# Understanding Power Good Signal in TPS54719

I'm using TI TPS54719 DC-DC and I'm trying to understand the PWRGD signal functionality.

Definition of PWRGD pin in datasheet: An open drain output, asserts low if output voltage is low due to thermal shutdown, overcurrent, over/undervoltage or EN shut down.

This is an illustration from datasheet that demonstrates sequencing of two TPS54719 devices:

Also, according to the datasheet:

The PWRGD pin output is an open drain MOSFET. The output is pulled low when the VSENSE voltage enters the fault condition by falling below 91% or rising above 110% of the nominal internal reference voltage. There is a 2% hysteresis on the threshold voltage, so when the VSENSE voltage rises to the good condition above 93% or falls below 108% of the internal voltage reference the PWRGD output MOSFET is turned off. It is recommended to use a pull-up resistor between the values of 1kΩ and 100kΩ to a voltage source that is 6 V or less. The PWRGD is in a valid state once the VIN input voltage is greater than 0.8 V, typically.

I didn't understand why we need the Pull-Up resistor for the PWRGD signal, and why for example in the picture above they didn't use this Pull-Up resistor. when I tried to do a simulation in https://webench.ti.com/power-designer, the PWRGD signal was automatically connected to VIN through 86K Pull-Up resistor. how in this case I should use this signal for sequencing?

what I expect from PWRGD is to go from LOW (0V) to HIGH (some value above EN threshold) when VOUT is above 91% of it's final value. so first, I'm confused with the fact that PWRGD signal changes according to VSENSE and not VOUT. and second, according to the explanation above, I understand that if we want to sequence two devices (like in the image below) the signal between PWRGD1 and EN2 should be connected to VDD through a pull up resistor. why it's not connected?

here is an image of the internal circuitry:

• It’s 93% to turn on and 91% to turn off. Open drain like open collector must have a pullup from some current source in the power supply itself or the cascaded enable from next supply voltage Commented May 7, 2021 at 20:13