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Can TI TL431 tolerate continuous 150mA current ?

David Zhang16358
Expert 1860 points
Other Parts Discussed in Thread: TL431

Sincere Thanks.

  • 0
    TI__Guru**** 152966 points

    Hello David,

    The data sheet has absolute maximum values on page 10.
    The abs max cathode current is 150mA. but it come with this warning...
    Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings
    only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating
    conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

    The best way to maximise lifetime is to keep the device cool. If the cathode and reference are shorted the power dissipation is 2.5V*.15A=375mW. Most packages can dissipate this power. However, If the cathode voltage is programmed higher (feedback resistors) then it will be difficult to keep the device from overheating.

    Perhaps there is a better device for your application. What are your input and output requirements?

    Regards,
    Ron Michallick


  • 0 in reply to Ron Michallick
    Expert 1860 points

    Ron,

    Thank you for your answers.

    I have used TL431 to build a variable 2.5V to 12.5V output voltage and 2A current sink.

    Based on my simulation by TINA, the current into TL431 can reach 134mA.

    I really want to find some things looks like TL431 but with higher current sink ability such as 200mA.

    Thanks.

  • 0 in reply to David Zhang16358
    TI__Guru**** 152966 points

    David,

    Figure 19 in the data sheet shows a circuit that can output 2A and keep a low cathode current.
    The right transistor need to be rated for maximum VIN and maximum output current.
    The left transistor can be rated for much less current.
    The Darlington transistor setup requires little     base current so R can be large and keep cathode current low.

    Ron.

  • 0 in reply to Ron Michallick
    Expert 1860 points

    My sincere thanks for your great answers.

    Right now the cathode current is lowered to 90mA in TINA simulatiom.