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'low-loss voltage reg [OT?]'
2000\02\09@122551 by Opdahl, Patrick G

picon face
hi,

i've got a small datalogger based on a 12C672 and a 24LC128 that i supply 5V
via a 9V battery through a 7805(1A) regulator.  The pic wakes up every 1.5
minutes, records a single datapoint, then goes back to sleep.

my problem is that the new 9V battery runs out ~7 days (7000 datapoints) and
i believe its because of the regulator- my circuit only uses ~33mA (as close
as i can tell) maximum, and it is sleeping most of the time.  first
question: is this typical life for a 9V battery, or could it be the
regulator or something else?

does anyone out there have a small inexpensive 5V regulator they can
suggest?  i'd like to stick with the 9V battery due to size issues...

the lower the parasitic losses the better- i'd like to be able to at least
fill up the 16K of memory i have available!

any inputs or help are greatly appreciated

regards
Pat

2000\02\09@125043 by jamesnewton

face picon face
See
http://techref.massmind.org/power/regulators.htm

---
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http://techref.massmind.org NEW! FINALLY A REAL NAME!
Members can add private/public comments/pages ($0 TANSTAAFL web hosting)


{Original Message removed}

2000\02\09@125444 by Don Hyde

flavicon
face
The 7805's are pretty good regulators and they're cheap, but their quiescent
current isn't good at all (like nearly 1mA).  We've been using a Seiko
S-81250SGUP-DQD_B on a project, and it's great for quiescent current, though
it's not nearly as stiff as a 7805.  It'll help your battery life, but you
may need to pay extra attention to analog noise from the supply line.

> {Original Message removed}

2000\02\09@135252 by Maverick

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<x-flowed>> > does anyone out there have a small inexpensive 5V regulator they can
> > suggest?  i'd like to stick with the 9V battery due to size issues...

I would suggest the MAX667.   About a year and a half ago we did quite a
bit of research for a low-power project we were working on (several weeks
off of four AAs), and these are great low dropout regs - 20uA of current
draw just sitting there, and they have a ultra-low power shutdown mode,
though by your application I don't think this would probably be of use to
you.  In addition, the voltage drop over them is much lower than a 7805 or
other conventional linreg, so you'll be able to discharge the 9V to a
deeper state.  In addition, it has a built-in low battery comparator, so
you could conceivably signal the PIC to stop taking readings after the
power became unreliable.  At least this was an issue I had to deal with...

One thing I might suggest, though, is changing from a 9V to either four
AAAs or AAs.  The reason for this is because you are using a linear
regulator, any extra voltage is just being burned as heat.  Yet a 9V
battery sacrifices mAh of storage to produce this potential.

With a 9V system and a linreg, you burn 4/9 of the battery's capacity as
heat.  According to what I've read, the usable ampacity of a 9V is about
350mAh.  So usably, you're extracting 5V*350mAh=1.75Wh of energy.
That lasts you a week, meaning you us about 0.25 Wh/day.  And that's with a
standard 7805, which suck down unbelievable amounts of power when a load is
placed on them...

A 6V system of AAAs would give you 600mAh of capacity, so
5*600m=3Wh.  Assuming a 7805 would work with four AAAs (which isn't true,
but a low dropout reg like a 667 will), you'd still get 71% more run time -
almost another week - in close to the same space and weight.  Plus AAAs are
cheaper...

With AAs, the gains would be even greater, but then the size and weight are
getting much larger.  For reference, an AA I believe is 1500mAh.

Hope that helps.

Nathan
--------------------------------------------------------------------------
 Nathan D. Holmes   .....maverickKILLspamspam@spam@drgw.net, ndholmesspamKILLspamiastate.edu
   122 Shepard #3  Box 328  Gilbert, IA 50105  Iowa State University - EE
   http://www.drgw.net/~maverick   PH: 515-663-9368
-------------------------------------------------------------------------

</x-flowed>

2000\02\09@144525 by l.allen

picon face
> > > does anyone out there have a small inexpensive 5V regulator they can
> > > suggest?  i'd like to stick with the 9V battery due to size issues...
>
> I would suggest the MAX667.   About a year and a half ago we did quite a
> bit of research for a low-power project we were working on (several weeks
> off of four AAs), and these are great low dropout regs - 20uA of current
> draw just sitting there, and they have a ultra-low power shutdown mode,
> though by your application I don't think this would probably be of use to
> you.  In addition, the voltage drop over them is much lower than a 7805 or
> other conventional linreg, so you'll be able to discharge the 9V to a
> deeper state.  In addition, it has a built-in low battery comparator, so
> you could conceivably signal the PIC to stop taking readings after the
> power became unreliable.  At least this was an issue I had to deal with...
>
The Max883 (LDO) has a capacity of 200mA with 220mV drop out
and quiescent current of lee than 15 uA with the added advantage
that as it reaches drop out it doesnt suddenly draw a large
quiescent current as with the 667.
But it is fair to say there are large numbers of new LDOs being
made by the big boys (TI, National etc) that have even better specs
under certain circumstances. The trade off may be lower quiescent
current for a larger drop out or lower max input voltage. Check them
out.
I would check out the miriad of switching regulator options
available, some of the lower power ones dont even need an
inductor, just one or two caps. The best solution will depend on
what youre power usage needs are.


