UCD90124A: Pin Selected Rail States + CONTROL pin

Peter Nemeth1

Part Number: UCD90124A

Hello TI team,

We have a design with 11 power rails sequenced by the UCD90124A and with a main power enable/disable signal coming from a MCU connected to the PMBUS_CNTRL pin.
Now, we would like to have a different variant of the same design where two power rails in the middle of the current power sequence will be missing (the PSUs and the powered components will be physically removed).

Our question is if it is possible to support both variants with the same UCD90124A configuration?
We have an additional (currently unused) GPIO signal between the MCU and the GPI 1 pin of the sequencer. The MCU can set that pin to a state indicating the variant of the board before it toggles the PMBUS_CNTRL signal.

Is it possible to use the Pin Selected Rail States feature together with the PMBUS_CNTRL pin to achieve the following operation?

PMBUS_CNTRL pin	GPI 1 pin	State of the power rails
LOW	X	All rails are OFF
HIGH	LOW	All rails are ON
HIGH	HIGH	All rails are ON, except for two rails in the middle of the sequence (Those two rails should be ignored during the on-/off-sequence)

Thanks for any help in advance.

9 months ago

0 yihe 9 months ago

TI__Guru 60800 points

if you have the two power rails are missing(PSU and powered component are removed), why does it matter UCD turn on those ENABLE those signals or not?

You can use the same control pin to do all.

Regards

Yihe.

0 Peter Nemeth1 9 months ago in reply to yihe

Prodigy 80 points

Hello,

My issue with this is that those 2 rails are part of the sequence ON dependencies of other rails. During power on the sequence will hang due to the missing voltages and if it is possible I would like to keep those dependencies for the base variant (where all power rails are present).

+1 yihe 9 months ago in reply to Peter Nemeth1

TI__Guru 60800 points

if other rails have dependencies on these two rails, I do not see how you can bypass these just by not turning on.

the dependencies are not bypassed just because of you do not turn on rail.

You have to remove the dependencies for the case.

Regards

Yihe

0 Peter Nemeth1 9 months ago in reply to yihe

Prodigy 80 points

Hello,

I thought that I can exclude those 2 rails from the sequence by setting the Turn Off Mode to "Immediate Off" (instead of "Soft Off") for those two rails in the Pin Selected Rail States config.
Can you confirm that it is not true?

0 yihe 9 months ago in reply to Peter Nemeth1

TI__Guru 60800 points

No, as replied in the previous post, disabling the rail won't help.

Regards

Yihe

0 Peter Nemeth1 9 months ago in reply to yihe

Prodigy 80 points

Hello,

OK. Thank you for your help and for the information.

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UCD90124A: Pin Selected Rail States + CONTROL pin