0-30 V common mode range, 120 dB CMRR, and 10 nV/ noise floor current shunt monitor IC with an embedded I I" pound modulated digital interface
Sensing and controlling current flow is a fundamental requirement for many electronic systems, including power management (DC-DC converters and LDOs), battery chargers, electric vehicles, solenoid positioning, motor control, and power monitoring. Current shunt monitor (CSM) system enables current measurement across an external sense resistor (R (S) ) in series to current flow. Proposed CSM system can sense a system (power supply) current from 1 to 500 mA across a typical board Cu-trace resistance of 1 Omega with less than 10 mu V input-referred offset, 150 nV/A degrees C offset drift and 0.1% accuracy. Instead of using a costly zero-TC sense resistor (R (S) ) that is used in typical CSM systems; proposed method uses existing Cu board trace for sensing. The sense amplifier uses chopper stabilization in the signal chain of the amplifier to suppress input-referred offset down to less than 10 mu V. Switching current-mode (SI) FIR filtering is used at the instrumentation amplifier output to filter out the chopping ripple at the harmonics of the chopping frequency. A frequency domain Sigma Delta (I I"FD) pound ADC enables a digital interface to processor applications. The CSM is fabricated on a 0.7 mu m CMOS process with three levels of metal with maximum Vds tolerance of 8 V, and operates across a common mode range of 0-30 V achieving less than 10 nV/ of flicker noise at 100 Hz. By using a semi-digital SI FIR filter, residual chopper ripple is suppressed by more than 7.5 mV(pp) from the base line of 8 mV(pp), which is equivalent to 25 dB suppression.
power monitoring chopper stabilization instrumentation amplifier current sensor sigma delta (sigma delta) frequency discrimination