Volker Strutz

A miniature digital current sensor with differential Hall probes using enhanced chopping techniques and mechanical stress compensation

A 10kHz bandwidth 50Amax current sensor using a Hall effect gradiometer without magnetic core provides 80kHz update rate with a digital interface. Very low un-calibrated offset of 30mA (1σ) and after calibration typical 10mA over temperature is accomplished by a chopped multi-bit feedback continuous-time 3rd order ΔΣ-ADC. This also realizes low noise of 13mArms in 1kHz signal bandwidth. The ADC uses enhanced chopping techniques and additional digital feedback loops to avoid chopper ripple. New analog and digital stress-compensation circuits with lateral and vertical n-doped resistors achieve lifetime gain drifts below 1% and temperature compensation. Auto-zeroing ping-pong comparators offer a fast over-current detection of 1...2μs on a dedicated output pin. The monolithic integrated sensor chip and the 4kV galvanic isolated current rail fit into a very small 7×7×1mm3 package.