• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 1178 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

TL431: Life Span When Keep Working in Unstable Status

KevinZhang123
Expert 5750 points
Part Number: TL431

Hi, Team

My communication customer is using TL431AIDBZ for reference voltage of a DAC. Here is schematic.

They find the TL431 ouput is not stable and oscillating. The Vpp = 247mV

If they remove the 0.1uF C85, The TL431 output return to stable.

According to TL431 datasheet and test result, the issue is casued by TL431 unstablt.

As the oscillation does not affect whole system performance, and this product has already mass production for 6000 units, customer do not want to change anything of the 6000 units.

Will life span of TL431 be decreased if it keep working in unstable (oscillating) status?

Thanks

Kevin

  • 0
    TI__Mastermind 19580 points
    Hi Kevin,

    The TL431 is oscillating because the Cload on the TL431 is 0.1uF which is in the unstable region. Check out figure 18 on the TL431 DS it shows the area that the TL431 is unstable.

    To fix this problem you need a larger capacitor than 10uF or smaller than 10uF. The TL431 architecture is known for its poor Cload driving capability.

    Another and possibly better option is the new TL431LI that we are sampling now. The TL431LI has a smaller unstable region and you can use caps around 2.2uF to 4.7uF easily.

    I cannot recommend using the device in its unstable region.

    -Marcoo