TL431: Stability Boundary test condition

Jerry Zhao

Part Number: TL431

Hi team,

Wish you have a nice day!

Currently my customer is using TL431 in their design, and they want to know the stability boundary is tested under the right circuit. They also want to know how to test the stability boundary if the resistor markEd by red circle is not 150ohm.

Thanks a lot!

over 2 years ago

0 Walter Zollinger over 2 years ago

TI__Genius 9790 points

Hello Jerry,

Yes the boundaries in figure 7-16 are tested with the circuit in figure 7-17.

The 150 Ohm resistor sets the supply current into the device and load. The current into the device is shown on the Y-axis of the figure 7-16 graph and the stability boundary curves remains the same if the 150 Ohm resistor is changed. The cathode current can be calculated as Ika = ((Vin - Vka) / R) - Iload. Use a load capacitance that is 10X smaller or larger from the boundary.

Best,

Walter

0 Jerry Zhao over 2 years ago in reply to Walter Zollinger

TI__Intellectual 1070 points

Hi Walter,

Thanks for your explanation!

For test circuit for curve A, could we remove CL when Ika is 2mA?

Thanks a lot.

0 Walter Zollinger over 2 years ago in reply to Jerry Zhao

TI__Genius 9790 points

Hello Jerry,

Yes the part should be stable with no load capacitance and Ika = 2mA.

Best,

Walter

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TL431: Stability Boundary test condition