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  1. #1
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    tl431 pspice

    What modifications are needed to convert C. Bassos TL431 Pspice model
    to a TLVH431 model? The TLVH431 is the Low Voltage low current version of the TL431.

    I tried the obvious switching the 2.495V to 1.24V but I get a
    reference of 1.49V when I do this, it should be 1.24V.

    This is the TL431 model.
    Code:
    .SUBCKT TL431 7 6 11
    V1 1 6 2.495
    R1 6 2 15.6
    C1 2 6 .5U
    R2 2 3 100
    C2 3 4 .08U
    R3 4 6 10
    G2 6 8 3 6 1.73
    D1 5 8 DC
    D2 7 8 DC
    V4 5 6 2
    G1 6 2 1 11 0.11
    .MODEL DC D 
    +IS=13.5N RS=25M N=1.59 
    + CJO=45P VJ=.75 M=.302 
    + TT=50.4N BV=34V IBV=1MA
    .ENDS
    ********
    Thanks

    TL431

    Code:
    http://www.fairchildsemi.com/ds/TL/TL431A.pdf
    TLVH431

    Code:
    http://www.ti.com/lit/gpn/tlvh431

    •   Alt24th August 2008, 21:38

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  2. #2
    FvM
    FvM is offline
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    tl431 spice model

    It's a functional model only. To get it working at 1.24 V, you must at least reduce the V4 limiting voltage source. And shouldn't expect, that it describes the TLVH431 behaviour unless you adjusted the functional model to the device parameters.


    1 members found this post helpful.

    •   Alt25th August 2008, 07:10

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  3. #3
    Full Member level 5
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    tl431 model

    I found a more accurate TL431 behavioral model. Basso derives it in his second book. He provides comparisons of all the data sheet graphs, and the model reproduces them with pretty good accuracy. There doesn’t seem to be any significant difference with the LV version of the 431 other then the bias current and the reference voltage. The model doesn’t include bias current anyways.




    Code:
    .SUBCKT TL431 a k ref
    C1 7 a 1n
    Q1 k 2 1 QN3904
    R1 1 7 240
    R2 7 a 6.6k
    Q2 k 7 a QN3904 50
    D1 ref k D4mod
    D2 a k D2mod
    V1 5 a DC=2.49
    D3 a 2 D3mod
    C4 k 2 43p
    G2 a 2 5 ref -250u
    *
    .MODEL QN3904 NPN AF=1.0 BF=300 BR=7.5 CJC=3.5PF CJE=4.5PF
    + IKF=.025 IS=1.4E-14 ISE=3E-13 KF=9E-16 NE=1.5 RC=2.4
    + TF=4E-10 TR=21E-9 VAF=100 XTB=1.5
    .MODEL D3mod D N=0.01
    .MODEL D2mod D BV=36 CJO=4PF IS=7E-09 M=.45 N=1.3 RS=40
    + TT=6E-09 VJ=.6V
    .MODEL D4mod D BV=100V CJO=4PF IS=7E-09 M=.45 N=2 RS=.8
    + TT=6E-09 VJ=.6V
    *
    .ENDS
    I just changed V1 to 1.24V.Could anyone recommend any additional changes?

    I have a bunch of TLVH431’s ,I use them a lot as inexpensive low current comparators and EA’s. So a reasonably accurate model would come in handy.

    I’m using one for the EA in an LDO Vin = 6 -5.25V. Vo = 5.1V, 2mA TO 15mA. The FDV304P allows for worst case Drop out of 90mV (Tj 125 deg C) but with the reference and resistor tolerances’ the min input for regulation is 5.25V. I have bread boarded this and it works to 50mV drop out.




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