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RE: TPS61164EVM Board Failures

Niel Mazurek
Prodigy 60 points
Other Parts Discussed in Thread: TPS61165

 

Hi,

I am using the TPS61165EVAL board to run the backlighting on a protoype LCD display product.

The TPS61165EVAL board is configured to drive 4 parallel strings of LEDs ( 20ma @ 24V x 4 = 80ma @ 24Vl).  The only change to the TPS61165EVAL board is the current sense resistor was changes to 2.37_OHM. The TPS61165EVAL board is powered by 5V.

I have several failures now of the TPS61165 on the eval board. The backlight will operate properly for several days and then fail. If I let the board sit for several hours it will worrk again for several minutes and then fail. After several times times it no longer works at all. The failure mode is that the output is 5V and (no switching present) and that the CTL input measures a short to ground.

Any comments on what may be wrong here will be appreciated.

Thanks,

Niel

 

 

 

 

 

 

 

  • 0
    TI__Guru**** 165766 points

    Intermittent failures such as you describe have historically been caused by either poor solder joints or a damaged IC.  Poor solder joints should be able to be reflowed in an oven or with a hot air machine.  See app note SLUA271.  The damaged IC could be caused by a power supply or CTRL line signal that over/under shoots when rising/falling.  Alternatively, this IC's small package can be easily damaged when using a soldering iron to change any component.  The package expands on one corner due to the soldering iron being placed near that corner and the internal bond wire and package get hairline cracks.  Proving the damaged IC theory is difficult without performing an XRAY of the package.

    Did you have several EVMs or one EVM and you changed out the ICs?  Were the top markings on all of the ICs the same?

  • 0 in reply to Jeff F
    Prodigy 60 points

     

    Hi Jeff,

    Thank you for the quick reply.

    I had read about the the solder issue and though that may be the culprit, but I figured I would as around in case i missed something obvious.

    The control input pin is just hook to a port on a micro-controller.

    I have several of the eval PCBs. One I have keep as my "golden unit" for now and have not attached it to my PCB.

    I did replace the TPS 6115 with parts we purchased from Digikey. It would appear only the date code is different.

    The first several times we used a standard solder station iron to replace the part.  Now that we know the possible issue we will try to replace the part with the hot air tool attachement.

    Thanks,

    Niel

     

    BTW, thanks for the advice on the alternate LED driver part. As you can tell I am a bit of a novice with selection and use of the large varirty of LED driver parts now available.