TL431 is an adjustable precision voltage reference.

The output voltage is determined by the signal applied to the reference pin.
Consult the TL431 datasheet for typical applications and implementation.

Can we lay this one to rest now?

 

Terminology: Here is a "programmable current source"

https://www.analog.com/en/products/lt3092.html#

 

Even more confusing…..
Back in the day, early 70s, there was a “programmable” unijunction transistor, or PUT.
The 2N6027 and 2N6028 were the most ubiquitous devices.

It was the “triple lie” semiconductor.
1- It was not programable, but its intrinsic stand-off ratio was adjustable with external resistors.
2- It was no unijunction, but actually had 3 junctions like a SCR.
3- It wasn’t really a transistor which could be controlled linearly, but a thyristor with a snap action. Again similar to a SCR.

 

What's interesting to me is that if I want to program it I can calculate various values for the resistors to change the Vref.

 

Why use the word "program" when you could use the word "adjust"?

 

Why use the word "program" when you could use the word "adjust"?

You might want to direct that question to the manufacturer.
See posted Datasheet and use of the word "Programmable"

For your convenience......
1-800-842-2737
TI-Cares Customer Support Worldwide

 

You might want to direct that question to the manufacturer.
See posted Datasheet and use of the word "Programmable"

For your convenience......
1-800-842-2737
TI-Cares Customer Support Worldwide

Nope. I don’t have an issue with the manufacturer or the datasheet.
I understand the meaning of the word Programmable.