_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand

http://www.psych.auckland.ac.nz

_____________________________

2000\02\09@175510 by William K. Borsum

flavicon
face
At 09:24 AM 2/9/00 -0800, you wrote:
>hi,
>
>i've got a small datalogger based on a 12C672 and a 24LC128 that i supply 5V
>via a 9V battery through a 7805(1A) regulator.  The pic wakes up every 1.5
>minutes, records a single datapoint, then goes back to sleep.
>
>my problem is that the new 9V battery runs out ~7 days (7000 datapoints) and
>i believe its because of the regulator- my circuit only uses ~33mA (as close
>as i can tell) maximum, and it is sleeping most of the time.  first
>question: is this typical life for a 9V battery, or could it be the
>regulator or something else?
>
>does anyone out there have a small inexpensive 5V regulator they can
>suggest?  i'd like to stick with the 9V battery due to size issues...
>
>the lower the parasitic losses the better- i'd like to be able to at least
>fill up the 16K of memory i have available!

We get 1 year plus off a 9-volt battery--we do NOT use a 7805!
Get some of Telecom's TC55 series--about 3-6 uA quiescent current versus
the 1-5 mA on the 7805s.
Available from Digikey.  Also, run you system at 3.5 volts if at all
possible--will cut power by about half.
Kelly

William K. Borsum, P.E. -- OEM Dataloggers and Instrumentation Systems
<.....borsumKILLspamspam.....dascor.com> & <http://www.dascor.com>San Diego, California, USA

2000\02\09@195150 by Russell McMahon

picon face
Patrick,


>i've got a small datalogger based on a 12C672 and a 24LC128 that i supply
5V
>via a 9V battery through a 7805(1A) regulator.  The pic wakes up every 1.5
>minutes, records a single datapoint, then goes back to sleep.
>my problem is that the new 9V battery runs out ~7 days
>- my circuit only uses ~33mA
>is this typical life for a 9V battery, or could it be the
>regulator or something else?

Along with all the other parts that have been recommended consider the
LM2936.

TO92 3 pin pkg.
Only 50mA max AFAIR.
About 10 - 20 uA actual quiescent draw.
Very low dropout (voltage across regulator when it stops working) around
100mV AFAIR.

I use these in various low power equipment designs and am very happy with
them.

A 9v alkaline battery will typically have 500 mAH capacity so a 7 day life
corresponds to an average current drain of about 3 mA.

Assuming a duty cycle of 1 second in 1.5 minutes at 33mA your device draws
1/90*33 ~~ 300uA
If it is awake for 10 seconds every 1.5 minutes this is 3mA.

With the LM2936 and a 1 second awake period every 9 seconds the PIC load
will predominate and you can expect a battery life of around 50 days.
Battery capacity will usually be larger than nominal at very low drains so
2+ months is possible. YMMV.





     Russell McMahon
_____________________________

>From other worlds - http://www.easttimor.com
                               http://www.sudan.com

What can one man* do?
Help the hungry at no cost to yourself!
at  http://www.thehungersite.com/

(* - or woman, child or internet enabled intelligent entity :-))


{Original Message removed}

2000\02\09@195803 by Alice Campbell

flavicon
face
I just talked to Mouser and they are out of all Seiko's LDO
regulators and restock is in APRIL! Telco strikes again.  They also
mentioned the tantalum capacitor drought.  you might call around
and see who has any LDOs in stock.

{Quote hidden}

2000\02\09@200811 by andy howard

flavicon
face
> I just talked to Mouser and they are out of all Seiko's LDO
> regulators and restock is in APRIL! Telco strikes again.  They also
> mentioned the tantalum capacitor drought.  you might call around
> and see who has any LDOs in stock.


Someone else on the list mentioned a shortage of tantalums too.  I've
had no trouble sourcing them in medium volumes here in the UK so maybe
there's some business to be done...

If anyone has any specific needs let me know.





.

