TPS25940: Output dip observed - At power ON condition.

guru sai

Part Number: TPS25940

Dear Team,

We are using TPS25940AQR for circuit protection.

At power ON, we are getting voltage dip as per the below image.

We had verified EN/UVL, OVP as per the graph mentioned in the datasheet. EN/UVL, OVP is exactly the same as mentioned in datasheet.

Also, we had isolated all the output components from the board(output of Efuse) and an external resistive load of 1A is connected.

The below waveform explains the issue

Ch1: FLT# pin voltage with pull up 5V

Ch2: Output 5V supply.

The schematic file is provided.

over 6 years ago

0 Rakesh over 6 years ago

TI__Guru** 105361 points

Hi Guru,

Can you check whether the device is soldered perfect ?
Please provide waveforms of Vin, Vout, Iin and FLT

Best Regards,
Rakesh

0 Rakesh over 6 years ago in reply to Rakesh

TI__Guru** 105361 points

Hi Guru,

Any updates?

Best Regards,
Rakesh

0 guru sai over 6 years ago in reply to Rakesh

Intellectual 550 points

Hi Sir,

We had tested and found the following issue.

We had connected 1A load.

We had switched ON & OFF randomly. At some instance, we didn't find any voltage dip. Please find the below waveform.

Ch1: input voltage; ch2: I_Mon pin; ch3 : FLT# pin ; ch4 : output voltage

But the majority of the times (if we tested for 10 times, around 8 times dip is observed). Please find the below waveform.

Ch1: input voltage; ch2: I_Mon pin; ch3 : FLT# pin ; ch4 : output voltage

0 Rakesh over 6 years ago in reply to guru sai

TI__Guru** 105361 points

Hi Guru,

Thanks for the waveforms.
I see IMON pin OPEN in your schematic. How are you measuring IMON voltage? It would be better to probe direct current (input current) using current probe while debug.
you mentioned 1A load. Is it a resistive load of 5Ohm? or using any electronic load

Please check voltages at EN/UVLO, OVP

Best Regards,
Rakesh

0 guru sai over 6 years ago in reply to Rakesh

Intellectual 550 points

Hi Sir,

For IMON Pin we had connected 10K Ohm resistor and other end connected to GND. We are probing at 10KOhm.

We had verified the voltages at EN/UVLO, OVP. All the voltages are Ok.

We are testing with a resistive load.

0 Rakesh over 6 years ago in reply to guru sai

TI__Guru** 105361 points

Hi Guru,

For 1A load, with 10kOhm resistor on IMON pin should give 520mV voltage at IMON pin. I see 1V in your test waveform.
Is the same behavior observed at no-load and on multiple boards?
To rule out noise dependency remove R3 at EN/UVLO, OVP pins while testing.

Best Regards,
Rakesh

0 Rakesh over 6 years ago in reply to Rakesh

TI__Guru** 105361 points

Hi Guru,

Can you confirm on the behavior repeat-ability. If needed we can have call to close this issue

Best Regards,
Rakes

0 guru sai over 6 years ago in reply to Rakesh

Intellectual 550 points

Hi Sir,

Sorry for the delay.

We had verified the voltage across IMON Pin, for 1A load. It is around 0.59V.

0 Rakesh over 6 years ago in reply to guru sai

TI__Guru** 105361 points

Hi Guru,

I have sent you private message. Please respond to schedule a call and discuss.

Best Regards,
Rakes

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TPS25940: Output dip observed - At power ON condition.