CN101515795B - High accuracy switching capacitance circuit based on comparator - Google Patents
High accuracy switching capacitance circuit based on comparator Download PDFInfo
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- CN101515795B CN101515795B CN2009100974402A CN200910097440A CN101515795B CN 101515795 B CN101515795 B CN 101515795B CN 2009100974402 A CN2009100974402 A CN 2009100974402A CN 200910097440 A CN200910097440 A CN 200910097440A CN 101515795 B CN101515795 B CN 101515795B
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- comparator
- capacitor
- electric capacity
- extreme
- capacitance
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Abstract
The invention discloses a high accuracy switching capacitance circuit based on a comparator, comprising a first capacitance with a first extremity and a second extremity for sampling, a comparator with a first input end connected with the second extremity of the first capacitance and a second input end, a charge pump controlled by the output of the comparator, a second capacitance with two ends connected with the output end of the charge pump and the second extremity of the first capacitance respectively, a third capacitance with a first extremity and a second extremity, wherein the second extremity of the third capacitance is connected with the first extremity of the first capacitance, the first extremity of the third capacitance is connected with the second input end of the comparator or in the same potential with the second input end of the comparator. The circuit in the invention reduces the error charge, improves the processing precision of the switching capacitance circuit based on comparator and enhances the application range of switching capacitance circuit based on comparator.
Description
Technical field
The present invention relates to the switched-capacitor circuit field, particularly a kind of high accuracy switching capacitance circuit based on comparator.
Background technology
Switched-capacitor circuit is widely used in the various electronic signal process system, like filter, and data converter, sensor network etc.
As shown in Figure 4, comprise based on traditional switched-capacitor circuit of comparator: a comparator, charge pump and three electric capacity of comparator output control.C
1, C
2, C
LBe electric capacity.V
CMIt is common-mode voltage.Current source I
1, I
2The composition charge pump (Charge Pump, CP).A work period of circuit comprises two non-overlapped phase places: sampling phase (
), translate phase (
).At sampling phase (
), input signal is sampled by sampling capacitance.At translate phase (
); Sampled signal on the sampling capacitance; Through using the charge pump of being controlled by comparator output, be switched on the another one electric capacity.Because there is certain time delay in comparator, there is error in traditional switched-capacitor circuit output, so its processing accuracy is not high.
Sampling phase (
), input voltage V
InBy capacitor C
1Sampling.Sampling phase (
) when finishing, C
1On storing certain electric charge.
Ensuing translate phase (
), V
XAnd output voltage V
OWaveform as shown in Figure 5.
Translate phase (
), from t
1Begin to t
5Finish.
(1) at t
1To t
2Constantly, a reset signal (P) is passed through V
OWith V
SSConnect, to capacitor C
LZero clearing resets.Make V simultaneously
X＜V
CM
(2) at t
2To t
3Constantly, at V
X＜V
CMThe time, current source I
1To by C
L, C
1, C
2The capacitance network charging of forming makes V
O, V
XVoltage rises with certain slope.In case comparator detects V
X=V
CM, current source I
1Close.But, because comparator is detecting V
X=V
CMWith turn off current source I
1Between have certain time delay, so V
O, V
XVoltage can overshoot, makes V
X＞V
CM
(3) at t
3To t
4Constantly, at V
X＞V
CMThe time, current source I
2To by C
L, C
1, C
2The capacitance network discharge of forming.Because current source I is set
2Much smaller than I
1So, V
O, V
XVoltage descends with slow slope.In case comparator detects V
X=V
CM, current source I
2Close.But, because comparator is detecting V
X=V
CMWith turn off current source I
2Between have certain time delay, make V
O, V
XVoltage has overshoot, makes V
X＜V
CMSuppose that comparator is detecting V
X=V
CMAnd having time-delay τ between the turn off current source, this moment, switched-capacitor circuit was at output point V so
OError electric charge Δ Q
(prior art)For:
(4) at t
4To t
5Constantly, current source I
2, I
1Close.Capacitor C
L, C
1, C
2On electric charge remain unchanged.So far, whole translate phase (
) finishes.
Because comparator exists time-delay, the output V of switched-capacitor circuit
OHave overshoot, this error electric charge is relevant with the time-delay of comparator, thereby has influenced the precision of switched-capacitor circuit, and then has limited its utilization scope.
In various electronic signal process system, precision is had higher requirements, thereby improve the precision of switched-capacitor circuit, the performance for improving various electronic signal process system has great significance.
