TPS54225 fails to restart after VIN drop

Kazuhiko Ogawa

Other Parts Discussed in Thread: TPS54526, TPS54225, TPS54525

Our customer inquire the issue that the TPS54225 does not restart after the momentary power outage. I looked over this Forum and I think this issue is similar to the reports as “ TPS54526 fails to restart after VIN dip ” and “ TPS54525 recovery from brown-out “.
The customer circuits conditions are the following;
VIN & VCC = 12V
VO = 5V
EN pin is tied to VIN through the 10K-ohm pull-up resistor.

I have the questions.
Our customer mentioned that this issue was cleared up by directly connecting EN pin to VIN without the pull-up resistor.
Is this addressing proper or just only better?
Why does this behavior occur?

Regards,

Kazu Ogawa

over 10 years ago

0 JohnTucker over 10 years ago

TI__Guru**** 191445 points

When Vin momentarily drops out the device may fall out of regulation. If the UVP is activated, then the device will latch off. You may need to cycle EN to restart. I would doubt the EN connection directly to VIN is a permanent cure.

0 JohnTucker over 10 years ago in reply to JohnTucker

TI__Guru**** 191445 points

Also, can you post waveforms to verify the latching mechanism? be sure to include Vout, Vin, VREG5 and EN. We may also need to see SW node.

0 Kazuhiko Ogawa over 10 years ago in reply to JohnTucker

Intellectual 985 points

John-san,

Yesterday was a holiday in Japan.

Thank you very much for your answer.
I will ask the customer the waveforms.
But I don't know whether he can.

Best Regards,
Kazu Ogawa

0 Kazuhiko Ogawa over 10 years ago in reply to JohnTucker

Intellectual 985 points

Is there the recommended solution for this issue?

If there is, would you please let me know?

Best Regards,

Kazu Ogawa

0 JohnTucker over 10 years ago in reply to Kazuhiko Ogawa

TI__Guru**** 191445 points

The most common solution would be to cycle the EN pin after the VIn voltage drop to restart the IC. The under voltage protection is built into the device and is not defeat-able. Some of our later devices have non latching UVP. I don't believe there is a pin compatible part though, only the 8 pin devices have that.

Power management

Power management forum

TPS54225 fails to restart after VIN drop