[SOLVED] getting 3.4V DC from 24V DC supply

[dexxxx]

Hi guys, i am a bit rusty on this. Please i like to know how best to obtain a 3.4V DC output from a 24V DC supply. The 3.4V output is to drive the digital input of an RTU (remote terminal unit) which draws a current of 50mA.
Thanks guys

 

[barry]

You can use a linear regulator. The only concern is that this regulator will dissipate about 1 watt.

 

[salmanliaquat]

And you can use a switching adjustable step-down regulator, if you don't want much of power loss.

 

[kam1787]

not sure how you define 'best'
mriad of ways: from LM317 to plain old series pass regulator with a zener diode.

 

[barry]

not sure how you define 'best'
mriad of ways: from LM317 to plain old series pass regulator with a zener diode.

Or a voltage divider. Cheapest solution. And possibly worst solution.

 

[dick_freebird]

At 50mA, maybe you just want to eat the power loss in
the name of simplicity. But I'd look at the worst case,
there, which could be well more than the 50mA under
"ugly normal" let alone fault conditions ("remote" implying
opportunities for things to go wrong between here and
there).

There are now micromodule switching converters that
purport to offer small implementation-sizes, low BOM
cost and high efficiency - Linear Tech, Intersil are both
busy here, I expect other majors and upstarts as well
(but LTC and Intersil are the most aggressive about
sending me emails about theirs).

A current limit / short circuit protection is desirable
any time you have an exposed output pin that is
idiot-with-screwdriver accessible. If the distance is
long and the wiring cheap and the load variable, a
remote sense is a good idea. Some schemes have a
"predictive" load-droop compensation to eliminate
the return wire-pair, this can be neat as long as you
can reliably predict the end-end resistance (but it
had better stay as-designed, which things like
connector corrosion would make untrue over time).

 

[kam1787]

Or a voltage divider. Cheapest solution. And possibly worst solution.

lol. that too