JPH05335955A - Analog/digital converter - Google Patents

Abstract

PURPOSE:To suppress a voltage fluctuation in a power supply of a chopper amplifier by providing a 1st chopper amplifier comparing an analog input voltage and a reference voltage and a 2nd chopper amplifier in the complementary operation thereto to the A/D converter. CONSTITUTION:An analog input voltage 1 is inputted to an inverting input terminal of a chopper amplifier 6 and a current correction chopper amplifier 7 and a reference voltage 2 from a digital/analog converter 5 is inputted to other input terminals. A digital signal being an output of the chopper amplifier 6 is given to a successive approximation register 9 and inputted to the digital/ analog converter 5 via a bus. A chopper control signal 3 from a control circuit 8 is inputted to a control terminal of the chopper amplifier 6 and a current correction chopper amplifier control signal 4 is inputted to a control terminal of a current correction chopper amplifier 7. Thus, when a power supply current flowing through the chopper amplifier 6 is increased (or decreased), a power supply current flowing through the chopper amplifier 7 is decreased (or increased) to make the voltage of the power supply stable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analog / digital converter for comparing an analog input voltage with a reference voltage by a chopper amplifier and converting an analog signal into a digital signal based on the comparison result.

[0002]

2. Description of the Related Art FIG. 1 is a block diagram of a main part of a conventional analog / digital converter. The analog input voltage 1 which is an analog signal is input to one input terminal of the chopper amplifier 6, and the reference voltage 2 which is a reference signal from the digital / analog converter 5 is input to the other input terminals. Control circuit 8
The chopper amplifier control signal 3 from is supplied to the control terminal of the chopper amplifier 6. The digital signal which is the output signal of the chopper amplifier 6 is given to the successive approximation register 9, and the digital signal which is the data of the successive approximation register 9 is digital / digital.
It is given to the analog converter 5.

FIG. 2 is a block diagram showing the configuration of the chopper amplifier 6. The chopper amplifier 6 has a two-stage amplification structure in which two inverters are connected in series. This number of stages is selected according to the required amplification factor. Analog input voltage 1 is N-channel transistor _10a and capacitor _17a
Is input to the inverter 18 _a via a series circuit. Reference voltage 2 is N-channel transistor _10b and capacitor 17
through a series circuit of _a is input to the inverter 18 _a. N
The sample signal 11 is applied to the gate of the channel transistor _10a.
Is input, and the inverted sample signal 12 is input to the gate of the N-channel transistor 10 _b . Inverter 18 output signal of _a second inverter 18 _b through a capacitor 17 _b
Is input to. An N-channel transistor _10c is connected in parallel to the inverter 18a, and _a bias signal 13 is input to its gate. An N-channel transistor _10d is connected in parallel to the inverter _18b , and a bias signal 13 is input to its gate. Chopper amplifier output signal 15 is output from the inverter 18 _b. This chopper amplifier 6 is N
The analog input voltage 1 or the reference voltage 2 is selected by the channel transistors _10a and _10b . When the bias signal 13 is at H level, the inverters _18a and _18b are biased to the operating point.

Next, the operation of the analog / digital converter will be described. When the first digital / analog conversion is performed by the digital / analog converter 5, a digital code corresponding to a voltage half the reference voltage 2 is set in the successive approximation register 9, and the digital code is set. Converts to an analog signal. Then, the result of comparison between the analog input voltage 1 and the reference voltage 2 is fed back to the successive approximation register 9. In the case of the n-bit digital / analog converter 5, such an operation is performed n times to convert an analog signal into a digital signal.

