TPS54425EVM-608: What happens when the control loop is broken during operation?

Kevin Lai

Part Number: TPS54425EVM-608

Hello,

I am working with the EVM and there were no pads included to place a small resistor in the control loop to test for stability via a gain/phase analyzer.

So I soldered on the resistors in a way that may have led to a bad connection. after plugging it in and powering up, I noticed the output voltage and current drop to 0V and discovered that the input of the inductor was shorted to ground via a continuity test.

After replacing the inductor and fixing the control loop connection, everything was functional again.

what could have happened? did the inductor exceed its maximum rating?

thanks,

Kevin

over 5 years ago

0 Sam(MPAA) Zhang over 5 years ago

TI__Mastermind 19080 points

Hi,

Does the "input of inductor" means SW node? If the device can work again, seems there is no IC damage, so it should not be shorted to ground.
Due to Chinese New Year holiday, the reply may be delayed. Thanks for understanding!

Regards,
Hao

0 Kevin Lai over 5 years ago in reply to Sam(MPAA) Zhang

TI__Intellectual 2916 points

Hi Hao,

Happy Chinese new year!

Yes, the SW node. the device works so there is no IC damage.

I'm curious as to how the inductor was damaged here. do you know why?

thanks,

Kevin

0 Sam(MPAA) Zhang over 5 years ago in reply to Kevin Lai

TI__Mastermind 19080 points

Hi Kevin,

Well, I think the device is under some protection state, such as OVP. You may refer to the description about OVP in datasheet. When the device detected an over voltage event, it will turn off the high side MOSFET and turn on the low side MOSFET(such protection behavior is quite normal in DC/DC converters). That's why you had observed SW was short to GND.

Regards,

Hao

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TPS54425EVM-608: What happens when the control loop is broken during operation?