CN202889330U - Front-end circuit of ADC used for current input - Google Patents
Front-end circuit of ADC used for current input Download PDFInfo
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- CN202889330U CN202889330U CN 201220472317 CN201220472317U CN202889330U CN 202889330 U CN202889330 U CN 202889330U CN 201220472317 CN201220472317 CN 201220472317 CN 201220472317 U CN201220472317 U CN 201220472317U CN 202889330 U CN202889330 U CN 202889330U
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- integrator
- adc
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- discharge
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Abstract
The utility model discloses a front-end circuit of an ADC used for current input. An integrator is disposed between the ADC and a current input end. The integrator has integrating capacitor. Especially, the front-end circuit based on the integrator also comprises an overcurrent discharge circuit of a detection module and a discharge module, wherein the detection module is at least a voltage comparater. An input end of the detection module is connected with a voltage output end V1 of the integrator, and the other input end is a threshold voltage Vthr of the integrator. The discharge module at least comprises a discharging capacitor Cdis, and a plate electrode on a side of the discharging capacitor Cdis is connected with a positive plate X1 of the integrating capacitor. A plate electrode on the other side is connected with a reference voltage end. Discharge voltage Vf in the circuit is Vf=[delta]VxCdis/Cint, wherein the [delta]V is voltage drop of the reference voltage end. The front-end circuit obviously improves an input dynamic range of current input the ADC under capacity limitation of the integrator, and solves stress of taking space in a chip caused by expansion of the integrator. The front-end circuit provides an effective solution for a design of connecting the ADC after simplification.
Description
Technical field
The utility model relates to a kind of integrated circuit (IC) design, relates in particular to a kind of front end circuit design of the current input adc for photodiode sensor, x-ray detector or CT scan system etc.
Background technology
In integrated circuit (IC) design, when the input of ADC is electric current, need to change into voltage to electric current with integrator, and when the electric current of input with when the duration, product was excessive, can make integrator saturated.Can address this problem and strengthen integrating capacitor, but strengthening integrating capacitor has two shortcomings: on the one hand, large electric capacity in IC, the area that can cost a lot of money; On the other hand, large electric capacity also can limit the speed of integrator.
As shown in Figure 1, be the configuration diagram of conventional current input ADC.Be exactly the integrator that an electric current turns voltage between electric current input Iin and the ADC wherein.This integrator includes an integrating capacitor Cint and three Resetting Switching PH1～PH3 that are used for control integration/three phase place break-makes of sampling.The voltage that integrator is sent can be as the input of back segment ADC.The output voltage of this integrator is determined by input current, the time of integration and integrating capacitor, and input current and the time of integration are determined by system and application.So normally control the integrator degree of unsaturation by the value of regulating Cint.But adopt larger integrating capacitor Cint need to pay large chip area and the cost that underspeeds.
The utility model content
Defective in view of above-mentioned prior art, the utility model aims to provide a kind of front-end circuit for current input adc, the ADC Front-end Design that surpasses the saturation voltage scope of integrator mainly for input current and integration period, solve in the situation that do not strengthen integrating capacitor on the one hand, can support large electric current input, also can finish on the other hand the conversion of high several bit of ADC, thereby connect the design of ADC after simplifying.
For realizing above-mentioned the purpose of this utility model, its technical solution is: the front-end circuit that is used for current input adc, be provided with an integrator that is used for electric current is changed into voltage between described ADC and the current input terminal Iin, described integrator has integrating capacitor Cint and is used for the Resetting Switching PH1～PH3 of control integration/three phase place break-makes of sampling, it is characterized in that: described front-end circuit is for comprising the two-part overcurrent discharge circuit of detection module and discharge module, wherein said detection module is at least a voltage comparator, an input of detection module is connected to the voltage output end V1 of integrator, another input is the threshold voltage Vthr of integrator, described discharge module comprises a discharge capacity Cdis at least, the battery lead plate of discharge capacity Cdis one side is connected to the positive plate X1 of integrating capacitor, the battery lead plate of opposite side is connected to reference voltage end, the discharge voltage of described overcurrent discharge circuit satisfies: discharge voltage Vf=△ V*Cdis/Cint, wherein △ V is the pressure drop of reference voltage end.
Further, the output negate of described voltage comparator is connected to a counter, and described counter is used for the discharge time binary system in the integration period is converted into the high Mbit of ADC output.
Further, be provided with sampling between described ADC and the front-end circuit and keep capacitor C _ samp.
The application of technical solutions of the utility model, the remarkable advantage that its front-end circuit that compares to traditional ADC has is presented as: significantly improved the input dynamic range of current input adc under the integrator capacity limit, solved the pressure that the integrator dilatation occupies the chip inner area; Can also finish simultaneously the high bit conversion of ADC, for the design that meets ADC after simplifying provides effective solution.
Description of drawings
Fig. 1 is the configuration diagram of conventional current input ADC Front-end Design.
Fig. 2 is the configuration diagram of the utility model current input adc new front design.