FIG. 3 is a timing chart showing the operation timing of the chopper amplifier 6. Sample signal 11 as shown in FIG. 3 (a) is turned on N-channel transistor 10 _a is becomes H level charged capacitor 17 _a is the analog input voltage 1, also capacitor 17 _b is charged. After that, when the bias signal 13 becomes H level as shown in FIG. 3 (c), both the N-channel transistors _10c and _10d are turned on, the inverters _18a and _18b are short-circuited and biased to the operating point. After that, the bias signal 13 is shown in FIG.
As shown in FIG. 3, when the L-level is turned off, the N-channel transistors 10 _c and 10 _d are turned off, the inverters 18 _a and 18 _b are opened, and then the inverted sample signal 12 is turned to the H level as shown in FIG. 3B. N-channel transistor 10 _b is turned on, the capacitor 17 _a, 17 _b is charged by the reference voltage 2, and the analog input voltage 1 and the reference voltage 2 is amplified and compared by the inverter 18 _a, 18 _b. When the inverter 18 _a, 18 _b are biased to an operating point, to the inverter 18 _a, 18 _b, the supply current from a power supply (not shown) to the inverter 18 _a, 18 _b as shown in FIG. 3 (d) Flow , Keeps flowing for the duration of the bias.

[0006]

By the way, the reason why the power supply current increases when the inverter is biased to the operating point is that the signal change when the bias signal becomes L level is given to the inverter through the parasitic capacitance. As a result, one of the P-channel transistor and the N-channel transistor forming the inverter is turned on, and the output voltage of the chopper amplifier does not become half the voltage of the power supply of the inverter. Usually, the external power supply also has impedance, and the power supply line inside the device also has impedance, so the voltage of the inverter power supply fluctuates due to this current change, and the accuracy of conversion into a digital signal by the chopper amplifier decreases. There's a problem. In view of such a problem, it is an object of the present invention to provide an analog / digital conversion device that suppresses fluctuations in power supply current flowing in a chopper amplifier and highly accurately converts an analog signal into a digital signal.

[0007]

An analog / digital converter according to a first aspect of the present invention comprises a first chopper amplifier for comparing an analog input voltage with a reference voltage and a second chopper amplifier for complementary operation. .. An analog / digital conversion device according to a second aspect of the invention is configured to include a second chopper amplifier that operates by complementary operation with the first chopper amplifier only during an analog / digital conversion operation. In the analog / digital conversion device according to the third aspect of the present invention, the layouts of the first chopper amplifier and the second chopper amplifier are the same. An analog / digital conversion device according to a fourth aspect of the invention is configured by interposing resistors having equal resistance values on the power supply side and the ground side, where the power supply current of the chopper amplifier flows.

[0008]

In the first invention, when the power supply current flowing through the first chopper amplifier increases (or decreases), the power supply current flowing through the second chopper amplifier decreases (or increases). As a result, the current of the sum of the power supply currents flowing through the first chopper amplifier and the second chopper amplifier does not fluctuate, and the voltage of the power supply becomes stable. In the second invention, the power supply current flowing through the first chopper amplifier increases during the analog / digital conversion operation.
When (or decreased), the power supply current flowing through the second chopper amplifier decreases (or increases). When the conversion operation is not performed, the power supply current of the second chopper amplifier does not increase. As a result, during the analog / digital conversion operation, the sum current of the power supply currents flowing through the first chopper amplifier and the second chopper amplifier does not change. The power supply current is reduced when the analog / digital conversion operation is not performed.

In the third invention, a power supply current equal to the power supply current flowing through the first chopper amplifier flows through the second chopper amplifier. As a result, the power supply current flowing through the first chopper amplifier and the power supply current flowing through the second chopper amplifier are reliably offset, and the sum of the power supply currents does not fluctuate.
In the fourth invention, when the power supply current flows through the first chopper amplifier, the voltage drops due to the resistors interposed on the power supply side and the ground side become equal, and the voltage at the operating point of the first chopper amplifier is equal to that of the power supply. It is half the voltage. This allows
When the first chopper amplifier is biased to the operating point,
The operating point does not deviate from half the power supply voltage.

