[SI-LIST] A short story
- From: Suresh Subramaniam <Suresh.Subramaniam@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Sat, 09 Apr 2005 00:05:14 -0700
Hello All,
I am faced with the following situation: A fairly complex bare board
shows no shorts between any of the power rails (1.2,2.5,3,3,5 and 12V)
and GND. However, before power up, on a fully populated board, I am
measuring about 10 Ohms on the 1.2V, 6 Ohms on 3.3V and 0.5 Ohms on 2.5V
(measured with a standard Fluke multimeter) and the others are showing
readings in the 1-2K Ohm range! Since we had several boards on hand, I
decided to power up one of the boards anyway. There was no smoke or
hotspots on the board (the 1.2V and 2.5V switching regulators are rated
for 14A).. And more importantly, majority of the interfaces tested are
operating as advertised. I remeasured the board after power off . Now
the readings are ~100 Ohms on 2.5V and about the same as before on the
other rails.
(Note: The pattern is the same on all boards.)
I have also checked to make sure there are no symbol/footprint errors.
Before I start to depopulate individual ICs to trace this short on an
unpowered board, I thought I would check in to find out if others have
had this experience.
Also, is there a better/correct method to measure pwr/gnd shorts ?
Thanks
Suresh
--
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/ 7\'7 Suresh Subramaniam suresh.subramaniam@xxxxxxxxxx
\ \ Xilinx Telephone: 408-559-7778
/ / 2100 Logic Drive Direct: 408-879-6172
\_\/.\ San Jose, CA 95124 FAX: 408-377-9013
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