TPSM63606: Burning during power up phase?

Eohan George22

Intellectual 620 points

Part Number: TPSM63606

Hi,

We have a board where two of the TPSM63606 dc dc convertors have caught on fire when the input power was connected.

Input : 18-24V low internal resistance battery

Output of one TPSM63606 : 14.4v

Output of other TPSM63606 : 3.5v

There was no load on 3.5v unit and maybe few 100mA at max on the 14.4v unit.

Not able to figure out why the both the units fried. There are no inrush regulating circuitry, but none is recommended and all our attempts to break another board with sudden powerup has been unsuccessful.

The layout is as shown below and the circled area is burnt

The SW(14 pin) traces had been pulled up to the VCC during the event.

After the event, input and output had been shorted with ~6ohm.

10 months ago

0 Henry Kou 10 months ago

TI__Expert 3766 points

Hi Eohan,

Please send the schematic and layout along with the design input parameters. I'll take a look and there may be a need to run a failure analysis procedure.

Regards,

Henry

0 Eohan George22 10 months ago in reply to Henry Kou

Intellectual 620 points

Is there a way to send a PM ?

0 Henry Kou 10 months ago in reply to Eohan George22

TI__Expert 3766 points

Hi Eohan, just accepted you friend invite. Feel free to send the materials there.

Regards,

Henry

0 Eohan George22 10 months ago in reply to Henry Kou

Intellectual 620 points

A team mate of mine sent you the details.

0 Henry Kou 10 months ago in reply to Eohan George22

TI__Expert 3766 points

Thanks for the info, I was able to look, but ran into some software issues. Were these files from Eagle CAD software?

0 Suphakorn Lertruchtkul 10 months ago in reply to Henry Kou

Prodigy 55 points

Yes

0 Henry Kou 10 months ago in reply to Suphakorn Lertruchtkul

TI__Expert 3766 points

Hi Suphakorn,

If possible can you generate PDF versions of the sch and board? I tried importing to Altium but the symbols and routing were incomplete.

I can try to download Eagle, but this will take time with the firewall.

Thanks,

Henry

0 Suphakorn Lertruchtkul 10 months ago in reply to Henry Kou

Prodigy 55 points

Please kindly check my private message

0 Henry Kou 10 months ago in reply to Suphakorn Lertruchtkul

TI__Expert 3766 points

Received! Thanks for the support. Will take a look.

Regards,

Henry

0 Henry Kou 10 months ago in reply to Henry Kou

TI__Expert 3766 points

Hi Suphakorn,

Do you have an input bulk electrolytic cap with high ESR in between the battery and the TPSM63606 device? It seems like you are running into a "hot-plug" electrical overstress issue which is undamped. Due to a high enough input inductance (due to long input leads) and CIN, LC resonance occurs that can shoot the input voltage to ring almost double the input voltage. This might be what caused your devices to catch fire. I recommend adding a 50V rated 100uF electrolytic capacitor with a few hundred mOhms of ESR resistance to your input line. See the simulation below for a depiction of what is probably happening at the VIN of your devices.

Regards,
Henry

0 Suphakorn Lertruchtkul 10 months ago in reply to Henry Kou

Prodigy 55 points

Hi Henry,

Thank you so much for your help. There are some electrolytic cap in between the battery and the TPSM63606 but they are all close to the battery and follow by a long copper pour without any cap in between. We will definitely try this and let you know if there's any update. Thanks!

0 Henry Kou 10 months ago in reply to Suphakorn Lertruchtkul

TI__Expert 3766 points

Hi Suphakorn,

I would also measure the VIN close to your device to see what ringing your IC is experiencing during the hot plug event. Feel free to reopen this thread if more issues come up.

Regards,

Henry

0 Suphakorn Lertruchtkul 10 months ago in reply to Henry Kou

Prodigy 55 points

Will do. Thank you!

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TPSM63606: Burning during power up phase?