TPS61089: IC goes into an unknown status

Dear Sir,

This is a boost IC, so in the disabled state, when Vin=4.5V, Vo=3.9V.

What is your target Vout in the application?

Hi Helen,
https://youtu.be/4Sk0CmV8UrY

Please see my video link above and you can see that the Vout is 3.92V at time 0':42" and the ENABLE voltage is still 3.97V at time 1':10"~1':17".

During this situation, the voltage I measured were :
Vin : 4.52V
Ven : 3.97V
Vout = 3.92V (abnormal)
Vfb = 0.55V (abnormal)

On the same boards, it only happened after hundreds of Power on/off and the issue would happen on each board.

On my SCH below, it shows that :
VOUT (Booster out) is set to 9.02V

Thanks.

Terry

Hi Helen,

Unknown state means the Vin and Ven is ready but Vout is not boosted to the voltage I set.

As you said, it seems to be in disable mode, however the Vin and Ven is ready.

Please let me know if you have any comments.

Thanks.

Terry

Hi Terry,

I'm wondering whether the duration of the EN high is not long enough?

Hi Helen,

Thanks for your quicky reply.

Please see the below measurement result for one of these NG boards.

The EN is from TPS22954 PG (power good) open-drain pin and it is pulled up to TPS61089 Vin by 100K ohm.

So EN is almost the same as Vin with slightly delay.

It seems that there is no chance that the EN high is not long enough.

I am looking forward to your suggestion, thank you.

Terry

Thanks Terry for the update.

"one of these NG boards"  .......  Do you mean the phenomenon just happens on some boards? If it is, I guess this is due to the soldering issue.

Hi Helen,

Thanks for your input.

We have 1000 pcs PCBA and we found that there were about 20 pcs NG boards had this kind of issue. However, in these 20 pcs NG boards, this issue were not always happened when Vin power on.

It is hard to said that it is the soldering issue. Anyway, I will check if it is or not.

As you said, only EN is disable that Vout will output only 3.xV, am I correct?

By the way, would you please help to check the components value about Cin,Cout, L, and compensation filter is suitable or not?

Vin is 2.8V～4.5V,

Vout = 9V,

Iout =1.5A max.

Thanks.

Best regards,

Terry

Hi Terry,

Could you please post the schematic?  I can't find it!

SCHEMATIC1 _ Booster.pdf

Hi Helen,

I have attached SCH to this discussion thread several times. It seems all pictures I attached are removed by your system.

Now I attached SCH in PDF format. Please check it. 

Thank you.

Terry

Hi Terry,

The schematic is OK! I'm quite sure this is due to the soldering issue.

Hi Helen,
We have received 20 defective products returned from my customer. 
The defects are that TPS61089 sometimes fails to work properly, resulting in abnormal VOUT.

At present, there are still 50 bad boards similar to this phenomenon that will be RMA one after another. 
If these 50 units are also included, the current defect rate is about 70/400.

I selected 7 of them to do repeated ON/OFF power experiments, and found that in thousands of ON/OFFs, 
two of them can replicate this bad phenomenon.
Both of these two units are VOUT abnormal, but the ENABLE of TPS61089 is HIGH at that time. 

In order to verify whether it is a soldering problem, I just short-circuited R6 pin1 and GND and then released it. 
At this time, the TPS61089 VOUT of the two bad boards returned to normal.

Apart from the soldering problem, is there any possible reason to explain this strange phenomenon?

PS: 
R6 is the PG pin pull-up resistor of TPS22954 in the circuit diagram (SCHEMATIC1 _ Booster.pdf).
By the way, you can find SCHEMATIC1 _ Booster.pdf in the previous discussion thread.

Thanks.

Terry

6521.SCHEMATIC1 _ Booster.pdf

Dear Sir,

Thanks for the detailed information. Please connect a 10nF-100nF ceramic from the EN pin to GND(PG to GND) then check again.

I'm wondering whether it is caused by the a too high slew rate.