TPS62822: Overshoots when in PSM mode

Ryu Yamashita

Part Number: TPS62822

Tool/software:

Hi team,

The following circuit is used to step down from 5V to 3.3V.
When operating in discontinuous mode, more than the rated voltage is applied to the SW pin.
In this case, should the absolute maximum rating of the SW pin be based on DC or AC?
Is there any problem if I use it as it is?
Also, what should I do to prevent this?

Best Regards,
Ryu.

3 months ago

+1 Josef Marsmann 3 months ago

TI__Expert 6510 points

Hi Ryu,

Thanks for using E2E.

At the switching point the AC values is valid. Everything looks fine, this is the default behavior.

Best regards,
Sepp

0 Ryu Yamashita 3 months ago in reply to Josef Marsmann

Genius 3600 points

Hi Sepp,

Thanks for the reply.
I understand what you see in the AC characteristic.
But the AC characteristic is up to 10ns, whereas this waveform is about 12ns.
Can I assume that this is not a problem?
Also, how can I reduce this overshoot?

Best Regards,
Ryu.

+1 Josef Marsmann 3 months ago in reply to Ryu Yamashita

TI__Expert 6510 points

Hi Ryu,

There is no problem at 12ns, correct. You reduce the overshoot with a snubber means C/R combination on the SW pin to GND, see App note:

https://www.ti.com/lit/an/slyt465/slyt465.pdf?ts=1748942993882&ref_url=https%253A%252F%252Fwww.google.com%252F

Best regards,
Sepp

0 Ryu Yamashita 3 months ago in reply to Josef Marsmann

Genius 3600 points

Hi Sepp,

The only time 12ns is OK is when it is under light load, right?
Please let me know because I am unclear about the difference between when it is OK to exceed 10ns and when it is not.

Best Regards,
Ryu.

+1 Josef Marsmann 3 months ago in reply to Ryu Yamashita

TI__Expert 6510 points

Hi Ryu,

The AC spec is valid at each time when the device is switching independent of the load / mode. The voltage peak could be up to 10V for a short period (10ns). If you have e.g. a 8V peak for 12ns it won't be an issue in my opinion.

Best regards,
Sepp

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TPS62822: Overshoots when in PSM mode