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No regulation at VADJ in Microzed FMC carrier board when SOC plugged in

rwong1231

Hi everyone,

 

I've recently designed our own custom Microzed carrier board that uses the 7020 boards that we purchased last year (so no errata's from Microzed apply to them I believe).

 

The in-house carrier board design models the same schematic layout as the MBCC-FMC_RevB schematic itself - including the POR# Button for J5 Power Good testing.

This is what is happening:

 

1. No Microzed (SOC) board plugged in.

- J5 is jumpered. 12V power is applied to the board and depending on the jumper configuration (J6) I close at REG5, VADJ is outputting 1.8V, 2.5V, or 3.3V

 

2. Microzed (SOC) board IS plugged in.

- J5 jumper is removed. 12V power is applied to the board and no matter what jumper is applied to J6, TP8 is measuring 3.5V - ie no regulation(?).

 

On our custom carrier board, VADJ is tied directly to the same pins in the PMODs, JX1 and JX2 (to Microzed) connectors as in the MBCC.

The Microzed does power up correctly on the custom carrier board, with the final stage D5 LED (on Microzed) turning on.

 

Does anyone have any insight/experience to this problem? I've tested REG5.PG_3V3 and REG5 is enabled.

 

VADJ powers the VCCIO34, VCCIO35 and VCCIO13 banks of the SOCs.

 

[1] MBCC-FMC_RevB_Schematic_140211.pdf

  • 0

    If it were the Avnet carrier, the most common user mistake is not seating the SOM all the way down into the mating connectors, so definitely check that you have fully seated the SOM in your Carrier.

     

    Is your 12V input stable?

     

    Are there any differences whatsoever in your REG5 connections with the Avnet Carrier?

     

    We could go through the sequencing between Carrier and SOM, but I don't think that is it since PG_3V3 is enabling REG5. The fact that it works with J5 seated but not with the MicroZed is not making sense to me if PG_3V3 is good.

     

    Bryan