MPQ8633A Series DC Converters design side effect

DC-DC Power Converters
1

Hi Sirs,

Current have one project use MPS.MPQ8663A converters designed-in and adopted Series diagram as picture shown.

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For this diagram, can see one is support 5-Vout and the other one is support 3.3-Vout; now, we find the system possible cannot power-on successfully during execute power on-off cycle testing. therefore, I would like to asking does MPQ8633A series converter design have any potential risk? or, do you have any debug idea to go further analyze on here?

Plz help to confirm and many tks!!

BRs

By Neil

2

Hi,

Thank you for posting on the MPS Technical Forum.

Are you seeing the first MPQ8633 turn on and never the second? Your PG pin is tied to VCC, which looks good. I am concerned that the PG pin from the first converter is not able to fully drive the EN pin on the second converter.

VCC is the output of an internal LDO and should be around 3.3V. The EN pin recommended operating voltage is 3.6V.

Allison