TPS2492: F\L\T\ can't be reset by toggling UVEN

Youxi Shao

Part Number: TPS2492

Hi TI team,

We use TPS2492 as a hotplug controller for a 24V bus. During the test when TPS2492 triggers overload protection, F\L\T\ pin can't be reset by toggling UVEN after the overload fault is removed.

Interestingly this problem is solved by lower the bus voltage to 22V. I double checked the threshold for OV and UVEN and basically I have 100KOhm, 4.99KOhm and 4.99KOhm as R1, R2, R3 shown in the typical application circuit in datasheet. From this the OV threshold voltage is 1.35/4.99K*(100K+4.99K+4.99K)=29.75V and it is also confirmed from test that when bus voltage is 24V, the OV pin voltage always shows 1.1V.

Here's my question,

1. Do you think there are any other reason will cause TPS2492 F\L\T\ not being reset by toggling UVEN?

2. If OV is not the reason to cause F\L\T\ stays low when overload fault is removed, can you explain why this looks like is solved by lowering down the bus voltage?

Thank you

over 6 years ago

0 Rakesh over 6 years ago

TI__Guru** 105361 points

Hi YS,

Welcome to E2E!
I will reply on your questions soon

Best Regards,
Rakesh

0 Rakesh over 6 years ago in reply to Rakesh

TI__Guru** 105361 points

Hi YS,

This behavior is not expected.
Are you testing on EVM TPS2492/3EVM ?

Can you please share test waveforms of
1. Vin, Vout, GATE, Timer during overload
2. Vout, GATE, Timer, Input current during overload

If you built your design board, please share the schematic.

Best Regards,
Rakesh

0 Youxi Shao over 6 years ago in reply to Rakesh

Prodigy 30 points

Hi Rakesh,

Thank you for your quick response. Attached are the schematics for our application and waveforms you asked for.

Yellow: Vin; Blue: Vout; Purple: Timer; Green: Gate

Yellow: Iload(measured across shunt resistor); Blue: Vout; Purple: Timer; Green: Gate

Thanks,

0 Rakesh over 6 years ago in reply to Youxi Shao

TI__Guru** 105361 points

Hi YS,

Thanks for the details.

Sorry, I would have asked for waveforms during UVEN toggle

Can you capture test waveforms of
1. GATE, Timer, UVEN pin voltage, F\L\T\ pin
2. GATE, Timer, Input current, UVEN pin voltage

Best Regards,
Rakesh

0 Youxi Shao over 6 years ago in reply to Rakesh

Prodigy 30 points

Hi Rakesh,

I figured out the cause of this phenomenon is that not enough pull down for UVEN when toggle this pin so the voltage does not drop down enough.

After I put enough pull down for UVEN, the circuit works properly.

Thank you,

Power management

Power management forum

TPS2492: F\L\T\ can't be reset by toggling UVEN