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Keywords: serial, link, serdes, gmsl, power over coax, poc, line fault, detection, protection, overcurrent,
overvoltage, automotive, camera, infotainment, adas, serializer, deserializer, image sensor
APPLICATION NOTE 6612
HOW TO USE GMSL LINE-FAULT DETECTION
FOR POWER OVER COAX
Abstract: Many of Maxim GMSL SerDes parts have built-in line-fault detection circuits for a short to ground,
short to the battery, and a disconnected cable. When power over coax (PoC) is used, a different configuration
is required for proper line-fault operation. This application note explains the line-fault circuitry, how to adapt it
for PoC, and a solution to protect against overvoltage and overcurrent conditions.
Introduction
In any application that uses a cable between devices, it is good to be able to diagnose faults in the line without
needing to physically inspect the devices. Many of Maxim’s GMSL parts include line-fault circuitry to detect a
short to ground, short to the battery, and a disconnected cable. This application note discusses how to adapt
GMSL line-fault circuitry for power over coax (PoC) and offers a solution to protect against overvoltage and
overcurrent conditions. The MAX96705 and MAX96706 SerDes pair are an example.
When both serializer and deserializer have local power sources, the coax cable is biased through external
resistors R1, R2, and R5 as shown in Figure 1.