Embodiment
Following constipation closes the embodiment accompanying drawing, embodiment of the present utility model is described in further detail, so that technical solutions of the utility model are easier to understand, grasp.
As shown in Figure 2, the utility model front-end circuit is on the framework basis of conventional current input ADC Front-end Design, increased an overcurrent discharge circuit, this circuit can be by the detection to integrator output voltage, when integrator output will surpass threshold voltage Vthr, can discharge to the left pole plate of integrating capacitor, thereby make integrator can not surpass normal range of operation.Wherein threshold voltage Vthr is the default thresholding that integrator discharges.This overcurrent discharge circuit comprises detection module and discharge module two parts, wherein detection module is at least a voltage comparator, the input of voltage comparator CMP is connected to the voltage output end V1 of integrator, another input is the threshold voltage Vthr of integrator, and voltage comparator CMP output one detects decision content.Again discharge module its comprise at least a discharge capacity Cdis, the battery lead plate of discharge capacity Cdis one side is connected to the positive plate X1 of integrating capacitor, the battery lead plate of opposite side is connected to reference voltage end.This reference voltage end has reference voltage V2, V3, and the each discharge voltage of discharge module determined by reference voltage V2, V3 and discharge capacity Cdis, and its relational expression satisfies: Vf=△ V*Cdis/Cint.Wherein △ V(is V2-V3) be that the pressure drop of reference voltage end, Cdis/Cint are the amount of capacity ratio of discharge capacity and integrating capacitor.In the diagram, voltage comparator CMP has an output EN, and the output behind inverter is ENB.
According to the testing result of voltage comparator CMP, change the signal condition of output EN and negate output ENB thereof, implement discharge with this discharge capacity Cdis that drives discharge module.Realize the high dynamic range design of ADC front end with this.
As shown in Figure 2, the output that can also see voltage comparator also negate is connected to a counter Counter, and this counter is used for the discharge time binary system in the integration period is converted into the high Mbit of ADC output.And remainder can be delivered to ADC, if ADC is Nbit, that final output is exactly (M+N) bit.Thereby for the design that meets ADC after simplifying provides effective solution.
Describe as seen by above example about circuit structure and function realization, use front end circuit design of the present utility model, under the integrator capacity limit, significantly improve the input dynamic range of current input adc, solved the pressure that the integrator dilatation occupies the chip inner area.
Claims (3)
1. the front-end circuit that is used for current input adc, be provided with an integrator that is used for electric current is changed into voltage between described ADC and the current input terminal Iin, described integrator has integrating capacitor Cint and is used for the Resetting Switching PH1～PH3 of control integration/three phase place break-makes of sampling, it is characterized in that: described front-end circuit is for comprising the two-part overcurrent discharge circuit of detection module and discharge module, wherein said detection module is at least a voltage comparator, an input of detection module is connected to the voltage output end V1 of integrator, another input is the threshold voltage Vthr of integrator, described discharge module comprises a discharge capacity Cdis at least, the battery lead plate of discharge capacity Cdis one side is connected to the positive plate X1 of integrating capacitor, the battery lead plate of opposite side is connected to reference voltage end, the discharge voltage of described overcurrent discharge circuit satisfies: discharge voltage Vf=△ V*Cdis/Cint, wherein △ V is the pressure drop of reference voltage end.
2. the front-end circuit for current input adc as claimed in claim 1, it is characterized in that: the output negate of described voltage comparator is connected to a counter, and described counter is used for the discharge time binary system in the integration period is converted into the high Mbit of ADC output.
3. the front-end circuit for current input adc as claimed in claim 1 is characterized in that: be provided with sampling between described ADC and the front-end circuit and keep capacitor C _ samp.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220472317 CN202889330U (en) | 2012-09-17 | 2012-09-17 | Front-end circuit of ADC used for current input |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220472317 CN202889330U (en) | 2012-09-17 | 2012-09-17 | Front-end circuit of ADC used for current input |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN202889330U true CN202889330U (en) | 2013-04-17 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 201220472317 Withdrawn - After Issue CN202889330U (en) | 2012-09-17 | 2012-09-17 | Front-end circuit of ADC used for current input |
Country Status (1)
| Country | Link |
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| CN (1) | CN202889330U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102832940A (en) * | 2012-09-17 | 2012-12-19 | 江苏国石半导体有限公司 | Front-end circuit for current input ADC (Analog to Digital Converter) |
-
2012
- 2012-09-17 CN CN 201220472317 patent/CN202889330U/en not_active Withdrawn - After Issue
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102832940A (en) * | 2012-09-17 | 2012-12-19 | 江苏国石半导体有限公司 | Front-end circuit for current input ADC (Analog to Digital Converter) |
| CN102832940B (en) * | 2012-09-17 | 2015-05-06 | 江苏国石半导体有限公司 | Front-end circuit for current input ADC (Analog to Digital Converter) |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| AV01 | Patent right actively abandoned |
Granted publication date: 20130417 Effective date of abandoning: 20150506 |
|
| RGAV | Abandon patent right to avoid regrant |