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Original question:

LM53603-Q1: Question about BIAS protection

LM53603-Q1: BIAS pin failure mode

NOBUO FUJIHARA
Expert 8755 points
Part Number: LM53603-Q1
Other Parts Discussed in Thread: LM53603

Hi Team,

My customer is using LM53603 and asked questions about BIAS pin failure mode.

Q.1) BIAS pin Open

 - How LM53603 will behave with this condition? 

 - Will regulated output be seen on VOUT?

Q.2) BIAS pin short to GND

 - How LM53603 will behave with this condition? 

 - Will huge current flow to GND through BIAS pin and break internal circuitry?

Thanks and best regards,

  • 0
    TI__Expert 6215 points
    Hello Nobuo,

    During validation, we tested the LM53603 with both BIAS open and BIAS connected to ground. In both cases, VCC voltage is derived from VIN rather than BIAS while the chip is operating. (When shut down and initially during startup, output is low, which is the equivalent of grounding it.) Since VCC is derived from VIN which is a higher voltage than output voltage when BIAS is open or grounded, efficiency a little lower and unloaded current consumption (Iq) is about 2 times higher. The chip is reliable in either condition.

    Regards, Robert
  • 0 in reply to Robert Blattner
    TI__Expert 8755 points

    Robert-san,

    Thanks a lot for your prompt support.

    BR