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'[EE] new battery technologies, causing problems?'
2005\08\15@203726 by William Chops Westfield

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Is anyone experiencing product difficulties with the new lithium
"1.5V" cells in their products/projects?  I mean, it used to be
that you could use 3AA batteries in a project and directly power
electronics.  If there were "normal" batteries, you got about 4.5V
which was good, and if someone used rechargables you got 3.6V, which
was still OK.  But I hear that some of Lithium AA batteries have
new-cell voltages over 1.8V, which is getting up near the max
limits of most PICs and such, and I'm wondering if that is likely
to cause problems (more so if you were already using 4 cells for
4.8 to 6V...)

BillW

2005\08\15@205951 by Sean Schouten

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I am not able to answer your question on the new lithium cells because
I haven't ever used any in any of my projects, but might it not be
wize to either create a small voltage regulation circuit using a
zener, or even a circuit with an LM7805?

Sean.

2005\08\15@212154 by William Chops Westfield

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On Aug 15, 2005, at 5:59 PM, Sean Schouten wrote:

> might it not be wize to either create a small voltage regulation
> circuit using a zener, or even a circuit with an LM7805?

That's what I'm trying to figure out.  a 7805 is completely out,
since it needs close to 3V of headroom to regulate and consumes
a lot  of current on its own.  There are low-dropout regulators
with low quiescent current, but the closer to perfect they get,
the more expensive they get.

I was also thinking along the lines of overvoltage detect and
refuse-to-work circuits, which I imagine is easier said than
done, unfortunately...

BillW

2005\08\15@222850 by Jinx

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I thought Lithiums had always been about 1.8V - isn't the
electrochemical potential 1.82V ?

Are you trying to protect a circuit from having lithiums put in
instead of alkalines or NiCd ? I'd be tempted to take the easy
(and reasonable IMHO) option of a sticker saying "Don't put
lithiums in this or it'll break". The same situation could arise with
another product if alkalines (1.65V) are used in place of NiCd
(1.2V). Or even freshly-charged NiCd for that matter (1.4V)

That said, PICs have a maximum voltage that is some margin
higher than the recommended operating voltage, so having a
battery that's "too enthusiastic" might not necessarily kill it and
things will come more into spec as the batteries drain



2005\08\15@234302 by William Chops Westfield

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On Aug 15, 2005, at 7:28 PM, Jinx wrote:

> I thought Lithiums had always been about 1.8V - isn't the
> electrochemical potential 1.82V ?

Which chemistry are YOU talking about?  There seem to be at
least 4 major classes of chemistry involved, and some of them
have several subclasses.  (hmm.  Li/FeS and Li/Fe2S at 1.5V "nominal",
Li/MnO2 at 3V, Li/Thionl-chloride (sp?) at 3.6V, and Li/ion at 4.1 or
4.2V (but also "3.6V nominal" or so.))

I was referring to reports on Candlepower forums that the Energizer
"L92" style Li battery (aimed at digital cameras, nominally 1.5V)
put out 1.75V fresh, while some of the clones put out as much as 2V.
(I think these are Li/FeS of some variety.)

BillW

2005\08\16@004425 by Jinx

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> I was referring to reports on Candlepower forums that the
> Energizer "L92" style Li battery (aimed at digital cameras,
> nominally 1.5V) put out 1.75V fresh, while some of the
> clones put out as much as 2V. (I think these are Li/FeS of
> some variety.)

Admitedly my Mastermind specialist subject would not be
"Lithium Battery Chemistry". If a clone's potential is 1/7th
higher then is it actually a clone, or a variant ? If this were
a product of mine I'd advise caution when fitting  new
batteries(or else buyer beware). What exactly is the problem
you're experiencing or hoping to avoid ?

2005\08\16@020044 by Russell McMahon

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> Which chemistry are YOU talking about?  There seem to be at
> least 4 major classes of chemistry involved, and some of them
> have several subclasses.  (hmm.  Li/FeS and Li/Fe2S at 1.5V
> "nominal",
> Li/MnO2 at 3V, Li/Thionl-chloride (sp?) at 3.6V, and Li/ion at 4.1
> or
> 4.2V (but also "3.6V nominal" or so.))
>
> I was referring to reports on Candlepower forums that the Energizer
> "L92" style Li battery (aimed at digital cameras, nominally 1.5V)
> put out 1.75V fresh, while some of the clones put out as much as 2V.
> (I think these are Li/FeS of some variety.)

Just to add confusion.
Note that standard "Alkalines" peak at just over 1.5v but Le Clanche
and Zinc Chlorides (really variations on a theme) peak at just over
1.6v. This can be the difference between JUST working on new batteries
and not working at all.

I'm attracted by the idea of a discrete low dropout low quiescent
current regulator to address this sort of task. Really good LDOs cost
an arm and several legs. I've never understood why. On paper only I've
designed an LDO that should offer zero current quiescent current under
50 uA, dropout under 0.1v at a load of a few 10's of mA. Enabling
technology is the glorious LM385 and a discrete long tailed pair.
Maybe a new design challenge is in order. Probably 3 transistors if
lucky plus LM385. Still cheap.

