US20200204188A1 - Comparator circuit and analog to digital converter - Google Patents
Comparator circuit and analog to digital converter Download PDFInfo
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- US20200204188A1 US20200204188A1 US16/430,953 US201916430953A US2020204188A1 US 20200204188 A1 US20200204188 A1 US 20200204188A1 US 201916430953 A US201916430953 A US 201916430953A US 2020204188 A1 US2020204188 A1 US 2020204188A1
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/12—Analogue/digital converters
- H03M1/34—Analogue value compared with reference values
- H03M1/38—Analogue value compared with reference values sequentially only, e.g. successive approximation type
- H03M1/46—Analogue value compared with reference values sequentially only, e.g. successive approximation type with digital/analogue converter for supplying reference values to converter
- H03M1/466—Analogue value compared with reference values sequentially only, e.g. successive approximation type with digital/analogue converter for supplying reference values to converter using switched capacitors
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/12—Analogue/digital converters
- H03M1/34—Analogue value compared with reference values
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
- H03K3/02—Generators characterised by the type of circuit or by the means used for producing pulses
- H03K3/353—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of field-effect transistors with internal or external positive feedback
- H03K3/356—Bistable circuits
- H03K3/356017—Bistable circuits using additional transistors in the input circuit
- H03K3/356052—Bistable circuits using additional transistors in the input circuit using pass gates
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
- H03K3/02—Generators characterised by the type of circuit or by the means used for producing pulses
- H03K3/353—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of field-effect transistors with internal or external positive feedback
- H03K3/356—Bistable circuits
- H03K3/356104—Bistable circuits using complementary field-effect transistors
- H03K3/356113—Bistable circuits using complementary field-effect transistors using additional transistors in the input circuit
- H03K3/35613—Bistable circuits using complementary field-effect transistors using additional transistors in the input circuit the input circuit having a differential configuration
- H03K3/356139—Bistable circuits using complementary field-effect transistors using additional transistors in the input circuit the input circuit having a differential configuration with synchronous operation
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
- H03K5/22—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral
- H03K5/24—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral the characteristic being amplitude
- H03K5/2472—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral the characteristic being amplitude using field effect transistors
- H03K5/249—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral the characteristic being amplitude using field effect transistors using clock signals
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/12—Analogue/digital converters
- H03M1/34—Analogue value compared with reference values
- H03M1/36—Analogue value compared with reference values simultaneously only, i.e. parallel type
- H03M1/361—Analogue value compared with reference values simultaneously only, i.e. parallel type having a separate comparator and reference value for each quantisation level, i.e. full flash converter type
Definitions
- the present disclosure relates to a comparator circuit, in particular to a comparator circuit applied to an analog to digital converter (ADC).
- ADC analog to digital converter
- a high-speed and high-resolution converter is required.
- a conversion speed of a flash ADC is relatively high.
- a conventional flash ADC compares an input voltage and a reference voltage by use of a comparator circuit to generate a thermometer code and then converts the thermometer code into a digital code by use of a decoder.
- the comparator circuit used by the conventional flash ADC mostly adopts an auto zero comparator, and a circuit structure of the auto zero comparator usually consists of a preamplifier and a latch.
- a comparator circuit is relatively high in power consumption and relatively complex in wiring.
- Another common comparator circuit substantially consists of four input metallic oxide semiconductor field effect transistors (MOSFETs).
- MOSFETs metallic oxide semiconductor field effect transistors
- Such a comparator circuit requires input of the four input MOSFETs and parasitic capacitance of output ends is relatively high, which may reduce a conversion speed.
- an offset calibration circuit is designed at an output end and thus its conversion speed is also relatively low.
- a comparator circuit is applied to comparing an input voltage and a reference voltage to generate a comparison result.
- the input voltage includes a first input voltage and a second input voltage.
- the comparator circuit includes a resistor circuit, a current source circuit and a transistor switching circuit.
- the resistor circuit receives the first input voltage and the second input voltage.
- the current source circuit provides a first current and a second current, and the first current, the second current and the resistor circuit generate the reference voltage.
- the transistor switching circuit includes an input end and an output end, and generates the comparison result at its output end according to a first control voltage and a second control voltage at its input end.
- the current source circuit and the resistor circuit generate the first control voltage according to the first current and the first input voltage, and generate the second control voltage according to the second current and the second input voltage.
- a comparator circuit is applied to comparing an input voltage and a reference voltage to generate a comparison result.
- the comparator circuit includes a resistor circuit, a current source circuit and a transistor switching circuit.
- the resistor circuit receives the input voltage.
- the current source circuit provides a first current.
