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TL431A: Stability and AC Analysis of TINA-TI

Yuto Sakai
Mastermind 6100 points

Part Number: TL431A

Hi,

Could you tell me about the stability of TL431A.
I analyzed AC circuit of customers using TINA-TI.
The simulation results are attached below.

TL431A_AC.TSC

From Figure 16 of datasheet P.16, the phase margin is low even under "Stable" condition (CL = 5 μF),
so I think that the result of AC analysis is not correct.
Do I mistake the way of simulation?
Or is there a mistake in the circuit?

I would be appreciate if you give me advice.

Best regards,
Yuto Sakai

  • 0
    TI__Mastermind 19580 points
    Hi Sakai,

    Figure 16 and 17 are typical graphs and the stability curve can vary from device to device. The SPICE model probably has a different stability region or the stability region isn't as well defined. The border line for each graph is 0 degree phase margin so while a result might be on the "stable" side, the phase margin can be poor. I always recommend to design with at least half a decade boundary on each side.

    I would refer to figure 2 on the following document for a more stable graph.
    www.ti.com/.../slva482a.pdf

    -Marcoo