Analysis of thermal-offset drift of a high-resolution current probe using a planar Hall resistance sensor

Abstract

We developed a pin-type current probe with high sensitivity, targeting electrical-probing printed circuit boards (PCBs). The developed sensor showed good enough characteristics, with 1 mA resolution on current measurements and up to 1 MHz operating frequency for analyzing highly integrated PCBs. During its characterization, however, we experienced a monotonously varying output signal in the time range of a few tens of minutes. We modeled it as the thermal-offset drift, being caused by Joule heating during sensor operation, and showed several solutions for reducing the offset by modifying the planar Hall resistance (PHR) layout and electric operation conditions and applying sensor circuitry with pulse width modulation.