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TL431-Q1: Is Ika related to accuracy?

Part Number: TL431-Q1
Other Parts Discussed in Thread: TL431

Dear team,

1. Below specs are reference voltage's accuracy, and the test condition is Ika=1mA. If Ika>1mA, will the accuracy change? Is Ika related to accuracy?

 

2. How to calculate the Ika? In my understanding, for TL431X-Q1, the min current is 1mA which means this device can't work normally at Ika<1mA. If TL431 has no load, it is better to adjust R1 value to set Ika=1mA, in this way, R1 has minimum dissipation, Ika*R1. If TL431 has load, input=5V, Vka=2.5V. The current that load needs is 2.5/12.5=0.2mA, then Ika=(5-2.5)/R1-0.2, right?

Thanks & Best Regards,

Sherry

  • Hi Sherry,

    To answer your questions:

    1. If IKA > 1mA, the reference voltage will change by a little bit, but there is not a direct relationship between that current and the reference voltage. Nominally, that line in figure 3 is perfectly vertical, but in reality the cathode voltage goes down slightly with increased current, although the amount that it goes down is not characterized as a function of IKA.
    2. Yes, your equation is correct.

    -Tony

  • Hi Tony,

    Thanks for your reply!

    For the question 1, maybe my description is not clear. Below table, the accuracy of ATL43XLIAx is 1%, and the test condition is Ika=1mA. My question is if the Ika is not 1mA, for example, >1mA. What is the accuracy, still 1%? Or the accuracy will be changed?

    Thanks & Best Regards,

    Sherry

  • Hi Sherry,

    Sorry for my confusion and thank you for the clarification!

    If you increase IKA, the accuracy will stay at 1%. Keep in mind that the voltage will predictably shift, even if the tolerance stays the same.

    See https://www.ti.com/lit/an/slva445/slva445.pdf

    -Tony