[0010]

The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. FIG. 4 is a block diagram showing a main configuration of an analog / digital conversion device according to the present invention. The analog input voltage 1 which is an analog signal is input to one input terminal of the chopper amplifier 6 and the current correction chopper amplifier 7, and the reference voltage 2 which is a reference signal from the digital / analog converter 5 is input to each of the other input terminals. .. The digital signal output from the chopper amplifier 6 is given to the successive approximation register 9, and the digital signal from the successive approximation register 9 is inputted to the digital / analog converter 5 via the bus. The chopper amplifier control signal 3 from the control circuit 8 is input to the control terminal of the chopper amplifier 6, and the current correction chopper amplifier control signal 4
Is input to the control terminal of the current correction chopper amplifier 7.

FIG. 5 is a sub-block diagram showing the configurations of the chopper amplifier 6 and the current correction chopper amplifier 7. Chopper amplifier 6, the analog input voltage 1 is input to the inverter 18 _a via a series circuit of N-channel transistor 10 _a and a capacitor 17 _a. Reference voltage 2 is input to the inverter 18 _a via a series circuit of N-channel transistors 10 _b and the capacitor 17 _a. The inverter 18 _a N-channel transistor 10 _c are connected in parallel. The sample signal 11 is applied to the gate of the N-channel transistor 10 _a , and the inverted sample signal 12 is applied to the gate of the N-channel transistor 10 _b.
Is entered. Bias signal 13 is input to the gate of the N-channel transistor 10 _c, chopper amplifier output 15 from the inverter 18 _a is output.

The current correction chopper amplifier 7 has an analog input voltage 1 of N channel transistor 10 _e and capacitor.
Is input to the inverter 18 _c through a series circuit of 17 _c.
Reference voltage 2 is input to the inverter 18 _c through a series circuit of N-channel transistor 10 _f and capacitor 17 _c. The inverter 18 _c N-channel transistor 10 _g are connected in parallel. The inverted sample signal 12 is applied to the gate of the N-channel transistor 10 _e ,
_The sample signal 11 is input to the gate of _f . The inverted bias signal 14 is input to the gate of the N-channel transistor 10 _g .

This current correction chopper amplifier 7 has no logical connection for analog / digital conversion. That is, it is for correcting the power supply current flowing through the chopper amplifier 6. Although FIG. 5 shows a one-stage amplification chopper amplifier 6 and a current correction chopper amplifier 7 using one inverter, in order to increase the amplification factor, as shown in FIG. 6, a capacitor 17 _a (or 17 _c ) , Inverter _18a (or _18c )
, A capacitor 17 _b, and an inverter 18 _b are connected in series, an inverter 18 _a (or 18 _c ) is connected in parallel with an N-channel transistor 10 _c , and an inverter 18 _b is connected in parallel with an N-channel transistor 10 _d. A structure for performing stage amplification may be used.

Next, the operation of the chopper amplifier 6 shown in FIG. 5 will be described with reference to FIG. 7 showing a signal timing chart. Now, when the analog / digital conversion operation of the first bit is started, the sample signal 11 changes to H level as shown in FIG. 7 (a).
Level, and capacitor 17 _a chopper amplifier 6 is charged by the analog input voltage 1. After that, the bias signal 13 becomes H level as shown in FIG. 7 (c), the N-channel transistor _10c is turned on, and the inverter _18a is biased to a voltage of 1/2 of the voltage of its power source (not shown).
(Input voltage = output voltage = half the power supply voltage). Thus P-channel transistors and N-channel transistors (not shown) constituting the inverter 18 _a are both turned on, flowing supply current 19 shown from the power supply side to the through-current serving FIG 7 (e) to the ground side. Thereafter, the bias signal 13, as shown in FIG. 7 (c) becomes L level, the state in which a short circuit of the inverter 18 _a is opened. After that, the sample signal 11 becomes L level as shown in FIG.
Becomes H level as shown in FIG. 7 (b), the N-channel transistor _10b is turned on, the N-channel transistor _10a is turned off, and the capacitor _17a is charged by the reference voltage 2.
As a result, the chopper amplifier 6 receives the analog input voltage 1 and
The reference voltage 2 is compared and amplified. In this way, when the bias signal 13 becomes H level as shown in FIG. 7 (c), FIG. 7 (e)
The supply current 19 flowing through the inverter 18 _a as shown in increases, the bias signal 13 is reduced and becomes L level.

