Input Current Compensation during Current Measurement

摘要

A current measurement circuit may include unbuffered inputs, and the current may be sampled directly from the input pins. The input current created from each sample may be cancelled by injecting opposite charge on the subsequent sample. This direct sampling from the pins increases the common mode input range of the sense path without having to build high linearity rail-to-rail input buffers, hence lowering cost and power consumption of the current measurement path. It also allows for high-impedance input sampling. The measurement circuit may include multiple sampling stages, with a first sampling stage implemented as a switched-capacitor based circuit. A compensator circuit coupled in a feedback loop from the output of the first sampling stage to the input pins may be operated to provide the equivalent charge back to the input pins every cycle to cancel the input current required to charge the sampling capacitors of the first sampling stage.

主权项

1. A method for input current compensation during current measurements, the method comprising:
sampling a current sense signal derived from a current at an input during a first sampling cycle, comprising drawing a first amount of charge from the input; and injecting a second amount of charge back into the input according to the drawn first amount of charge during a second sampling cycle subsequent to the first sampling cycle.