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Original question:

LM5119: how to set VCCDIS pin and DEMB pin?

LM5119: What risks will arise if the VCCDIS is left floating ,meanwhile the externally supplied bias which is coupled to the VCC pins through a diode is 12V?

user6072694
Prodigy 105 points
Part Number: LM5119

What risks will arise if the VCCDIS is left floating ,meanwhile the externally supplied bias which is coupled to the VCC pins through a diode is 12V?

In addition,can you help provide the internal power supply schematic of VCC?

Best Regards~

  • 0
    TI__Mastermind 24075 points

    Hello, 

    If VCCDIS is floating (pulled down by internal 500k resistor) and VCC pin is charged by external 12V via diode, VCC pin voltage will override internal LDO voltage. 

    As we did not fully test the part at this condition, I'm not sure if there is any risk or not. 

    To play safe, I would suggest to avoid this situation. 

    The simplified diagram of internal circuit is available on datasheet page 12. Sorry, we can not provide detailed circuit. 

    Thanks

    Qian