- the first current and the resistor circuit generate the reference voltage.
- the transistor switching circuit includes an input end and an output end, and generates the comparison result at its output end according to a control voltage at its input end.
- the current source circuit and the resistor circuit generate the control voltage according to the input voltage and the reference voltage.
- an ADC is applied to converting an input voltage into a digital signal.
- the input voltage includes a first input voltage and a second input voltage.
- the ADC includes a resistor circuit, a current source circuit, a transistor switching circuit and a decoder.
- the resistor circuit receives the first input voltage and the second input voltage.
- the current source circuit provides a first current and a second current.
- the transistor switching circuit includes an input end and an output end, and generates a comparison result at the output end according to a first control voltage and a second control voltage at the input end.
- the current source circuit and the resistor circuit generate the first control voltage according to the first current and the first input voltage, and generate the second control voltage according to the second current and the second input voltage.
- the decoder converts the comparison result into the digital signal.
- output capacitance of the output end of a comparison stage can be lowered by adopting the comparator circuit and ADC of the present disclosure, so that the overall conversion speed may be improved.
- FIG. 1 is a schematic diagram of a comparator circuit according to an embodiment of the present disclosure.
- FIG. 2 is a flowchart of a comparison method according to an embodiment of the present disclosure.
- FIG. 3 is a circuit schematic diagram of a comparator circuit according to an embodiment of the present disclosure.
- FIG. 4 is a general schematic diagram of an ADC according to an embodiment of the present disclosure.
- FIG. 1 is a general schematic diagram of a comparator circuit according to an embodiment of the present disclosure.
- the comparator circuit is configured to compare an input voltage and a reference voltage to generate a comparison result. Description is made below with a differential input voltage as an example but is not intended to limit the present disclosure.
- the comparator circuit of the present disclosure may also be configured for a single-ended input voltage.
- the comparator circuit 100 includes a transistor switching circuit 110 , a resistor circuit 120 and a current source circuit 130 .
- the resistor circuit 120 is coupled between an input end of the comparator circuit 100 and an input end of the transistor switching circuit 110
- the current source circuit 130 is coupled to the input end of the transistor switching circuit 110 . That is, a first end of the resistor circuit 120 is coupled to the input end of the comparator circuit 100 , and a second end of the resistor circuit 120 is coupled to the input end of the transistor switching circuit 110 .
- the resistor circuit 120 is configured to receive in put voltages Vip and Vin, and the current source circuit 130 inputs a current to the second end of the resistor circuit 120 or drains the current from the second end of the resistor circuit 120 .
- the current source circuit 130 inputs currents Irn and Irp to the second end of the resistor circuit 120 or drains the currents Irn and Irp from the second end of the resistor circuit 120 to provide the reference voltage at the second end of the resistor circuit 120 .
- the second end of the resistor circuit 120 outputs or receives the currents Irn and Irp from the current source circuit 130 . Therefore, according to the Ohm law, the currents Irn and Irp and resistance of the resistor circuit 120 may be combined to generate the reference voltage.
- the current source circuit 130 may be implemented by one or more current sources.
- the currents Irn and Irp are constant currents respectively.
- the current source circuit 130 includes a constant current source circuit 131 .
- the constant current source circuit 131 is coupled to the resistor circuit 120 , and the constant current source circuit 131 outputs the constant currents Irn and Irp to the second end of the resistor circuit 120 (or drains the constant currents Irn and Irp from the second end of the resistor circuit 120 ).
- the input end of the comparator circuit 100 receives the input voltages Vip and Vin, the input voltages Vip and Vin are provided for the first end of the resistor circuit 120 and the currents Irn and Irp flow through the resistor circuit 120 to provide the reference voltage to further form control voltages Vcp and Vcn (Step S 11 ).
- the current source circuit 130 and the resistor circuit 120 generate the control voltages Vcp and Vcn according to the input voltages Vip and Vin and the currents Irn and Irp.
- the control voltages Vcp and Vcn are provided for the input end of the transistor switching circuit 110 .
- the control voltages Vcp and Vcn are related to the reference voltage.
- the transistor switching circuit 110 When the control voltages Vcp and Vcn are received at the input end of the transistor switching circuit 110 , the transistor switching circuit 110 generates the comparison result according to the control voltages Vcp and Vcn (Step S 13 ).
- the comparison result may be thermometer codes Dp and Dn. Furthermore, when Vcp>Vcn, the thermometer code Dp is 1, and the thermometer code Dn is 0; and on the contrary, when Vcp ⁇ Vcn, the thermometer code Dp is 1, and the thermometer code Dn is 0.
- the comparator circuit 100 further includes a latch circuit 150 .
