TPS62160: Short Circuit and Burn when feed by Lead-Acid 12V Battery

Hi Artur,

did you check voltage on Lead-Acid battery?

would you please share:

• schematic
• layout
• oscilloscope screenshot:
  
  • Vin voltage
  • SW pin voltage
  • inductor current

What is the end application?

Best regards

Lubomir

Hi Lubomir,

I've checked the battery voltage, and was something about 13V. The chip was suppose to work good up to 17V.

Unfortunately, I can't share the full board schematic and layout at this moment. But, I've used the TPS62160DGK with the same components suggested in the datasheet, and a very close layout of the datasheet as well. The inductor current is about 1,4 A.

The end application is to acquire some data from sensors and control some relays. Nothing outstanding.

I don't have an oscilloscope picture also, because if I try to reproduce the problem I lost more components. And to acquire the signals it's a little bit trick, all components are very small, and burn a chip in your face under a x4 magnifying glass is complicate.

Thanks for the response, I'll try to get some more information.

My best regards,

Artur

Hi Artur,

how is DCDC converter connected to the battery?
Do you use long wires?

Regards

Lubomir

Hello Lubomir,

Very short wires. About 15 cm from the battery to the board, and more 1 or 2 cm from the pins to the dcdc.

Have you seen this before? I'm wondering if batteries internal resistance could cause this, probably this is the main difference between lead acid types and others that I've tried.

My best regards,
Artur

Hello Artur,

is something else connected to the battery?
Do you have capacitor bigger capacitor on the input of the DCDC converter?
Please look into this blog: e2e.ti.com/.../what-is-that-giant-tantalum-cap-on-the-input-of-the-evm

Regards

Lubomir

Hi Lubomir,

No. Just the DCDC converter it's connected to the battery.
I don't have this cap, just the input capacitor of the converter circuit (22 uF - Ceramic). Very nice blog, I'll look forward to see if this solve the problem. Do you think that if I change the tantalum cap for an electrolytic could work as well? As a rule of thumb bigger capacitance better?

Thanks for the help!

My best regards,

Artur

Were you able to test out the cap? Based on what you describe, I think you probably should have one. This can be confirmed by a simple scope measurement of the input voltage waveform on your PCB. Either tantalum or electrolytic is ok--their ESR also helps makes a snubber to clamp the ringing.