JP2005301410A - Constant current source, and amplifier circuit and constant voltage circuit using constant current source thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a constant current source that is not restrained by a manufacturing process therefor, not affected by a variation in the threshold value of an MOS transistor and the temperature dependence, and can be jointly used with an ED type standard voltage source, and an amplifier circuit and a constant voltage circuit using the constant current source. <P>SOLUTION: A correction is made to an output current of the constant current source 1 in which a deviation of a monitoring current i1 supplied from a monitoring current source 2 is checked accurately, the amount of the deviation is outputted to each of constant current circuits A1-An as a digital signal, a current value i2 proportional to the monitoring current i1 is supplied, and a standard current source 25 in the constant current circuits A1-An is used as a standard current, The constant current source 1 is used in a constant voltage circuit equipped with an amplifier circuit and an error amplifier circuit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a constant current source capable of self-calibration, and in particular, converts a current value of a monitor current source into a time, and sets a current value of a plurality of constant current circuits by a digital signal based on the converted time. The present invention relates to a constant current source, an amplifier circuit using the constant current source, and a constant voltage circuit.

FIG. 8 is a diagram showing a circuit example of a conventional reference current source 100 that is often used in a semiconductor device.
In FIG. 8, the reference current source 100 includes a depletion type NMOS transistor M101 and an enhancement type NMOS transistor M102. In the following description, all MOS transistors not particularly specified are of the enhancement type.
The gate of the NMOS transistor M101 is connected to the source, and the connection is connected to the drain of the NMOS transistor M102. The gate and drain of the NMOS transistor M102 are connected.

FIG. 9 is a diagram illustrating a relationship example between the gate voltage and the drain current in the NMOS transistors M101 and M102.
As can be seen from FIG. 9, in the NMOS transistor M101, a drain current having a current value i0 flows even when the gate voltage is 0V. Since the gate of the NMOS transistor M101 is connected to the source, the drain current of the NMOS transistor M101 has a current value i0. Since the drain current of the NMOS transistor M102 is the same as the drain current of the NMOS transistor M101, the current value is also i0. The gate voltage Vg102 of the NMOS transistor M102 is set to a voltage value at which the drain current of the NMOS transistor M102 becomes a current value i0, and the reference current source 100 is also used as a simple reference voltage source.

However, the depletion type NMOS transistor has a large variation in the manufacturing process, and the variation of the current value i0 of the drain current is in the range of + 100% to −60%. Further, since the temperature dependency is large, the circuit as shown in FIG. 8 cannot be used for applications requiring current accuracy.
Therefore, there is a constant current source as shown in FIG. 10 that is not affected by variations in the manufacturing process (for example, see Patent Document 1).
The constant current source 110 in FIG. 10 includes three NMOS transistors M112 to M114 and a depletion type NMOS transistor M111 that is made from the three NMOS transistors M112 to M114 by only one implantation of donor ions. In the NMOS transistors M111 to M114, the substrate gate and the source are respectively connected.

  In the channel coefficient that is the product of the channel width and length ratio and the conductivity coefficient, the square root of the ratio of the channel coefficient of the NMOS transistor M111 and the channel coefficient of the NMOS transistor M112, the channel coefficient of the NMOS transistor M111, and the NMOS transistor M113 The NMOS transistors M111 to M114 are connected in a physical dimension pattern in which the sum of the square root of the ratio and the channel coefficient is 1.

As a result, in the constant current source 110 of FIG. 10, the pattern of the NMOS transistors M111 to M114 is set to a specific size, and the NMOS transistor M111 is formed by only one implantation of donor ions from the NMOS transistors M112 to 114. The total number of implanted ions can be accurately controlled, variation in the constant current value manufacturing process can be reduced, and temperature characteristics can be easily controlled.
Japanese Patent Laid-Open No. 6-4160

  However, such a conventional constant current source has a problem in that the manufacturing process is restricted, so that another manufacturing process cannot be used to improve other characteristics. In addition, while the temperature characteristics can be easily controlled, there is a problem that the temperature characteristics themselves become large, and further, the variation in the threshold voltage of the transistor itself has not been improved. There was a problem that it remained. In addition, both the depletion-type and enhancement-type MOS transistors have restrictions on the size ratio of W (channel width) / L (channel length), so a W / L size ratio different from the restrictions is required, and temperature characteristics There is a problem in that it cannot be shared with a flat ED type reference voltage source, resulting in an increase in total current consumption.

