 119, the signal is input to the core CPU 101a via the I / O circuit 118 and the internal bus 120. The core CPU 101a executes a predetermined sequence control based on a predetermined program written in the ROM 121 based on the input signal.
[0018]
Hereinafter, a control circuit (CPU) 1 and a peripheral circuit such as a digital / analog (D / A) converter 102 and an operational amplifier (operational amplifier) circuit 103 are collectively referred to as a control circuit (CPU) 1. I will call it.
[0019]
In the CPU 1 according to the first embodiment, the values held in the first register 104 and the second register 105 can be set via the internal bus 120.
First, ON / OFF of the analog switches 107a to 107d is controlled according to the value set in the second register 105. Further, the divided voltage of the resistor array 106 changes depending on the on / off state of the switches 107a to 107d, so that various voltages corresponding to the on / off states of the switches are supplied to the operational amplifier circuit 103. . That is, when the switch 107a is turned on and the other switches are turned off, a high voltage is supplied to the operational amplifier circuit 103. When the switch 107d is turned on and the other switches are turned off, a low voltage is supplied. It is supplied to the operational amplifier circuit 103.
[0020]
Here, for the sake of simplicity, it is shown that four types of output voltages of the switches 107a to 107d can be supplied, but in practice, switching of 8 to 10 bits is possible.
[0021]
The first register 104 controls switching of the analog switches 108, 110, 124, and 125. By controlling on / off of a switch 108 composed of two switches in the figure, the output from the D / A converter 102 is selectively supplied to either the negative terminal or the positive terminal of the operational amplifier 109. Input.
[0022]
FIG. 2A is a schematic diagram of one of the switches 108. That is, the switching unit 108d in the switch 108 can be switched according to the control signal 140 from the first register, and the signal from the terminal 108a can be selectively input to either the terminal 108b or the terminal 108c.
[0023]
Note that this switch 108 can also be configured as shown in FIG. That is, FIG. 2B is a combination of the switching units 108e and 108f that switch between on and off. In this case, on / off of the switching unit 108f is controlled by the control signal 140. The control signal 140 is also input to the inverter 108g, and the inverter 108g outputs an inverted signal of the control signal 140. As a result, a signal having a signal level opposite to that of the switching unit 108f is always input to the switching unit 108e, so that the signal from the terminal 108a is selectively input to one of the terminals 108b and 108c. Is done.
[0024]
In FIG. 1, two switches 108 are provided at the input part of the operational amplifier 109. If the output of the operational amplifier 109 is further connected to the external terminal 123 by the switch 110 while the switches 124 and 125 of FIG. 1 are turned off by the setting of the first register, the circuit configuration as shown in FIG. Alternatively, an operational amplifier circuit having a circuit configuration as illustrated in FIG. 3C can be selectively formed. The external terminal 123 can be fixed to a high (H) level output or a low (L) level output by the switch 110 without being connected to the operational amplifier 109. That is, the switch 110 connects the output terminal of the operational amplifier 109 to the external terminal 123, opens the output terminal of the operational amplifier 109, fixes the potential level of the external terminal 123 to H level, and sets the potential level of the external terminal 123 to L level. Fixed, four types of switching are performed.
[0025]
Note that in this embodiment mode, the switch 110 has a circuit configuration in which the potential state of the external terminal 123 can be changed. However, the switch 110 may be configured so that the potential state of the output of the operational amplifier 109 can be changed. .
[0026]
Further, the external terminal 123 is disconnected from the output terminal of the operational amplifier 109, and the switch 125 is turned off and the switch 124 is turned on. When the output from the D / A converter 102 is input to the + side of the operational amplifier 109 by the switch 108, a buffer circuit as shown in FIG.
[0027]
1, the + input of the operational amplifier 109 is connected to the external terminal 122, the-input is disconnected from the D / A converter 102, the switch 125 is turned on, and the switch 110 is connected to the external terminal 123 and the operational amplifier 109. 3D, an operational amplifier circuit as shown in FIG. 3D can be formed. In this case, the switch 124 is turned off. Even if the operational amplifier 109 is configured on the same chip as the control CPU 101 by such a device, the three external terminals shown in FIG. 4 are not required. In other words, since only the two external terminals 122 and 123 perform the same function as the operational amplifier circuit having three external terminals, it is possible to maximize the characteristics of the operational amplifier 109 only with the external terminals 122 and 123. is there.
