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Original question:

TLV62130: Multiple dead TLV62130-based devices in the field

TLV62130: Strange behaviour of EN pin on 'faulty' TLV

Riemer
Prodigy 20 points
Part Number: TLV62130
Other Parts Discussed in Thread: TPS62903

On another device that returned 'dead', we noticed again a low voltage on the EN pin: 0.48V when pulled up to Vin@5.0V over a 1K resistor. This indicates a much higher current than what's stated in the datasheet.

Moreover, we found that actually the device can be revived by increasing the voltage on the EN pin. This draws about 10mA when forcing 2V on the EN pin, increasing to 50mA when 2.8V is put on the pin. At 2.9V the current hit the limiter which we set at 200mA.

The EN pin is powered from the V_In net through an RC, with 1K resistor and 100nF cap. So indeed, at unpowering the device, there will be a voltage higher than Vin until the 100nF has been depleted -- but could this tiny amount of energy damage the chip? Counter evidence would be that we have other designs using the same chip, with a 100Kohm and 100nF cap on the net and there the TLV never dies.

  • 0
    TI__Expert 8100 points

    Hi Riemer,

    Due to thanksgiving holiday, my colleague will give you reply by next week!

    BRs

    Zixu

  • 0
    TI__Mastermind 25960 points

    Hi Riemer,

    Yes the EN pin voltage exceeding VIN+0.3V can cause IC damage. Are you adding a delay on the EN pin to turn on the device at a certain threshold? If so, adding a schottky diode from EN to VIN with 10k ohm resistor in series may help here. Another option is to use TPS62903 instead which does not have this EN voltage limitation.

    Thanks,

    Amod

  • 0
    Prodigy 170 points

    Thank you for the fast reply. Your suggestions make a lot of sense and are very valuable.

    At this moment we're looking for a way to prove this is the root cause of the failures, to ensure we're not waiting for new PCBs to arrive to find out there was another root cause.

    To this end, we tried 2 approaches:

    - changing the 1Kohm+100nF RC on the EN pin to 1Kohm+10uF. The idea is that if the EN pin is damaged by the leftover voltage on the cap, enlarging the cap x100 should surely damage the EN pin. Tried on 2 new devices, after 100 reconnects: not a single impact or negative effect on the EN pin.

    - putting voltage on the EN pin of an unpowered device: at 3.4V the EN pin starts drawing a bit of current; but even after 100mA of current there remains no imact of negative effect on the EN pin.

    --> therefore, we're a bit doubtful that this is the real or only rootcause of the issue we're seeing.

    Could we send you the schematics/gerbers + node measurments for a quick review? How can we get them to you privately?

  • 0 in reply to Riemer
    TI__Expert 7860 points

    Hi Riemer,

    I sent a private request to connect on E2E with my contact. Amod and I can help support this directly over email.

    Thanks,

    Joseph