What is the reason for R7 in 317 regulator ?

L

little billy

Guest
Hello,

Does anyone know the 5A COnstant Volatge/Constant Current Regulator
from the LM117/LM317A/LM317 regulator, it's on page 16 and is
downloadable from

http://www.national.com/ds.cgi/LM/LM117.pdf

I am curious as to the reason from R7=220.
What will happen if we put R7=0R ?
 
"little billy" <littlebilly@btinternet.com> wrote in message
news:24fcdb4a.0408020934.4ac2e2f9@posting.google.com...
Hello,

Does anyone know the 5A COnstant Volatge/Constant Current Regulator
from the LM117/LM317A/LM317 regulator, it's on page 16 and is
downloadable from

http://www.national.com/ds.cgi/LM/LM117.pdf

I am curious as to the reason from R7=220.
What will happen if we put R7=0R ?
Click to expand...
i think it sets the voltage but it looks like theyve got vout and adj pin
names transposed in that circuit.

Colin =^.^=
 
little billy wrote:

Hello,

Does anyone know the 5A COnstant Volatge/Constant Current Regulator
from the LM117/LM317A/LM317 regulator, it's on page 16 and is
downloadable from

http://www.national.com/ds.cgi/LM/LM117.pdf

I am curious as to the reason from R7=220.
What will happen if we put R7=0R ?
Click to expand...
It clamps the output when in constant current mode: if the load
wants to be less than 5A, the voltage wants to climb to I * R.
R7 is there to prevent that.

Rich
 
little billy wrote:
Hello,

Does anyone know the 5A COnstant Volatge/Constant Current Regulator
from the LM117/LM317A/LM317 regulator, it's on page 16 and is
downloadable from

http://www.national.com/ds.cgi/LM/LM117.pdf

I am curious as to the reason from R7=220.
What will happen if we put R7=0R ?
Click to expand...
I haven't analyzed it, but I think it may be necessary
for stability. Without it, the opamp looks like it
would be driving a capacitive load.

--
local optimization seldom leads to global optimization

my e-mail address is: <my first name> <my last name> AT mmm DOT com
 
R7 is in the circuit for Iadj. Take the time end read the instructions!
"Roy McCammon" <rbmccammon@mmm.com> wrote in message
news:411006EC.5020306@mmm.com...
little billy wrote:
Hello,

Does anyone know the 5A COnstant Volatge/Constant Current Regulator
from the LM117/LM317A/LM317 regulator, it's on page 16 and is
downloadable from

http://www.national.com/ds.cgi/LM/LM117.pdf

I am curious as to the reason from R7=220.
What will happen if we put R7=0R ?

I haven't analyzed it, but I think it may be necessary
for stability. Without it, the opamp looks like it
would be driving a capacitive load.

--
local optimization seldom leads to global optimization

my e-mail address is: <my first name> <my last name> AT mmm DOT com
Click to expand...
 
Hello my dear half baked engineers of this thread.
I am afraid you were all wrong. I wonder, shall I
tell, or shall I let you burn some more midnight
oil over this one?
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top