Next, the operation of the current correction chopper amplifier 7 will be described. When starting the first bit of the analog / digital converter, samples the signal 11 becomes the H level as shown in FIG. 7 (a), whereby the capacitor 17 of the chopper amplifier 7 by the reference voltage 2 N-channel transistor 10 _f is turned on
_c is charged. After that, the reverse bias signal 14 is shown in FIG.
When it goes to L level, the N-channel transistor
10 _f is turned off and the power supply current 20 flowing from the power supply to the inverter 18 _c is decreased as shown in FIG. 7 (f). After that, Fig. 7 (d)
When the inversion bias signal 14 becomes the H level as shown in FIG. 7, the N-channel transistor 10 _g is turned on, the inverter 18 _c is biased to the operating point, and the power supply current 20 increases as shown in FIG. 7 (f). Thus, when the bias signal 13 and the inverted bias signal 14 are inverted, the power supply current 19 of the chopper amplifier 6 increases as shown in FIG. 7 (e), while the power supply current 20 of the current correction chopper amplifier 7 is It decreases as shown in 7 (f). That is, the power supply current 19 of the chopper amplifier 6 and the power supply current 20 of the current correction chopper amplifier 7 change in a complementary manner. Therefore, the sum of the power supply current 19 of the chopper amplifier 6 and the power supply current 20 of the current correction chopper amplifier 7 is the bias signal 13 and the inverted bias signal as shown in FIG. 7 (g).
Although it slightly fluctuates near the time when 14 reverses, the current stabilizes in other periods. In order to make the potential difference between the analog input voltage 1 and the reference voltage 2 the same as that of the chopper amplifier 6, an inverted sample signal 12 is input to the N channel transistor 10 _e of the current correction chopper amplifier 7 and a sample signal is input to the N channel transistor 10 _f. You have entered 11.

On the other hand, if the layouts of the chopper amplifier 6 and the current correction chopper 7 are the same, the power supply currents 19 and 20 flowing through them can be made equal and can be offset.
It is possible to further suppress fluctuations in the sum of the power supply currents 19 and 20.

FIG. 8 is a block diagram showing another embodiment of the chopper amplifier 6 and the current correction chopper amplifier 7. The bias signal 13 input to the gate of the N-channel transistor 10 _c of the chopper amplifier 6 is input to one input terminal of the NOR circuit 30. Analog / digital converter is analog /
The H-level operation signal 22 indicating that the digital conversion operation is being performed is input to the other input terminal of the NOR circuit 30 via the inverter 31. Bias signal 23 output from NOR circuit 30
Is input to the gate of the N-channel transistor 10 _g of the current correction chopper amplifier 7. The other configuration is the same as that shown in FIG. 5, and the same components are designated by the same reference numerals.

Next, this operation will be described with reference to the timing chart shown in FIG. Since the operation signal 22 is at the L level while the analog / digital conversion operation is not performed, the bias signal 23 which is the output signal of the NOR circuit 30 is shown in FIG.
As shown in FIG. 9 (d), when the analog / digital conversion operation is performed, the operation signal 22 becomes H level, and the bias signal shown in FIG. 9 (d) is inverted in synchronization with the bias signal 13.
23 is input to the N-channel transistor 10 _g . Thereby operates similarly to inverter 18 _a, 18 _c is described above, the sum of the currents of respective power source current 19, 20 is stabilized as shown in FIG. 9 (g). In addition, the inverter 18 of the current correction chopper amplifier 7 is operated while the analog / digital conversion operation is not performed.
Since not bias the operating point _c supply current stops flowing to the inverter 18 _c. Therefore, when the analog / digital conversion operation is not performed, the sum current of the power supply currents 19 and 20 flowing through the chopper amplifier 6 and the current correction chopper amplifier 7 decreases as shown in FIG. 9 (g).

