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TL431: Capacitor limitation on comparator application case.

Motoyasu Hattori
Expert 8675 points
Part Number: TL431

Hi,
My customer consider the comparator application with TL431.  Could you please answer the following questions?

  1. This following circuit does not require a capacitor in the Vin or Vout part when implementing a Comparator like the following. Is it correct?   Please advise me.



  2. Is there any limitation to add capacitor on VIN-GND?

  3. On the case of adding capacitor on VOUT-GND, does he need confirming that the capacitance is within the stability criteria shown in Figure 16 and Figure 18 of datasheet?

Please advise us.

Thanks and best regards,
M.HATTORI

  • 0
    TI__Mastermind 19370 points

    Hi Hattori-san,

    1. The TL431 in comparator mode does not require a capacitor on REF or VOUT.

    2/3. A capacitor around 0.47uF to 1uF can cause stability issues. An increase in IKA current can increase instability when using capacitors around this value. We do not have a figure of instability to show the capacitor range.

    Figure 16/Figure 18 will not apply because that is closed loop regulation vs this open-loop.