MP3391 internal LDO short

DC-DC Power Converters
1

I’ve used MP3391 IC, provided 24V to Vin, 2V to enable pin. I left OVP and ISET open. Based on datasheet IC goes to shut down mode or disabled. But result is VDD ans VCC short to ground pin number 8.

Please tell me OVP and ISET floating is the reason for internal short or any other

2

Hi,

Thank you for posting on the MPS Technical Forum.

Since you are leaving the OVP pin open, the part is going to be disabled, which is why you will see VCC and VDD pulled to GND.

ISET cannot be left open since that pin will set the LED current.

Is there a particular reason you have left OVP and ISET open?

Best,

Allison

3

I have three different OVP and ISET settings implemented using solder links. By soldering one of the links, I can select the desired OVP level and current level. Before soldering the selected OVP and ISET links, I applied 24V to the VIN pin and 2V to the ENABLE pin.Testes the VCC and VDD, measured milli volt only. After removing the MP3391 from the PCB, I tested the VCC and VDD pins with respect to ground and found that they are shorted. Why did the IC develop an internal short instead of going into shutdown mode?

4

kindly reply for the above doubt

5

How can an internal LDO short be prevented through circuit design? Frequently facing internal LDO short issue

6

Hi,

Internal shorts (such as VCC to GND) usually indicate electrical overstress. I would first check to make sure that the VCC and VDD pin is decoupled with a 470nF or larger ceramic capacitor. I would also check and make sure that the LDO outputs are not powering any additional devices, since these are small LDOs meant for internal circuitry to work properly.

If you could also provide your schematic this would also be helpful for debugging.

Thanks,

Champers