OMAP power rail bypass capacitor locations

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1

Hi all,

I'm trying to measure the effective resistance of the OMAP chip's
power rails with a 4-wire Ohmmeter looking in from the TPS65950 power
management chip. Thus, my two test points are at the output of the
TPS65950 (e.g. to measure the effective resistance of VOCORE, I would
place leads across C78) and at the bypass capacitors directly next to
the OMAP chip itself (e.g. for VOCORE they are numbered C9, C10, ...,
C135 see schematics for details).

My issue is finding exactly where the OMAP's bypass capacitors are
located. I looked through all the PCB design files, but couldn't find
anything helpful other than an xy-location (which doesn't help when
you're actually looking at the board). Is it possible to identify the
location of these caps? I was able to find bypass caps for VDD2 (C38)
and VIO (C13) because they are labelled on the board, but I can't seem
to find any for VOCORE.

Any help with identifying the unmarked caps on the bottom of the board
would be appreciated. Thanks.

George

2

Download the free viewer from Cadence. You need the 15.x version.

http://www.cadence.com/products/pcb/Pages/downloads.aspx

Download the Allegro database corresponding to the board you are working with…

http://beagleboard.org/hardware/design

Look at the schematic and write down the capacitors reference designators you are interested in finding.
Open the Allegro CAD file using the Cadence Viewer.
Enable the top and bottom silkscreen layers.
With the mouse over the board area, hit F5.
Go to the right column and select the Find tab.
Check the component item in the check boxes.
Type in the reference designator in the find area and hit enter.
It will highlight that component.
Most likely the capacitors you are looking for will be on the back side of the board.

.Gerald