A Capacitive Digital Isolator Featuring 160 kV/μs CMTI and 11 ns Delay

Conventional capacitive digital isolators face an inherent trade-off between high-speed operation and robustness against common-mode transient disturbances, as the parasitic coupling capacitance introduces a path for high-frequency common-mode noise. To address this issue, this paper proposes an on-off keying (OOK)-modulated capacitive isolator with a differential-output transmitter and a receiver front-end that combines an active-inductor-loaded preamplifier, a dynamic clamping circuit, and a dedicated common-mode transient immunity (CMTI) enhancement stage. The active-inductor load shapes a band-pass frequency response that maximizes gain at the carrier frequency while rejecting low-frequency interference, and the auxiliary clamping and enhancement circuits collectively suppress large-amplitude common-mode transients. Measured results from a 0.18 μm CMOS process show a CMTI of 160 kV/μs, delay of 11 ns, PWD of 4.7 ns, and breakdown voltage of 6.51 kV. The proposed design thus achieves high robustness, validating its effectiveness for isolated interface applications.