TPS53915: What is the reasonable waveform for Vin to SW node waveform(High side VDS)?

Oliver Lin

Part Number: TPS53915

Hi expert,

My customer is validating the TPS53915, we are measuring the high side Vds waveform, please see condition below

Vin = 12V, Vout = 1.8V, with 10A, is this waveform reasonable or this fit our datasheet's spec? Cause we can not find from the datasheet.

Value we measure min Vds is -10.92V, does this value relate to the low side switching?

over 1 year ago

0 Miranda Gu over 1 year ago

TI__Genius 9056 points

Hi Oliver,

Our US team are checking this and will reply you soon.

0 Tomoya Ide over 1 year ago

TI__Expert 3901 points

This is just a switch node ringing caused by the parasitic inductances and capacitances. To mitigate this, place VIN decoupling capacitor as close to the VIN and PGND pins as possible, and place snubber on the SW node (recommend Csnub: 1.0nF 0603 minimum 25V and Rsnub: 0805 1-ohm resistors from SW to PGND. Ensure the resistor is rated for 1.5*Fsw*Csnub*Vinmax^2). Optionally you can place a 0 to 2 ohm 0402 resistor between the VBST pin and bootstrap capacitor to reduce noise caused by aggressive switching.

0 Oliver Lin over 1 year ago

TI__Intellectual 2110 points

Hi Tomoya,

Thank you for the suggestion, may I know that from our datasheet point of view, what is the reasonable value if we measure this high-side VDS?

0 Tomoya Ide over 1 year ago in reply to Oliver Lin

TI__Expert 3901 points

The high-side VDS is equal to VIN-SW, and SW's maximum recommended operating condition is 27V from the datasheet (as shown below). So if you're running at VIN=18V, then the SW will be at 18V-(-10.92V)=28.92V, which exceeds the maximum recommended operating condition.

The ringing is still within a reasonable range, considering it does not exceed the abs max. Still, I would suggest following the recommendation I provided earlier or follow the layout guideline in the datasheet:

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TPS53915: What is the reasonable waveform for Vin to SW node waveform(High side VDS)?