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LM2734X-EVAL: Input Voltage Above Nominal Failure Mode

Peter Marinov
Prodigy 10 points
Part Number: LM2734X-EVAL

LM2734X part has 20V maximum operation input voltage and 24V absolute maximum input voltage. What would happen if the input voltage is between 20 and 24V, or accidentally overshoots above 24V for example. Since I am looking into the FMEA of a design with 18V input, but powered from a Li-ION battery it can reach 21V when fully charged. What is the most likely failure mode of LM2734X due to input voltage overshoot? 

  • 0
    TI__Mastermind 47020 points

    Hi Peter,

    The input voltage beyond 24V even accidentally may cause permanent damage to the device. The input voltage beyond 20V may affect device long term reliability. Please use a part with higher input voltage rating for your application.

    Hope this helps,

    Thanks,

    Nancy

  • +1
    Prodigy 10 points

    Hi Nancy,

    Thank you for your swift answer. I have a few further questions:

     - what do you mean by 'voltage beyond 24V even accidentally'? Is short transient of a few milliseconds also dangerous?

     - what is the most likely failure mode if the device is subjected to 24V and above? Do I need to add a crowbar circuit to the output in event of MOSFET failure and a shoot-through  

     - how is the long term reliability affected by 21V supply voltage? Reduced lifetime, running hotter or some other phenomenon?

    Thanks and best regards,

    Peter

  • 0
    Prodigy 10 points

    Hi Nancy,

    Thank you for your swift answer. I have a few further questions:

     - what do you mean by 'voltage beyond 24V even accidentally'? Is short transient of a few milliseconds also dangerous?

     - what is the most likely failure mode if the device is subjected to 24V and above? Do I need to add a crowbar circuit to the output in event of MOSFET failure and a shoot-through  

     - how is the long term reliability affected by 21V supply voltage? Reduced lifetime, running hotter or some other phenomenon?

    Thanks and best regards,

    Peter

  • +1 in reply to Peter Marinov
    TI__Mastermind 47020 points

    Hi Peter,

    1. 24V is Vin absolute max rating. Even short transient of a few milliseconds would damage the device.

    2. The most likely failure mode if the device is subjected to 24V or above is device internal MOSFET permanently damaged. I am not sure if the crowbar circuit is working as fast enough.

    3. Regarding the long-term reliability of 21Vin, overstress internal MOSFET to reduce life time.

    Please use the link as below to select 30V Vin device for your application.

    Buck converters (integrated switch) product selection | TI.com

    Hope this helps,

    Thanks,

    Nancy