0-30 V common mode range, 120 dB CMRR, and 10 nV/{the square root of}(Hz) noise floor current shunt monitor IC with an embedded ΣΔ modulated digital interface

摘要

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 Ω with less than 10 μV input-referred offset, 150 nV/℃ 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 μV. 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 (ΣΔFD) ADC enables a digital interface to processor applications. The CSM is fabricated on a 0.7 μm 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/{the square root of}(Hz) 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.