FIG. 10 is a block diagram showing still another embodiment of the chopper amplifier 6. Between the power supply V _CC and the ground V _SS , a resistor 24 _a , a P-channel transistor 10 _P forming an inverter, an N-channel transistor 10 _N, and a resistor
A series circuit of the 24 _b is interposed. Gates of the P-channel transistor 10 _P and the N-channel transistor 10 _N are commonly connected. The connection between the gate of the P-channel transistor 10 _{P and} the gate of the N-channel transistor 10 _N , and the P-channel transistor 10 _P and the N-channel transistor 10
_N- channel transistor 10m between _N series connection
Is intervened. The resistors 24 _a and 24 _b are selected to have the same resistance value, and the P channel transistor 10 _P and the N channel transistor 10 _N form an inverter. The other configuration is the same as that of the chopper amplifier 6 shown in FIG. 5, and the same components are designated by the same reference numerals.

In the chopper amplifier 6, when the power source current flowing through the P channel transistor 10 _P and the N channel transistor 10 _N fluctuates, the voltage of the power source V _CC fluctuates.
Since the power supply V _CC side and the ground V _SS side change at the same voltage value due to the voltage drop of the resistors 24 _a and 24 _b , the chopper amplifier 6
Is biased to the operating point, the operating point does not deviate from half the voltage of the power supply V _CC . Thereby, the analog signal can be converted into a digital signal with high accuracy by using only the chopper amplifier 6. If it is necessary to incorporate a resistor inside the chip to improve the surge resistance and latch-up resistance of the analog / digital converter power supply line,
A resistor with the same resistance value like this chopper amplifier 6,
The accuracy of analog / digital conversion can be improved by providing the power supply side and the ground side.

[0021]

As described in detail above, the first aspect of the present invention provides both chopper amplifiers by providing a second chopper amplifier that complementarily operates with a first chopper amplifier that compares and amplifies an analog input voltage with a reference voltage. It is possible to suppress the fluctuation of the sum current and suppress the fluctuation of the voltage of the power supply of the chopper amplifier. According to a second aspect of the present invention, by providing a first chopper amplifier and a second chopper amplifier that performs a correction operation, and complementarily operating the second chopper amplifier only during an analog / digital conversion operation, the voltage of the power supply of the chopper amplifier is increased. If the fluctuation can be suppressed and the analog / digital conversion operation is not performed, the power supply current can be reduced. The third invention is
By making the layout configurations of the first chopper amplifier and the second chopper amplifier the same, the power supply currents flowing in the respective chopper amplifiers can be reliably offset, fluctuations in the sum of the power supply currents can be suppressed, and the power supply Voltage fluctuation can be suppressed. According to the fourth aspect of the present invention, the operating point of the first chopper amplifier is always ½ of the voltage of the power source by interposing the resistors having the same resistance value on the power source side and the ground side of the first chopper amplifier. The voltage can be Therefore, according to the present invention, the voltage of the power supply of the chopper amplifier can be stabilized, or the operating point of the chopper amplifier can be prevented from deviating from the voltage of 1/2 of the power supply voltage. It has an excellent effect of providing an analog / digital conversion device having high cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a conventional analog / digital conversion device.

FIG. 2 is a block diagram showing a configuration of a chopper amplifier.

FIG. 3 is a timing chart of signals at various parts of the chopper amplifier.

FIG. 4 is a block diagram showing a main configuration of an analog / digital conversion device according to the present invention.

5 is a block diagram showing configurations of a chopper amplifier and a current correction chopper amplifier in FIG.

FIG. 6 is a circuit diagram in which the chopper amplifier is amplified in two stages.

7 is a timing chart of signals of respective parts in the chopper amplifier and the current correction chopper amplifier shown in FIG.

FIG. 8 is a block diagram showing a configuration of another embodiment of the chopper amplifier and the current correction chopper amplifier.

