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

Abstract

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 13mA rms in 1kHz signal bandwidth. The ADC uses enhanced chopping techniques and additional digital feedback loops to avoid chopper ripple. New analog and digital stresscompensation 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 7x7x1mm 3 package.

Package Stress Monitor to Compensate for the Piezo-Hall Effect in CMOS Hall Sensors

“…In [12] a method to compensate for the piezo-Hall effect was presented which is based on a calculation in digital integrated circuitry and is therefore not suitable for high speed analog Hall sensors. An analog implementation was presented in [19] capable of compensating only partially for the piezo-Hall effect. However, an additional digital processing is required to fully eliminate the sensitivity drift.…”

“…The active compensation of the piezo-Hall effect by means of electronic circuitry is more recent. A digital compensation approach was presented in [12] which may be combined with a partial analog compensation [19]. Our particular interest is a versatile, 1530-437X/$31.00 © 2013 IEEE independent, and differential stress signal, which may be combined with both digital and high speed analog circuitry.…”

“…The remaining drift may be compensated with the use of an integrated magnetic coil and a self-calibration functionality [15]- [17], at the cost, however, of an additional current consumption for the generation of the reference magnetic field [18]. An alternative is to independently measure the relevant stress components and to perform a subsequent correction of the Hall plate sensitivity [12], [19]. This technique is the subject of this paper.…”

Compensation of Assembly Tolerances in Magnetic Current Sensors with External Conductor

“…The nominal vertical distance between the Halls and the current rail`s middle layer is z Hall =0.25 mm (Table 1). Since the vertical differential magnetic field is measured, the homogeneous portion of the external magnetic disturbances is suppressed [3]. At low frequency for the vertical component of the magnetic field in the test point (x,y,z), assuming x trace =z trace =0 conductor position, and neglecting the effect of the trace thickness, we get: The differential Hall-signal assuming nominal sensor-IC position is given by: field.…”

“…Advanced spinning and Since the sensitivity of Hall-devices is strongly temperature dependent, on-chip temperature compensation is necessary. The chip is typically isolated from the current rail, the potential of which might reach several kV-s [3]. Unlike current sensors with field concentrators, they offer the advantages of reduced cost and size, which are critical factors in the automotive arena, and since lacking all kinds of soft-magnetic cores, they show virtually no hysteresis-effects.…”