  The present invention has been made to solve the above-described problems, has no manufacturing process restrictions, is not affected by variations in threshold values of the MOS transistors, and is not affected by temperature dependence. Further, the ED type reference voltage is provided. It is an object to obtain a constant current source that can be shared with a power source, and an amplifier circuit and a constant voltage circuit using the constant current source.

The constant current source according to the present invention is a constant current source that generates and outputs a constant current having a set current value.
A monitor current source for generating and outputting a predetermined monitor current i1;
A current-time conversion circuit unit that starts an operation of converting the monitor current value from the monitor current source into time according to the input control signal S2, and outputs a predetermined conversion end signal S3 when the conversion is completed; ,
A current setting code that outputs and outputs the control signal S2 to the current-time conversion circuit unit and generates and outputs a current setting code S4 corresponding to the time required for the conversion by the current-time conversion circuit unit A generation circuit unit;
At least one constant current circuit unit that generates and outputs a current according to the current setting code S4 output from the current setting code generation circuit unit;
With
The current setting code generation circuit unit causes the current-time conversion circuit unit to start time conversion of the monitor current value according to the input control signal S1, and the current setting code according to the time required for the conversion S4 is generated and output, and the constant current value output from the constant current circuit unit is corrected.

Specifically, the current-time conversion circuit unit includes:
A first proportional current generation circuit that generates and outputs a current proportional to the monitor current value;
A capacitor charged by the output current of the first proportional current generating circuit;
A reference voltage generation circuit that generates and outputs a predetermined reference voltage Vr;
A comparison circuit for performing a voltage comparison between the terminal voltage Vc of the capacitor and the reference voltage Vr and outputting a signal according to the comparison result;
A discharge circuit for discharging the electric charge charged in the capacitor in response to the control signal S2,
With
When starting the operation of converting the monitor current value into time according to the control signal S2, the discharge circuit stops discharging the capacitor and charges it with the output current of the first proportional current generation circuit, The comparison circuit outputs the predetermined conversion end signal S3 when the terminal voltage Vc of the capacitor reaches the reference voltage Vr.

In addition, the current setting code generation circuit unit
A conversion control circuit for causing the current-time conversion circuit unit to start time conversion of a monitor current value in response to the control signal S1;
The time from when the conversion control circuit starts time conversion of the monitor current value to the current-time conversion circuit unit until the current-time conversion circuit unit outputs the predetermined conversion end signal S3 is measured. A time measurement circuit;
A code generation circuit that generates and outputs a current setting code S4 that is a digital signal of m (positive integer) bits corresponding to a difference between the measurement time T1 of the time measurement circuit and a predetermined reference time Ts;
I was prepared to.

The constant current circuit section is
A reference current source for generating and outputting a predetermined reference current i2;
A second proportional current generation circuit that generates and outputs a plurality of currents proportional to the reference current i2,
A selection circuit that selects and outputs at least one of the respective proportional currents output from the second proportional current generation circuit in accordance with the current setting code S4;
I was prepared to.

  On the other hand, the monitor current i1 and the reference current i2 may be in a proportional relationship, and the reference current source may be a monitor current source.

  The current setting code generation circuit unit receives the control signal S1 instructing the current-time conversion circuit unit to start time conversion of the monitor current value at power-on or startup. I made it.

  Further, the current setting code generation circuit unit receives the control signal S1 instructing the current-time conversion circuit unit to start time conversion of the monitor current value every predetermined time. May be.

  The monitor current source, current-time conversion circuit unit, current setting code generation circuit unit, and constant current circuit unit are integrated in a one-chip semiconductor device, and the monitor current source, current-time conversion circuit unit, and current setting code generation circuit One unit may be integrated on each chip.

