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'{EE:] Whis is the better regulator to use? Was Re:'
2004\03\16@075118 by Anthony Toft

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> Not stupid in the least. In fact a lot of novices brag about using low power
> parts with a battery. But further into the discussion you realize that they
> are using a linear regulator that's sucking down almost half the battery's
> power.

So which are the better regulators to use? As a non EE I generally stick
to what I know, and I have used the 78l05 in my project, but if that's
not the best (and it strongly sounds like it) I would like to educate
myself in the better devices.

The thing I like with the 'l05 is that it works great with a handful of
caps, in a 'cookbook' solution, if I want 12v just use the 'l12. Are
there other devices with similar recipe solutions, I'd like something
that's in the manner of do this, do that and feed volts in here and get
smooth volts out there.

I don't really need the recipe as I realize the datasheets are out
there, but which datasheets should I read and why.

Thanks
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2004\03\16@104003 by llile

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Any step away from the trusty 78xxx series will involve tradeoffs.  You
can save a few cents with a 5.1 volt zener, at the price of more power
dissipation, more heat, and poorer regulation.  Pics work great with zener
regulators, though, in many circuits.  (for instance in 1 million steam
irons  I designed.)

Anything else you design with will take more design effort.  If minimizing
your design effort is a goal, 78xxx parts are ideal.  When you have to
bang out a quickie lab instrument by noon, scratching your head over a
complex regulator isn't what you want.

Low dropout regulators will generally cost a little more, maybe a little
or maybe a lot more, but still retain the cookbook low-parts count quality
in many situations.

Buck or boost regulators using a flyback coil can make 5 volts out of 1.5,
can make 5 volts out of 24, (maybe they can even make water out of
wine?<grin> ) wihtout consuming a lot of power in the process, at the
price of extra cost and parts count plus design headaches.  National has
reduced this to a cookbook process in some of their parts, though.

I have actually found very few situations where the good ol' 78XX series
doesn't serve well.  Of course, nothing I design is optimized for long
battery life so your mileage will vary.  For hobby use or lab one-offs, I
try to keep 78L05's, 78M05's (TO220 case) , 78M12's, and a few 317T's
(adjustable) in stock at all times.  I can't count how many handbuilt
prototypes I have built using these handy little parts.

-- Lawrence Lile





Anthony Toft <toftatspamKILLspamCOWSHED.8M.COM>
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03/16/2004 06:50 AM
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       Subject:        {EE:] Whis is the better regulator to use? Was Re: [OT:] What Does
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> Not stupid in the least. In fact a lot of novices brag about using low
power
> parts with a battery. But further into the discussion you realize that
they
> are using a linear regulator that's sucking down almost half the
battery's
> power.

So which are the better regulators to use? As a non EE I generally stick
to what I know, and I have used the 78l05 in my project, but if that's
not the best (and it strongly sounds like it) I would like to educate
myself in the better devices.

The thing I like with the 'l05 is that it works great with a handful of
caps, in a 'cookbook' solution, if I want 12v just use the 'l12. Are
there other devices with similar recipe solutions, I'd like something
that's in the manner of do this, do that and feed volts in here and get
smooth volts out there.

I don't really need the recipe as I realize the datasheets are out
there, but which datasheets should I read and why.

Thanks
--
Anthony Toft <toftatspamspam_OUTcowshed.8m.com>

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2004\03\16@120623 by Dwayne Reid

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At 05:50 AM 3/16/2004, Anthony Toft wrote:
> > Not stupid in the least. In fact a lot of novices brag about using low
> power
> > parts with a battery. But further into the discussion you realize that they
> > are using a linear regulator that's sucking down almost half the battery's
> > power.
>
>So which are the better regulators to use? As a non EE I generally stick
>to what I know, and I have used the 78l05 in my project, but if that's
>not the best (and it strongly sounds like it) I would like to educate
>myself in the better devices.

BTW - please use a capital "L" in that part number - the lower case "l"
looks like a "1".

The 78Lxx family is great for most line-powered applications.  Its just too
darned inexpensive to ignore.  That said - I find I now use more LP2950A
regulators than any other chip regulator - its initial accuracy is 0.5% and
that makes it excellent for the medium accuracy a/d readings that many of
my products use.  Its also OK for most of the battery operated devices that
I design - the regulator uses about 100 uA quiescent but that is small
compared to the overall consumption.

If a battery-powered product needs to keep the regulator live all the time,
I use the TC55 series from Telcom (now Microchip).  But - its being
discontinued and I have not yet investigated alternatives.

