TPS53355: Why the output is 0v

amin cheraghi

Part Number: TPS53355

Hi there,

We have multiple boards with TPS53355 on them. The part is working well on all boards except one. I was wondering if you can help me debug this issue. Here is the schematics:

The en is 4v, input is 12v, vreg and vbst are 5v. output is 0v. When disable the part by putting a jumper on JP19, the vreg goes down to 0v.

There is a chance that on this board the 12v ATX goes unstable for a while. If it caused the part to be dead, I was wondering if there is a way to confirm that?

Thanks,

Amin

over 5 years ago

0 JohnTucker over 5 years ago

TI__Guru**** 191445 points

Can you show the Waveform on SW? (LLx)

0 amin cheraghi over 5 years ago in reply to JohnTucker

Prodigy 200 points

Hi John,

Here is the waveform in 3 time scales:

Thanks,

Amin

0 JohnTucker over 5 years ago in reply to amin cheraghi

TI__Guru**** 191445 points

Amin,

It looks like the circuit is trying to start up then shuts down. Can you check to see if it is current limited? Does this behavior repeat periodically? Or does it try to start up once only? Also, you have abnormally high amount of overshoot on the SW node.

0 amin cheraghi over 5 years ago in reply to JohnTucker

Prodigy 200 points

Hi John,

Yeah, that's right. As shown in the first waveform, this happens periodically T~40ms.
We have 187k for Rtrip which sets the over current limit at around 30A. We use the same value on our other boards and they are working fine. I measured this resistor to confirm.
Also, I disable this rail and use an external 3.3v supply to check other parts of the board. That was fine too.
What is the chance of this part being damaged? Do you suggest replacing it?

Thanks,
Amin