TL431: Output Oscillation Query

Sandeep Varma

Part Number: TL431

Hi,

In TL431, While testing, Oscillations are observed at output while operating it as simple shunt regulator. We changed the feedback resistance value to higher(i.e. 30k ) than previous(Two 10k's), Oscillations are not observed(i.e. stable output) with 30k feedback resistors. How the oscillations are controlled by feedback resistors ? I couldn't see any thing from data sheet about the same. I only knew the load capacitance requirement to meet the stability which we strictly maintained.

Thanks,
Sandeep.

over 1 year ago

0 Joshua Garcia over 1 year ago

TI__Genius 11740 points

Hi Sandeep,

I believe this error occurs due to a stability boundary condition or oversaturated reference current, would you mind sharing your schematic and design parameters?

Thanks,
Joshua

0 Sandeep Varma over 1 year ago in reply to Joshua Garcia

Prodigy 170 points

Hi Joshua,

We used simple shunt regulator circuit as specified in data sheet with R1,R2 as 10k(also specified in data sheet) and 2.2k in series.

Exception is that, we used 10n cap across R2. Will it cause any unstability condition ?

0 Joshua Garcia over 1 year ago in reply to Sandeep Varma

TI__Genius 11740 points

Hi Sandeep,

We do not recommend using a capacitor across R2. When this capacitor is removed, do you observe the error with 10 kOhm resistors?

Thanks,
Joshua

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TL431: Output Oscillation Query