TPS22971: Behaviour of PG(OOD)

Peter Kaeser

Part Number: TPS22971

Dear Forum

I have a whole cascade of high side switches in my design and am somewhat stuck with the PG output of TPS22971

Now, I have the following situation VIN1/2 = 0V (i.e. the input voltage is not yet enabled), ON (PGOOD9) = 0V (i.e. disabled), VOUT1/2 (0V85_PL) = 0V (measured, as expected).
I observe that PG(OOD) ramps up with 3V3_CON in this situation.

Since i found no hint in the datasheet for this situation please advise.

Best regards,
Peter

over 5 years ago

0 Peter Kaeser over 5 years ago

Prodigy 20 points

0 Aleksandras_Kaknevicius over 5 years ago in reply to Peter Kaeser

TI__Genius 15760 points

Hi Peter,

In this case, when the device is unpowered, the PG pull down circuitry will not be active. Because this is an open drain output, it is either left floating or is actively pulled down. With no voltage on VIN, the pull down circuitry cannot pull the PGOOD10 node down and the voltage will float to 3V3_CON. Once the voltage on VIN is applied, the PG pin will be able to pull down to 0V rather than stay left floating.

Thanks,

Alek Kaknevicius

Power management

Power management forum

TPS22971: Behaviour of PG(OOD)