Summary of the invention
The present invention provides a kind of high accuracy switching capacitance circuit based on comparator, and in translate phase, electric capacity of extra introducing makes the precision of switched-capacitor circuit be improved.
A kind of high accuracy switching capacitance circuit based on comparator comprises:
It is first extreme and second extreme that the 1st electric capacity that is used to sample, the 1st electric capacity have; At the sampling phase of high accuracy switching capacitance circuit, the 1st electric capacity is sampled to input voltage;
The comparator that has the first input end and second input; Wherein second of the 1st electricity extremely links to each other with the first input end of comparator;
Receive the charge pump of comparator output control; In the translate phase of high accuracy switching capacitance circuit, the sampled signal of storing on the 1st electric capacity is transformed on the 2nd electric capacity through using charge pump;
The 2nd electric capacity, a termination charge pump output of the 2nd electric capacity, another termination the 1st electric capacity of the 2nd electric capacity second extreme;
Be provided with the 3rd electric capacity; It is first extreme and second extreme that the 3rd electric capacity has; The second extreme switch (K that passes through of the 3rd electric capacity
1) extremely be connected with first of the 1st electric capacity, first of the 3rd electric capacity extremely inserts comparator second input or keeps same potential with comparator second input;
Switch (K
1) break off at the sampling phase based on the high accuracy capacitive circuit of comparator, closed in translate phase based on the high accuracy capacitive circuit of comparator.
Circuit of the present invention is compared traditional switched-capacitor circuit and has been reduced the error electric charge, has improved the precision of its signal processing, has enlarged the utilization scope of switched-capacitor circuit.
Description of drawings
Fig. 1 is the structural representation of a kind of high accuracy switching capacitance circuit based on comparator of the present invention;
Fig. 2 is the oscillogram of high accuracy switching capacitance circuit when translate phase that the present invention is based on comparator;
Fig. 3 is based on the structural representation of the high-precision difference switched-capacitor circuit of comparator;
Fig. 4 is based on the conventional switch condenser network structural representation of comparator;
Fig. 5 is based on the waveform sketch map of conventional switch condenser network when translate phase of comparator.
Embodiment
A kind of high accuracy switching capacitance circuit of the present invention based on comparator, as shown in Figure 1, this circuit comprises:
The 1st capacitor C that is used to sample
1, the 1st capacitor C
1Have first extreme and second extreme; At the sampling phase of high accuracy switching capacitance circuit, the 1st capacitor C
1Input voltage is sampled;
The comparator 130 that has the first input end and second input; The 1st capacitor C wherein
1Second extremely link to each other with the first input end of comparator (130);
Receive the charge pump 140 of comparator output control, charge pump is by current source I
1, I
2Form current source I
1Voltage be V
DD, current source I
2Voltage be V
SSIn the translate phase of high accuracy switching capacitance circuit, the 1st capacitor C
1The sampled signal of last storage is transformed into the 2nd capacitor C through using charge pump 140
2On;
Two ends are connected to charge pump output and the 1st capacitor C respectively
1Second extreme the 2nd capacitor C
2, the 2nd capacitor C wherein
2First extremely connect the charge pump output, the 2nd capacitor C
2Second extremely connect the 1st capacitor C
1Second extreme;
Be provided with the 3rd capacitor C
3The 3rd capacitor C
3Have first extreme and second extreme; The 3rd capacitor C
3Second extremely pass through K switch
1With the 1st capacitor C
1First extremely connect the 3rd capacitor C
3First extreme insert comparator 130 second inputs or keep same potential with comparator 130 second inputs, described same potential is common-mode voltage V
CMThe 1st capacitor C
1Second extreme or the 2nd capacitor C
2First extreme be comparison point V
X
The 2nd capacitor C
2The first extreme or charge pump output be signal output point V
OK switch
1Sampling phase at described switched-capacitor circuit breaks off, and is closed in the translate phase of described switched-capacitor circuit.The 1st capacitor C in implementation process
1With the 4th capacitor C
LBig or small value equate and be the 3rd capacitor C
310 times, the 4th capacitor C
LSize get the 1st capacitor C
15 times.
At sampling phase
Input voltage V
InBy the 1st capacitor C
1Sampling.At sampling phase
During end, the 1st capacitor C
1On stored certain electric charge.
Sampling phase enters into translate phase after finishing
As shown in Figure 2 in the translate phase oscillogram, translate phase
From t
1Begin to t
5Finish.
