TPS1663: TPS1663 not starting up

Jugal Mistry

Part Number: TPS1663

We are using TPS16630RGER efuse in one of the circuits which sources power to other secondaries. Attached is the snapshot from schematics. The load connected to it is secondaries (DC:DC converts, MCU LDOs, comparators, etc) and an active constant current sink which in total draws 3Amps from the efuse. During the power up, I heard the monitored voltage rail trying to rise up but eventually fail and then repeat the cycle.

Changes I did for debugging:

Disabled slow ramp up: Removed C312
Added a startup delay: Changed R320 to 132kR, added another 132kR in series to COM. Added a 2.2uF cap from nSHDN to COM.

The issue: The device is entering thermal regulation and still not starting up.

Yellow is Vin

Blue is Vout

Magenta is Iout

Vout goes flat for 1.25sec and later the device enters shutdown mode.

Do you have any suggestions here, or could the thermal regulation be a bottleneck?

4 months ago

0 Bandaru Hemanth 4 months ago

TI__Genius 12220 points

Hi,

It seems like a thermal shutdown.

few follow up questions:

1) without downstream load is the device powering up properly? if you haven't tested yet, can you test without downstream load?

2)Why can't you turn on the load after efuse fully powers up?

3) can you test after reducing the output cap? this might improve.

thanks,

Hemanth.

0 Jugal Mistry 4 months ago in reply to Bandaru Hemanth

Prodigy 20 points

Hi Hemanth

1) Yes, without the load, it works as expected.
2) That could be the next step. Wanted explore other options before a PCB change.
3) Yeah I will try that.

Thank you

0 Bandaru Hemanth 4 months ago in reply to Jugal Mistry

TI__Genius 12220 points

Hi Jugal,

please try that, keep me posted.

thanks,

Hemanth

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TPS1663: TPS1663 not starting up