The amplifier circuit according to the present invention is an amplifier circuit to which a bias current is supplied from a constant current source.
The constant current source is:
A monitor current source for generating and outputting a predetermined monitor current i1;
A current-time conversion circuit unit that starts an operation of converting the monitor current value from the monitor current source into time according to the input control signal S2, and outputs a predetermined conversion end signal S3 when the conversion is completed; ,
A current setting code that outputs and outputs the control signal S2 to the current-time conversion circuit unit and generates and outputs a current setting code S4 corresponding to the time required for the conversion by the current-time conversion circuit unit A generation circuit unit;
At least one constant current circuit unit that generates and outputs a current according to the current setting code S4 output from the current setting code generation circuit unit;
With
The current setting code generation circuit unit causes the current-time conversion circuit unit to start time conversion of the monitor current value according to the input control signal S1, and the current setting code according to the time required for the conversion S4 is generated and output, and the constant current value output from the constant current circuit unit is corrected.

Further, the constant voltage circuit according to the present invention is a constant voltage circuit using an error amplifier circuit to which a bias current is supplied from a constant current source.
The constant current source is:
A monitor current source for generating and outputting a predetermined monitor current i1;
A current-time conversion circuit unit that starts an operation of converting the monitor current value from the monitor current source into time according to the input control signal S2, and outputs a predetermined conversion end signal S3 when the conversion is completed; ,
A current setting code that outputs and outputs the control signal S2 to the current-time conversion circuit unit and generates and outputs a current setting code S4 corresponding to the time required for the conversion by the current-time conversion circuit unit A generation circuit unit;
At least one constant current circuit unit that generates and outputs a current according to the current setting code S4 output from the current setting code generation circuit unit;
With
The current setting code generation circuit unit causes the current-time conversion circuit unit to start time conversion of the monitor current value according to the input control signal S1, and the current setting code according to the time required for the conversion S4 is generated and output, and the constant current value output from the constant current circuit unit is corrected.

According to the present invention, the current value of each constant current circuit unit is measured by measuring the current value of each constant current circuit unit of the semiconductor device in which a large number of constant current sources are integrated on one chip, and the current value of the monitor current source. And a design value are examined, a signal for correcting the current value of the constant current circuit unit is generated based on the deviation amount, and the current value of each constant current circuit unit is corrected by the correction signal. From this, it is possible to obtain a highly accurate constant current source that is not affected by restrictions on the manufacturing process and variations in the threshold voltage of the MOS transistor and that can be shared with the ED type reference voltage source.
In addition, since the current value measurement of the monitor current source is repeated every predetermined time and the current correction amount is updated each time, even in a constant current source having a large temperature dependence, the current change due to the temperature change Correction can be performed, and a highly accurate current can be output.

Next, the present invention will be described in detail based on the embodiments shown in the drawings.
First embodiment.
FIG. 1 is a block diagram showing a configuration example of a constant current source according to the first embodiment of the present invention.
In FIG. 1, a constant current source 1 includes a monitor current source 2 that generates a predetermined monitor current, a current-time conversion circuit 3 that converts a current value generated by the monitor current source 2 into time, and the current- Based on the conversion end signal S3 input from the time conversion circuit 3, a current setting code generation circuit 4 that generates and outputs a current setting code S4; a control circuit 5 that controls activation of the current setting code generation circuit 4; A plurality of constant current circuits A1 to An (n is an integer of n> 0) that generates and outputs a constant current having a current value corresponding to the current setting code S4.

The control circuit 5 is composed of a CPU or the like, and outputs a start signal S1 to the current setting code generation circuit 4 as necessary. The activation signal S1 may be output only once when the device is turned on or activated from the standby state, or may be output every time a predetermined time elapses. .
The constant current circuits A1 to An each include a reference current source. When the temperature characteristics of the monitor current source 2 or the reference current source are large, the monitor current source 2 Or the current value of the reference current source changes. For this reason, it is desirable to correct the current change of the reference current source caused by the temperature change so that the start signal S1 is output every time a predetermined time elapses.

  When the activation signal S1 is input, the current setting code generation circuit 4 generates a measurement start signal S2 and outputs it to the current-time conversion circuit 3. A monitor current source 2 is connected to the current-time conversion circuit 3, and when the measurement start signal S2 is input, the current-time conversion circuit 3 converts the current value of the monitor current source 2 into time, When the conversion is completed, a conversion end signal S3 is generated and output to the current setting code generation circuit 4. The current setting code generation circuit 4 measures a time T1 from the output of the measurement start signal S2 to the input of the conversion end signal S3, and compares the measured time T1 with a predetermined reference time Ts. A current setting code S4, which is an m (positive integer) bit digital signal corresponding to the difference, is generated and output to the constant current circuits A1 to An, respectively.

