LMR51450: Problem with input Power toggle

Rob Keij

Part Number: LMR51450

I made a pcba with the LMR51450SDRRR a very nice chip.
But I have a problem:

Input 25V
Output 5V
Load 8R
load current 0,625A

After powered for a longer time (1 hour or so) and I toggle the 25V the chip is damaged.
I tested this issue on 4 pcba and al are damaged.

befor this test I tested al 10 pcba's with a 5A load (5V/1R) and every thing was ok.

So the chip can not handle power toggles at the input (what can happen in real time)

best regards,

Rob Keij

over 1 year ago

+1 Ben C over 1 year ago

TI__Guru 56345 points

HI Rob,

Are you connecting and disconnecting the load or the power supply voltage to the board? After viewing your video, the setup has long leads to the PCB board, which is inductive, and may be the cause of the failure you are seeing. Therefore, if you are disconnecting the VIN power supply, you may be causing a hot plug event where the VIN seen at the chip is spiking higher than the VIN ABS MAX rating. Try adding a 22uF or 47uF tantalum or electrolytic capacitor on VIN of the PCB board.

Ben

0 Rob Keij over 1 year ago in reply to Ben C

Intellectual 390 points

Hi Ben,

Thanks for the quick response,
I connect and disconnect Vin,
I'm going to added a extra capacitor to the input and test if this helps.
I let you know when I have test this.

Rob

0 Ben C over 1 year ago in reply to Rob Keij

TI__Guru 56345 points

Hi Rob,

Please keep me posted.

Ben

0 Rob Keij over 1 year ago in reply to Ben C

Intellectual 390 points

Hi Ben,

I added a 100uF electrolytic elco on Vin,
Tried everything, including with a 1R resistor on the output (5A).
Have everything sparking well at the entrance but problem is solved,

thanks for the advice!

Rob

0 Ben C over 1 year ago in reply to Rob Keij

TI__Guru 56345 points

Hi Rob,

Glad to hear that you fixed your issue. Good luck to you!

Ben

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LMR51450: Problem with input Power toggle