On Fri, 16 Sep 2011 15:49:49 -0700, "Robbie Hatley"
put finger to keyboard and composed:

For example, one of the circuits this part appears in is the Hyundai N100
motor controller. The power supply board on that looks like this:
http://www.well.com/~lonewolf/schematic.gif

Note that if you envision a zener diode in the "3B" device with
cathode on pin 3 and anode on pin 2, it becomes much like the
appnote I link-to above. (As to what pin 1 is connected to
internally, I have no idea yet.)

ZD3 in that schematic looks exactly like the TL431 whit3rd alluded to.

A TL431 is effectively a programmable precision zener diode. It has an
internal 2.5V reference. The potential divider consisting of R13 and
R11 sets the output voltage to ...

Vo = 2.5 x [1K / (1K + 1K)] = +5V

http://www.fairchildsemi.com/ds/TL/TL431A.pdf
http://www.ti.com/lit/ds/symlink/tl431a.pdf

- Franc Zabkar
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