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.

[1]  Kofi A. A. Makinwa,et al.  A Current-Feedback Instrumentation Amplifier with 5μV Offset for Bidirectional High-Side Current-Sensing , 2008, 2008 IEEE International Solid-State Circuits Conference - Digest of Technical Papers.

[2]  F. Fiori.  Design of an Operational Amplifier Input Stage Immune to EMI , 2007, IEEE Transactions on Electromagnetic Compatibility.

[3]  Henry Ott,et al.  Electromagnetic Compatibility Engineering , 2009 .

[4]  M. Steyaert,et al.  A CMOS source-buffered differential input stage with high EMI suppression , 2008, ESSCIRC 2008 - 34th European Solid-State Circuits Conference.

[5]  Franco Fiori.  Susceptibility of chopper OpAmps to EMI , 2015, 2015 IEEE International Symposium on Electromagnetic Compatibility (EMC).

[6]  Jean-Michel Redoute,et al.  A fundamental approach to EMI resistant folded cascode operational amplifier design , 2013, 2013 International Symposium on Electromagnetic Compatibility.

[7]  K. Makinwa,et al.  A Current-Feedback Instrumentation Amplifier With 5 $\mu{\hbox{V}}$ Offset for Bidirectional High-Side Current-Sensing , 2008, IEEE Journal of Solid-State Circuits.