2000\02\09@200816 by andy howard

flavicon
face
> I just talked to Mouser and they are out of all Seiko's LDO
> regulators and restock is in APRIL! Telco strikes again.  They also
> mentioned the tantalum capacitor drought.  you might call around
> and see who has any LDOs in stock.












.

2000\02\10@093125 by Jim Hartmann

flavicon
face
Another chip that looks nice is the National LM2936: LDO, 5V out, 40V max
in, 15ua quiescent @ 100uA out.

2000\02\11@102014 by Edson Brusque

face
flavicon
face
Hello,

   We have a portable gadget that uses a PIC16F873 and consumes about
100mA. It could not go to sleep mode. I'm currently using a 9V batery with a
78L05, but the waste of energy is very high. What do you suggest? A
switching regulator I could simply put in place of a 78L05 would be super.

   Thanks,

   Brusque

+------------------------+
|     Edson Brusque      |
| Research & Development |
|  http://www.citronics.com.br  |
+------------------------+

2000\02\11@111905 by Steve Landry

flavicon
face
Brusque,

I have used both the LTC1475 (switching) and the LT1761 (LDO linear) both
from Linear Technology to power PIC's from 9V batteries.

 - Steve

{Original Message removed}

2000\02\12@030531 by Russell McMahon

picon face
This is the 3rd such request in about as many days.
The LM2936 does very well if you need less than 50mA maximum current drain.

There are a number of other alternatives.



     Russell McMahon
_____________________________

>From other worlds - http://www.easttimor.com
                               http://www.sudan.com

What can one man* do?
Help the hungry at no cost to yourself!
at  http://www.thehungersite.com/

(* - or woman, child or internet enabled intelligent entity :-))


{Original Message removed}

2000\02\12@131533 by Jameel Ahed

picon face
Has anyone found a 5V Voltage regulator with an output of approximately 1A..
that can handle a 30+ Volt input?
Jameel


----- Original Message -----
From: Jim Hartmann <EraseMEJim_Hartmannspam_OUTspamTakeThisOuTSILENTKNIGHT.COM>
To: <PICLISTspamspam_OUTMITVMA.MIT.EDU>
Sent: Thursday, February 10, 2000 8:26 AM
Subject: Re: low-loss voltage reg [OT?]


> Another chip that looks nice is the National LM2936: LDO, 5V out, 40V max
> in, 15ua quiescent @ 100uA out.
>

2000\02\12@131739 by Jameel Ahed

picon face
I found the LM109...  Are there any others?
Jameel

----- Original Message -----
From: Jim Hartmann <@spam@Jim_HartmannKILLspamspamSILENTKNIGHT.COM>
To: <KILLspamPICLISTKILLspamspamMITVMA.MIT.EDU>
Sent: Thursday, February 10, 2000 8:26 AM
Subject: Re: low-loss voltage reg [OT?]


> Another chip that looks nice is the National LM2936: LDO, 5V out, 40V max
> in, 15ua quiescent @ 100uA out.
>

2000\02\12@132602 by Wagner Lipnharski

flavicon
face
Are you talking about a linear voltage regulator that will dissipate 25
Watts???  You should go for a switching step down regulator... lots of
space and power savings. Just the 25W heat sink would cost more than the
switching parts.

The LM2936 can ouputs a max of 50mA, 40V max input, it means at the
limit it will dissipate less than 2Watts.

Jameel Ahed wrote:
{Quote hidden}

2000\02\12@141700 by Mark Willis

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face
Depends;  I had one application where the metal body of the unit was
accessible and worked rather well as a heat sink!  So heat sinks don't
necessarily cost anything (Drilling that 1/4" stainless piece was a
bear, OTOH <G>)

For a linear I'd at least put in a series power resistor to drop the
input voltage to say 9 or 10V at 1A 'full-bore' draw, that'd reduce your
regulators' heat sinking requirements to about 5W or so (30V in so 20V
drop, at 1A means 20 ohms, 20 watts gets dissipated across that
resistor.  May have to bolt that resistor to a heat sink to keep it from
melting <G>)

Switchers are good for high voltage to low voltage conversions,
definitely.  The inductors are 'a pain' IMO though.

 Mark

Wagner Lipnharski wrote:
{Quote hidden}

> > {Original Message removed}

2000\02\12@194908 by Robert A. LaBudde

flavicon
face
<x-flowed>At 12:19 PM 2/12/00 -0600, you wrote:
>Has anyone found a 5V Voltage regulator with an output of approximately 1A..
>that can handle a 30+ Volt input?

