TPS55340: SW pin undershoot

Julian Chen

Part Number: TPS55340

Dear E2E member,

1. Our customer use TPS55340 and measure the SW pin, the undershoot is reach for -640mV.
Does it have any risk for this IC? The SPEC of IC which is -0.3V only.

2. If no risk, Does TI have any technical document to confirm it?

3. If have risk, How can we improve from this design?

over 7 years ago

0 Helen chen over 7 years ago

TI__Mastermind 40080 points

What is your input voltage range, output voltage range and output current? So that we can double check it.

0 Julian Chen over 7 years ago in reply to Helen chen

Expert 2550 points

Dear Helen,

1. Vin Range : 10 to 13V

2. VOut Range : 19V +/-5%

3. IOUT Range : 0A to 1.5A

0 Helen chen over 7 years ago in reply to Julian Chen

TI__Mastermind 40080 points

Did you calibrate your oscilloscope before testing?

0 Julian Chen over 7 years ago in reply to Helen chen

Expert 2550 points

Yes!

0 Julian Chen over 7 years ago in reply to Helen chen

Expert 2550 points

Dear Helen,

So, does it have any risk for this IC?

0 Helen chen over 7 years ago in reply to Julian Chen

TI__Mastermind 40080 points

I'm output of office these days. Will double check the undershoot in the lab. -0.3V is a DC voltage requirement. For the transient value, it can be much lower than -0.3V. So generally, it will not cause any risk.

I'll reply you wednesday.

0 Julian Chen over 7 years ago in reply to Helen chen

Expert 2550 points

Dear Helen,

Thanks a lot!

0 Julian Chen over 7 years ago in reply to Helen chen

Expert 2550 points

Dear Helen,

I measure the system board, and find the Gnd of Probe is bad connection, so 0V had offset.

BUT undershoot is under-1V during 20ns.

Does TI have guarantee letter or report for negative voltage of undershoot?

0 Helen chen over 7 years ago in reply to Julian Chen

TI__Mastermind 40080 points

-1V/20ns undershoot will not cause any damage. Lets discuss through email.

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TPS55340: SW pin undershoot