The constant current circuits A1 to An each include a reference current source that generates and outputs a current whose current value is proportional to (and is equal to) the monitor current source 2, and the current value of the reference current source is set to the current setting code S4. A current having a value corrected accordingly is output.
As the reference current source of the monitor current source 2 and the constant current circuits A1 to An, a reference current source having a configuration as shown in FIG. 8 in which the current value greatly varies depending on the manufacturing process can be used. The current setting code generation circuit 4 compares the current value of the monitor current source 2 with a high-accuracy current-time conversion by the current-time conversion circuit 3 and a high-accuracy reference time Ts. , And the data for correcting the variation amount is output to each of the constant current circuits A1 to An as the current setting code S4 which is a digital signal. By doing in this way, it can correct | amend so that the electric current output from each constant current circuit A1-An may become a predetermined electric current value.

FIG. 2 is a diagram showing a circuit example of the current-time conversion circuit 3 of FIG.
In FIG. 2, the current-time conversion circuit 3 is connected to PMOS transistors M1 and M2 that form a current mirror circuit that outputs a current proportional to the current value supplied from the monitor current source 2, and to the drain of the PMOS transistor M2. The capacitor C1, the NMOS transistor M3 connected in parallel to the capacitor C1, and discharging the electric charge of the capacitor C1, the reference voltage generating circuit 11 for generating and outputting a predetermined reference voltage Vr, the terminal voltage Vc and the reference of the capacitor C1 The comparator circuit CMP1 compares the voltages Vr. The PMOS transistors M1 and M2 form a first proportional current generation circuit, and the NMOS transistor M3 forms a discharge circuit.

  The sources of the PMOS transistors M1 and M2 are connected to the power supply voltage Vdd, the gates of the PMOS transistors M1 and M2 are connected, and the connection is connected to the drain of the PMOS transistor M1. A monitor current source 2 is connected between the drain of the PMOS transistor M1 and the ground voltage, and a capacitor C1 and an NMOS transistor M3 are connected in parallel between the drain of the PMOS transistor M2 and the ground voltage. The terminal voltage of the capacitor C1, that is, the voltage Vc at the connection portion between the PMOS transistor M2, the NMOS transistor M3, and the capacitor C1, is input to the non-inverting input terminal of the comparison circuit CMP1, and the reference voltage Vr is applied to the inverting input terminal of the comparison circuit CMP1. Is entered. The measurement start signal S2 is input to the gate of the NMOS transistor M3, and the output signal of the comparison circuit CMP1 forms the conversion end signal S3.

FIG. 3 is a timing chart showing waveform examples of the respective parts in FIG.
In FIG. 3, since the NMOS transistor M3 is on while the measurement start signal S2 is at the high level, the current output from the PMOS transistor M2 is bypassed by the NMOS transistor M3, and the terminal voltage Vc of the capacitor C1 is 0V. It is. Next, when the measurement start signal S2 changes to a low level, the NMOS transistor M3 is turned off, the capacitor C1 is charged by the current output from the PMOS transistor M2, and the terminal voltage Vc increases as time passes. When the terminal voltage Vc becomes the reference voltage Vr, the output signal of the comparison circuit CMP1 changes from the low level to the high level, and the output signal is output as the conversion end signal S3.

  The time T1 from when the measurement start signal S2 changes from the high level to the low level until the conversion end signal S3 changes from the low level to the high level is proportional to the current value i1 of the monitor current source 2. The time T1 varies depending on the accuracy of the capacitance of the capacitor C1 and the reference voltage Vr in addition to the current value of the monitor current i1, but these accuracy are compared with the current value i1 of the monitor current source 2. The variation in the manufacturing process can be reduced. When it is necessary to further increase the accuracy, either the capacitor C1 and the reference voltage Vr or both can be adjusted by trimming, and the accuracy can be increased by trimming.

Next, FIG. 4 is a block diagram showing a configuration example of the current setting code generation circuit 4 of FIG.
In FIG. 4, the current setting code generation circuit 4 includes a measurement start signal generation circuit 21, a time measurement circuit 22, and a code generation circuit 23. Note that the measurement start signal generation circuit 21 forms a conversion control circuit.
When a predetermined activation signal S1 is input, the measurement start signal generation circuit 21 generates a measurement start signal S2 and outputs the measurement start signal S2 to the current-time conversion circuit 3, and also generates a start signal S5 to the time measurement circuit 22. Output.

