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TPS62400 failures

Angelo Pietroforte
Prodigy 200 points
Other Parts Discussed in Thread: TPS62403

I've been using the TPS62400eval as part of a bigger development system for a while.  It has worked fine and I am successfully programming the outputs via the 1 wire using a microcontroller.  Problem is that every once in a while it simply fails for "supposedly" no reason whatsoever.  I use the standard TPS62400EVM-167 and I did change the feedback resistors on both rails.  I have Vo1 that outputs 1.4V and Vo2 that programs between 2.8V and 2.1V.  I'm a little frustrated that I get periodic failures.  The last part I soldered to the board worked fine, and then when I started to program the outputs, using the provided USB Interface adapter, I was able to get the outputs to change, but then the chip failed.  The rails where not loaded at all, and JP4 is unpopulated.  PU is jumpered to MODE.  When the rails are loaded Vo1 delivers 30mA and Vo2 delivers 50mA.  

I solder the parts myself and have successfully done 40QFN packages, with heat slug center pads, successfully, dozens of times, so I believe my solder skills are solid having used heat guns and tools for years.

The previous part had SW1 node shorted to GND.

2)  Wouldn't I just be able to use part number for TPS62403 without feedback resistors for Vo1 programmed to 1.4V, and Vo2 that programs to 2.8V and to 2.1V?

  • 0
    TI__Guru*** 148310 points

    Yes, if you are going to use the interface, then you can use a fixed output voltage device like TPS62403.  Do you plan to change Vout during operation in the final system?

    A waveform of Vin and each Vout when the failures occur would help determine what is at issue.  I would also recommend looking at these signals when Vout is decreased from 2.8V to 2.1V.  What Vin are you using?

    Since you operate in forced PWM mode (MODE pin high), when the output voltage is changed, the IC should reduce the output voltage to the new setpoint by moving energy from output to input.  This will increase the input voltage.  It is conceivable that this increase could exceed the rating of the Vin pin.