Susceptibility to EMI of high side current sensors based on chopper OpAmps

Current sensors are usually protected against electromagnetic interference (EMI) by means of filters placed at the PCB level. The literature has plenty of solutions aimed at keeping EMI filters´ attenuation as high as possible in the widest possible frequency range. However such filters are less effective than expected because of the parasitic elements introduced by interconnects. As a consequence, EMI can be propagated into ICs causing temporary or definitive operation failures. This paper points out the causes of EMI-induced errors in high-side current sensors based on low-offset chopper OTAs. Analyses presented in the paper are supported by direct power injection measurements carried out on a test chip.