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Could you tell me about LM431's "Fast Turnon Response"?

Pokkun
Genius 4695 points
Other Parts Discussed in Thread: TL431, LM431

I'm sorry.

Since I have not been replying, I will post the same post.

--------------------------------------------------------------------------------------------------------

Hello.

My customer is evaluating for the purpose of adopting LM431.,now.

I have gotten a question about this product .

So, please teach me about LM431.

Could you help us?

＜Background＞

・My customer uses this product for detection purposes for overvoltage protection.

・When overvoltage is detected with this product, it shut down the system with FET.

・So my customers consider the speed from Supplying 2.5V into Vref PIN to until the operation begins.

＜Question＞

　Data sheet (English version) There is a description of "Fast Turnon Response" in p1.

How is Fast Turnon Response stipulated?

　Example Request Answers

　- For example, it is test the start speed against this item and specify it ...

　- Since there is no delay on the design (or theoretical), if there is a worst case assuming XXX sec, there is no problem in design ...

Best Regards,

Masumi Sekiguchi

  • 0
    Genius 4695 points
    I have not received a reply for 5 days since I first made an inquiry.

    At the beginning, I had time to spare, but I began being prompted by customers.

    Just the even situation, please let me know.
  • 0 in reply to Pokkun
    TI__Mastermind 24485 points

    Hello,

    I am moving your post to the Voltage References forum for better support.

    Best,
    Michael

  • 0 in reply to Michael J Schultis
    TI__Intellectual 1745 points

    Hi,

    Sorry for the delay in response time.  There is a detailed example and explanation of using a shunt reference as a comparator in the TL431 datasheet in section 10.2.1 on page 23.     This example shows that the response time of the shunt is dependent on the current through the device, set by the external resistor between VIN and the cathode.  There is no maximum time listed because it is dependent on this resistor.  You may want to test out some resistor values to decide if you want a faster edge at the cost of Iq, or if you want to save some power with a slightly slower edge.  It sounds like you would like a fast edge, in which case I would suggest a smaller resistor.  You cannot make this arbitrarily small as you must not let the current exceed the maximum of the device. For the LM431, the maximum cathode current is 100mA.

    Hope that helps,

    Chris

  • 0 in reply to Christopher Dean
    Genius 4695 points
    Thank you for answering.

    the external resistance between VIN and cathode that's name is "Rsup"?

    Also, what I want to know is about LM 431, but can I consider it to be the same except TL 431 and cathode current?

    Colud you help us?
    Best Regards,
    Masumi Sekiguchi
  • 0 in reply to Christopher Dean
    Genius 4695 points

    Thank you for answering.

    ・the external resistance between VIN and cathode that's name is "Rsup"?

    ・Also, what I want to know is about LM 431, but can I consider it to be the same except TL 431 and cathode current?

    Colud you help us?

    Best Regards,

    Masumi Sekiguchi

  • 0 in reply to Pokkun
    TI__Intellectual 1745 points

    Yes, sorry for not clarifying that. Rsup is the external resistor I was talking about.  The LM431 and Tl431 are functionally very similar, they can be used interchangeably, and both can be used in a comparator circuit.

    Chris