1. Use two 1A regulators in series, with decreasing control voltages.

2. Use a switching supply to reduce wastage.


================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: TakeThisOuTralEraseMEspamspam_OUTlcfltd.com
Least Cost Formulations, Ltd.                   URL: http://lcfltd.com/
824 Timberlake Drive                            Tel: 757-467-0954
Virginia Beach, VA 23464-3239                   Fax: 757-467-2947

"Vere scire est per causae scire"
================================================================

</x-flowed>

2000\02\12@211308 by engalt

picon face
I don't know what the maximum voltage input on a 7805 is, but I have used them at
28V.  The big problem with using them with higher voltages is that they dissipate
a lot of power.  At 30V input is is 30V-5V+25V times 1A=25W of heat dissipated.
I manufacture some devices that run on 28V and don't have room for a heat sink on
the regulator so I use a 12V zeener in series with the input voltage to knock it
down some.

There are some switching regulators that work up to about 50V and don't generate
a lot of heat, but they are a whole lot more expensive than a 7805.

"Robert A. LaBudde" wrote:

{Quote hidden}

2000\02\12@213140 by Wagner Lipnharski

flavicon
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So how do you get rid of the 12W dissipation at the zener without a
heatsink?

Brian kraut wrote:
{Quote hidden}

2000\02\12@215045 by Wagner Lipnharski

flavicon
face
Who is interested to develop a "charge down pump"?

Look at the design:
48V charge C1-C4 with 12Vdc each, consider low dc leakage caps.

S1 = A, S2 = B, S3 = a, 500µs, S3 = b, 500µs.
S1 = B, S2 = C, S3 = a, 500µs, S3 = b, 500µs.
S1 = C, S2 = D, S3 = a, 500µs, S3 = b, 500µs.
S1 = D, S2 = E, S3 = a, 500µs, S3 = b, 500µs.
cycle repeats.

What would be the best electronic switching at S1, S2 and S3?

How can we implement a PIC to control the switchings, based on
productivity of voltage transfer and 500µs adjustments?

What is the capacitive transfer loss?

This is a step down capacitive switching unit with a flying capacitor.
Low power loss if we can get a low electronic switching resistance.

   +48Vdc
     o
     |             S1   a  S3   b  
     o-------o A   <----o   ^   o----------o-----> +12Vdc
     |                      |              |
    ---                    ---             |
C1   ---                    --- C5         --- C6
     |             S2       |             ---
     o-------o B   <----o   v   o--.       |
     |                     S3      |       |
    ---                           Gnd     Gnd
C2   ---                    
     |
     o-------o C
     |
    ---
C3   ---
     |
     o-------o D
     |
    ---
C4   ---
     |
     o-------o E
     |
    Gnd

2000\02\12@224526 by Russell McMahon

picon face
>Has anyone found a 5V Voltage regulator with an output of approximately
1A..
>that can handle a 30+ Volt input?


Jameel,


If you MUST use a linear regulator in such a high drop application then use
of a series resistor that drops most of the voltage at maximum current will
allow your semiconductor to run cooler. This can be a desirable arrangement
from a  reliability point of view.
Resistors are generally designed to run in a free air non-heatsunk
configuration (but watch your air flow).

eg 24v i, 5v out, 1A max.
Assume 24 volt is absolute minimum Vin. if not use the real Vin min.
Look at regulator dropout voltage WORST CASE across output current range.
Allow a suitable safety margin. Most older tech regulators will require 2
volts or so worst case.

Vdrop max = (24-5-2) = 17 volts.
A 17r resistor would drop all of this at 1A.
Choose something smaller to give you a little more headroom - say 15r or
even 12r.
At 1A a 15r will dissipate 15 watts. Check to see what conditions this is
under (ambient temperature, mounting etc). Allow a factor of 2 or so so you
need a resistor that can nominally dissipate 30 watts continuous (!) Running
a resistor at its full rated value is asking for trouble.
The regulator now still needs to dissipate 4 watts (  (24 - 5 -15) = 4 volts
x 1A = 4 watts) so watch your heatsinking.

A switching regulator is fairly attractive with this amount of voltage drop.




     Russell McMahon
_____________________________

>From other worlds - http://www.easttimor.com
                               http://www.sudan.com

What can one man* do?
Help the hungry at no cost to yourself!
at  http://www.thehungersite.com/

(* - or woman, child or internet enabled intelligent entity :-))

2000\02\12@231101 by Rob

picon face
I *have* seen LTC1044s used in synths.. The are supposedly low dropout, and
if you need hi power you can use a LTC1054.

I think they were spawned from the LM738 design, but Im not sure..
The LTC1044s are a type of switching voltage regulator. Low power
consumption is the key for these, but also they have low output power unless
you pay the 3.50usd for the 1054s..

Rob

{Original Message removed}

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