- the latch circuit 150 is coupled to an output end of the transistor switching circuit 110 .
- the transistor switching circuit 110 generates the comparison result according to the control voltages Vcp and Vcn, and outputs the comparison result to the latch circuit 150 from the output end of the transistor switching circuit 110 .
- the latch circuit 150 latches the thermometer codes Dp and Dn generated by the transistor switching circuit 110 , and outputs the thermometer codes Dp and Dn from an output end of the comparator circuit 100 according to a clock pulse signal CK.
- currents Ion and Iop are further received by or drained from the second end of the resistor circuit 120 to provide a calibration voltage.
- the currents Ion and Top and the resistance of the resistor circuit 120 may be combined to achieve the calibration voltage to eliminate a voltage offset caused by a factor such as internal circuit mismatch.
- the current source circuit 130 may further include an adjustable current source circuit 132 , and the adjustable current source circuit 132 is coupled to the second end of the resistor circuit 120 .
- the adjustable current source circuit 132 provides the currents Ion and Top for the second end of the resistor circuit 120 or drains the currents Ion and Iop from the second end of the resistor circuit 120 to provide the calibration voltage at the second end of the resistor circuit 120 .
- the adjustable current source circuit 132 may be arranged outside the current source circuit 130 or the comparator circuit 100 .
- the adjustable current source circuit 132 is controlled by a control circuit 30 , and the control circuit 30 may be arranged inside or outside the comparator circuit 100 .
- the control circuit 30 may short-circuit the two ends (the first end and the second end) of the resistor circuit 120 (which may be implemented by use of a switch controlled by the control circuit 30 ) and sense the output end of the comparator circuit 100 to obtain output of the latch circuit 150 . Then, the control circuit 30 generates a setting signal Ss according to the output of the latch circuit 150 (for example, a comparison result obtained without comparison of the comparator circuit 100 ), and outputs the generated setting signal Ss to a control end of the adjustable current source circuit 132 to enable the adjustable current source circuit 132 to provide (output or drain) the required currents Ion and Iop according to the setting signal Ss. In an example, the control circuit 30 may find the setting signal Ss corresponding to the output of the latch circuit 150 by use of a lookup table.
- the adjustable current source circuit 132 may be implemented by one or more current sources.
- the comparator circuit 100 may further include a coupling circuit 160 , and the coupling circuit 160 is connected in parallel with the resistor circuit 120 .
- the coupling circuit 160 may couple an alternating current (AC) signal to avoid a signal delay.
- AC alternating current
- a parasitic capacitor exists at the input end of the transistor switching circuit 110 , and the parasitic capacitor forms an equivalent low-pass filter with the resistor circuit 120 respectively to further reduce the overall conversion speed of the comparator circuit 100 .
- the input voltages Vip and Vin are coupled from the input end of the comparator circuit 100 to the input end of the transistor switching circuit 110 through the coupling circuit 160 .
- the resistor circuit 120 may not form an equivalent low-pass filter with the parasitic capacitor of the transistor switching circuit 110 , so that the overall conversion speed of the comparator circuit 100 is further improved.
- the coupling circuit 160 may be implemented by a capacitor with high capacitance.
- the comparator circuit 100 may further include a regulation current source circuit 180 , and the regulation current source circuit 180 is coupled to the input end of the transistor switching circuit 110 .
- the regulation current source circuit 180 provides a regulation current for the input end of the transistor switching circuit 110 so as to provide an input working voltage, in which the input working voltage is for the transistor switching circuit 110 to enable the transistor switching circuit 110 to work in a normal operating region.
- the working voltage may also be called a common mode voltage.
- FIG. 3 is a circuit schematic diagram of a comparator circuit 100 according to an embodiment of the present disclosure.
- the transistor switching circuit 110 includes a transistor M 1 and a transistor M 2 , and a source of the transistor M 1 is coupled to a source of the transistor M 2 .
- a drain of the transistor M 1 and a drain of the transistor M 2 are coupled to the latch circuit 150 .
- the source of the transistor M 1 and the source of the transistor M 2 are also coupled and grounded through a switching transistor M 5 .
- the switching transistor M 5 is controlled by the clock pulse signal CK.
- the resistor circuit 120 includes a resistor R 1 and a resistor R 2 .
- a first end of the resistor R 1 is coupled to a first input end of the comparator circuit 100 , and a second end of the resistor R 1 is coupled to a gate of the transistor M 1 .
- a first end of the resistor R 2 is coupled to a second input end of the comparator circuit 100 , and a second end of the resistor R 2 is coupled to a gate of the transistor M 2 .