  The time measurement circuit 22 receives a clock signal CP having a predetermined frequency, a conversion end signal S3 from the current-time conversion circuit 3, and a start signal S5 from the measurement start signal generation circuit 21, and a data signal indicating the measurement time T1. S6 is generated and output to the code generation circuit 23. Furthermore, the data signal Ss indicating the predetermined reference time Ts is input to the code generation circuit 23, and the code generation circuit 23 compares the measured time T1 with the predetermined reference time Ts and compares the current according to the difference. A setting code S4 is generated and output to each of the constant current circuits A1 to An.

FIG. 5 is a timing chart showing examples of signals in FIG.
In FIG. 5, the measurement start signal generation circuit 21 receives the activation signal S1 from the control circuit 5, generates a measurement start signal S2, outputs it to the current-time conversion circuit 3, and generates a start signal S5 to measure time. Output to the circuit 22. Note that the measurement start signal S2 and the start signal S5 may be the same signal.
The time measurement circuit 22 counts the number of pulses of the clock signal CP input from when the start signal S5 changes to the low level until the conversion end signal S3 changes to the high level, and the data signal indicating the measurement time T1 S6 is generated.
The code generation circuit 23 compares the data signal S6 indicating the measurement time T1 with the data signal Ss indicating the reference time Ts, and outputs a data signal corresponding to the difference as the current setting code S4. The data signal Ss indicating the reference time Ts is the same as the data signal S6 output from the time measuring circuit 22 when the current value of the monitor current source 2 is the same as the design value.

FIG. 6 is a diagram illustrating a circuit example of the constant current circuits A1 to An of FIG. Since the constant current circuits A1 to An have the same circuit configuration, FIG. 6 shows an arbitrary constant current circuit Ak (k = 1 to n) as an example.
The constant current circuit Ak is formed by a depletion type NMOS transistor M10 and NMOS transistors M11 to M18. The NMOS transistor M10 and the NMOS transistor M11 form a reference current source 25 that generates and outputs a current value i2 that is the same as or proportional to the current value i1 of the monitor current source 2, and the NMOS transistors M11 to M15 have the current value i2. A current mirror circuit 26 for generating and outputting proportional currents is formed. The NMOS transistors M16 to M18 form switches connected to the output terminals of the current mirror circuit 26, respectively. The current mirror circuit 26 forms a second proportional current generation circuit, and the NMOS transistors M16 to M18 form a selection circuit.

The reference current source 25 outputs a current proportional to the output current i1 of the monitor current source 2 and preferably has the same circuit configuration as the monitor current source 2 in order to match the temperature characteristics with the monitor current source 2.
In the current mirror circuit 26, the gates of the NMOS transistors M11 to M15 are connected to each other, and the sources of the NMOS transistors M11 to M15 are connected to the ground voltage. Therefore, the drain currents i12 to i15 of the NMOS transistors M12 to M15 are currents proportional to the constant current i2. The proportionality constant is determined by the ratio between the transistor size of the NMOS transistor M11 and the transistor sizes of the NMOS transistors M12 to M15. Further, the drain currents i12 to i15 of the NMOS transistors M12 to M15 may all be the same, or may be set to be different currents.

In the NMOS transistors M16 to M18, each source is connected to a corresponding drain of the NMOS transistors M13 to M15. A bit data signal corresponding to the current setting code S4 is input to each gate of the NMOS transistors M16 to M18. Further, the drain of the NMOS transistor M12 and the drains of the NMOS transistors M16 to M18 are connected to each other, and the connection portion forms an output terminal OUTk.
The reason why the transistor forming the switch is not connected to the drain of the NMOS transistor M12 is that the minimum output current value is secured even when all the bit data signals of the current setting code S4 are all at the low level. is there. Needless to say, depending on the application, a transistor may be provided for each drain of the NMOS transistors M12 to M15.