[0028]
That is, the area of the IC is largely determined not only by the scale of the built-in circuit but also by the number of terminals (pins). Therefore, no matter how small the built-in circuit is, if the number of terminals is large, the area of the entire IC does not decrease. That is, in the terminal of the IC, a wire, a solder ball, or the like is used to connect to an external circuit. However, a predetermined area is also required for a pad portion for connecting these. Therefore, if the number of terminals is large, the area of the entire IC also becomes large.
[0029]
In the present embodiment, many kinds of operational amplifier circuits can be configured by the above-described device, and a circuit that requires three external terminals can be configured with two external terminals. As a result, the number of pads can be reduced, so that the size of the IC can be reduced, that is, the cost can be reduced.
[0030]
FIG. 5 shows an example of a circuit incorporating two operational amplifiers described above. This example is an example of a circuit built in the camera.
The operational amplifier 109a has the above-described switches controlled based on the setting of a register (not shown), and has the format shown in FIG. 3B. The other operational amplifier 109b has a format shown in FIG. 3D based on the setting of a register (not shown).
[0031]
The output of the operational amplifier 109a controls the base potential of the transistor 204. The positive terminal of the operational amplifier 109a monitors the collector potential of the transistor 204, that is, the voltage applied to the motor 203.
[0032]
When the transistor 130 and the transistor circuit 201 are turned on, the transistor 202 is turned on. As a result, current flows from the power supply 200 to the motor 203, and the motor 203 is driven. The operational amplifier 109a monitors the voltage of the motor 203 and determines whether the voltage applied to the motor 203 is equal to the output level V of the D / A converter. _M The current flowing through the transistor 204 is controlled so that
The shunt resistor 205 is provided to improve the transmission characteristics of the circuit.
[0033]
If the shutter drive of the camera, zooming of the zoom lens, and the like are performed using the motor 203 having such a circuit configuration, the motor can be driven at a stable speed independent of the power supply voltage. As a result, accurate exposure and zoom position control can be performed, and a beautiful photograph can be taken.
[0034]
The output of the operational amplifier 109a can be opened by turning off the switch 110 in FIG. Further, the switch 125 is turned on, the minus terminal of the operational amplifier 109 is connected to the external terminal 122 by the switch 108, and the plus terminal is connected to the D / A converter 102a. In this case, the voltage determined by the D / A converter 102a is output from the external terminal 122.
[0035]
That is, in this case, when the transistor 130 in FIG. 5 is turned off and the transistor 131 is turned on, the voltage determined by the D / A converter 102a is output from the input terminal of the operational amplifier 109a in FIG. Constant current driving is performed by the resistor 213. Thus, the LED 212 emits light at a constant brightness regardless of the deterioration of the battery.
[0036]
It should be noted here that a voltage is output from the negative terminal of the operational amplifier 109a. That is, the operational amplifier 109a is sometimes used in the format of FIG. 3C, and is sometimes used in the format of FIG. Even if only two terminals are out of the IC by such a contrivance, the operation of the two elements (here, the motor 203 and the LED 212) can be selectively controlled by the positive voltage control function of the operational amplifier. is there.
[0037]
Next, the operational amplifier 109b will be described. The operational amplifier 109b has a format as shown in FIG. In FIG. 3D, the operational amplifier 109b is separated from the D / A converter 102b. A photodiode 210 is connected to two terminals of the operational amplifier 109b, and stabilizes the photodiode 210 at zero bias. Then, from the photodiode 210, a photocurrent corresponding to the brightness of light incident from the outside flows toward the capacitor 211. Here, when the N-channel open-drain transistor 132 is turned off from on, after a predetermined time has elapsed, a voltage V according to the brightness of light incident on the photodiode 210 is applied to the capacitor 211. _INTO Occurs. This voltage V _INTO Is detected by the analog / digital (A / D) converter 214, the brightness of the subject can be detected. If the brightness of the subject detected by such a method is detected and the control CPU 101 determines an exposure condition according to the brightness of the subject, appropriate exposure control according to the brightness of the subject can be performed. it can. During exposure, the motor 203 is driven via the operational amplifier 109a to drive a shutter (not shown).
