[论文解读] A Low Cost Discrete Digital Isolator Circuit

T. J. Conway|arXiv (Cornell University)|Mar 25, 2026

Electrostatic Discharge in Electronics被引用 0

一句话总结

该论文提出了一种完全离散、低成本的数字隔离器，使用通用晶体管和 PCB 路由线变压器实现 >1 kV 隔离、约 200 ns 延迟，以及 1 Mbps NRZ 数据速率。

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.

研究动机与目标

• Motivate the need for discrete digital isolation to avoid vendor lock-in and obsolescence risks.
• Propose a fully discrete isolator implemented with general-purpose transistors and PCB‑embedded air-core transformers.
• Demonstrate isolation performance, timing, and data-rate capabilities suitable for UART/SPI-like interfaces and half-bridge signaling.

提出的方法

• Use a cross-coupled MOSFET pair to form a fast startup oscillator on the transmitter side.
• Couple transmitter and receiver using PCB trace spiral coils acting as air-core transformers across two PCB sides.
• Rectify and amplify the induced signal on the receiver side with NPN transistors to produce a digital output.
• Achieve isolation through FR4 PCB material and eliminate the need for high-voltage discrete components.
• Characterize performance with 1 Mbps NRZ signaling and eye diagrams to validate data rate and integrity.

Figure 2: Layout of transmitter (top side) and receiver (bottom side) for 2 layer PCB

实验结果

研究问题

• RQ1 Can a fully discrete digital isolator achieve practical isolation (>1 kV) without specialized ICs?
• RQ2 What data rate and propagation delay can be achieved with PCB trace transformers and discrete transistors?
• RQ3 Is the design suitable for half-bridge gate-driver signaling with inherent lockout functionality?

主要发现

• Isolation exceeding 1 kV is achieved using FR4 PCB material and discrete components.
• Propagation delay is measured around 200 ns.
• The design supports NRZ data rates of 1 Mbps, with an eye diagram indicating reliable transmission at this rate.
• Prototype PCB layout uses a 2-layer board with 8-turn PCB trace coils and no vias through the transformer path.
• Estimated cost per unit is about 50 cents, with TX power up to 25 mW and RX power up to 5 mW.
• The circuit demonstrates a hardware lockout feature suitable for half-bridge driver signaling.

Figure 3: Measured logic transfer for the prototype PCBs with a 1 Mbps NRZ random data signal