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TL431: TL431CLP-Z Shunt Current Data Sheet Question

Tom Dunn
Prodigy 80 points
Part Number: TL431
Other Parts Discussed in Thread: TL432,

I am a hobbyist. I purchased a few TL431CLP-Zs to get to know the adjustable xx431, i.e. there was no specific circuit design criteria to meet.

As is typical of my purchasing method, I went to Mouser and selected several xx431 models to compare features and prices. Most all makes/models of the xx431 list 100mA as their maximum shunt current limit. However, the Mouser Compare Function lists the TI TL431CLP-Z as having a maximum shunt current limit of 400mA. Therefore, I bought the TI model TL431CLP-Z for its higher current shunting ability.

The data sheet provided for the TL431CLP-Z is the generic data sheet for the TL431/TL432. The TL431C section of this data sheet does not provide the specifics of the TL431CLP-Z's higher shunt current capability; 400mA.

The only information that I have found regarding the difference in the shunt current limit is the TI product page for the TL431CLP-Z = https://www.ti.com/product/TL431. It states two criteria:
- Iz for regulation (Min) (uA) 400
- Iout/Iz (Max) (mA) 100

Please explain these two criteria and there differences in applying them. Thank you for you help.

  • 0
    Prodigy 80 points

    Upon additional study, I see that the Dynamic Impedance of the common model TL431C is: VKA = Vref, f ≤ 1 kHz, IKA = 1 mA to 100 mA. Is the difference that the TLCLP-Z begins regulating at 400uA, whereas the TL431C begins regulating at 1mA?

  • 0 in reply to Tom Dunn
    TI__Mastermind 47215 points

    Hi Tom,

    For minimum cathode current for 2.495V regulation, the TL431C requires a typical of 400uA if VREF is connected to the cathode.  See below:

    Maximum current going into the cathode will be 100mA for all variations of TL431.  So at a typical 400uA, voltage at VKA and VREF will be at 2.495V.  This is the definition of IMIN.

    Regarding the dynamic impedance, figures 3 and 4, when measuring this spec, it easier when the curve is linear.  Therefore, the data was measured when the cathode current was 1mA and above.

    As you can see, the dynamic impedance can be taken from these curves because impedance = VKA / IKA.  Once VKA = VREF and IKA is 1mA and higher, the dynamic impedance can be measured, as shown in figure 3.

    I hope I have answered your questions.

    Ben

  • 0 in reply to Ben C
    Prodigy 80 points

    Thank you, Ben. If I understand correctly, the TL431CLP-Z model has the same 100mA shunt current maximum specification as all the other TL431 models and that the Mouser Comparison Chart was both incorrect and misleading... What  Mouser states as the 400mA maximum shunt current limit is actually the typical 400uA minimum cathode current required for operations. I will spread the word and notify Mouser.

  • 0 in reply to Tom Dunn
    TI__Mastermind 47215 points

    Hi Tom,

    That is correct.  All variants of the TL431 family have the same 100mA shunt current max spec.  Mouser is stating the wrong max cathode current for the TL431CLP-Z.

    Ben