Impedance measurement circuit

A circuit comprising:

• an excitation source coupled between a first input switch and a second input switch;
• a sense circuit coupled to a first set of output switches;
• a calibration resistor coupled to the first input switch at a first excitation terminal;
• and
• an impedance network coupled to the calibration resistor, the second input switch and the first set of output switches.

A method comprising:

• generating an excitation signal;
• providing the excitation signal to a switched resistor network to generate an output signal;
• generating a sense signal in response to the output signal;
• comparing the sense signal with a reference signal to generate a clock signal;
• multiplying the clock signal and the sense signal to generate a rectified signal;
• filtering the rectified signal to generate an averaged signal;
• and
• measuring a body impedance from the averaged signal.

A computing device comprising:

• a processing unit;
• a memory module coupled to the processing unit;
• and
• an impedance measurement circuit coupled to the processing unit and the memory module, the impedance measurement circuit comprising:
• an excitation source configured to generate an excitation signal,
• a switched resistor network coupled to the excitation source, and configured to generate an output signal in response to the excitation signal;
• a sense circuit coupled to the switched resistor network, and configured to generate a sense signal in response to the output signal;
• a comparator coupled to the sense circuit, and configured to generate a clock signal in response to the sense signal;
• a mixer coupled to the sense circuit, and configured to multiply the sense signal and the clock signal to generate a rectified signal;
• a low pass filter coupled to the mixer and configured to filter the rectified signal to generate an averaged signal;
• and
• a processor coupled to the low pass filter and configured to measure a body impedance from the averaged signal.