• Locked Locked
  • Replies 3 replies
  • Subscribers 62 subscribers
  • Views 362 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Re: TPS61161 FB pin fixed at 600mV cannot be changed.

David Fansler
Prodigy 70 points

Jeff,

I too have found that the "A" parts will not work.  I first ordered 10 TPS61161DRVT and got my circuits working.  Ordered 10 more but of the TPS61161ADRVT model and out of seven I have tried, not one of them has worked.  I finally shrunk my board down to just the driver components without the LED's  - one with a copper ground plane, one without and still no joy.

I contacted Newark, from where I got the A parts about the problem - but have not heard back from them.  I just ordered some more non-A parts from Digikey.

I still have 3 of the A parts and the two test PCBs if you would like to figure out what the problem is.

Thanks,

David

 

I do not have the same lot – the new lot is 08T  9CK  C66T

I checked from ground to FB  and get 200mv on the working  units and 0.0mv on the not working units.
So it appears I have a problem other than the 200mV/600mV issue.

Thanks,

 

David

Upon closer examination, the lot number is

0BT
9CK
C66T

David

 

  • TI__Guru**** 166626 points

    The resolution to the original email was that the lot of ICs were mis-processed.  The customer has contacted his distributor and is in the process of getting replacement parts.  Is the lot code on your ICs the same as in the original post? If so, then you have the same problem.  If not, then you likely still have the same problem if your ICs regulate FB to 600mV.

  • TI__Guru**** 166626 points

    I split your post from the original post to which you attached since your problem seems to be different.

    I am not aware of ICs that were misprocessed and that resulted in 0V output.  However, I do know that the small 2x2 QFN requires special care when soldering or the IC will be damaged internally.  The app note at http://focus.ti.com/lit/an/slua271a/slua271a.pdf explains the problem. Essentially, if the IC is heated assyemtrically, then the package and internal bond wires may crack and cause the IC to stop functioning properly.  If you are absolutely certain that this is not the problem, then please send a schematic for me to review.  If the schematic looks reasonable, then I likely will not be able to help further, since the ICs are non-functional, and the next step would be for you to return the ICs to your distributor.

  • TI__Guru**** 166626 points

    Not sure if you saw the answer after I split the thread so I copied it below.

    "I split your post from the original post to which you attached since your problem seems to be different.

    I am not aware of ICs that were misprocessed and that resulted in 0V output.  However, I do know that the small 2x2 QFN requires special care when soldering or the IC will be damaged internally.  The app note at http://focus.ti.com/lit/an/slua271a/slua271a.pdf explains the problem. Essentially, if the IC is heated assyemtrically, then the package and internal bond wires may crack and cause the IC to stop functioning properly.  If you are absolutely certain that this is not the problem, then please send a schematic for me to review.  If the schematic looks reasonable, then I likely will not be able to help further, since the ICs are non-functional, and the next step would be for you to return the ICs to your distributor."

    There is no easy way to confirm the solder damage on the bench.  You could try measuring each IC pin's resistance to ground and compare to a working IC (both out of circuit) but the pins on good ICs are very high impedance anyway so you might not measure a difference.   The only way to confirm this type of soldering damage is through an X-ray of the IC.  That is performed by our failure analysis team, once the ICs have been returned back through the original channel of purchase.  If the any pin other GND measures as a short to GND, that would be another problem.

    Do you have access to a hot plate, solder reflow station or oven?

    I looked in our return tracking system and did not see any returns related to your specific lot code.