TPS544C20: About detection method of PGOOD

Yuto Sakai

Part Number: TPS544C20

Hi,

I understand that the PGOOD signal judges only depending on whether the FB voltage exceeds the threshold of PGH or PGL, is it correct?
If Yes, how long does it take from detecting the FB voltage to invert the PGOOD signal (H→L, L→H)?

Best regards,
Yuto Sakai

over 6 years ago

0 Mathew Jacob1 over 6 years ago

TI__Expert 5910 points

Sakai-san,
There is no delay once the FB voltage crosses the limits. There is hysteresis based on voltage levels but no time delay once it is detected.

Regards,
Mathew

0 Yuto Sakai over 6 years ago in reply to Mathew Jacob1

Mastermind 6100 points

Hi Mathew-san,

Thank you for your reply.
What about the first line of the first post?
>I understand that the PGOOD signal judges only depending on whether the FB voltage exceeds the threshold of PGH or PGL, is it correct?

For example, in the case of OC or OT, does the PGOOD signal level invert at the moment of protection of OC and OT?
Or does the PGOOD signal level be inverted when the output is stopped by OC or OT and the FB voltage is decreased to below the PGL threshold?

Best regards,
Yuto Sakai

0 Mathew Jacob1 over 6 years ago in reply to Yuto Sakai

TI__Expert 5910 points

Hi,

PG can also be affected by OCP, EN signal and soft start done signal. If you are using some sort of AVS control on FB pin please filter it due to fast rise times can cause false tripping.

Regards,
Mathew

0 Yuto Sakai over 6 years ago in reply to Mathew Jacob1

Mastermind 6100 points

Hi Mathew-san,

Sorry if it was not enough.
Please let me organize the trip conditions of PG.
Is the condition that PG inverts during normal operation only when the FB voltage exceeds the threshold (PGH, PGL)?

Best regards,
Yuto Sakai

0 Mathew Jacob1 over 6 years ago in reply to Yuto Sakai

TI__Expert 5910 points

Sakai-san,

Yes during normal study state condition PG can go low only if the FB voltages crosses the thresholds for PGH and PGL. If you have a PG glitch during normal operation in steady state please put inductor current probe and see if any OCP condition is not being caused.

Regards,

Mathew

0 Yuto Sakai over 6 years ago in reply to Mathew Jacob1

Mastermind 6100 points

Hi Mathew-san,

Thank you for your reply.
Datasheet P.5 In the description of the PGOOD pin, "Any fault condition causes this pin to pull low. "
I understand that the FB voltage crosses the threshold value (PGH, PGL) by protection operation at all fault detections and the PGOOD signal goes low , is it correct?

I am concerned whether the PGOOD signal may go low by only detecting the fault condition regardless of the FB voltage.

Best regards,
Yuto Sakai

0 Mathew Jacob1 over 6 years ago in reply to Yuto Sakai

TI__Expert 5910 points

Sakai-san,

The datasheet is accurate and PG can go low when triggered by a internal fault condition such as OCP regardless of FB voltage. However in actual use case I don't think these are mutually exclusive events since OCP causes switching to turn off and output falls etc. However in the case of over voltage or undervoltage condition the PG acts first since the OVP and UVP thresholds are above and lower than PG thresholds.

Regards,

Mathew

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TPS544C20: About detection method of PGOOD