LM 317 question

[zerafiel]

I was wondering. Why use 2 lm137 to regulate voltage and current when one might suffice? Less voltage drop this way.

Between the adj pin and the vout pin have your usual limiting resistor and potentiometer combo to control current. AND have another pot between ground and the limiting resistor or pot to control the voltage.

Would this not work? Why or why not?


Vin_lm317__C-pot_____Vout
| |
| R1
Iadj_________|___
|
V-pot
|
Grd

I left out the caps and diodes.

 

[chimo]

Short answer - No.

 

[Daedal]

If you'd like... try either one of these...

GL;
DDL

 

[Daedal]

.

 

[chimo]

If you really want to control voltage and current from one device, you can get the L200 (link below).

http://www.st.com/stonline/products/literature/ds/1318.pdf

 

[Daedal]

Seems like I missed something in my DigiKey order... ;D

Thanx Chimo;
DDL

 

[zerafiel]

I saw those in the spec sheet as well but I'm just looking for something simple without taking too many volts. the lm200 looks nice.

Why won't it work? Medium answer?

 

[chimo]

The device will likely function - but not how you expect it. Adjusting one pot will affect the setting of the other.

I saw those in the spec sheet as well but I'm just looking for something simple without taking too many volts. the lm200 looks nice.

Why won't it work? Medium answer?

 

[Hemlock_Mike]

This looks NICE --- Gotta get a few !!  ;D  
I didn't see this in Digikey either ...

Mike

I just ordered a few -- $1.92 each !!! Data sheet looks promising - Thanks.

 

[Shilood]

So Mike... what's the prognosis? How did the LM200's work?

I still think 2xRCR123's should work for the BluRay GB diode even using the LM317T. Can anyone confirm this through observation?

Thanks