TL431: REF output is not steady

Hi Haiwen,

What is the cathode current, Ika, that you are observing during operation?

What is the value of your Vcc?

Which capacitor is the 2.2nF capacitor that is causing instability, C6?

Thanks,
Joshua

Hi Joshua:

Ika is 2.6mA, Vcc is 12.2V.

Yes, remove C6 can work steady. change new capacitor also can cause TL431 instable.

Hi Joshua:

Sorry for late respond. Customer tried small capacitor, it can work well. 2.2nF is also out of the curve C.

So far customer's question is : They use these parameters in many projects and only found failure in recent. Could you please help give your suggestion? Thanks.

Hi Haiwen,

I cannot pinpoint as to why this worked prior, but typically you want to be at least one order of magnitude away from your boundary condition to avoid any temperature, manufacture error, design error faults. It was likely one of these three conditions that caused this case not to work.

Thanks,
Joshua

Hi Joshua:

Do you know which parameter can impact this issue ? Customer want to know the difference.