- parasitic capacitors exist at the gates of the transistor M 1 and the transistor M 2 , and the parasitic capacitors may form equivalent low-pass filters with the corresponding resistor R 1 and resistor R 2 respectively to further reduce the overall speed of the comparator circuit 100 .
- the coupling circuit 160 is connected in parallel with the resistor circuit 120 , and, that is, a capacitor C 1 is connected in parallel with the resistor R 1 , and a capacitor C 2 is connected in parallel with the resistor R 2 .
- the capacitor C 1 and the capacitor C 2 couple the input voltage Vip and the input voltage Vin to the gates of the transistor M 1 and the transistor M 2 respectively. Therefore, influence of the parasitic capacitors of the transistor M 1 and the transistor M 2 on the speed of the comparator circuit 100 is further eliminated.
- the latch circuit 150 includes a transistor cross-coupled pair.
- the transistor cross-coupled pair includes two cross-coupled transistors (for example, a transistor M 3 and a transistor M 4 ).
- a drain of the transistor M 3 is coupled to the drain of the transistor M 1 and a second output end of the comparator circuit.
- a drain of the transistor M 4 is coupled to the drain of the transistor M 2 and a first output end of the comparator circuit 100 .
- a source of the transistor M 3 and a source of the transistor M 4 are coupled to a power supply VDD.
- a switching transistor M 7 is connected in parallel between the source and the drain of the transistor M 3
- a switching transistor M 8 is connected in parallel between the source and the drain of the transistor M 4 .
- the switching transistors M 7 and M 8 are controlled by the clock pulse signal CK.
- the first end of the resistor R 1 receives the input voltage Vip, and the second end of the resistor R 1 receives the current Irn from the current source circuit 130 or drains the current Irn from the current source circuit 130 .
- the first end of the resistor R 2 receives the input voltage Vin, and the second end of the resistor R 2 receives the current Irp from the current source circuit 130 or drains the current Irp from the current source circuit 130 .
- the transistor M 1 and the transistor M 2 form the thermometer codes Dn and Dp according to a level control voltage Vcp and a level control voltage Vcn.
- thermometer code Dp is 1 and the thermometer code Dn is 0; and correspondingly, when Vip ⁇ Vin ⁇ (Irp ⁇ Irn)*R, the thermometer code Dp is 0 and the thermometer code Dn is 1.
- (Irp ⁇ Irn)*R may be considered as the reference voltage.
- the latch circuit 150 outputs the thermometer codes Dn and Dp from the second output end and the first output end of the comparator circuit, respectively, according to the clock pulse signal CK.
- the constant current source circuit 131 includes two constant current sources 131 a and 131 b .
- the constant current source 131 a is coupled to the second end of the resistor R 1 , and is configured to provide the current Irn.
- the constant current source 131 b is coupled to the second end of the resistor R 2 , and is configured to provide the current Irp.
- the adjustable current source circuit 132 may include two groups of adjustable current sources 132 a and 132 b .
- the adjustable current source 132 a is coupled to the second end of the resistor R 1 , and is configured to provide the current Ion.
- the adjustable current source 132 b is coupled to the second end of the resistor R 2 , and is configured to provide the current Top.
- the currents Ion and Iop and the resistance of the resistors R 1 and R 2 may be combined to achieve the calibration voltage to eliminate the voltage offset caused by a factor such as internal circuit mismatch.
- the currents Ion and Iop provided by the adjustable current sources 132 a and 132 b may be regulated by a control signal (for example, the control signal Ss shown in FIG. 1 ).
- the regulation current source circuit 180 may include two groups of regulation current sources 180 a and 180 b .
- the regulation current source 180 a is coupled to the second end of the resistor R 1
- the regulation current source 180 b is coupled to the second end of the resistor R 2
- the regulation current sources 180 a and 180 b are configured to provide the currents for the second ends of the resistors R 1 and R 2 respectively to provide input common mode voltages for the transistor M 1 and the transistor M 2 to enable the transistor M 1 and the transistor M 2 to work in the normal operating region.
- the comparator circuit 100 may also compare a single-ended input voltage and the reference voltage.
- the input voltage Vip is considered as a single-ended input voltage
- the reference voltage is generated by use of the constant current source 131 a and the resistor R 1
- the thermometer code Dn is considered as the comparison result.
- the comparator circuit 100 may be applied to a flash ADC.
- the flash ADC may include the comparator circuit of any above-mentioned embodiment and a decoder 20 . An output end of the comparator circuit is coupled to the decoder 20 .
- the comparator circuit includes at least a transistor switching circuit 110 , a resistor circuit 120 and a constant current source circuit 131 . Configurations and operations of these circuits are substantially the same as those described above and thus is not elaborated.
