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TPS62291: Output (Switching) Side Failure

Hari C
Prodigy 10 points
Part Number: TPS62291

Tool/software:

Hi,

TPS62291DRV - This is the IC we are using in our product. 

Product powered by usb (5VDC) & that is supplied to Vin, EN & Mode pin.

We did Damp Heat Cyclic (Thermal)Test for the product.

Test description:

  • Temperature: 30°C at 95% RH and 55°C at 93% RH with non-condensing.
  • Number of Cycles: 2 cycles
  • Duration: 12 hours dwell per cycle

6Hrs on 30degree & 6Hrs on 55degree with the above-mentioned humidity in a cycle.

The ramp up from 30°C to 55°C will be happening at a rate of 3 degree/ min and this time is excluded from the dwell time.

Issue:

After the thermal test 2 Products didn't work, the root cause for both product's failure is TPS62291DRV's output side failure.

One board is shorted on O/P side (SW to gnd).

Other board is giving 2.9V as O/p for a short time (less than a min) & goes to 0.3V. This is also checked with isolating the regulator from rest of the circuit.

Did observe 60 & 144ohms impedance in both boards across Vin to Gnd pin. 

Pls share the cause of behavior of this regulator. 

Regards,

C.Hari

  • 0
    TI__Mastermind 21580 points

    Hi C.Hari,

    TPS62291DRV has passed the following qualification tests which include biased and unbiased HAST as well as temp cycling.

    One cause for the leakages you observe on the output and input could be related to remaining flux after board assembly. Moisture may be helping the flux particles form leakage paths. 

    My suggestion would be to run ultrasonic cleaning on the boards to make sure there is no remaining flux particles before the qualification tests

    Best regards,

    Varun

  • 0 in reply to Varun John
    Prodigy 10 points

    Hi   

    Appreciate the response i do have a query. We tested our product in 93% - 95% RH as mentioned in my previous comment, however the HAST testing which you shared was on 85% RH. 

    Does testing at 93% - 95% RH can cause the TPS62291DRV to fail? 

    There is no humidity data in datasheet.

    Regards,

    C.Hari

  • 0 in reply to Hari C
    TI__Mastermind 21580 points

    Hi Hari,

    The 85% RH used is according to the corresponding JEDEC standard.

    I don't believe the higher RH of 95% used in your test is the reason. The qual tests run for this part at 85C were run at a much higher temperature (130C) and for a longer time duration (96 hours) compared to the test you mentioned. I would consider this as a more stressful qual for the device compared to the test you mentioned.

    Best regards,

    Varun