The output current of the constant current circuit Ak is output from the output terminal OUTk, and the output current value is determined by the drain current i12 of the NMOS transistor M12 not connected to the switch and the switch that is turned on according to the current setting code S4. This is the total current value with the drain current of the connected NMOS transistor. For example, the set current value when the NMOS transistors M16 and M18 are turned on is (i12 + i13 + i15).
When the transistor size of the NMOS transistor M13 is 1, the transistor size of the NMOS transistor M14 is 2, and the transistor size of the NMOS transistor M15 is 4, eight current values can be set. In FIG. 6, a switch is provided for each of the three NMOS transistors M13 to M15 forming the current mirror circuit 26. However, depending on the application, the number of NMOS transistors connected to the switch is increased or decreased to obtain a desired current accuracy. What should I do?

  When many current sources are integrated in a one-chip semiconductor device, it has conventionally been necessary to perform trimming so that each current source has a predetermined current value. However, since the variation in the current value of the reference current source 25 occurs due to variations in the manufacturing process, even if the variation differs greatly for each semiconductor wafer, the variation is small on the same wafer, and on the wafer. The closer the distance, the smaller the variation. Further, since there is almost no difference if they are on the same chip, the variation in the current ratio between the monitor current source 2 and the reference current source 25 made on the same chip is extremely small. Therefore, by examining the deviation from the design current value only for the monitor current source 2, the deviation from the design current value for the other reference current sources 25 on the same chip is almost the same as that for the monitor current source 2. Can be estimated.

  Further, many reference current sources 25 are formed on the same chip, and one of them can be used as the monitor current source 2. In FIG. 6, an NMOS transistor M19 forms a current mirror circuit with the NMOS transistor M11, and a terminal 27 is connected to the current-time conversion circuit 3. The drain current i1 of the NMOS transistor M19 is a current proportional to the current value i2 from the reference current source 25 and constitutes the monitor current source 2. Further, since one of the reference current sources 25 in the constant current circuits A1 to An is also used as the monitor current source 2, it is not necessary to separately provide the monitor current source 2.

FIG. 7 is a diagram showing an example in which the constant current source 1 is used in the error amplifier circuit that constitutes the constant voltage circuit. In FIG. 7, a series regulator is shown as an example of the constant voltage circuit.
In FIG. 7, the constant voltage circuit 30 generates a predetermined constant voltage from the power supply voltage Vdd, which is an input voltage, and outputs it from the output terminal OUT as the output voltage Vo.
The constant voltage circuit 30 includes a reference voltage generation circuit 31 that generates and outputs a predetermined reference voltage Vs, and output voltage detection resistors R1 and R2 that divide the output voltage Vo to generate and output a divided voltage VFB. The output driver transistor M24, which is a PMOS transistor that controls the current output to the output terminal OUT in accordance with the signal input to the gate, and the operation of the output voltage control transistor M24 so that the divided voltage VFB becomes the reference voltage Vs. And an error amplifier circuit 32 that performs control.

  The error amplification circuit 32 includes PMOS transistors M20 and M21 forming a current mirror circuit, NMOS transistors M22 and M23 forming a differential pair, and the constant current source 1. The current mirror circuit of the PMOS transistors M20 and M21 constitutes a load of the differential pair of the NMOS transistors M22 and M23, and the constant current source 1 has a predetermined value with respect to the circuit formed by the current mirror circuit and the differential pair. Supply bias current. The sources of the PMOS transistors M20 and M21 are connected to the power supply voltage Vdd, the gates of the PMOS transistors M20 and M21 are connected, and the connection is connected to the drain of the PMOS transistor M21. The drain of the PMOS transistor M20 is connected to the drain of the NMOS transistor M22, and the connection portion forms the output terminal of the error amplifier circuit 32 and is connected to the gate of the output driver transistor M24.

The drain of the PMOS transistor M21 is connected to the drain of the NMOS transistor M23. The reference voltage Vs is input to the gate of the NMOS transistor M22, and the divided voltage VFB is input to the gate of the NMOS transistor M23. The sources of the NMOS transistors M22 and M23 are connected, and the constant current source 1 is connected between the connection portion and the ground voltage. That is, the connection portions of the sources of the NMOS transistors M22 and M23 are connected to the output terminal OUT1 of the constant current circuit A1 of the constant current source 1.
In such a configuration, since the constant current source 1 is used as the bias current source of the error amplifier circuit 32, the bias current of the error amplifier circuit 32 can be set with high accuracy.

