TPS62177: TPS62177DQCR Error power good signal

Sergey Slobodenuk

Part Number: TPS62177

Hello, I am having trouble with TPS62177.

Input voltage 12V, output 3.3V, R12 not soldered. And although the output voltage is 3.309V there is no PG signal. The voltage on the PG (7) leg is 3.3V and the transistor VT1 is closed. This is tested on more than 10 chips and the effect is repeated.

Why could this be?

over 3 years ago

0 JohnTucker over 3 years ago

TI__Guru**** 191445 points

Sergey,

Can you post your schematic?

0 Sergey Slobodenuk over 3 years ago in reply to JohnTucker

Prodigy 40 points

Hi, John.

Here is part of my circuit with TPS62177.
Thank you for participating.

0 JohnTucker over 3 years ago in reply to Sergey Slobodenuk

TI__Guru**** 191445 points

Sergey,

You state that the pin 7 (PG) voltage is 3.3 V. PG is pulled up to 3.3 V by R14 and R15, so that is normal. I don't see any issue here.

0 Sergey Slobodenuk over 3 years ago in reply to JohnTucker

Prodigy 40 points

John,

the problem is that when the voltage at the output of the converter (pin 10) is 3.3V, the internal transistor PG must open and the voltage at pin PG (7) should be close to 0.3V

0 JohnTucker over 3 years ago in reply to Sergey Slobodenuk

TI__Guru**** 191445 points

Sergey,

Yes when Vout is within regulation, the internal PG FET is turned off. When the FET is off, the output is pulled up to 3.3 V. See figure 40 from the datasheet below. You can see that channel 2, PG goes high when the output reaches regulation.

0 Sergey Slobodenuk over 3 years ago in reply to JohnTucker

Prodigy 40 points

Wow!
Thanks, John!
I did not read the manual very carefully! Now everything is clear to me and I have to redo my scheme.
Thanks again!

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TPS62177: TPS62177DQCR Error power good signal