A Low Cost Discrete Digital Isolator Circuit

TL;DR

This paper introduces a cost-effective, fully discrete digital isolator using general-purpose transistors and an air core transformer, achieving high voltage isolation and suitable data rates without specialized ICs.

Contribution

It presents a novel low-cost digital isolator design that eliminates vendor lock-in and obsolescence risks, with detailed performance validation and PCB layout guidance.

Findings

>1 kV isolation voltage achieved

~200 ns propagation delay

1 Mbps data rate validated

Abstract

This work presents a fully discrete, low cost digital isolator requiring no specialized ICs and implemented entirely with general purpose transistors and a two layer PCB embedded air core transformer. The design avoids vendor lock in and long term component obsolescence risks, while providing >1 kV isolation, ~200 ns propagation delay, and validated NRZ data rates of 1 Mbps. A modified dual oscillator architecture enables inherent hardware lockout suitable for half bridge gate driver applications. Measured performance and PCB layout guidelines are provided.