TPS61096A: Feedback Pin Voltage

Hi Andrew:

What's the Vin and load condition? Is the issue exist with no load?

Please measure the Vin, SW together with Vout.

The load is probably 12mA.

Blue is Switch, Green is Vin, Magenta is Vout, and Cyan is FB pin.

Hi Andrew:

Sorry, I little confused with color. Just double check with you if the Channel 2 is the Vin or FB?

According to your previous post, the Vout is square, right?

And according to the SW signal, the converter seems not operate well. May you check the soldering and components healthy at first, and then share the schematic and layout for me to check. 

1- SW

2- Vin

3- Fb

4- Vin

I was concerned about the square like behavior on the Fb pin.

Hi Andrew:

I'm still confused.

May you confirm the signals once again. Otherwise, it's hard to believe the FB is so high.(If there is no soldering or damaged issue.)

Sorry,

1- SW

2- Fb

3- Vout

4- Vin

Hi Andrew:

May you check the soldering and components healthy at first, and then share the schematic and layout for me to check?

The FB should follow the Vout as it only through the divided resistance.

All our PCBs do the same thing.  I also purchased a TPS6109A eval board and it has the same behavior.  I did notice that in the block diagram in the datasheet there is a FET in the part connects VOS to VOUT.  It appears to be driven by the controller.  So maybe this is all normal?

Hi Andrew:

The internal  FET has parasitic diode, so the VOSNS won't be zero when Vout is high enough.

Beside with FB signal, the SW signal is also wired. Have you observed same same phenomenon on EVM?

I would like to double check in our lab. But unfortunately, my team's lab is not available these days. Maybe need one more week. It's appreciate if you would wait with patience. 

Hi Andrew:

I just arrived the office today. May I know if there any update in you side? If the phenomenon is the same as before, I will prepare the bench for the test in my side.

I still see the same behavior on both the Eval board from TI and my design