TPS62262: How much undershoot voltage is allowed at SW terminal?

Kazuya Nakai59

Guru 20450 points

Part Number: TPS62262

Hello guys,

One of my customers is evaluating TPS62262 on their own board for their new products.

In their evaluation, they found SW terminal went down to about -1.2V during less than 50ns.

They know the cause is inductor current flow into the parasitic diode of low side internal FET when both FETs of high and low side are turned off.

But they want to know how much undershoot voltage and duration are allowed.

Could you please give me the voltage and duration?

Your reply would be much appreciated.

Best regards,

Kazuya.

over 4 years ago

0 Davor Pavlovski over 4 years ago

TI__Expert 3611 points

Hi Kazuya,

Could you please send the waveform of the SW node voltage.

Regards,

Davor

0 Davor Pavlovski over 4 years ago in reply to Davor Pavlovski

TI__Expert 3611 points

Hi Kazuya,

The AC spec for the SW node of this device is a minimum voltage of -3V for 10ns.

Regards,

Davor

0 Kazuya Nakai59 over 4 years ago in reply to Davor Pavlovski

Guru 20450 points

Hello Davor,

Thank you very much for your reply.

I got 2 waveforms of SW node from the customer as the attached.

I think those would be not problem accoording to your previous reply.

Could you please give me your comment?

Thank you again and best regerds,

Kazuya.

0 Davor Pavlovski over 4 years ago in reply to Kazuya Nakai59

TI__Expert 3611 points

Hi Kazuya,

Looking at the pictures you have attached, I would say that everything seems normal to me.

Just as a side note, more information about the proper way to measure the SW node voltage and minimizing the voltage spike on the SW node by following good layout practices can be found in the following app-note: Understanding the Absolute Maximum Ratings of the SW Node.

Kind Regards,

Davor

0 Kazuya Nakai59 over 4 years ago in reply to Davor Pavlovski

Guru 20450 points

Hi Davor,

Thank you very much for your checking for the waveform and telling the side note me.

The note is very helpful for the customer and me.

Thank you again and best regards,

Kazuya.

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TPS62262: How much undershoot voltage is allowed at SW terminal?