A mixed-signal ASIC in CMOS technology for industrial AC current sensing with galvanic isolation

Numerous industrial applications such as power control or automotive appliances require low cost and reduced-size current measurement systems. Measuring current with galvanic isolation mainly rhymes with sensing the magnetic field produced by this current. However, integrated on the same substrate the sensing device together with its conditioning electronics is challenging. This paper presents an alternative to conventional current transformer widely used for industrial range current sensing. It proposes a low cost mixed-signal ASIC in CMOS technology for 5A nominal AC current measurement with 5kV galvanic isolation and 0.5% accuracy over 1.5kHz bandwidth, which allows up to 30th (25th) harmonic detection in 50Hz (60Hz) applications. It features an AC current sensing front-end based on Hall effect devices with its self-balancing differential analog signal conditioning. First, the current measurement principle and the resulting ASIC architecture are discussed. Then, the embedded self-balancing control unit achieving the auto-balancing sequence is detailed and functional simulation results using VHDL-AMS language are presented. Finally, the final ASIC prototype is presented with experimental auto-balancing and current measurement results.