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PICList Thread
'Any Favorite 3V Regulator for PIC?'
1998\02\06@085234 by Mark Jurras

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I have a battery power PIC application that I have the opportunity to reduce the
power by running
the PIC at 3V. I looked at Linear Technology, Maxim, National Semiconductor and
Harris for a LDO
micropower 3V regulator and found MAX663 666 and 689. I was hoping for a three
terminal TO-92
type part. The circuit has 4 Alkaline cells (6V) and draws 1.4ma @6V at 3V the
draw is 0.74mA and
runs continuously until the batteries need replacement.

I don't  any experience using  switching regulators for battery power. Is this a
viable option or is a
linear regulator a better choice for battery life.

Any  favorites??

- -Mark

1998\02\06@090921 by Ray Gardiner

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The Seiko S-81330HG is 3 volt, 40 mA out, 16uA quiescent, and
120mV dropout. Sorry I don't have pricing.


Ray Gardiner (DSP Systems) spam_OUTrayTakeThisOuTspamdsp-systems.com http://www.dsp-systems.com
private email to:- .....rayKILLspamspam@spam@netspace.net.au

1998\02\06@094707 by John Ellenz

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Mark,

The MAX666 is a good low power part.  It does not have a real low output
impedance but assuming you do not have large pulse loads in addition to
your 1mA continuous current it will work fine.  BTW Analog Devices
clones it now so that has made it a little cheaper - it used to be
fairly expensive for a regulator.

It seems to me that both National and Linear should have 3 pin 3V fixed
LDO regulators but I can't recall the numbers.  National 29XX series and
Linear LT11?? maybe.

If you are happy with the packaging and size of the 4 cell product now I
would definitely stay with the linear.  You will already more than
double your battery life from the 5V version.  If you want to cut the
size consider going to 2 cells and using a Maxim switcher like the
MAX866 which will have low enough queiscent  to be efficient in a 1ma
application.

John Ellenz

1998\02\06@112942 by Darryl Newberry

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Mark,

>I have a battery power PIC application that I have the opportunity to reduce
>the power by running the PIC at 3V. I looked at Linear Technology, Maxim,

A linear LDO regulator is probably your best bet, the only reason I would
go with a switcher is if you needed supply voltages higher than Vbat. We
use MAX666 and MAX667 in SO-8 packages. If your system can be powered off,
you can also use shutdown to really conserve power. Also, are you utilizing
SLEEP on the PIC? Are you making sure that the ports are not sinking current?

-dn

1998\02\06@114828 by Morgan Olsson

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At 08:34 1998-02-06 -0500, you wrote:
>I have a battery power PIC application that I have the opportunity to
reduce the
> power by running
>the PIC at 3V. I looked at Linear Technology, Maxim, National
Semiconductor and
> Harris for a LDO
>micropower 3V regulator and found MAX663 666 and 689. I was hoping for a
three
> terminal TO-92
>type part. The circuit has 4 Alkaline cells (6V) and draws 1.4ma @6V at 3V
the
> draw is 0.74mA and
>runs continuously until the batteries need replacement.
>
>I don't  any experience using  switching regulators for battery power. Is
this a
> viable option or is a
>linear regulator a better choice for battery life.
>
>Any  favorites??
>
>- -Mark

Zetex (and others?) have a 3V or 3,3 V in 3-pin, poth TO92 or compatible
and also in SMT. But you don«t need the expensive low drop types if you
have 5V from battery.

But now as you want to exactly half the voltage, is seem stupid to burn off
half of the battery power, plus power consumption of the regualtor.

Small inductive switchers are expensive and have significant internal
cuonsumption.

Instead, use a charge pump, and your batteries will not last twice as long
(as with linear regulator, but four times! (output is half input voltage
and double input current)

The Harris ICL7660 and clones are by datasheet defined as voltage doubler
or inverter. They also with careful design work great as a voltage
halver/current doubler. Own consumption is almost nothing, and noise low.

