TPS2561: FAULT line not asserted during overcurrent event

Corey Lange

Part Number: TPS2561

I am using the TPS2561 to current limit a pair of USB ports, with each port limited to 560mA. When I create a short to GND on the output using an NFET circuit, the current is limited to around 560mA and the voltage falls to around 150mV. However, the FAULT line is not asserted low during this event. FAULT is being pulled up by a 100kOhm resistor. The Ilim resistor value is 100kOhm.

I have also tried a current limit of 1A using a 48.7kOhm resistor and had similar results, with the current being limited at 1.082A and the voltage falling to 1.186V. In this case as well the FAULT signal remains high.

over 5 years ago

0 Kevin-Cheng over 5 years ago

TI__Expert 3135 points

Hi Corey Lange,

could you please send me the schematic and the figure out test point, it would be better if you could provide the waveform.

Best Regards,

Kevin

0 Corey Lange over 5 years ago in reply to Kevin-Cheng

Prodigy 50 points

Hi Kevin,

I've attached a waveform and schematic here. In this case I applied the short for about 1 second.

Thanks,

Corey

0 Kevin-Cheng over 5 years ago in reply to Corey Lange

TI__Expert 3135 points

Hi Corey,

the schematic seems doesn't have any wrong, can you check if the Fault Pin you tested is according with the channel you shorted ?

Kevin

0 Corey Lange over 5 years ago in reply to Kevin-Cheng

Prodigy 50 points

Hi Kevin,

Yes, I checked both pins just in case and they both exhibit the same behavior.

Thanks,

Corey

0 Kevin-Cheng over 5 years ago in reply to Corey Lange

TI__Expert 3135 points

Hi Corey,
I will check it on EVM again, and get back to you soon.
Kevin

0 Kevin-Cheng over 5 years ago in reply to Kevin-Cheng

TI__Expert 3135 points

Hi Corey,

I have re-verified and tested it on the EVM, but I still can't replicate your problem, below is the test waveform. Could you please check your connections and test points again. If you have our EVM on hand, you can verify on it, and you can do a swap test by swapping the chip on the EVM board with the chip on your board.

Kevin

0 Corey Lange over 5 years ago in reply to Kevin-Cheng

Prodigy 50 points

Hi Kevin,

Yes, I can try to replace the part. Also, I noticed on your capture that the current limits to 2.4A. Are you able to verify the same functionality with 560mA limit (using 100k for Rilim)?

Thanks,

Corey