- the decoder 20 implements conversion from thermometer codes Dp and Dn into a digital signal A 0 , i.e., a digital signal A 0 in a binary form.
- output capacitance of the output end of a comparison stage can be lower by adopting the comparator circuit, comparison method and flash ADC of the present disclosure, so that the overall speed may be relatively improved.
Abstract
Description
- This non-provisional application claims priority under 35 U.S.C. §119(a) to Patent Application No. 201811577291.5 filed in China, P.R.C. on Dec. 21, 2018, the entire contents of which are hereby incorporated by reference.
- The present disclosure relates to a comparator circuit, in particular to a comparator circuit applied to an analog to digital converter (ADC).
- In common signal processing applications, for example, digital wireless communication system, digital voice processing and digital image processing applications, a high-speed and high-resolution converter is required. In various high-speed ADCs, a conversion speed of a flash ADC is relatively high.
- A conventional flash ADC compares an input voltage and a reference voltage by use of a comparator circuit to generate a thermometer code and then converts the thermometer code into a digital code by use of a decoder. Herein, the comparator circuit used by the conventional flash ADC mostly adopts an auto zero comparator, and a circuit structure of the auto zero comparator usually consists of a preamplifier and a latch. However, such a comparator circuit is relatively high in power consumption and relatively complex in wiring.
- Another common comparator circuit substantially consists of four input metallic oxide semiconductor field effect transistors (MOSFETs). However, such a comparator circuit requires input of the four input MOSFETs and parasitic capacitance of output ends is relatively high, which may reduce a conversion speed. Although there is a comparator circuit adopting two input MOSFETs, an offset calibration circuit is designed at an output end and thus its conversion speed is also relatively low.
- In an embodiment, a comparator circuit is applied to comparing an input voltage and a reference voltage to generate a comparison result. The input voltage includes a first input voltage and a second input voltage. The comparator circuit includes a resistor circuit, a current source circuit and a transistor switching circuit. The resistor circuit receives the first input voltage and the second input voltage. The current source circuit provides a first current and a second current, and the first current, the second current and the resistor circuit generate the reference voltage. The transistor switching circuit includes an input end and an output end, and generates the comparison result at its output end according to a first control voltage and a second control voltage at its input end. The current source circuit and the resistor circuit generate the first control voltage according to the first current and the first input voltage, and generate the second control voltage according to the second current and the second input voltage.
- In an embodiment, a comparator circuit is applied to comparing an input voltage and a reference voltage to generate a comparison result. The comparator circuit includes a resistor circuit, a current source circuit and a transistor switching circuit. The resistor circuit receives the input voltage. The current source circuit provides a first current. The first current and the resistor circuit generate the reference voltage. The transistor switching circuit includes an input end and an output end, and generates the comparison result at its output end according to a control voltage at its input end. The current source circuit and the resistor circuit generate the control voltage according to the input voltage and the reference voltage.
- In an embodiment, an ADC is applied to converting an input voltage into a digital signal. The input voltage includes a first input voltage and a second input voltage. The ADC includes a resistor circuit, a current source circuit, a transistor switching circuit and a decoder. The resistor circuit receives the first input voltage and the second input voltage. The current source circuit provides a first current and a second current. The transistor switching circuit includes an input end and an output end, and generates a comparison result at the output end according to a first control voltage and a second control voltage at the input end. The current source circuit and the resistor circuit generate the first control voltage according to the first current and the first input voltage, and generate the second control voltage according to the second current and the second input voltage. The decoder converts the comparison result into the digital signal.
- Based on the above, output capacitance of the output end of a comparison stage can be lowered by adopting the comparator circuit and ADC of the present disclosure, so that the overall conversion speed may be improved.