  On the other hand, in the constant voltage circuit 30, since a large amount of negative feedback is performed, phase compensation is performed to prevent oscillation of the constant voltage circuit 30 although not shown. Since the constant voltage circuit 30 oscillates when the amount of phase compensation is small, the amount of phase compensation is set large. However, if the amount of phase compensation is too large, there arises a problem that the response speed becomes too slow. Further, since the amount of phase compensation is related to the bias current of the error amplifier circuit 32, the bias current of the error amplifier circuit 32 falls within a predetermined current value range in order to appropriately set the amount of phase compensation. It is important that

  Therefore, by using the constant current source 1, a highly accurate bias current can be supplied to the error amplifying circuit 32. Therefore, the amount of phase compensation can be reduced, and the response speed of the constant voltage circuit 30 can be reduced. In addition, it is possible to suppress the variation in current consumption of the constant voltage circuit 30. Further, even if a large number of constant voltage circuits having the circuit configuration shown in FIG. 7 are provided in a one-chip semiconductor device, all of the constant voltage circuits can be measured only by measuring the monitor current i1 of one monitor current source 2. Each bias current can be stored in a predetermined current range.

  As described above, the constant current source in the first embodiment accurately checks the deviation of the monitor current i1 supplied from the monitor current source 2, and uses the deviation amount as a digital signal to the constant current circuits A1 to An. Each is output, and the current value i2 of each reference current source 25 in each constant current circuit A1 to An is corrected. Thus, the output current can be set to a predetermined current value without using a circuit that is restricted by the manufacturing process as in the prior art.

It is the block diagram which showed the structural example of the constant current source in the 1st Embodiment of this invention. It is the figure which showed the circuit example of the current-time conversion circuit 3 of FIG. FIG. 3 is a timing chart showing an example of waveforms at various parts in FIG. 2. FIG. FIG. 2 is a block diagram illustrating a configuration example of a current setting code generation circuit 4 in FIG. 1. 5 is a timing chart showing an example of each signal in FIG. 4. It is the figure which showed the circuit example of constant current circuit Ak (k = 1-n) of FIG. It is the figure which showed the example at the time of using the constant current source 1 for the error amplifier circuit which comprises a constant voltage circuit. FIG. 6 is a diagram illustrating a circuit example of a conventional reference current source 100. FIG. 9 is a diagram illustrating a relationship example between a gate voltage and a drain current in the NMOS transistors M101 and M102 of FIG. It is the circuit diagram which showed the example of the conventional constant current source.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Constant current source 2 Monitor current source 3 Current-time conversion circuit 4 Current setting code generation circuit 5 Control circuit 21 Measurement start signal generation circuit 22 Time measurement circuit 23 Code generation circuit 25 Reference current source 26 Current mirror circuit 30 Constant voltage circuit 31 Reference voltage generation circuit 32 Error amplification circuit A1 to An constant current circuit M24 Output driver transistor R1, R2 resistance

Claims (11)

