TPS74801: When can PG drive low during startup?

Hi George,

If only VBIAS is applied and VIN is not present, there will be no VOUT. The PG output is high-impedance when VOUT is greater than VIT + VHYS. If VOUT drops below VIT or if VBIAS drops below 1.9 V, the open-drain output turns on and pulls the PG output low. So, in the absence of VOUT, PG pin will be low with only VBIAS applied.

Best regards

Ishaan

That is not what I meant. If VBIAS is present but VIN is absent, then VOUT will be 0V. As long as PG is connected to any 5.5-V or lower rail through an external pullup resistor, the comparator for the PG function will trigger and drive the FET to force PG low.