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TL431-Q1: Ika cathode current minimum vs Imin

Jared Becker
Genius 11495 points
Part Number: TL431-Q1
Other Parts Discussed in Thread: TL431LI-Q1, , TL431

Hi Team,

I am a bit confused by the minimum cathode current spec in the datasheet. Under recommended operation conditions, the minimum is specified at 1mA. However, the Imin spec in table 6.6 shows 0.7mA max and 0.4mA nominal, with no minimum spec. Can you please help me understand why these numbers are different and why Imin is spec'd with a max value and not a min value?

Thank you,

Jared

  • 0
    TI__Mastermind 19370 points

    Hi Jared,

    There is no clear answer to this question. I feel it has to do with tradition as the TL431-Q1 was based of the original TL431 which has a 1mA current in the initial release. If you need a device that has the RoC to match the EC, check out the TL431LI-Q1.

    The Ika(min) is the minimum current for regulation and I see no issue with using the device around this operating current. At Ika(min) the TL431-Q1 will be operational and functional as per the EC table.

    Keep in mind that the TL431-Q1 also has AC parameters that are based off of the internal op amp. When the TL431-Q1 is closer to the ika(min) the device has lower gain on the gain/phase but it will still be fully functional. I often see customers bias the device at 1.5x - 2x the Ika(min) for margin and higher gain. This can be critical in AC/DC applications.

  • 0 in reply to Marcoo Z
    TI__Genius 11495 points

    Hi Marcoo,

    The LI version will not work for my application b/c I need more than 15mA Ika. The Ika(min) spec and Imin spec need to match for the automotive grade device. Can you please track down the real min value for me?

    Thank you!

    Jared

  • 0 in reply to Jared Becker
    TI__Mastermind 19370 points

    Hi Jared,

    Let me look into this for you. If you want, feel free to email so we can take this offline and discuss it.

    To elaborate, The no grade TL431-Q1 has a Ika(min) of 1mA so it matches the RoC. I assume your question is over making the RoC match the TL431B-Q1 grade? Or have a separate line item for this grade?