However I use to design own cap pumps for two reasons. 1) The above chips
are relatively expensive. 2) I sometimes don«t need as much power as they
deliver, and sometimes I use much more.
/Morgan
/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
\  mrtspamKILLspaminame.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /

1998\02\06@133439 by wwl

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On Fri, 6 Feb 1998 08:34:36 -0500, you wrote:

>I have a battery power PIC application that I have the opportunity to reduce the
> power by running
>the PIC at 3V. I looked at Linear Technology, Maxim, National Semiconductor and
> Harris for a LDO
>micropower 3V regulator and found MAX663 666 and 689. I was hoping for a three
> terminal TO-92
>type part. The circuit has 4 Alkaline cells (6V) and draws 1.4ma @6V at 3V the
> draw is 0.74mA and
>runs continuously until the batteries need replacement.
>
>I don't  any experience using  switching regulators for battery power. Is this a
> viable option or is a
>linear regulator a better choice for battery life.
>
>Any  favorites??
>
>- -Mark
My fave is the Holtek HT10xx series (xx = 50,33,30 etc. ) - very low
dropout, and 1-2uA or so quiescent. Needs virtually no in/out caps for
stability, but load transient response isn't great unless you whack a
few uF on the output. TO-92 or SOT-89 and VERY CHEAP (UKP 0.32
50-off).
Using this with a PIC in sleep is as good as being switched off!
Ricoh, Seiko and Telcom do similar devices in TO-92, SOT23-5 and
SOT-89, but I've found Holtek is easiest to get - the others often had
silly leadtimes (>12 weeks, which in my book means 'forget it').
Presumably you need 6V for something else, otherwise 3v straight from
the batteries would be an alternative choice.
    ____                                                           ____
  _/ L_/  Mike Harrison / White Wing Logic / .....wwlKILLspamspam.....netcomuk.co.uk  _/ L_/
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/_W_/  Industrial / Computer Peripherals / Hazardous Area      /_W_/

1998\02\06@174219 by William Chops Westfield

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It might depend on the type of battery you are using.  If you're using
a battery technology with a steady downward ramp in output voltage (ie
carbon/zinc), there may be significant engery remaining in the battery
AFTER the voltage drops below that which will allow a linear regulator
to operate your equipment.  Some of the switchers are starting to publish
boost/buck designs that provide correct output voltage with input ranges
from below to above the target voltage.  After all, you're not really
optimizing for current, you're optimizing for batery life...

BillW

1998\02\06@183554 by John Payson

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> It might depend on the type of battery you are using.  If you're using
> a battery technology with a steady downward ramp in output voltage (ie
> carbon/zinc), there may be significant engery remaining in the battery
> AFTER the voltage drops below that which will allow a linear regulator
> to operate your equipment.  Some of the switchers are starting to publish
> boost/buck designs that provide correct output voltage with input ranges
> from below to above the target voltage.  After all, you're not really
> optimizing for current, you're optimizing for batery life...

If you use such a best, however, be very careful to ensure that your system
behaves reasonably (i.e. shuts down) when the battery voltage gets too low.
Without attention to this seemingly-minor detail, you may discover that as
the battery goes down the current goes up to the point that either the bat-
tery or the regulator explodes.  Unlikely with low-power applications, but
something that should be checked for nonethtless (if there are two or more
cells in series and one of them is completely dead, letting the others drive
excessive current through it is a good way of promoting a cell rupture).

1998\02\09@045829 by Steve Lawther

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    Mark,
   
    Another name to drop into the heap is Micrel, if you are building more
    than just a one off - look at the Mic52xx series in sot23-5 (or is it
    sot323-5?) can't remember if they do it in TO92. If you can stand
    running the application at 2.6V at end of battery life, you could use
    only 3 alkalines, as the regulator is very low drop out, and follows
    the battery down without any crazies. It's quesient current is very
    small. Should give you about 2000hours / battery set (give or take)
   
    If you can keep the required current below a 1mA, and the linear reg's
    quiescent is uAs, a switcher is probably not worth using.
   
       Steve Lawther


______________________________ Reply Separator _________________________________
Subject:      Any Favorite 3V Regulator for PIC?
Author:  MIME:EraseMEJURRAMspam_OUTspamTakeThisOuTTORRINGTON.COM at INTERNET-HUSKY
Date:    06/02/98 17:24


I have a battery power PIC application that I have the opportunity to reduce the
power by running
the PIC at 3V. I looked at Linear Technology, Maxim, National Semiconductor and
Harris for a LDO
micropower 3V regulator and found MAX663 666 and 689. I was hoping for a three
terminal TO-92
type part. The circuit has 4 Alkaline cells (6V) and draws 1.4ma @6V at 3V the
draw is 0.74mA and
runs continuously until the batteries need replacement.
   
I don't  any experience using  switching regulators for battery power. Is this a
viable option or is a
linear regulator a better choice for battery life.
   
Any  favorites??
   
- -Mark
   

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