(1) at t
1To t
2Constantly, switch S is closed, K switch
1Closure, the 4th capacitor C
LFirst extremely meet common-mode voltage V
CM, a reset signal (P) is passed through signal output point V
OWith V
SSConnect, to the 4th capacitor C
LZero clearing resets.Make V simultaneously
X＜V
CM
(2) at t
2To t
3Constantly, at V
X＜V
CMThe time, current source I
1To by the 4th capacitor C
L, the 1st capacitor C
1, the 2nd capacitor C
2, the 3rd capacitor C
3The capacitance network charging of forming makes V
O, V
XVoltage rises with certain slope.In case comparator 130 detects V
X=V
CM, current source I
1Close.But, because comparator is detecting V
X=V
CMWith turn off current source I
1Between have certain time delay, so V
O, V
XVoltage has overshoot, makes V
X＞V
CM
(3) at t
3To t
4Constantly, at V
X＞V
CMThe time, current source I
2To by the 4th capacitor C
L, the 1st capacitor C
1, the 2nd capacitor C
2, the 3rd capacitor C
3The capacitance network discharge of forming.Because current source I is set
2Much smaller than I
1, make V
O, V
XVoltage descends with slow slope.In case comparator detects V
X=V
CM, current source I
2Close.But, because comparator is detecting V
X=V
CMWith turn off current source I
2Between have certain time delay, so V
O, V
XVoltage can overshoot, makes V
X＜V
CM, the actual signal output valve b of circuit of the present invention is less than desirable signal value output a, and the signal value output c of traditional switched-capacitor circuit based on comparator is littler than actual signal output valve b of the present invention, and error is bigger.At this moment, V
XThere is error voltage in point, is expressed as V
ErrorTherefore, the 1st capacitor C
1On error voltage C is arranged
3V
Error/ (C
1+ C
3), the 3rd capacitor C
3On error electric charge C is arranged
1V
Error/ (C
1+ C
3).But, because at sampling phase
The 3rd capacitor C
3Last error electric charge remains unchanged, so in next translate phase
In the time of beginning and end, the 3rd capacitor C
3Last voltage is the C that remains unchanged
1V
Error/ (C
1+ C
3).So the 3rd capacitor C
3Not to output V
OProduce error, make the 1st capacitor C simultaneously
1To output V
OThe error that produces reduces, and has improved the precision of switched-capacitor circuit.If comparator is detecting V
X=V
CMAnd having time-delay τ between the turn off current source, this moment, switched-capacitor circuit was to signal output point V so
OError electric charge Δ Q
(the invention)For:
(4) at t
4To t
5Constantly, switch S is broken off, current source I
2With current source I
1Close the 1st capacitor C
1, the 2nd capacitor C
2, the 3rd capacitor C
3, the 4th capacitor C
LElectric charge remain unchanged.So far, whole translate phase
finishes.
Though there is certain time delay in comparator, capacitor C of extra introducing
3Make the error voltage of circuit reduce, thereby make the precision based on the switched-capacitor circuit of comparator be improved.The error charge ratio traditional circuit of circuit of the present invention and control method is little, has improved the precision of its signal processing.
Wherein, Δ Q
(the invention)Be the error electric charge of the high accuracy switching capacitance circuit that the present invention is based on comparator, Δ Q
(prior art)Be error electric charge based on the conventional switch condenser network of comparator.
This shows that in the present invention, the error electric charge has been reduced one 1 the factor
See from the computing formula of error reduction ratio F of the present invention, because
So F is always less than 1, the high accuracy switching capacitance circuit that therefore the present invention is based on comparator is compared traditional switched-capacitor circuit error and is always being reduced.Along with the 3rd capacitor C
3Reduce, the F value is also reducing, error is reducing.
In integrated circuit technology, the accurate coupling of two electric capacity can be merely able to reach 1/20 at most.So under the actual conditions, the 1st capacitor C
1, the 2nd capacitor C
2, the 3rd capacitor C
3, the 4th capacitor C
LBig or small ratio satisfied at most: C
1=C
2=C
L=20C
3, the F minimum value is 0.13.So in actual process, F changes between 1 to 0.13.But, if C in the ideal case
3Can accomplish infinitely smallly, error has just all been eliminated so.
