Tuesday, February 3, 2015

Cisco 3560 power supply hacking

An odd project was dropped on my desk today. It's more of a "how would you do this?" scenario. We've been recently required to replace our existing switchgear on some systems with pre-approved Cisco switches. The catch? The systems are 28v DC. At first look, it's not as bad as I though.
Power is supplied from a Lite-On PA-3131-3-IF power supply, on a separate board. The voltage range is... well a bit odd. At least to an electronics novice such as myself. I was expecting the dual 12v rails and 3.3v supply/return- but what I wasn't expecting was a -53v supply/return. Maybe someone who has designed power supplies can chime in here, but what the heck are they using -53v for? Anyways, for now this project is sidelined, but it sure looks easy enough to toss in a DC-DC power supply and backer board.