lm7804 does it exist

SimonTHK

Member

• Feb 17, 2010

• #1

I am looking for an LM to stabilize 4volt. I cant find any datasheets for it...

Also where is best place for datasheets to find?

cheers

 

Hero999

Banned

• Feb 17, 2010

• #2

No, it doesn't exist so why not use an LM317?

 

SimonTHK

Member

• Feb 17, 2010

• #3

Ill do that then ;D

 

SimonTHK

Member

• Feb 17, 2010

• #4

it has a reference voltage at 3v < and I have 5 volt so that should be ok

 

MikeMl

Well-Known Member

Most Helpful Member

• Feb 17, 2010

• #5

The reference in a LM317 is 1.25V. It has a dropout voltage of ~2V, so if you want to make 4V out of 5V, it will not work. You will have to find a special LOW-DROPOUT adjustable regulator.

 

SimonTHK

Member

• Feb 17, 2010

• #6

can that be very accurate?

 

MikeMl

Well-Known Member

Most Helpful Member

• Feb 17, 2010

• #7

SimonTHK said:

can that be very accurate?

Click to expand...

A typical adjustable regulator like an LM317 is stable within a few mV over the temperature range, over input voltage range, and over the output current range.

 

Hero999

Banned

• Feb 17, 2010

• #8

How much current do you need?

If it's just a low current reference, you could use the TL431.

EDIT:
The LM317 has a voltage tolerance of 4%

 

Last edited: Feb 17, 2010

MikeMl

Well-Known Member

Most Helpful Member

• Feb 17, 2010

• #9

Hero999 said:

...
The LM317 has a voltage tolerance of 4%

Click to expand...

If you initially trim it to a specific voltage, how stable is it thereafter, based only on temperature, input variation, output load changes?

 

Hero999

Banned

• Feb 17, 2010

• #10

I wasn't disagreeing with you.

The OP asked an ambiguous question about accuracy so I thought I should let him know the voltage tolerance of the LM317.