Another embodiment of the present invention is a kind of high-precision difference switched-capacitor circuit based on comparator.As shown in Figure 3, a kind of high-precision difference switched-capacitor circuit based on comparator comprises:
The 1st capacitor C that is used to sample
1+With mirror image the 1st capacitor C
1-, the 1st capacitor C
1+With mirror image the 1st capacitor C
1-Have first extreme and second extreme respectively;
The comparator 230 that has the first input end and second input, wherein the 1st capacitor C
1+Second extremely link to each other mirror image the 1st capacitor C with the first input end of comparator 230
1-Second extremely link to each other with second input of comparator 230;
Receive the charge pump 240 of comparator output control;
Two ends are connected to charge pump output and the 1st capacitor C respectively
1+Second extreme the 2nd capacitor C
2+Two ends are connected to charge pump output and mirror image the 1st capacitor C respectively
1-Second extreme mirror image the 2nd capacitor C
2-
Be provided with the 3rd capacitor C
3+, the 3rd capacitor C
3+Have first extreme and second extreme; The 3rd capacitor C
3+Second extreme through the 1st K switch
1With the 1st capacitor C
1+First extremely connect the 3rd capacitor C
3+The first extreme common-mode voltage V that inserts
CM
Be provided with mirror image the 3rd capacitor C
3-, mirror image the 3rd capacitor C
3-Have first extreme and second extreme; Mirror image the 3rd capacitor C
3-Second extreme through the 2nd K switch
2With mirror image the 1st capacitor C
1-First extremely connect mirror image the 3rd capacitor C
3-The first extreme common-mode voltage V that inserts
CM
The 1st K switch
1With the 2nd K switch
2Sampling phase at the differential switch condenser network breaks off, and is closed in the translate phase of described switched-capacitor circuit.
High-precision difference switched-capacitor circuit based on comparator is as shown in Figure 5 in the oscillogram of translate phase; E is desirable signal value output; F is actual signal value output, and the differential switch condenser network error based on comparator that the error ratio of the signal value output of reality of the present invention is traditional is little.
The precision of differential switch condenser network is improved, thereby has enlarged the differential switch condenser network scope of application based on comparator.
Claims (2)
1. switched-capacitor circuit based on comparator comprises:
The 1st electric capacity (C that is used to sample
1), the 1st electric capacity (C
1) have first extreme and second extreme;
The comparator (130) that has the first input end and second input, wherein the 1st electric capacity (C
1) second extremely link to each other with the first input end of comparator (130);
Receive the charge pump (140) of comparator output control;
Two ends are connected to charge pump output and the 1st electric capacity (C respectively
1) second extreme the 2nd electric capacity (C
2);
It is characterized in that, be provided with the 3rd electric capacity (C
3), the 3rd electric capacity (C
3) have first extreme and second extreme; The 3rd electric capacity (C
3) second extreme through switch (K
1) and the 1st electric capacity (C
1) first extremely connect the 3rd electric capacity (C
3) first extreme insert comparator (130) second inputs or keep same potential with comparator (130) second inputs;
Switch (K
1) break off at the sampling phase of described switched-capacitor circuit, closed in the translate phase of described switched-capacitor circuit.
2. the switched-capacitor circuit based on comparator as claimed in claim 1 is characterized in that, the 1st electric capacity (C
1) and the 2nd electric capacity (C
2) equal and opposite in direction and be the 3rd electric capacity (C
3) 20 times of size.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009100974402A CN101515795B (en) | 2009-04-02 | 2009-04-02 | High accuracy switching capacitance circuit based on comparator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009100974402A CN101515795B (en) | 2009-04-02 | 2009-04-02 | High accuracy switching capacitance circuit based on comparator |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101515795A CN101515795A (en) | 2009-08-26 |
| CN101515795B true CN101515795B (en) | 2012-03-28 |
Family
ID=41040116
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2009100974402A Expired - Fee Related CN101515795B (en) | 2009-04-02 | 2009-04-02 | High accuracy switching capacitance circuit based on comparator |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN101515795B (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101051839A (en) * | 2006-03-29 | 2007-10-10 | 瑞昱半导体股份有限公司 | Error reducing switch capacitor circuit and method thereof |
| CN101051832A (en) * | 2006-03-29 | 2007-10-10 | 瑞昱半导体股份有限公司 | Error averaging switch capacitor circuit and method thereof |
-
2009
- 2009-04-02 CN CN2009100974402A patent/CN101515795B/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101051839A (en) * | 2006-03-29 | 2007-10-10 | 瑞昱半导体股份有限公司 | Error reducing switch capacitor circuit and method thereof |
| CN101051832A (en) * | 2006-03-29 | 2007-10-10 | 瑞昱半导体股份有限公司 | Error averaging switch capacitor circuit and method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| CN101515795A (en) | 2009-08-26 |
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Granted publication date: 20120328 Termination date: 20160402 |
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