Current measurement circuit

A high side current measurement circuit, comprising:

• a sense resistor having a resistance R which carries a current I and develops a voltage V across it which varies with I,
• an attenuation network which attenuates said voltage V by a factor Z and provides the attenuated voltage at a pair of outputs,
• a first pair of cross-coupled switches which have respective input terminals and output terminals and which are operated with respective control signals, said input terminals connected to receive said attenuated voltage,
• a second pair of cross-coupled switches which have respective input terminals and output terminals and which are operated with respective control signals,
• a pair of input capacitors, each of which has a capacitance Cin and is connected between a respective one of said output terminals of said first pair of cross-coupled switches and a respective one of said input terminals of said second pair of cross-coupled switches,
• a differential amplifier having inverting and non-inverting inputs and outputs, said inverting and non-inverting inputs connected to respective ones of said output terminals of said second pair of cross-coupled switches,
• a pair of feedback capacitors, each of which has a capacitance Cf, one of which is connected between the inverting output and non-inverting input of said differential amplifier and the other of which is connected between the non-inverting output and inverting input of said differential amplifier,
• a pair of auto-zero switches which are connected across respective ones of said feedback capacitors and which are operated with respective control signals, and
• a control circuit connected to provide said control signals to said first and second pair of cross-coupled switches and said pair of auto-zero switches and arranged to operate said first and second pair of cross-coupled switches in accordance with a switching cycle during which the connections between said first pair of cross-coupled switches and said input capacitors are interchanged, after which the connections between said second pair of cross-coupled switches and said differential amplifier's inputs are interchanged, such that said attenuated voltage is sampled on said input capacitors and transferred to said feedback capacitors to produce a differential output voltage Vout from said differential amplifier given by:
• Vout=Z*N*[(Cin/Cf)*2(I*R)]
• where N is the number of consecutively performed switching cycles, said control circuit further arranged to operate said pair of auto-zero switches to initially discharge said feedback capacitors prior to initiating a first switching cycle.