应用于电感耦合型隔离通讯的芯片设计

王彤 赵野 陈杰

摘 要：为增强信号在恶劣的电气噪声环境中传输的安全性和可靠性，提出并设计了一款利用SPI数据链路实现设备远程控制的隔离通讯芯片.分析目前两种SPI总线隔离方案的优缺点，折中隔离方式、电路复杂性、成本和可靠性等因素，利用“平衡”双线技术，采用双绞线作为传输介质，将四路SPI信号编码成能够通过变压器耦合的无直流脉冲，提高了数据传输的准确性和系统工作的可靠性.芯片基于GSMC 0.18 μm CMOS标准工艺设计，核心面积为1.33×1.45 mm2.流片测试结果表明，芯片可实现1 Mbps的通讯速率，误码率小于10-9，在通信速率为0.5 Mbps的条件下支持的最大电缆长度可达50 m，实现了远程受控器的灵活网络化配置，与同类隔离方案相比，是一种兼具低成本、高可靠和结构优化的远程控制解决方案.

关键词：SPI；远程控制；隔离通讯；双绞线；电感耦合

中图分类号：TN402；TN79 文献标志码：A

Abstract：In order to enhance the security and reliability of the signal transmission in the harsh electrical noisy environment， an isolated communication chip was proposed and designed to realize the remote control of the equipment by SPI data link. The advantages and disadvantages of two current SPI isolation schemes were analyzed. Considering the isolation method， circuit complexity， cost， reliability， and other factors， the chip uses the “balanced” two-wire technology and encodes the four SPI signals into DC-free pulse that can be coupled by a transformer， which can improve the accuracy of data transmission and system reliability. The chip was designed and fabricated in GSMC 0.18 μm CMOS standard process， with a total chip area of 1.33×1.45 mm2. Test results show that the chip can reach a bit error ratio of 10-9 at 1 Mbps. The maximum cable length supported at a data rate of 0.5 Mbps can be up to 50 meters. It achieves the flexible network configuration of the remote controlled device. Compared with other similar isolation schemes， the designed chip is a low-cost， highly reliable and structural optimization solution for remote control.

Key words：SPI； remote control； isolated communication； twisted pair； inductive coupling

SPI（serial peripheral interface）是一種同步串行外设接口，能够方便地实现MCU与外部设备之间的通信，具有接口线少、数据速率高、支持全双工操作等特点，在电路集成设计中得到了广泛应用[1].SPI通信可采用接口直接对接的方式，实现主设备和外部设备间的通信.但在工业现场的数据采集中，由于设备工作环境复杂，各通信节点具有很高的共模电压，干扰较大，造成SPI接口无法正常工作，严重时甚至会烧毁芯片和仪器设备.因此，为了保证设备正常通信以及核心控制电路和操作人员的安全，对SPI总线各个通信节点实行电气隔离是非……