In the constant current source that generates and outputs a constant current of the set current value,
A monitor current source for generating and outputting a predetermined monitor current i1;
A current-time conversion circuit unit that starts an operation of converting the monitor current value from the monitor current source into time according to the input control signal S2, and outputs a predetermined conversion end signal S3 when the conversion is completed; ,
A current setting code that outputs and outputs the control signal S2 to the current-time conversion circuit unit and generates and outputs a current setting code S4 corresponding to the time required for the conversion by the current-time conversion circuit unit A generation circuit unit;
At least one constant current circuit unit that generates and outputs a current according to the current setting code S4 output from the current setting code generation circuit unit;
With
The current setting code generation circuit unit causes the current-time conversion circuit unit to start time conversion of the monitor current value according to the input control signal S1, and the current setting code according to the time required for the conversion A constant current source characterized by generating and outputting S4 and correcting the constant current value output from the constant current circuit section. The current-time conversion circuit unit includes:
A first proportional current generation circuit that generates and outputs a current proportional to the monitor current value;
A capacitor charged by the output current of the first proportional current generating circuit;
A reference voltage generation circuit that generates and outputs a predetermined reference voltage Vr;
A comparison circuit for performing a voltage comparison between the terminal voltage Vc of the capacitor and the reference voltage Vr and outputting a signal according to the comparison result;
A discharge circuit for discharging the electric charge charged in the capacitor in response to the control signal S2,
With
When starting the operation of converting the monitor current value into time according to the control signal S2, the discharge circuit stops discharging the capacitor and charges it with the output current of the first proportional current generation circuit, 2. The constant current source according to claim 1, wherein the comparison circuit outputs the predetermined conversion end signal S3 when the terminal voltage Vc of the capacitor reaches the reference voltage Vr. The current setting code generation circuit unit includes:
A conversion control circuit for causing the current-time conversion circuit unit to start time conversion of a monitor current value in response to the control signal S1;
The time from when the conversion control circuit starts time conversion of the monitor current value to the current-time conversion circuit unit until the current-time conversion circuit unit outputs the predetermined conversion end signal S3 is measured. A time measurement circuit;
A code generation circuit that generates and outputs a current setting code S4 that is a digital signal of m (positive integer) bits corresponding to a difference between the measurement time T1 of the time measurement circuit and a predetermined reference time Ts;
The constant current source according to claim 1, further comprising: The constant current circuit section is
A reference current source for generating and outputting a predetermined reference current i2;
A second proportional current generation circuit that generates and outputs a plurality of currents proportional to the reference current i2,
A selection circuit that selects and outputs at least one of the respective proportional currents output from the second proportional current generation circuit in accordance with the current setting code S4;
The constant current source according to claim 1, 2, or 3.   5. The constant current source according to claim 4, wherein the monitor current i1 and the reference current i2 are in a proportional relationship.   6. The constant current source according to claim 4, wherein the reference current source is a monitor current source.   The current setting code generation circuit unit is supplied with the control signal S1 for instructing the current-time conversion circuit unit to start time conversion of a monitor current value at power-on or startup. The constant current source according to claim 1, 2, 3, 4, 5, or 6.   The current setting code generation circuit unit receives the control signal S1 instructing the current-time conversion circuit unit to start time conversion of a monitor current value at predetermined time intervals. The constant current source according to claim 1, 2, 3, 4, 5, or 6.   The monitor current source, current-time conversion circuit unit, current setting code generation circuit unit, and constant current circuit unit are integrated in a one-chip semiconductor device, and the monitor current source, current-time conversion circuit unit, and current setting code generation circuit 9. The constant current source according to claim 1, wherein one unit is integrated on one chip. In an amplifier circuit to which a bias current is supplied from a constant current source,
The constant current source is:
A monitor current source for generating and outputting a predetermined monitor current i1;
A current-time conversion circuit unit that starts an operation of converting the monitor current value from the monitor current source into time according to the input control signal S2, and outputs a predetermined conversion end signal S3 when the conversion is completed; ,
A current setting code that outputs and outputs the control signal S2 to the current-time conversion circuit unit and generates and outputs a current setting code S4 corresponding to the time required for the conversion by the current-time conversion circuit unit A generation circuit unit;
At least one constant current circuit unit that generates and outputs a current according to the current setting code S4 output from the current setting code generation circuit unit;
With
The current setting code generation circuit unit causes the current-time conversion circuit unit to start time conversion of the monitor current value according to the input control signal S1, and the current setting code according to the time required for the conversion An amplifier circuit characterized by generating and outputting S4 and correcting the constant current value output from the constant current circuit section. In a constant voltage circuit using an error amplification circuit to which a bias current is supplied from a constant current source,
The constant current source is:
A monitor current source for generating and outputting a predetermined monitor current i1;
A current-time conversion circuit unit that starts an operation of converting the monitor current value from the monitor current source into time according to the input control signal S2, and outputs a predetermined conversion end signal S3 when the conversion is completed; ,
A current setting code that outputs and outputs the control signal S2 to the current-time conversion circuit unit and generates and outputs a current setting code S4 corresponding to the time required for the conversion by the current-time conversion circuit unit A generation circuit unit;
At least one constant current circuit unit that generates and outputs a current according to the current setting code S4 output from the current setting code generation circuit unit;
With
The current setting code generation circuit unit causes the current-time conversion circuit unit to start time conversion of the monitor current value according to the input control signal S1, and the current setting code according to the time required for the conversion A constant voltage circuit that generates and outputs S4 and corrects the constant current value output from the constant current circuit unit.

Images