My high volume mains-powered products don't use a chip regulator at
all.  Instead, they use a simple series R shunt zener regulator - less than
a third the cost of the least expensive chip regulator and inherently
immune to transients.

dwayne

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2004\03\16@123946 by Mike Harrison

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On Tue, 16 Mar 2004 10:03:37 -0700, you wrote:

{Quote hidden}

Check out HT7150 (and others for other voltages) from Holtek - cheap, a microamp or two quiescent,
and takes inputs up to 24V.

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2004\03\16@183245 by Byron A Jeff

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On Tue, Mar 16, 2004 at 07:50:16AM -0500, Anthony Toft wrote:
> > Not stupid in the least. In fact a lot of novices brag about using low power
> > parts with a battery. But further into the discussion you realize that they
> > are using a linear regulator that's sucking down almost half the battery's
> > power.
>
> So which are the better regulators to use? As a non EE I generally stick
> to what I know, and I have used the 78l05 in my project, but if that's
> not the best (and it strongly sounds like it) I would like to educate
> myself in the better devices.

Actually it's better type of device for the application. First off if the
application is line connected, then the 78LXX parts are fine. They do have
high quiescent current consumption and require nearly 3V of headroom but...

>
> The thing I like with the 'l05 is that it works great with a handful of
> caps, in a 'cookbook' solution, if I want 12v just use the 'l12.

Which is why everyone uses them. Cheap and plentiful (i.e. it passes the
RatShack test) are reasons for using them too.

> Are
> there other devices with similar recipe solutions, I'd like something
> that's in the manner of do this, do that and feed volts in here and get
> smooth volts out there.

I think you missed my point. The 78LXX parts are fine for some applications.
However linear regulators will burn through any power budgeted applications
like a battery based one.

For that type of application you need a switcher. National's Simple Switcher
series is about as simple as it gets: Regulator, inductor, catch diode, and
low ESR filter cap. Check out the LN2574 and it's similar members.

>
> I don't really need the recipe as I realize the datasheets are out
> there, but which datasheets should I read and why.

Hope this helps,

BAJ

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2004\03\16@225631 by Robert L Cochran

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I had no idea my question on nanowatt technology would stimulate so much
discussion on voltage regulators. Byron, thanks a lot for your reply to
my original post. And everyone, thanks for teaching me about regulators.
I'm amazed at the quality and amount of technical discussion -- and I'm
glad of it, I'm learning a lot.

Bob Cochran


Byron A Jeff wrote:

{Quote hidden}

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http://greenbeltcomputer.biz/

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2004\03\17@013043 by William Chops Westfield

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On Tuesday, Mar 16, 2004, at 15:32 US/Pacific, Byron A Jeff wrote:

> I think you missed my point. The 78LXX parts are fine for some
> applications.  However linear regulators will burn through any power
> budgeted applications like a battery based one.

Nonsense.  As long as your actual application is low current, you CAN
design a linear regulator that is also low current.  It won't
necessarily be very efficient, but it can do much better than a 78L05.
The problem with the 78L is not so much the inherent inefficiency of
linear regulation, but the relatively high "idle" current (5mA, someone
said?), which is MUCH larger than a PIC in idle mode, for instance.
You can run for a long time using a linear regulator if the whole thing
draws an average of 0.5mA, even if the efficiency is relatively poor.
A simple zener regulator is probably a good example; given reasonably
accurate ideas of minimum and maximum current consumption of the
circuit, you can design a zener circuit that is "maximally efficient
for a linear regulator."

Don't forget that switchers frequently have restrictions on minimum
current supplied.  While they're great (relatively speaking) for
getting maximum EFFICIENCY for a relatively high-current application,
they are NOT always the best solution for a low-current device.  (Of
course, there are nice chips specifically aimed at high "stand-by"
times in devices like PDAs and Cell phones that ARE optimized for some
low-current delivery.  Interestingly enough, sometimes these include
linear portions for some of their outputs...)

BillW

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2004\03\17@023214 by Russell McMahon

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> A simple zener regulator is probably a good example; given reasonably
> accurate ideas of minimum and maximum current consumption of the
> circuit, you can design a zener circuit that is "maximally efficient
> for a linear regulator."

I'm afraid I have to disagree here.
Zener shunt regulators can be surprisingly tricky BECAUSE of their low
component complexity.

A zener shunt regulator works by ALWAYS drawing at least the maximum current
(via the dropping resistor) that the circuit will EVER need to draw. eg if
you have a circuit that draws from 0 mA to 10 mA then the zener regulator
MUST draw at least 10 mA at all times. The current not used by the load is
shunted through the zener. A linear regulator in the same application will
be more efficient than the zener regulator whenever the load current falls
more than Q mA below 10 mA where Q is the regulators operating current (ie
the current sent down its ground lead rather than through the load. Modern
regulators such as the LM317 (modern only compared with eg 7805 family)
operate their internals from the regulator differential voltage and only
have a small and relatively constant ground lead current so are potentially
more efficient than a zener across a wide range.

