TPS259824OEVM: Output cap at 0.4V

Hi Kunal Goel,

Load cap is 22uf. The voltage was 12V. With or without external loaded connected, the output of them were both only rampped up to 0.4V. VIN and VOUT wavefoems were shown in below. CH1 was the input and CH3 was the output. Due to it set as infinited retry mode, every 3.2s (0.2s was the retry delay time) he noisy segement happedn on the CH3. I assumed it's the retry period.  

Hi Tim,

Have you clicked on resolve button? 

What signal is channel 2? You are testing on EVM,right? Are you sure channel 3 is VOUT, because channel 2 looks like VOUT.

What is multimeter showing at VOUT?

You faced this issue on first time power up?

Regards

Kunal Goel

Hi Kunal,

Sorry for that I accidently clicked the "reloved" botton. But it's not been resloved yet.
The case here was I had some instances (same circuit), but only one had this issue. Multimeter showed value was also around 0.4V. Issue was presisited there, even by chaning different loads. I was not aware issue started from first time power up or not.

Thanks,

tim 

Hi Tim,

What signal is channel2? So you used EVM design on your own board? Only 1 board has issue and other are working fine?

Regards

Kunal Goel

Hi Kunal,

CH2 is the other same design of circuit output. And I used the same set up like EVM on my own board. Issue only happened on one on the board. 

Thanks,

tim

Hi Tim,

It could be device related. Can you replace with new device and check ?

Regards

Kunal Goel

Hi Kunal,

Yes, it's the plan currently I have. I plan to replace the part and also to issue a FA request for the case.
But at the same time, I am not sure there's any possibilty that the case is caused by any strapping value related. 

One question about the part. Could be any possibility that any protection feature will have this ourcome, capped the output at 0.4V?

thanks,

tim

Hi Tim,

What tests did you did before you saw this behavior? Most of the protection mechanism turn off part, thus VOUT=0. 0.4 means there could be a current path from IN to OUT. Can you probe other pins like dvdt , ITIMER? 

Can you share your schematic ?

Regards

Kunal Goel

Hi Kunal,

The itimer looks good. I said that because the waveform of good circuit and bad circuit are the same. For the dvdt, for the bad one, it did not come up either. The good bad one and good one are shown below.

Sorry for that I can not share the schematic here. But what I can say is that the good one and bad one are having the same circuit, the same instance. 

Thanks,

tim

Hi Tim,

What is Green and what is Yellow? Left is bad and right is good? You can share schematic , layout on personal messaging. You can also try placing bad part on EVM and test or you can submit for FA. Was bad part working before or it failed on first power up?

Regards

Kunal Goel

Hi Kunal,

CH1, Yellow, is the input. CH2, Green, is the dvdt. For design related file sharing, I need to check it. I will submit a FA request and I actually planned to.

Thanks,

tim

Hi Tim,

Just one thing is the scale for dvdt 200mv/div or 2v/div?

Regards

Kunal Goel

Hi Kunal,

The scale of CH2, dvdt is 200mv/div.

thanks,

tim

Hi Tim,

The good board waveform on right also looks not expected from dvdt perspective. dvdt should rise above VIN and finally settle to VIN. But if time scale is 0.2V/div then dvdt value is quite low and also looks dvdt is already at some voltage even when VIN is zero?

Regards

Kunal Goel

Hi Kunal,

That's becasue it's out of the screen. Below CH1 is the output vs CH3 is the dvdt for the good one.

Thanks,

tim

Hi Tim,

Lets see what FA says. But one thing it looks dvdt is always  following output in good part , it should actually go above output and then finally follow output.

Regards

Kunal Goel