[0038]
[Second embodiment]
Next, a second embodiment of the control circuit according to the present invention will be described. FIG. 6A is an electric circuit diagram showing a configuration of the second embodiment. That is, the second embodiment is a modified example of the above-described circuit for detecting the brightness of the subject including the photodiode 210 (hereinafter, referred to as a photometric circuit).
[0039]
That is, the transistor 132 is omitted in this embodiment. Instead, switching is performed using the D / A converter 102b and the switch 108. Thereby, the predetermined reference voltage V _ref Can be provided. That is, the integration is started when the D / A converter 102b is disconnected from the operational amplifier 109b (that is, when the transistor 132 is turned off in FIG. 5). The integrated voltage at this time, that is, the charging voltage of the capacitor 211 is V _INT Then, as shown in FIG. _INT Is V _ref Increases in proportion to the integration time.
[0040]
This V _INT To the + terminal of another operational amplifier 109c. The negative terminal of the operational amplifier 109c is connected to another D / A converter 102c. In this D / A converter 102c, V _ref V than _INTO A predetermined voltage that is only higher is generated. Thereby, the integral voltage V _INT Is V _INTO 5C, the output of the operational amplifier 109c is inverted as shown in FIG. The time t at this time and the set voltage V of the D / A converter 102c _INTO Thus, the amount of light incident on the LED 210, that is, the brightness of the subject can be detected.
[0041]
In the photometric circuit according to the present embodiment, the operational amplifier 109c is used as a comparator, and a higher-speed response is possible than the photometric circuit according to the above-described first embodiment. In such a high-speed photometric circuit, it is possible to detect the brightness of light that emits instantaneously, such as strobe light.
[0042]
In the first and second embodiments described above, it is possible to provide a versatile control circuit applicable to various circuits while having only two terminals taken out from the operational amplifier to the outside.
[0043]
[Third Embodiment]
Next, as a third embodiment of the present invention, an example of a circuit configuration of an entire camera system to which the above-described control circuit is applied will be described. Here, an example in which the configuration of the control circuit according to the present invention is applied to a power supply circuit instead of the above-described motor control circuit or photometric circuit will be described.
[0044]
That is, in the present embodiment, as shown in FIG. 7, the regulator 6 is further built in the same chip as the IC constituting the CPU 1. The output from the regulator 6 can be taken out to an external circuit via a buffer 55 of a connection type shown in FIG. Also, the output DC of the DC / DC converter _OUT Is input to the A / D converter 64, but is also input to the operational amplifier 54a provided in the CPU 1.
[0045]
In the DC / DC converter, the transistor 10 is turned on by a signal output from the transmitter 56 built in the CPU 1, and the current from the battery 2 flows into the inductor 3. At this time, the capacitor 5 is charged by the voltage generated in the inductor 3. The charging voltage of the capacitor 5 at this time is DC _OUT It is. And this DC _OUT Is divided by the resistor array 9, and the divided voltage is input to the A / D converter 64. The CPU 1 monitors the divided voltage based on the value detected by the A / D converter 64.
[0046]
However, a program that always monitors the result of the A / D converter 64 may not be sufficient. In other words, when high-speed control must be performed for a relatively long time, the time required to capture the result of the A / D converter 64 becomes a time lag, and precise control cannot be performed. I will. Examples of the need to perform such high-speed control include, for example, when controlling the imprint timing when imprinting a date on a film or detecting the position of a zoom lens at the same time. In some cases, the boosting of the DC / DC converter must be monitored.
[0047]
Therefore, in the present embodiment, the operational amplifier 54a is used as a comparator for comparing the predetermined voltages DA1 and DA2 (hereinafter, referred to as a comparator 54a). And DC within a predetermined level _OUT Is included, the determination circuit 54b that determines this turns off the oscillation OFF circuit 56a and stops the boosting operation of the boost DC / DC converter. The oscillation OFF circuit 56a not only stops the oscillation to the DC / DC converter but also fixes the output voltage when the oscillation is stopped so that the transistor 10 does not remain on when the oscillation is stopped. L level.