-
FIG. 1 is a schematic diagram of a comparator circuit according to an embodiment of the present disclosure. -
FIG. 2 is a flowchart of a comparison method according to an embodiment of the present disclosure. -
FIG. 3 is a circuit schematic diagram of a comparator circuit according to an embodiment of the present disclosure. -
FIG. 4 is a general schematic diagram of an ADC according to an embodiment of the present disclosure. - Referring to
FIG. 1 ,FIG. 1 is a general schematic diagram of a comparator circuit according to an embodiment of the present disclosure. The comparator circuit is configured to compare an input voltage and a reference voltage to generate a comparison result. Description is made below with a differential input voltage as an example but is not intended to limit the present disclosure. The comparator circuit of the present disclosure may also be configured for a single-ended input voltage. - As shown in
FIG. 1 , thecomparator circuit 100 includes atransistor switching circuit 110, aresistor circuit 120 and acurrent source circuit 130. Theresistor circuit 120 is coupled between an input end of thecomparator circuit 100 and an input end of thetransistor switching circuit 110, and thecurrent source circuit 130 is coupled to the input end of thetransistor switching circuit 110. That is, a first end of theresistor circuit 120 is coupled to the input end of thecomparator circuit 100, and a second end of theresistor circuit 120 is coupled to the input end of thetransistor switching circuit 110. - The
resistor circuit 120 is configured to receive in put voltages Vip and Vin, and thecurrent source circuit 130 inputs a current to the second end of theresistor circuit 120 or drains the current from the second end of theresistor circuit 120. In some embodiments, thecurrent source circuit 130 inputs currents Irn and Irp to the second end of theresistor circuit 120 or drains the currents Irn and Irp from the second end of theresistor circuit 120 to provide the reference voltage at the second end of theresistor circuit 120. In other words, the second end of theresistor circuit 120 outputs or receives the currents Irn and Irp from thecurrent source circuit 130. Therefore, according to the Ohm law, the currents Irn and Irp and resistance of theresistor circuit 120 may be combined to generate the reference voltage. Herein, thecurrent source circuit 130 may be implemented by one or more current sources. - In some embodiments, the currents Irn and Irp are constant currents respectively. In an example, the
current source circuit 130 includes a constantcurrent source circuit 131. The constantcurrent source circuit 131 is coupled to theresistor circuit 120, and the constantcurrent source circuit 131 outputs the constant currents Irn and Irp to the second end of the resistor circuit 120 (or drains the constant currents Irn and Irp from the second end of the resistor circuit 120). - Referring to both
FIG. 1 andFIG. 2 , the input end of thecomparator circuit 100 receives the input voltages Vip and Vin, the input voltages Vip and Vin are provided for the first end of theresistor circuit 120 and the currents Irn and Irp flow through theresistor circuit 120 to provide the reference voltage to further form control voltages Vcp and Vcn (Step S11). In other words, thecurrent source circuit 130 and theresistor circuit 120 generate the control voltages Vcp and Vcn according to the input voltages Vip and Vin and the currents Irn and Irp. In such case, the control voltages Vcp and Vcn are provided for the input end of thetransistor switching circuit 110. Herein, the control voltages Vcp and Vcn are related to the reference voltage. - When the control voltages Vcp and Vcn are received at the input end of the
transistor switching circuit 110, thetransistor switching circuit 110 generates the comparison result according to the control voltages Vcp and Vcn (Step S13). Herein, the comparison result may be thermometer codes Dp and Dn. Furthermore, when Vcp>Vcn, the thermometer code Dp is 1, and the thermometer code Dn is 0; and on the contrary, when Vcp<Vcn, the thermometer code Dp is 1, and the thermometer code Dn is 0. - In some embodiments, the
comparator circuit 100 further includes alatch circuit 150. Thelatch circuit 150 is coupled to an output end of thetransistor switching circuit 110. Thetransistor switching circuit 110 generates the comparison result according to the control voltages Vcp and Vcn, and outputs the comparison result to thelatch circuit 150 from the output end of thetransistor switching circuit 110. Thelatch circuit 150 latches the thermometer codes Dp and Dn generated by thetransistor switching circuit 110, and outputs the thermometer codes Dp and Dn from an output end of thecomparator circuit 100 according to a clock pulse signal CK. - In some embodiments, currents Ion and Iop are further received by or drained from the second end of the
resistor circuit 120 to provide a calibration voltage. In other words, according to the Ohm law, the currents Ion and Top and the resistance of theresistor circuit 120 may be combined to achieve the calibration voltage to eliminate a voltage offset caused by a factor such as internal circuit mismatch. - In an example, the
current source circuit 130 may further include an adjustablecurrent source circuit 132, and the adjustablecurrent source circuit 132 is coupled to the second end of theresistor circuit 120. The adjustablecurrent source circuit 132 provides the currents Ion and Top for the second end of theresistor circuit 120 or drains the currents Ion and Iop from the second end of theresistor circuit 120 to provide the calibration voltage at the second end of theresistor circuit 120. - In another example, the adjustable