But, then I found the AIC1722 that sells at about $US0.15 in Taiwan
!!!!!!!!!!!!!!!!!!!!!!!!!!
Possible the best value LDO I've ever met, with performance to beat
almost any other I've seen.

       http://www.metatech.com.hk/datasheet/aic/low_drop_regu_pdf/Aic1722.pdf


2005\08\16@030528 by Vasile Surducan

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On 8/16/05, Russell McMahon <spam_OUTruslTakeThisOuTspamparadise.net.nz> wrote:
> > Which chemistry are YOU talking about?  There seem to be at
> > least 4 major classes of chemistry involved, and some of them
> > have several subclasses.  (hmm.  Li/FeS and Li/Fe2S at 1.5V
> > "nominal",
> > Li/MnO2 at 3V, Li/Thionl-chloride (sp?) at 3.6V, and Li/ion at 4.1
> > or
> > 4.2V (but also "3.6V nominal" or so.))
> >
> > I was referring to reports on Candlepower forums that the Energizer
> > "L92" style Li battery (aimed at digital cameras, nominally 1.5V)
> > put out 1.75V fresh, while some of the clones put out as much as 2V.
> > (I think these are Li/FeS of some variety.)
>
> Just to add confusion.

No confusion here, 3.6V 4.1V and 4.2V are the most common Li battery
on the market. When one of these its burning at charging or
discharging time it's best to be at home.

> Note that standard "Alkalines" peak at just over 1.5v but Le Clanche
> and Zinc Chlorides (really variations on a theme) peak at just over
> 1.6v. This can be the difference between JUST working on new batteries
> and not working at all.
>
> I'm attracted by the idea of a discrete low dropout low quiescent
> current regulator to address this sort of task. Really good LDOs cost
> an arm and several legs.

On Digikey and only if are made by Linear Technology...
However 0.2V dropout at 500mA is a chalenge for any discrete LDO.
Vasile

I've never understood why. On paper only I've
{Quote hidden}

> -

2005\08\16@034522 by Russell McMahon

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> On Digikey and only if are made by Linear Technology...

Alas no. eg the very nice low Iq, very low dropout, albeit only 50 mA
LM2936 is never "well priced" in my experience.
If you can show me anywhere where they ARE well priced I'll buy a
small barrel full :-).

eg using http://www.findchips.com , 9 of the 20 sellers had LM2936s. Of those
who listed prices the cheapest price was $US0.9012 in 10,000 quantity
(!) and the seller was, drum roll
..................................... !!!, Digikey.

Comapring to the 78L05 showed what we'd LIKE to pay.
Best price from the 16 who had them in stock was about $US0.10/1000.
The lowest I could find was $US0.079  *BUT* you'd have to buy 96,000
of them. And that price was from Digikey.

The AIC1722 is as good generally, better in some ways and somewhat
worse on Iq. At $US0.15/?1000? in Taiwan it beats the LM2936 hands
down on value for money.

> However 0.2V dropout at 500mA is a challenge for any discrete LDO.

Indeed. Although it's hard to see why.  That's equivalent to 0.2/0.5 =
0.4 ohms. Getting a FET to better that is trivial. Getting a bipolar
transistor to better that is entirely doable. But few do so in LDO's.
The AIC1722 is rated at 300 mA and the graph shows 380 mV drop at 300
mA. Which is very good if not actually excellent.


       RM


       >>
http://www.metatech.com.hk/datasheet/aic/low_drop_regu_pdf/Aic1722.pdf


2005\08\16@042257 by William Chops Westfield

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On Aug 16, 2005, at 12:45 AM, Russell McMahon wrote:

> http://www.metatech.com.hk/datasheet/aic/low_drop_regu_pdf/Aic1722.pdf
>
>
And is there a hobbyist supplier for this?  It does look nice.
300mA is a much 'sweeter' spec than the 50 or 100mA typical
of TO92 regulators (Hmm.  OTOH, I don't see a power dissipation
spec, though there's a nice graph...)

BillW

2005\08\16@043428 by Vasile Surducan

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On 8/16/05, Russell McMahon <.....apptechKILLspamspam@spam@paradise.net.nz> wrote:
> > On Digikey and only if are made by Linear Technology...
>
> Alas no. eg the very nice low Iq, very low dropout, albeit only 50 mA
> LM2936 is never "well priced" in my experience.
> If you can show me anywhere where they ARE well priced I'll buy a
> small barrel full :-).

I've used LM2940 but right now my dealer ask for 3 euro/pcs, so maybe
it's crazy.
I found BA033 or BA05T from Rohm at ( typical declared voltage drop
0.3V, but minimum input voltage = Vout +1V in the datasheet) quite
cheap at $0.4
I also have seen some high current LDO's at International Rectifiers
like IRU 1030 at 1$/3A which is good.

On small current LDO there is huge offer, MCP1700 is about 0.4$ (4
times higher than the standard 78L05), but a good one is LT1763 indeed
expensive.
Maxim's has at least 50 different types from $0.7 to $2.

So depends what are you doing, for a commercial product maybe the
choice will be a 0.7 euro chinese 110-220V to 8V/500mA switching
supply. For a lithium battery powered device does not even count how
much will cost the LDO. :)

cheers,
Vasile

2005\08\16@062625 by Alan B. Pearce

face picon face
>> might it not be wize to either create a small voltage regulation
>> circuit using a zener, or even a circuit with an LM7805?
>
>That's what I'm trying to figure out.  a 7805 is completely out,
>since it needs close to 3V of headroom to regulate and consumes
>a lot  of current on its own.  There are low-dropout regulators
>with low quiescent current, but the closer to perfect they get,
>the more expensive they get.

maybe you need to look at the regulator I mentioned here recently. Linear
Technology LTC3448, but another possibility would be LT3470.

2005\08\16@161418 by Peter

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On Tue, 16 Aug 2005, Russell McMahon wrote:

>> On Digikey and only if are made by Linear Technology...
>
> Alas no. eg the very nice low Iq, very low dropout, albeit only 50 mA LM2936
> is never "well priced" in my experience.
> If you can show me anywhere where they ARE well priced I'll buy a small
> barrel full :-).

Does Digikey still carry S81250/81350 ? ;-)

Peter

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