9 is a timing chart of signals of respective parts in the chopper amplifier and the current correction chopper amplifier shown in FIG.

FIG. 10 is a block diagram showing the configuration of another embodiment of the chopper amplifier.

[Explanation of symbols]

5 Digital / analog converter 6 Chopper amplifier 7 Current correction chopper amplifier 8 Control circuit 9 Successive approximation register 10 _a , 10 _b … 10 _g N-channel transistor 17 _a , 17 _b Capacitor 18 _a , 18 _b Inverter 24 _a , 24 _b Resistance 30 NOR circuit 31 Inverter

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[Procedure amendment]

[Submission date] November 10, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction content]

FIG. 3 is a timing chart showing the operation timing of the chopper amplifier 6. Sample signal 11 as shown in FIG. 3 (a) is a capacitor 17 _a is charged by the analog input voltage 1 ON N-channel transistor 10 _a is becomes H level. After that, the bias signal 13 is shown in FIG.
When it goes to the H level as shown in (c), both the N-channel transistors 10 _c and 10 _d are turned on and the inverters 18 _a and 18 _d are turned on.
_b Each input side and output side are short-circuited and biased to the operating point. After that, when the bias signal 13 becomes L level as shown in FIG. 3C, the N-channel transistor 10 _c ,
When 10 _d is turned off and the inverters 18 _a and 18 _b are released from the short circuit , and then the inverted sample signal 12 becomes H level as shown in FIG. 3 (b), the N-channel transistor 10 _b is turned on and the reference voltage 2 capacitors 17 _a, 17 _b is charged, the analog input voltage 1 and the reference voltage 2 is amplified and compared by the inverter 18 _a, 18 _b by. Such a principle
Inverter because analog / digital conversion is performed by
When 18 _a and 18 _b are biased to the operating point, they are shown in Fig. 3 (d).
As described above, the power supply current constantly flows through the inverter.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

The object of the invention is to try to resolve the way to the inverter
No problem if constant power supply current continues, but bias
When the signal turns off, the power supply current of the inverter decreases.
It This is the signal when the bias signal becomes L level.
Signal change affects the inverter through the parasitic capacitance,
In addition, the operating point of the inverter should not be half the power supply voltage.
According to Normally, the chopper amplifier has a multistage amplification structure
Therefore, in the first stage, the operating point of the inverter is 1/2 of the power supply voltage.
If it deviates slightly from the voltage of
, One of the transistors that make up the inverter is off.
The power supply current stops flowing to the inverter. Normally, the external power supply also has impedance, and the power supply line inside the device also has impedance, so the voltage of the power supply of the inverter fluctuates due to this current change, and the accuracy of conversion into a digital signal by the chopper amplifier decreases. There's a problem. In view of such a problem, an object of the present invention is to provide an analog / digital converter that suppresses fluctuations in a power supply current flowing through a chopper amplifier and converts an analog signal into a digital signal with high accuracy.

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 10

[Correction method] Change

[Correction content]

[Figure 10]

Claims (4)

[Claims] 1. An analog / digital conversion device for comparing an analog input voltage and a reference voltage with a first chopper amplifier and converting the analog input voltage and a reference voltage into a digital signal based on the comparison result. Complementary operation to the first chopper amplifier. First from the power supply
Analog / characterized in that it is provided with a second chopper amplifier for correcting the power supply current flowing in the chopper amplifier of
Digital conversion device. 2. The analog / digital conversion apparatus according to claim 1, wherein the first conversion is performed only during an analog / digital conversion operation.
An analog / digital conversion device comprising a second chopper amplifier that performs a complementary operation to the chopper amplifier of, and corrects the power supply current. 3. The analog / digital converter according to claim 1, wherein the first chopper amplifier and the second chopper amplifier have the same layout. 4. An analog / digital conversion device, wherein resistors having equal resistance values are provided on each of a power supply side and a grounding side where a power supply current of the first chopper amplifier flows.