A Novel On-Chip Transformer With Patterned Ground Shield for High Common-Mode Transient Immunity Isolated Signal Transfer

Abstract

In this letter, a novel on-chip transformer (OCT) with patterned ground shield (PGS) is proposed and demonstrated for high common-mode transient immunity isolated signal transfer. By inserting the PGS between the stacked coils of the OCT, the capacitive coupling between the coils is effectively blocked, whereas the inductive coupling is almost unaffected. Consequently, during common-mode voltage transient, the induced displacement current due to the capacitive coupling is directed to the ground by the PGS instead of going through the secondary coil to affect the output signal. Experimental results show that the proposed OCT with PGS achieved a 27%–92% reduction of the common mode to secondary voltage gain compared to the conventional OCT without sacrificing the inductances, the primary-to-secondary voltage gain, the isolation capability, and the fabrication complexity.