current source circuit 132 may be arranged outside thecurrent source circuit 130 or thecomparator circuit 100. In some embodiments, the adjustablecurrent source circuit 132 is controlled by acontrol circuit 30, and thecontrol circuit 30 may be arranged inside or outside thecomparator circuit 100. - In an example, under the condition that the
comparator circuit 100 does not execute a comparison operation, thecontrol circuit 30 may short-circuit the two ends (the first end and the second end) of the resistor circuit 120 (which may be implemented by use of a switch controlled by the control circuit 30) and sense the output end of thecomparator circuit 100 to obtain output of thelatch circuit 150. Then, thecontrol circuit 30 generates a setting signal Ss according to the output of the latch circuit 150 (for example, a comparison result obtained without comparison of the comparator circuit 100), and outputs the generated setting signal Ss to a control end of the adjustablecurrent source circuit 132 to enable the adjustablecurrent source circuit 132 to provide (output or drain) the required currents Ion and Iop according to the setting signal Ss. In an example, thecontrol circuit 30 may find the setting signal Ss corresponding to the output of thelatch circuit 150 by use of a lookup table. - In some embodiments, the adjustable
current source circuit 132 may be implemented by one or more current sources. - It is to be noted that since offset calibration of the
comparator circuit 100 is implemented at the input end of thetransistor switching circuit 110, output capacitance at the output end of thecomparator circuit 100 is quite low and the overall conversion speed of thecomparator circuit 100 is further improved. - In some embodiments, the
comparator circuit 100 may further include acoupling circuit 160, and thecoupling circuit 160 is connected in parallel with theresistor circuit 120. Herein, thecoupling circuit 160 may couple an alternating current (AC) signal to avoid a signal delay. Furthermore, a parasitic capacitor exists at the input end of thetransistor switching circuit 110, and the parasitic capacitor forms an equivalent low-pass filter with theresistor circuit 120 respectively to further reduce the overall conversion speed of thecomparator circuit 100. The input voltages Vip and Vin are coupled from the input end of thecomparator circuit 100 to the input end of thetransistor switching circuit 110 through thecoupling circuit 160. From the input end of thecomparator circuit 100, theresistor circuit 120 may not form an equivalent low-pass filter with the parasitic capacitor of thetransistor switching circuit 110, so that the overall conversion speed of thecomparator circuit 100 is further improved. In some examples, thecoupling circuit 160 may be implemented by a capacitor with high capacitance. - In some embodiments, the
comparator circuit 100 may further include a regulationcurrent source circuit 180, and the regulationcurrent source circuit 180 is coupled to the input end of thetransistor switching circuit 110. The regulationcurrent source circuit 180 provides a regulation current for the input end of thetransistor switching circuit 110 so as to provide an input working voltage, in which the input working voltage is for thetransistor switching circuit 110 to enable thetransistor switching circuit 110 to work in a normal operating region. In the present embodiment, the working voltage may also be called a common mode voltage. - Referring to
FIG. 3 ,FIG. 3 is a circuit schematic diagram of acomparator circuit 100 according to an embodiment of the present disclosure. Thetransistor switching circuit 110 includes a transistor M1 and a transistor M2, and a source of the transistor M1 is coupled to a source of the transistor M2. A drain of the transistor M1 and a drain of the transistor M2 are coupled to thelatch circuit 150. The source of the transistor M1 and the source of the transistor M2 are also coupled and grounded through a switching transistor M5. Herein, the switching transistor M5 is controlled by the clock pulse signal CK. - The
resistor circuit 120 includes a resistor R1 and a resistor R2. A first end of the resistor R1 is coupled to a first input end of thecomparator circuit 100, and a second end of the resistor R1 is coupled to a gate of the transistor M1. A first end of the resistor R2 is coupled to a second input end of thecomparator circuit 100, and a second end of the resistor R2 is coupled to a gate of the transistor M2. - In some embodiments, parasitic capacitors exist at the gates of the transistor M1 and the transistor M2, and the parasitic capacitors may form equivalent low-pass filters with the corresponding resistor R1 and resistor R2 respectively to further reduce the overall speed of the
comparator circuit 100. In order to solve this problem, thecoupling circuit 160 is connected in parallel with theresistor circuit 120, and, that is, a capacitor C1 is connected in parallel with the resistor R1, and a capacitor C2 is connected in parallel with the resistor R2. Herein, the capacitor C1 and the capacitor C2 couple the input voltage Vip and the input voltage Vin to the gates of the transistor M1 and the transistor M2 respectively. Therefore, influence of the parasitic capacitors of the transistor M1 and the transistor M2 on the speed of thecomparator circuit 100 is further eliminated. - The
