Front-end circuit for current input ADC (Analog to Digital Converter)

A front-end circuit and input terminal technology, applied in the direction of analog-to-digital converters, etc., can solve the problems of limiting the speed of the integrator, reducing the speed, and large chip area, so as to improve the input dynamic range and simplify the design.

CN102832940AActive Publication Date: 2012-12-19江苏国石半导体有限公司
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Publication Date
2012-12-19

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Abstract

The invention discloses a front-end circuit for a current input ADC (Analog to Digital Converter). An integrator is arranged between the ADC and a current input end, and the integrator is provided with an integrating capacitor. Particularly, the front-end circuit based on the integrator also comprises an overcurrent discharge circuit which comprises a detection module and a discharge module, wherein the detection module at least comprises a voltage comparator, one input end of the detection module is connected to a voltage output end V1 of the integrator, the other input end of the detection module is connected with a threshold voltage V(thr) of the integrator, the discharge module at least comprises a discharge capacitor C(dis), an electrode plate at one side of the discharge capacitor C(dis) is connected to a positive plate X1 of the integrating capacitor, one electrode plate at the other side of the discharge capacitor C(dis) is connected to a reference voltage end, and the discharge voltage V(f) in the circuit meets the following formula: V(f)=deltaV*C(dis) / C(int), wherein deltaV is the voltage drop of the reference voltage end. According to the front-end circuit disclosed by the invention, the input dynamic range of the current which is input in the ADC is obviously increased under the limit of the capacity of the integrator, the pressure occupied by the inner area of a chip due to the capacity expansion of the integrator is avoided, and a useful solution is supplied for simplifying a lastly connected ADC design.
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Description

technical field

[0001] The present invention relates to an integrated circuit design, in particular to a front-end circuit design for current input ADCs used in photodiode sensors, X-ray detectors or CT scanning systems. Background technique

[0002] In integrated circuit design, when the input of the ADC is a current, an integrator is needed to convert the current into a voltage, and when the product of the input current and the duration is too large, the integrator will be saturated. Increasing the integral capacitor can solve this problem, but there are two disadvantages of increasing the integral capacitor: on the one hand, a large capacitor will consume a large area in the IC; on the other hand, a large capacitor will also limit the integrator speed.

[0003] Such as figure 1 Shown is a schematic diagram of the architecture of a traditional current-input ADC. The current-to-voltage integrator is between the current input Iin and the ADC. The integrator includes an i...

Examples

Embodiment Construction

[0011] In the following, the specific implementation manners of the present invention will be further described in detail in conjunction with the accompanying drawings of the embodiments, so as to make the technical solution of the present invention easier to understand and grasp.

[0012] Such as figure 2 As shown, the front-end circuit of the present invention is based on the architecture of the traditional current input ADC front-end design, and an overcurrent discharge circuit is added. This circuit will pass the detection of the output voltage of the integrator. When the output of the integrator exceeds the threshold voltage Vthr, Discharges the left plate of the integrating capacitor so that the integrator does not exceed the normal operating range. The threshold voltage Vthr is a preset threshold for the integrator to discharge. The overcurrent discharge circuit includes two parts, a detection module and a discharge module, wherein the detection module is at least one...