Zeners are also potentially poor when the input voltage varies widely and
sometimes closely approaches the output voltage. In such cases the series
pass element has to be sized to pass Imax with little voltage drop. When Vin
rises with no or low load the current in the zener rises to above Imax_out -
sometimes many times Imax_out.



       Russell McMahon

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2004\03\17@024912 by Roland

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If you want really low power, the Iq of a switching regulator can still be
too high. I've used the MC78LC50 (yes, 50, not 05, also 40 and 33) from
Motorola in the past. It has an Iq of 1uA. Hard to beat that. I tried to
download the data sheet again, but Motorola site doesn't seem to have it.
Can still buy them though.

Otherwise I see microchip has released the MCP1700 range, with 1.6uA
quiescent current.

Regards
Roland



MC78LC33HT1


At 07:50 AM 16/03/2004 -0500, you wrote:
>> Not stupid in the least. In fact a lot of novices brag about using low
power
{Quote hidden}

Regards
Roland Jollivet


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2004\03\17@163619 by Byron A Jeff

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On Tue, Mar 16, 2004 at 10:27:28PM -0800, William Chops Westfield wrote:
> On Tuesday, Mar 16, 2004, at 15:32 US/Pacific, Byron A Jeff wrote:
>
> >I think you missed my point. The 78LXX parts are fine for some
> >applications.  However linear regulators will burn through any power
> >budgeted applications like a battery based one.
>
> Nonsense.  As long as your actual application is low current, you CAN
> design a linear regulator that is also low current.  It won't
> necessarily be very efficient, but it can do much better than a 78L05.

I have to pull out an Olinism here. It doesn't matter if you're burning 40
percent at a microamp rate or 40 percent of 10A. In the end you'll waste 40
percent of your power budget.

> The problem with the 78L is not so much the inherent inefficiency of
> linear regulation, but the relatively high "idle" current (5mA, someone
> said?), which is MUCH larger than a PIC in idle mode, for instance.
> You can run for a long time using a linear regulator if the whole thing
> draws an average of 0.5mA, even if the efficiency is relatively poor.
> A simple zener regulator is probably a good example; given reasonably
> accurate ideas of minimum and maximum current consumption of the
> circuit, you can design a zener circuit that is "maximally efficient
> for a linear regulator."

Understood. However my point is still in place: all linear regulators operate
by dropping the excess voltage which converts the power into heat. That's
power that's not available to the target. A switching regulator will deliver
more power to the target, so no matter the current draw, a switching regulator
will last longer.

And if we're talking about 9V batteries, it's critical to deliver every
meager drop of power to the target.

>
> Don't forget that switchers frequently have restrictions on minimum
> current supplied.  While they're great (relatively speaking) for
> getting maximum EFFICIENCY for a relatively high-current application,
> they are NOT always the best solution for a low-current device.  (Of
> course, there are nice chips specifically aimed at high "stand-by"
> times in devices like PDAs and Cell phones that ARE optimized for some
> low-current delivery.  Interestingly enough, sometimes these include
> linear portions for some of their outputs...)

I looked for restrictions, and didn't find any in a cursory glance of
National's simple switchers or the Linear Tech datasheets. But LT's Burst
Mode seems to solve the issue that you are referring to. In short when
the current draw is low, then chip simply stops swtiching and lets the
target draw from the output capacitor until the voltage drops below a preset
level. Then the regulator cranks up again, refills the cap, then cycles.
In this mode the regulator only draws 10 uA from the supply.

The mode is available on both buck (LTC3404) and boost (LTC1700) applications
with input voltages as low a 0.9V! So 2 C cells in an application like this
could power a low current draw circuit virtually forever.

BAJ

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2004\03\17@205425 by Byron A Jeff

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On Wed, Mar 17, 2004 at 02:49:12AM -0500, Roland wrote:
> If you want really low power, the Iq of a switching regulator can still be
> too high. I've used the MC78LC50 (yes, 50, not 05, also 40 and 33) from
> Motorola in the past. It has an Iq of 1uA. Hard to beat that. I tried to
> download the data sheet again, but Motorola site doesn't seem to have it.

It's OnSemi now. Here's a link to the datasheet:

http://www.onsemi.com/pub/Collateral/MC78LC00-D.PDF

BAJ

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