trying to find a low-power regulator

G

gearhead

Guest
I have a circuit that calls for a constant current sink. The LM317
would be perfect, but it requires about 5 milliamps to operate. It's
too much for my battery-operated circuit to drain 5 mA all the time.
So I'm looking for a 1.2 volt three-terminal series regulator like the
LM317 that can run on lower current. 100 uA would fit the budget.
I remember a thread some time ago on sci.electronics.design where
somebody mentioned a three terminal negative regulator (pretty sure it
was Joerg) that can run on microamps. Might have actually been a 2.5
volt regulator, don't remember. I even remember looking up the
datasheet, but I can't remember the part number.
I spent some time slogging through the parametric parts search on
digikey but didn't find it. I came here to see if anybody knows the
part.
 
"gearhead" <nospam@billburg.com> wrote in message
news:fddd7625-ab5a-424d-af59-be592665c46a@e25g2000prg.googlegroups.com...
I have a circuit that calls for a constant current sink. The LM317
would be perfect, but it requires about 5 milliamps to operate. It's
too much for my battery-operated circuit to drain 5 mA all the time.
So I'm looking for a 1.2 volt three-terminal series regulator like the
LM317 that can run on lower current. 100 uA would fit the budget.
I remember a thread some time ago on sci.electronics.design where
somebody mentioned a three terminal negative regulator (pretty sure it
was Joerg) that can run on microamps. Might have actually been a 2.5
volt regulator, don't remember. I even remember looking up the
datasheet, but I can't remember the part number.
I spent some time slogging through the parametric parts search on
digikey but didn't find it. I came here to see if anybody knows the
part.
Click to expand...
I don't know what was discussed earlier, but look at the LP2951. It has
more than 3 terminals.

Also consider other ways of building a constant current sink, such as a
suitably biased transistor or a constant-current diode.
 
I thought of another one -- LM1117T-ADJ. There are also fixed-voltage
versions.
 
On Dec 20, 11:55 am, gearhead <nos...@billburg.com> wrote:
I have a circuit that calls for a constant current sink. The LM317
would be perfect, but it requires about 5 milliamps to operate. It's
too much for my battery-operated circuit to drain 5 mA all the time.
So I'm looking for a 1.2 volt three-terminal series regulator like the
LM317 that can run on lower current. 100 uA would fit the budget.
I remember a thread some time ago on sci.electronics.design where
somebody mentioned a three terminal negative regulator (pretty sure it
was Joerg) that can run on microamps. Might have actually been a 2.5
volt regulator, don't remember. I even remember looking up the
datasheet, but I can't remember the part number.
I spent some time slogging through the parametric parts search on
digikey but didn't find it. I came here to see if anybody knows the
part.
Click to expand...
Starting to remember now. It wasn't a negative series regulator Joerg
mentioned; it was a shunt refernce, LM385.
I think what I have to do is make the current sink using a low-power
shunt like the tlv431 or lmv431 and a transistor.
But if anybody can think of a low-power three-terminal regulator
(either positive or negative), give a shout.
Thanks
 
On Dec 20, 12:49 pm, "mc" <l...@www.ai.uga.edu.for.address> wrote:
"gearhead" <nos...@billburg.com> wrote in message

news:fddd7625-ab5a-424d-af59-be592665c46a@e25g2000prg.googlegroups.com...

I have a circuit that calls for a constant current sink. The LM317
would be perfect, but it requires about 5 milliamps to operate. It's
too much for my battery-operated circuit to drain 5 mA all the time.
So I'm looking for a 1.2 volt three-terminal series regulator like the
LM317 that can run on lower current. 100 uA would fit the budget.
I remember a thread some time ago on sci.electronics.design where
somebody mentioned a three terminal negative regulator (pretty sure it
was Joerg) that can run on microamps. Might have actually been a 2.5
volt regulator, don't remember. I even remember looking up the
datasheet, but I can't remember the part number.
I spent some time slogging through the parametric parts search on
digikey but didn't find it. I came here to see if anybody knows the
part.

I don't know what was discussed earlier, but look at the LP2951. It has
more than 3 terminals.

Also consider other ways of building a constant current sink, such as a
suitably biased transistor or a constant-current diode.
Click to expand...
That brings up another thing. I was wondering if it's possible to
build a current sink using discretes that has a temperature
coefficient as negligible as they get with band gap IC's. I incline
toward thinking no.
So anyway, as I mentioned in the post I put up before I saw yours, I
can do the same thing with a three-terminal shunt IC and a transistor
and get flat temperature response. So I'm in pretty good shape, I can
build my circuit. Thanks a lot, and have a Merry Christmas!
 
"mc" <look@www.ai.uga.edu.for.address> wrote in message
news:eFAaj.21811$Mu4.14509@bignews7.bellsouth.net...
I thought of another one -- LM1117T-ADJ. There are also fixed-voltage
versions.


Those work really well.........
Click to expand...
 
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