[0048]
Control of the DC / DC converter in the circuit having such a configuration will be described with reference to the timing chart of FIG. In this control, DC _OUT Is controlled to be within a predetermined level. The D / A converter 63 can switch the judgment voltage input to the comparator 54a according to a program written in a ROM (not shown). As a result, as the determination voltage of the comparator 54a, two types of voltages DA1 and DA2 shown in FIG. 8 can be selected.
[0049]
That is, at the time of boosting, the voltage DA1 on the high level side is used. On the other hand, when boosting is stopped, the low-level voltage DA2 is used. The determination circuit 54b has a DC _OUT Is determined based on the output of the comparator 54a. Then, the judgment voltage is set to DC _OUT When it is determined that the threshold value has been exceeded, the determination circuit 54b performs the switching control of the oscillation OFF circuit 56a and the operation program.
[0050]
After the battery voltage is boosted in this way, the output from the regulator 6 is supplied as a reference voltage for the D / A converter 63, the A / D converter 64, and the LCD driver 65, and is supplied to the outside of the CPU 1 via the buffer 55. Also functions as a constant voltage source for each circuit. For example, the output from the regulator 6 functions as a power source for a photo-interrupter circuit (referred to as MTPI in the figure) 30 for detecting rotation of the motor 16a, an LED 80 for display, and an EEPROM 81 for recording various data.
[0051]
The output of the regulator 6 can also be applied as a power supply for stabilizing the AF block 71 that detects the magnitude of the optical signal incident on the light receiving element 70 when the light emitting unit (not shown) is controlled to emit light.
[0052]
In the circuit of FIG. 7, the output pulse of the transmitter 56 is also used as a charging pulse of the strobe circuit 17. The A / D converter 64 also monitors the state of charge of the strobe in the strobe circuit 17.
[0053]
The output of the D / A converter 63 is also input to the operational amplifier 59, and drives the motor driver 16 with the transistor 16b at a constant voltage. Then, the motor driver 16 controls the speed of the motor 16a. This is similar to the configuration described in FIG. Note that the operational amplifier 59 for the motor driver does not supply power from the regulator 6 but uses a DC _OUT Power supply voltage directly from
[0054]
Further, in the circuit of FIG. 7, a pulse output from the transmitter 61 is measured by a clock circuit 60 for imprinting a date to perform time measurement. The output of the transmitter is multiplied by a multiplier (multiplier CK) 62 to generate a main clock of the CPU 1.
[0055]
Further, a reset (RESET) circuit 57 resets the CPU 1 when the remaining amount of the battery 2 is exhausted, and correctly restarts the CPU 1 when a new battery is loaded.
[0056]
Next, control of the operational amplifier circuit during operation of the camera will be described with reference to FIGS. 9A and 9B. Since the detailed operation of each circuit in the camera system has been described above, the description is omitted here.
[0057]
First, the control of the operational amplifier corresponding to the setting of a register (not shown) will be described with reference to FIG. Here, a case where the circuit configuration of the operational amplifier circuit does not need to be changed during control of the operational amplifier circuit, for example, a photometric circuit in FIG. 5 will be described.
[0058]
First, it is determined whether a power switch (not shown) of the camera is turned on (step S1). If it is determined that the power switch is not turned on, the CPU 1 waits until the power switch is turned on. On the other hand, when it is determined that the power switch has been turned on, the operation of the camera is started, and the CPU 1 sets an internal register (the first register 104 in FIG. 1) (step S2). Based on the setting of this register, switches 108, 110, 124, and 125 in FIG. 1 are switched to configure a desired operational amplifier circuit.
[0059]
Note that the setting of the circuit configuration of the operational amplifier circuit may be performed before the target circuit is operated, and may be performed in steps other than the above.
