TL431: TL431

That answered my question sure enough - I was hoping to use the 431 to clamp flyback pulses on an inductive system. 36V would've done, but more would be better. A Zener diode dimensioned; (36 - 2.5V) from k to I/P is as far as my thinking takes me to avoid breakdown.

Hi Ian,

I would recomend to use figure 31 from the datasheet. This is a combination of the TL431 + A BJT to allow for higher current. The main current paths will be the Ika through the TL431 and the Ice through the BJT. The Ika current can be controlled because the voltage across the biasing resistor will be (Vo - Vka). By using this you can keep the current on the TL431 below its RoC and the BJT can handle any excess. You can also use the ATL431LI if you have size constraints because it is available in X2SON (1mm x 1mm).

That misses the point entirely - the current rating is adequate. A cas-code arrangement would be nearer the mark, but I don't need THAT much higher voltage rating. The TL431 voltage limit is just about adequate. To use an analogy: I need to red line it without throwing a rod.........

Hi Ian,

Sounds like a plan. Make sure you are considering the thermal limitations of the device if you want to do 36V at high currents. That is the only issue I can see with this design.

-Marcoo