latch circuit 150 includes a transistor cross-coupled pair. The transistor cross-coupled pair includes two cross-coupled transistors (for example, a transistor M3 and a transistor M4). A drain of the transistor M3 is coupled to the drain of the transistor M1 and a second output end of the comparator circuit. A drain of the transistor M4 is coupled to the drain of the transistor M2 and a first output end of thecomparator circuit 100. A source of the transistor M3 and a source of the transistor M4 are coupled to a power supply VDD. A switching transistor M7 is connected in parallel between the source and the drain of the transistor M3, and a switching transistor M8 is connected in parallel between the source and the drain of the transistor M4. Herein, the switching transistors M7 and M8 are controlled by the clock pulse signal CK. - When the
comparator circuit 100 executes the comparison operation, the first end of the resistor R1 receives the input voltage Vip, and the second end of the resistor R1 receives the current Irn from thecurrent source circuit 130 or drains the current Irn from thecurrent source circuit 130. Similarly, the first end of the resistor R2 receives the input voltage Vin, and the second end of the resistor R2 receives the current Irp from thecurrent source circuit 130 or drains the current Irp from thecurrent source circuit 130. Then, the transistor M1 and the transistor M2 form the thermometer codes Dn and Dp according to a level control voltage Vcp and a level control voltage Vcn. Furthermore, if resistances of the resistors R1 and R2 are R, respectively, when Vip−Vin>(Irp−Irn)*R, the thermometer code Dp is 1 and the thermometer code Dn is 0; and correspondingly, when Vip−Vin<(Irp−Irn)*R, the thermometer code Dp is 0 and the thermometer code Dn is 1. Herein, (Irp−Irn)*R may be considered as the reference voltage. Then, thelatch circuit 150 outputs the thermometer codes Dn and Dp from the second output end and the first output end of the comparator circuit, respectively, according to the clock pulse signal CK. - In some embodiments, the constant
current source circuit 131 includes two constantcurrent sources current source 131 a is coupled to the second end of the resistor R1, and is configured to provide the current Irn. The constantcurrent source 131 b is coupled to the second end of the resistor R2, and is configured to provide the current Irp. - In an embodiment, the adjustable
current source circuit 132 may include two groups of adjustablecurrent sources current source 132 a is coupled to the second end of the resistor R1, and is configured to provide the current Ion. The adjustablecurrent source 132 b is coupled to the second end of the resistor R2, and is configured to provide the current Top. The currents Ion and Iop and the resistance of the resistors R1 and R2 may be combined to achieve the calibration voltage to eliminate the voltage offset caused by a factor such as internal circuit mismatch. Herein, the currents Ion and Iop provided by the adjustablecurrent sources FIG. 1 ). - In an embodiment, the regulation
current source circuit 180 may include two groups of regulationcurrent sources current source 180 a is coupled to the second end of the resistor R1, the regulationcurrent source 180 b is coupled to the second end of the resistor R2, and the regulationcurrent sources - In some embodiments, the
comparator circuit 100 may also compare a single-ended input voltage and the reference voltage. For example, the input voltage Vip is considered as a single-ended input voltage, the reference voltage is generated by use of the constantcurrent source 131 a and the resistor R1, and the thermometer code Dn is considered as the comparison result. - In some embodiments, the
comparator circuit 100 may be applied to a flash ADC. Referring toFIG. 4 , the flash ADC may include the comparator circuit of any above-mentioned embodiment and adecoder 20. An output end of the comparator circuit is coupled to thedecoder 20. - The comparator circuit includes at least a
transistor switching circuit 110, aresistor circuit 120 and a constantcurrent source circuit 131. Configurations and operations of these circuits are substantially the same as those described above and thus is not elaborated. Thedecoder 20 implements conversion from thermometer codes Dp and Dn into a digital signal A0, i.e., a digital signal A0 in a binary form. - Based on the above, output capacitance of the output end of a comparison stage can be lower by adopting the comparator circuit, comparison method and flash ADC of the present disclosure, so that the overall speed may be relatively improved.
Claims (20)
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CN102957430B (en) * | 2011-08-26 | 2016-06-01 | 比亚迪股份有限公司 | A kind of analog to digital conversion circuit |
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TWI646767B (en) * | 2017-05-22 | 2019-01-01 | 偉詮電子股份有限公司 | Power control device and power control system |
CN107733433B (en) * | 2017-11-13 | 2024-02-20 | 四川易冲科技有限公司 | Current source calibration device and method |
TWI635702B (en) * | 2017-11-23 | 2018-09-11 | 晶豪科技股份有限公司 | Compensation circuit for input voltage offset of error amplifier |
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US7777467B2 (en) * | 2006-11-21 | 2010-08-17 | Ricoh Company, Ltd. | Voltage rising/falling type switching regulator and operation control method thereof |
US10531036B2 (en) * | 2014-07-15 | 2020-01-07 | Sony Corporation | Comparator circuit, solid-state imaging apparatus, and electronic device |
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