[0060]
After the setting of the operational amplifier is completed, it is determined whether to operate the set operational amplifier circuit (step S3). When it is determined that the set operational amplifier circuit is operated, the operation of the operational amplifier circuit is controlled (step S4). After the above operation is completed, the process returns to step S1.
[0061]
On the other hand, if it is determined in step S3 that the set operational amplifier circuit is not to be operated, the process returns to step S1. If a power switch (not shown) is turned off during the control of this flowchart, the control of this flowchart ends.
[0062]
Next, referring to FIG. 9B, when changing the setting of the register, for example, the motor control circuit (hereinafter, referred to as circuit A) and the LED control circuit (hereinafter, referred to as circuit B) in FIG. ) Will be described.
First, it is determined whether a power switch (not shown) of the camera is turned on (step S11). If it is determined that the power switch is not turned on, the CPU 1 waits until the power switch is turned on. On the other hand, when it is determined that the power switch is turned on, the operation of the camera is started, and the CPU 1 initializes an internal register (step S12).
[0063]
Next, the CPU 1 determines whether or not to operate the internal operational amplifier circuit as the circuit A (step S13). For example, in the example of FIG. 5, it is determined whether or not to use as a motor control circuit. When it is determined that the operational amplifier circuit is operated as the circuit A (motor control circuit), the value of the register is set so that the operational amplifier circuit has the form of the circuit A, that is, the form of FIG. S14) The operation of the operational amplifier circuit in the form of the circuit A is controlled (step S15).
[0064]
On the other hand, if it is determined in step S13 that the operational amplifier circuit does not operate as the circuit A, it is determined whether the operational amplifier circuit operates as the circuit B (LED control circuit) (step S16). For example, in the example of FIG. 5, it is determined whether or not to use as an LED control circuit. If it is determined that the operational amplifier circuit is to be operated as the circuit B (LED control circuit), the value of the register is set so that the operational amplifier circuit is in the circuit B format (step S17). The operation of the circuit is controlled (step S18). After the above operation is completed, the process returns to the step S11.
[0065]
On the other hand, if it is determined in step S16 that the operational amplifier circuit in the form of the circuit B is not operated, the process returns to step S1. If a power switch (not shown) is turned off during the control of this flowchart, the control of this flowchart ends.
[0066]
By configuring the camera system as shown in FIG. 7 as described above, it becomes possible to configure the main components in the same chip as the IC constituting the CPU, which is advantageous in terms of cost and space. It is possible to provide a certain product. In FIGS. 9A and 9B, a timer (not shown) is operated after the power switch is turned on, and if there is no input signal for a predetermined time, the control of this flowchart may be terminated. Good.
[0067]
Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and various modifications and applications are possible within the scope of the present invention. is there.
[0068]
For example, two input / output terminals such as a comparator constituted by an operational amplifier formed on the same chip as the CPU may be switched to a CMOS input terminal or an interrupt terminal of the CPU.
[0069]
【The invention's effect】
As described in detail above, according to the present invention, by arranging a large number of versatile operational amplifiers on the same chip as an IC constituting a one-chip microcomputer, a small, low-cost, highly versatile control circuit can be realized. Can be provided.
[0070]
In addition, by reducing the number of terminals from the operational amplifier and reducing the number of terminals of the entire IC, the size of the IC can be reduced, and the space and cost of the IC body can be reduced.
[0071]
Further, since a very simple analog circuit is effectively incorporated, excellent versatility can be expected and a mass production effect can be expected.
[Brief description of the drawings]
FIG. 1 is an electric circuit diagram showing a configuration of a control circuit according to a first embodiment of the present invention.
FIG. 2A is a schematic diagram of a switch for switching an input to an input terminal of an operational amplifier, and FIG. 2B is a diagram illustrating a modification of the switch of FIG. 2A; .
FIG. 3 is a schematic diagram for explaining that an operational amplifier can be used as various circuits by switching a switch.
FIG. 4 is a diagram showing an example of a conventional IC chip having a built-in operational amplifier.
FIG. 5 is an electric circuit diagram showing a configuration of a motor control circuit and a photometry circuit of a camera configured to include two operational amplifiers.
FIG. 6 is an electric circuit diagram showing a configuration of a control circuit according to a second embodiment of the present invention.
