John Zigrang

MPC5125 External Power Issue

Discussion created by John Zigrang on Apr 21, 2011
Latest reply on Apr 26, 2011 by Andrea Cisco

We built a board for a tower that has a DC/DC to provide the tower with +5VDC.

If we use this power, for some reason, the 3.3VDC is not longer enabled on the TWR-MPC5125.

On schematic V2.0_121409, page 15 Q13 is not getting turned on.

It looks like there is a schematic error as the voltage applied to R331 on the gate of the FET is VDD_5V0. Which is +5V with external and USB power.

 

Note: I think the pin numbers on the FET are wrong as well.

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