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

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.

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...

AI Technical Summary

Problems solved by technology

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

However, the use of a larger integral capacitor Cint needs to pay the price of a large chip area and reduced speed

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