FIG. 7 is an electric circuit diagram showing an electric circuit configuration of a camera system to which a control circuit configuration according to a third embodiment of the present invention is applied.
FIG. 8 is a timing chart at the time of DC / DC converter control according to the third embodiment of the present invention.
FIG. 9 is a flowchart for controlling the operation of an operational amplifier incorporated in a CPU in a camera in accordance with register settings.
[Explanation of symbols]
101 One-chip microcomputer (control CPU)
101a core CPU
102 Digital / Analog (D / A) Converter
103 Operational amplification (operational amplifier) circuit
104 First register
105 Second register
106 resistor array
107a, 107b, 107c, 107d, 108, 110, 124, 125 switches
109 Operational Amplifier (Op Amp)
118 input / output (I / O) circuit
119 input terminal
120 internal bus
121 ROM
122, 123 external terminal

Claims (9)

A D / A converter capable of switching an output voltage based on a set value held in a register;
An operational amplifier having two input terminals and one output terminal;
Switching means for selectively inputting the output of the D / A converter to one of two input terminals of the operational amplifier;
Are configured on the same chip,
A control circuit, wherein an input terminal not selected by the switching means and an output terminal of the operational amplifier can be connected to an external circuit. Having an external terminal for connecting to the external circuit,
Second switching means capable of switching the potential state of the external terminal to a low level state, a high level state, or an open state when the operational amplifier is not operating is configured on the same chip. A control circuit, characterized in that: An external terminal for connecting to an external circuit;
An operational amplifier,
A D / A converter,
A first terminal that selects two terminals out of three terminals of a positive input terminal of the operational amplifier, a negative input terminal of the operational amplifier, and an output terminal of the operational amplifier, and switches the terminal to be connected to the external terminal. Switches and
A second switch for switching the remaining one terminal not selected by the first switch to be connected to the output of the D / A converter or the selected terminal;
A control circuit, comprising: A control circuit having an operational amplifier circuit on the same chip,
A first external connection terminal for connecting an output of the operational amplifier circuit to an external circuit,
A second external connection terminal for connecting one of the two inputs of the operational amplifier circuit to an external circuit;
An internal circuit connectable to another input of the operational amplifier circuit,
Setting means for setting the input of each of the operational amplifier circuits, the connection with the second external connection terminal and the internal circuit,
Switching means for switching connection of each input of the operational amplifier circuit according to the setting of the setting means,
A control circuit, comprising: The internal circuit includes a constant voltage circuit,
5. The control circuit according to claim 4, wherein the switching unit connects the constant voltage circuit and the operational amplifier circuit so as to supply a constant voltage from the constant voltage circuit to the operational amplifier circuit. Output connection switching means for switching a connection state of an output of the operational amplifier circuit to a connection state including a state connected to the first external connection terminal, a predetermined power supply, a ground state, or an open state;
5. The control circuit according to claim 4, wherein said output connection switching means switches an output connection state of said operational amplifier circuit according to a setting of said setting means. The setting means sets one input of the operational amplifier circuit to be connected to the first external connection terminal and the other input to be connected to the constant voltage circuit,
The switching means selectively switches one input of the operational amplifier circuit to be connected to the first external connection terminal in accordance with the setting of the setting means, and selectively switches the other input. The control circuit according to claim 4, wherein switching is performed so as to connect to a constant voltage circuit. The control circuit according to claim 4, wherein the constant voltage circuit includes a D / A converter, and is capable of changing an output voltage according to the setting by the setting unit. A control circuit having a plurality of operational amplifier circuits on the same chip,
A first external connection terminal group for connecting each output of the plurality of operational amplifier circuits to an external circuit,
A second external connection terminal group for connecting one of the two inputs of the plurality of operational amplifier circuits to an external circuit;
An internal circuit connectable to each of the other inputs of the plurality of operational amplifier circuits,
Setting means for independently setting inputs of each of the plurality of operational amplifier circuits and connection with the second external connection terminal and the internal circuit;
Switching means for switching connection of each input of the plurality of operational amplifier circuits according to the setting of the setting means,
A control circuit, comprising:

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