This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

  • TI Thinks Resolved

LM431: Vout oscillation

Intellectual 1395 points

Replies: 3

Views: 104

Part Number: LM431

Hi Experts:

i designed a reference voltage for the signal detection with LM431B , the schematic is below: 

  

Because the Cload selection could affect the Vout oscillation , i choose the 1nF for the Vout  (remove the 1uF ) , however, i still find the Vout oscillation like below: 

In the description of the datasheet, the Vout is in the stable range: 

When i replace the LM431B with the TLV431A in the same circuit , the Vout is stable , no oscillation . Please help me what's the reason , thanks!

  • Hi Jason,

    The stability boundary conditions chart is a typical graph that can vary from device to device and lot to lot.

    I cannot recommend to use 1.001uF on the output because it will be in the instability region of both device.

    A much smaller much larger cap is recommended. I would check out the app note below to understand stability charts.

    While this TL431 might not oscillate, other TL431 can oscillate.

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    If you feel your thread is resolved, please selected Answered.

    If you are using the TL431, check out the new ATL431LI for improved system performance in a p2p package or a ultra  small X2SON (1mm x 1mm x 0.4mm)

    Check out: Voltage Reference Design Tips For Data Converters a new app note that discusses voltage reference error and how it affects ADCs/DACs

  • In reply to Marcoo Z:

    Hi  Marcoo:

    Thanks for your reply.

    Yes, we are currently using the 1nF in the TL431 with no issue .  However, i don't know why the oscillation is still existing on the LM431 ? 

    if this TL431 oscillate and other TL431 can't oscillate , how can we make sure the capacitor is Ok in the mass production stage even it could pass in the evaluation stage.

  • In reply to Jason Fan:

    Hi Jason,

    Can you verify if it is 1nF or 1uF total cap?

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    If you feel your thread is resolved, please selected Answered.

    If you are using the TL431, check out the new ATL431LI for improved system performance in a p2p package or a ultra  small X2SON (1mm x 1mm x 0.4mm)

    Check out: Voltage Reference Design Tips For Data Converters a new app note that discusses voltage reference error and how it affects ADCs/DACs

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.