TPS51916: PG pulled down when VTT starts up

Joe Ji

Part Number: TPS51916

Hi Team

My customer spestech use TPS51916 in industrial PC, for DDR power supply.

When VTT power up, the PG drop can be tested, it will last for 1ms. below is the waveform, red line is PG yellow is VDDQSNS.

schematic is also attached:TPS51916 (1).pdf

what will cause this issue? since we didn't see VDDQSNS drop it is confusing.

thank you!

best regards

Joe

Nov 28

0 James Steenbock 7 months ago

Hi Joe,

Do you see this voltage drop on the pull-up source for PGOOD or only on the IC pin? Let's rule out an issue with the +3VSUS supply.

Also can you show a scope capture of VREF, VDDQ, S3, and VTT power up (rising edges)?

Regards,

James

0 Joe Ji 7 months ago in reply to James Steenbock

Hi James

where is +3VSUS? I cannot find it on DS.

thank you!

Joe

0 James Steenbock 7 months ago in reply to Joe Ji

Hi Joe,

+3VSUS is the pull up source for PGOOD in the schematic you shared in the original post above.

Regards,

James

Power management forum