A Fully Isolated Delta-Sigma ADC for Shunt Based Current Sensing

This paper presents the world’s first reported chip-level 5 kVrms isolated delta-sigma ADC architecture which realizes isolation in both the power and signal domains. The compact IC package contains an integrated isolated power converter which includes an on-chip transformer, oscillator and rectifier, three delta–sigma analog-to-digital converters, a voltage reference, a temperature transducer, on-chip data transformers, and a controller/communication chip. Because it includes all of the isolation units within the same package, no PCB level isolation components are needed. This solution displaces the need for isolation using opto-couplers or costly, bulky and frequency dependent current transformers, and enables lower cost shunt resistor based current sensing applications such as domestic and industrial energy monitoring. It also enables new portable current sensing applications where high voltage isolation is required. The system-in-package (SIP) draws 12.5 mA from a 3.3 V supply and achieves 74.4 dBFS SNDR and 80.8 dBFS SFDR in a bandwidth of 3.3 kHz. It achieves an insulation voltage rating of 400 Vrms continuous and 5 kVrms over a 1 minute duration.