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UCC28C43: PCN20221216002_device failed Flying Probe -wrong incircuit resistance

Szymon Jozwiak
Prodigy 70 points
Part Number: UCC28C43

Hello,

UCC28C43DR is used in one of our medical assembly. During latest production run, we noticed 100% production failed Flying Probe. The reason was a wrong in circuit resistance. We compared OK device (DC2022) and NOK (DC2349). 

Devices from DC2349 PIN 5 (GND) to 7 (VCC)=2,37MOhm.

Devices from DC2022 PIN5 to 7= 1,49MOhm

Prev Does the PCN mentioned in the title explains different resistance between leads? 

Thanks!
Simon

  • 0
    Prodigy 70 points

    Can anyone help out on this?

  • 0 in reply to Szymon Jozwiak
    TI__Guru 73215 points

    Hi,

    VDD pin 7 is to bias with a positive voltage to GND pin 5. The VDD pin current depends on the voltage above UVLO on or below UVLO off. There is no impendence specified but its current with associated current. Your measurement does not provide a proper root cause. Please provide your schematics and the fail descriptions so we can understand what possible root cause is for this fail.

  • 0 in reply to Hong Huang
    Prodigy 70 points

    Hello,

    Please note that the resistance check was done on desoldered component outside of the circuit. We used Fluke multimeter.   

  • 0 in reply to Szymon Jozwiak
    TI__Guru 73215 points

    Hi,

    As I explained, VDD resistance is not a parameter to define the device normal or not, I.e., it is not a datasheet specs so not to show in PCN, please provide your schematics for review. If you suspect VDD pin damage please check its UVLO on and off as well as its sink current.

  • 0 in reply to Hong Huang
    Prodigy 70 points

    Hi Hong,

    Thank you. I understand that resistance between PIN5-7 is not a datasheet parameter. neverthless we have In Circuit Test on our production, and we check resistance of other components in the cirucit. The resistance change on TI device caused production stoppage. I just want to get a confirmation that the resistance changed after PCN implementation. With this I could request our Test Engineers to redefine ICT limits.

    Regards,
    Simon

  • +1 in reply to Szymon Jozwiak
    TI__Guru 73215 points

    Hi,

    We do not test the VDD resistance so we cannot provide resistance specs for "old" or "new" devices. Please note VDD is an active pin its passive resistance is not an indicator when the pin is functional unless the unit gets damaged which can help to locate the issue. I suggest you re-define VDD resistance for the new devices if the resistance from all your received units are with similar resistance. If you see some new units resistance very different from others, I think you need to initiate a return process to request FA. The PCN has no such an entry as VDD resistance is not tested for either "old" or "new".