TPS25940L stops working after shorted output

Randy Mauger

Other Parts Discussed in Thread: TPS25940

I am using a TPS25940 EFuse to protect 8 high-side MOSFET power switches in a 12V system. I also have a diode in series with the 12V input to the EFuse for polarity protection. The EFuse is meant to protect against an overcurrent condition, above 3A, or a shorted output, like a wiring mistake. If I test the EFuse by shorting the MOSFET output to ground, the EFuse shuts down but, sometimes it fails to recover after a power cycle. From then on, the EFuse will not work.

I checked the EN/UVLO pin and it is at 1.11V and the OVP pin is at 0V (ground). However, the DVDT pin is at 0V. If I jump the DVDT pin to the 12V input, the output of the TPS25940 comes-up.

Any ideas why this is happening? This has happened to 4 or 5 EFuses now.

over 8 years ago

0 Rakesh over 8 years ago

TI__Guru** 105361 points

Hi Randy,

Can you please share your schematic.

Best Regards,
Rakesh

0 Randy Mauger over 8 years ago in reply to Rakesh

Prodigy 60 points

Hi Rakesh,

I attached a PDF of my schematic. The primary path that I am concerned about is the 12V input at J3 through the polarity protection diode D6 and finally the EFuse U3. The 12V output from U3 powers the 8 MOSFET high-side switches. If I short one of the MOSFET outputs to ground, which the EFuse was intended to protect against, the EFuse sometimes stops working. No smoke or any other apparent damage, it just turns off and never turns back on again.

Thanks,

Randy

RLC466-1 Schematic.pdf

0 Rakesh over 8 years ago in reply to Randy Mauger

TI__Guru** 105361 points

Hi Randy,

Thanks for sharing the schematic.
Can you please confirm the approximate load during startup. I see 470uF at the output of U3. Does all the 8 MOSFET high-side switches are in OFF state during startup?
Just to mention, please use high impedance probes if you are monitoring dVdT voltage. Also the ABS max. value at DVDT pin is 3.6V.

Best Regards,
Rakesh

0 Randy Mauger over 8 years ago in reply to Rakesh

Prodigy 60 points

Hi Rakesh,

The startup load current is really just the capacitor load. All 8 transistors power-up in the off state and the CPU only uses about 10mA at startup.

Thanks,

Randy

0 Rakesh over 8 years ago in reply to Randy Mauger

TI__Guru** 105361 points

Hi Randy,

The circuit configuration and all the parameter values are configured properly. I didn't see any concern even on CdVdT sizing. Is it possible to send some waveforms at Vin, Vout, EN, Devslp for analysis.

thanks
Rakesh

0 Rakesh over 8 years ago in reply to Rakesh

TI__Guru** 105361 points

Hi Randy,

I would be happy to see update on this. Are you able to capture waveforms or whether it resolved.
Please let me know if any support is needed in this regard

Thanks
Rakesh

0 Randy Mauger over 8 years ago in reply to Rakesh

Prodigy 60 points

Hi Rakesh,

Sorry that I did not get back to you sooner, I have been so busy with end of year stuff.

I determined that the problem must have been over-voltage spikes caused by the momentary short on the output. I put a TVS diode on the power input and that resolved the problem.

Thanks,

Randy

0 Rakesh over 8 years ago in reply to Randy Mauger

TI__Guru** 105361 points

Hi Randy,

Nice to hear that. Thanks for the update!

Best Regards,
Rakesh

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TPS25940L stops working after shorted output