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OBones
Guest
Sun Feb 07, 2010 11:54 pm
Hello,
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001 volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
Regards
Guest
Mon Feb 08, 2010 1:17 am
On Feb 7, 4:54 pm, OBones <obones_gfd__at__gfd_altern.org> wrote:
Quote:
Hello,
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001 volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
Regards
Take a look at the National Semiconductor applications notes for 317.
You'll find that by adding a small negative power supply, you can go
down to the ground rail.
Steve
Fred Bartoli
Guest
Mon Feb 08, 2010 2:13 am
OBones a écrit :
Quote:
Hello,
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001
volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
Regards
Make your own with an opamp and use the LM317 as the power pass element.
--
Thanks,
Fred.
mike
Guest
Mon Feb 08, 2010 2:37 am
Fred Bartoli wrote:
Quote:
OBones a écrit :
Hello,
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001
volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
Regards
Make your own with an opamp and use the LM317 as the power pass element.
I'd like to see your favorite circuit for this. The one you built and
extensively evaluated. Short circuit, open circuit, drive output
positive, drive output negative, load dump, input voltage dump,
transient response...the usual stuff.
Every time I've thought about doing this, it got real complex real fast.
Jamie
Guest
Mon Feb 08, 2010 4:21 am
OBones wrote:
Quote:
Hello,
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001
volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
Regards
Have you tried offsetting the common from the supply via 2 diodes?
You may need to put a limit R at the low side of the voltage set pot
to prevent - voltage at zero set point.
This should work if the supply operating the 317 is of it's own via a
xformer etc..
In other words, you're not using an external supply with a common that
could come in contact with other components.
Adam Seychell
Guest
Mon Feb 08, 2010 4:35 am
On 8/02/2010 11:37, mike wrote:
Quote:
I'd like to see your favorite circuit for this. The one you built and
extensively evaluated. Short circuit, open circuit, drive output
positive, drive output negative, load dump, input voltage dump,
transient response...the usual stuff.
Every time I've thought about doing this, it got real complex real fast.
And that's why most power sources do not include all of the above
features. Some fault protection are easy (e.g negative input), while
others (e.g negative output drive) are not so easy to implement,
especially at higher power levels.
ehsjr
Guest
Mon Feb 08, 2010 7:03 am
OBones wrote:
Quote:
Hello,
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001
volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
Regards
David Jones discussed a chip that does what you want
in his first EEVBLOG: the LT3085 from Linear Technologies
I've used it, and it does indeed go down to 0 volts,
but I didn't need precision of 1 mV so I didn't test
it that closely.
Ed
Jan Panteltje
Guest
Mon Feb 08, 2010 2:38 pm
On a sunny day (Sun, 07 Feb 2010 22:54:03 +0100) it happened OBones
<obones_gfd__at__gfd_altern.org> wrote in
<4b6f3677$0$20407$426a34cc_at_news.free.fr>:
Quote:
Hello,
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001 volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
Regards
If regulation is not that important just put 2 Si diodes in series with the output...
Bill Sloman
Guest
Mon Feb 08, 2010 2:49 pm
On Feb 7, 10:54 pm, OBones <obones_gfd__at__gfd_altern.org> wrote:
Quote:
Hello,
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001 volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
You might look at the the National Semiconductor LM395 "ultra reliable
power transistor" which does include thermal protection.
--
Bill Sloman, Nijmegen
George Herold
Guest
Mon Feb 08, 2010 6:50 pm
On Feb 7, 4:54 pm, OBones <obones_gfd__at__gfd_altern.org> wrote:
Quote:
Hello,
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001 volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
Regards
Sounds like the LT3080 might fit your bill.
It's got a constant current output, and you 'program' the voltage with
a resistor.
George H.
OBones
Guest
Mon Feb 08, 2010 7:54 pm
ehsjr wrote:
Quote:
OBones wrote:
Hello,
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001
volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
Regards
David Jones discussed a chip that does what you want
in his first EEVBLOG: the LT3085 from Linear Technologies
I've used it, and it does indeed go down to 0 volts,
but I didn't need precision of 1 mV so I didn't test
it that closely.
This one looks good, thanks for the tip.
And it even has a SPICE model, that's really good.
OBones
Guest
Mon Feb 08, 2010 7:54 pm
George Herold wrote:
Quote:
On Feb 7, 4:54 pm, OBones <obones_gfd__at__gfd_altern.org> wrote:
Hello,
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001 volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
Regards
Sounds like the LT3080 might fit your bill.
It's got a constant current output, and you 'program' the voltage with
a resistor.
Ah yes, seems like it is the bigger brother of the LT3085. Nice set of
components here
Richard Torrens (News)
Guest
Sun Feb 14, 2010 1:17 pm
In article <4b6f3677$0$20407$426a34cc_at_news.free.fr>,
OBones <obones_gfd__at__gfd_altern.org> wrote:
Quote:
Hello,
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001 volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
There a number of power supply circuits on
http://www.4qdtec.com/index.html
using transistors.
--
------------------------------------------------------------------
Richard Torrens. News email address is valid - for a limited time only.
http://www.Torrens.org.uk for genealogy, natural history, wild food, walks, cats
and more!
Baron
Guest
Sun Feb 14, 2010 7:12 pm
Richard Torrens (News) Inscribed thus:
Quote:
In article <4b6f3677$0$20407$426a34cc_at_news.free.fr>,
OBones <obones_gfd__at__gfd_altern.org> wrote:
Hello,
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to
0.001 volt? It doesn't need to supply much more than 100mA but it
would be nice if it was thermally protected like the LM317.
There a number of power supply circuits on
http://www.4qdtec.com/index.html
using transistors.
Fine ! If you are prepared to pay for membership. Google gets better
info.
--
Best Regards:
Baron.
Spehro Pefhany
Guest
Sun Feb 14, 2010 8:57 pm
On Sun, 14 Feb 2010 17:12:33 +0000, the renowned Baron
<baron.nospam_at_linuxmaniac.nospam.net> wrote:
Quote:
Richard Torrens (News) Inscribed thus:
In article <4b6f3677$0$20407$426a34cc_at_news.free.fr>,
OBones <obones_gfd__at__gfd_altern.org> wrote:
Hello,
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to
0.001 volt? It doesn't need to supply much more than 100mA but it
would be nice if it was thermally protected like the LM317.
There a number of power supply circuits on
http://www.4qdtec.com/index.html
using transistors.
Fine ! If you are prepared to pay for membership. Google gets better
info.
If you're doing a motor controller, membership is cheaper than one set
of blown power devices. ;-)
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff_at_interlog.com Info for manufacturers:
http://www.trexon.com
Embedded software/hardware/analog Info for designers:
http://www.speff.com
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