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something about TLV431A

Bay Pan
Prodigy 20 points
Other Parts Discussed in Thread: TLV431A

Hello

I have something wrong with TLV431A；

I use it as the reference voltage IC to  a DDR IC, and have a filter capacitor of  0,1uF/16V 0402 between GND and pin 1(REF), our package is SOT-23-3

In that case ,there is a  big ripple voltage about 370mv ，

and then I delete that capcaitor ,the ripple voltage disappered .

I'm wondering why,Please help me ,thanks.

I wish you could give me some literature,thank you very much.

BEST REGARDS

Bay Pan

  • 0
    TI__Guru**** 157446 points

    Bay Pan,

    The capacitor creates an output pole that creates lag (phase shift). This can cause the loop phase margin to be less then zero.
    The TLV431A is not compatible with direct capacitance on the cathode. (What is purpose of R88?)
    Please see data sheet figure 17 (page 17). Capacitor C74 will not cause any problem with stability.

  • 0 in reply to Ron Michallick
    Prodigy 20 points

    Hi Ron,

    Thank you for your reply.

    R88 is a filter too,in my understanding.

    Should we take out R88?