TPS513885: TPS51385VABR Not Starting with 22V Solar Input – Appears Shorted

dhruvil bhadani

Other Parts Discussed in Thread: TPS51385

Hi TI team,

We’re using the TPS51385VABR to convert a 22V solar input to 5V. With this solar input (open-circuit 22V), the buck fails to start — no 5V output, and the input appears shorted, though there’s no actual short on the board.

Could this be due to solar panel behavior at startup?
Is 22V too high, or is a protection feature triggering?

Looking for guidance on:

Safe operation with solar input
Recommendations for reliable startup

Thanks,
Dhruvil Bhadani
Sr.Embedded Hardware Engineer

2 months ago

0 Gautam Iyer 2 months ago

TI__Genius 10530 points

Hi Dhruvil,

What is the Voc of the solar panel?

Regards,

Gautam

0 dhruvil bhadani 2 months ago

Prodigy 20 points

21.6 volts

0 Haseen Reddy Siripi Reddy 2 months ago in reply to dhruvil bhadani

TI__Expert 5540 points

Hi Dhruvil,

When you say short >>Short between VIN to GND of TPS51385 ?

If Yes that means due to higher input voltage(More than ABS MAX 28V) appeared at VIN and device will get damage and show short to GND.

One suggestion is Can you put 220uF electrolytic capacitor at VIN pin of TPS51385.

Regards,

Haseen.

0 dhruvil bhadani 2 months ago in reply to Haseen Reddy Siripi Reddy

Prodigy 20 points

Sorry for the confusion earlier — I initially assumed the buck converter might have failed since it wasn’t providing any output. However, after further investigation, I confirmed that the TPS51385VABR is not damaged. All ESD protection ratings are within specification, and there is no short at the output, yet the output voltage remains at 0V instead of the expected 5V.

The design includes a 270µF capacitor at the output to handle voltage spikes. The circuit was working perfectly for three days, but then suddenly stopped regulating, with the output dropping to 0V.

I’m trying to understand what might cause the converter to stop functioning under these conditions, despite no apparent faults.

0 Haseen Reddy Siripi Reddy 2 months ago in reply to dhruvil bhadani

TI__Expert 5540 points

Hi Dhruvi,

Please capture the waveforms of VIN,EN,SW,Vout.

Also share your schematics.

Regards,

Haseen.

0 dhruvil bhadani 2 months ago in reply to Haseen Reddy Siripi Reddy

Prodigy 20 points

I was using the TPS51385 development board for this testing.
Oky will share you with the waveforms.

0 Haseen Reddy Siripi Reddy 2 months ago in reply to dhruvil bhadani

TI__Expert 5540 points

Ok Will wait for it.

Regards,

Haseen.

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TPS513885: TPS51385VABR Not Starting with 22V Solar Input – Appears Shorted