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Original question:

UCC21520: Reason for UCC21520A Device failure showing Impedance between INB and GND,VCCI and GND as 52 ohms

UCC21520: The reason for UCC21520 device failure showing error impedance between VCCI and GND, OUTB/VDDB and VSSB.

Gordon Xu
Prodigy 440 points
Part Number: UCC21520

Hi experts,

Customer met a failure issue about UCC21520. Could you help analysis the reason about the result? Plase see bleow test results of pin-to-pin impedance:

1.New device of UCC21520:  

VCCI-GND: 1.127MΩ

INA/INB/DIS-GND: 197kΩ

DT-GND: +∞

VDDA-VSSA: 1.36MΩ

VDDB-VSSB: 1.36MΩ

OUTA-VSSA: 1.63MΩ

OUTB-VSSB: 1.63MΩ

2.Failure device of UCC21520:  

VCCI-GND: 1.6Ω

INA/INB/DIS-GND: 197kΩ

DT-GND: +∞

VDDA-VSSA: 1.36MΩ

VDDB-VSSB: 0.8MΩ

OUTA-VSSA: 1.636MΩ

OUTB-VSSB: 0.8MΩ

Bleow is the schematic: 

  • 0
    TI__Prodigy 440 points

    Hi experts,

    If you could give the analysis results, please give the analysis process.

    Thanks.

    BR,

    Gordon

  • 0 in reply to Gordon Xu
    TI__Expert 4065 points

    Hi Gordon,

    I am analyzing this now, I will have feedback by tomorrow.

    Regards,

    Krystian

  • 0 in reply to Krystian Plaskota
    TI__Prodigy 440 points

    Please expedite the urgent case, thanks! 

  • 0
    TI__Expert 4065 points

    Hi Gordon,

    Can you describe what failure the customer was seeing?

    Are you able to share waveforms of the failure device switching, OUT, VDD?

    Under what conditions did you notice that this part failed?

    Is it possible that VDD went above the part's absolute max? I don't see any capacitance whatsoever on the output side of the gate driver. Perhaps a voltage transient could be the cause of this issue you are having. I recommend a 10uF and ≤100nF Cap on the VDD pins. 

    I also recommend having a gate to source resistor on both channels, this resistor is typically sized between 5.1kΩ and 20kΩ, depending on the Vth and ratio of CGD to CGS of the power device. It helps pull down the gate to the source voltage when the gate driver output is unpowered and in an indeterminate state. It also helps to mitigate the risk of dv/dt induced turn-on due to Miller current before the gate driver is able to turn on and actively pull low.

    Regards,

    Krystian