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ISO1042: Vcc1 Damage short to ground

Kuan Wei Chen (Kevin Chen)
Genius 9710 points
Part Number: ISO1042

Dear Team,

Can you help me to check is there any concern at the below schematic?

This IC's Vcc1 short to ground damage, the LDO provides power to Vcc1 still work normally.

This IC was damaged during whole system testing which might be a little bit noisy.

BR

Kevin

  • 0
    TI__Mastermind 49495 points

    Hi Kevin,

    Sorry to hear about the issue.

    1. Can you please confirm if the damage is on VCC1 or VCC2?
    2. If it is VCC1, can you please confirm the LDO part number? Is it LDL1117?
    3. I see LDL1117 abs max for VOUT is "VIN+0.3" which means that the device can withstand voltages upto 18V. It is possible that during testing a higher voltage transient could have passed through the LDO to VCC1 of ISO1042 causing VCC1/GND1 short while the LDO is undamaged. Fast transients can pass through the LDOs and hence, if such transients are expected at VCC1 of ISO1042 then we recommend customer to use suitable protection circuit, like TVS diode.
    4. Can you please also confirm what all testing were being carried out during device failure? Was there any EMC test like Surge, ESD or others?

    I do not see any other reason for VCC1/GND1 short, VCC1 abs max voltage violation can lead to such failure conditions. Let me know if there is anything else I can do here, thanks.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    TI__Expert 6955 points

    Kevin,

    Have you been able to gather the information that Koteshwar requested?

    Respectfully,

    Lucas

  • 0 in reply to Lucas Schulte9
    TI__Genius 9710 points

    Dear Team,

    Sorry for the late.

    Because the customer is difficult to duplicate the issue.

    So they will discuss add TVS or not in next build.

    To answer Rao's question:

    1.Yes, it is Vcc1

    2.Yes, it is LDL1117S33R

    3.I think we should check out accuracy which is Vo+-3%

    4.No specific test, just turn on the power with higher load

    BR

    Kevin

  • 0 in reply to Kuan Wei Chen (Kevin Chen)
    TI__Mastermind 49495 points

    Hi Kevin,

    Thank you for your response.

    On point (3), I meant to say that since the device is rated for upto 18V even at the output, the LDO will not be damaged if LDO output goes to higher than 5.5V while the VCC1 of ISO1042 can get damaged. Hence, my suspicion is that >5.5V has appeared at VCC1 of ISO1042 which damaged the ISO1042 device but not the LDO.

    I understand it could be difficult to replicate the issue. If customer is able to replicate the issue then do request customer to share the waveform at VCC1 during the damage. One way to capture this waveform is to keep the oscilloscope single-triggered at VCC1 for a threshold voltage >5.5V so that when voltage exceeds 5.5V, the scope will capture waveform.

    Apart from this, I do not see any other way to cause a damage to VCC1 of ISO1042.
    I will go ahead and mark this post closed, if you do see get any update from customer on this issue please do reply to this post. if this post gets locked by the time you have an update, then please create a related/new post. Let me know if you have any questions, thank you..

    Regards,
    Koteshwar Rao