Searching \ for '[EE:] Is this going to die?' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/index.htm?key=going+die
Search entire site for: 'Is this going to die?'.

Exact match. Not showing close matches.
PICList Thread
'[EE:] Is this going to die?'
2004\12\19@131109 by John Pearson

flavicon
face
I have a 5v voltage regulator where the data sheet states the absolute maximum input voltage is 9v DC. I want to use transistor batteries on it and the voltage that the regulator sees on the input side, with the full circuit operating, with a new battery, is about 9.2 - 9.3 volts.

I don't want to slip-in a diode because I want to get the maximum life out of the battery without a voltage drop penalty.

What do you think. Am I looking for trouble?

Thanks
John
___________________________________________

2004\12\19@135438 by michael brown

picon face
John Pearson wrote:
> I have a 5v voltage regulator where the data sheet states the
> absolute maximum input voltage is 9v DC. I want to use transistor
> batteries on it and the voltage that the regulator sees on the input
> side, with the full circuit operating, with a new battery, is about
> 9.2 - 9.3 volts.
>
> I don't want to slip-in a diode because I want to get the maximum
> life out of the battery without a voltage drop penalty.
>
> What do you think. Am I looking for trouble?

Tell us how much current you need to draw.  Unless you need the 9V for
something else in the circuit, you are going to waste nearly half of
your usable battery by heating the regulator.  Perhaps you could use a
low dropout regulator and 4 or 5 AA's or AAA's.  Or design the circuit
to run at lower voltages (if possible) and skip the regulator all
together.  Maybe a switching regulator would be worthwhile considering?

____________________________________________

2004\12\19@144734 by Roy J. Gromlich

picon face
This brings up a question I have been meaning to ask here - I have
been looking for a Switching Regulator which will replace a 7805
product in a TO-200 package. It's not that I need the full 1Amp
output - I do need to drop 12V to 24V down to 5V to power a
card which will pull about 150mA MAX.  Worst case is dropping
19volts @ 150mA which is 2.85 Watts - that's a lot of power to
throw away to get 0.75 watts.

The board was designed with a TO-220 standing up and thus
taking very little PCB realestate.  While there are small switching
regulators which will do this, they are invariably in DIP packages.
There is simply no way to get a 16-pin DIP in the place of a
TO-220.

Has anyone seen such a device?  A switcher in a TO-200 which
can deliver 5.0 volts @ 150mA from 12V - 24V? It certainly seems
like a product many people would have a use for.

RJG



{Original Message removed}

2004\12\19@151556 by olin_piclist

face picon face
John Pearson wrote:
> I have a 5v voltage regulator where the data sheet states the
> absolute maximum input voltage is 9v DC. I want to use transistor
> batteries on it and the voltage that the regulator sees on the input
> side, with the full circuit operating, with a new battery, is about
> 9.2 - 9.3 volts.
>
> What do you think. Am I looking for trouble?

What part of "absolute maximum" don't you understand?

> I don't want to slip-in a diode because I want to get the maximum
> life out of the battery without a voltage drop penalty.

OK, stop typing and trying thinking instead.  Whether there is a diode in
there dropping the input voltage to the regulator or the regulator drops the
additional voltage itself, you still have the same current drawn and
therefore the same efficiency.  At 9.3V in and 5V out, the efficiency is
only 54%, assuming the regulator ground current is minimal compared to the
load current (probably the case).  The only difference the diode will make
is raise the minimum battery voltage that will still produce regulated
output.  Let's say the regulator needs 500mV headroom.  Without a diode,
this voltage would be 5.5V.  With a 700mV diode drop, it would be 6.2V.
6.2V is still "dead" for a 9V battery.

If efficiency is really important, use a switching regulator.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com
____________________________________________

2004\12\19@152007 by olin_piclist

face picon face
Roy J. Gromlich wrote:
> Has anyone seen such a device?  A switcher in a TO-200 which
> can deliver 5.0 volts @ 150mA from 12V - 24V? It certainly seems
> like a product many people would have a use for.

Your unlikely to find that because an inductor needs to be in there
somewhere.  If you only want a 3 terminal device, this implies the inductor
is internal.  I don't imagine anyone has put an inductor and the associated
electronics into a TO-220 package.  If they did, it would be a lot more
expensive than a 7805.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com
____________________________________________

2004\12\19@152421 by David Challis

face picon face
Roy,

How about a pt78st105 integrated switching regulator from TI (Power trends).
Here is a link:
http://focus.ti.com/docs/prod/folders/print/pt78st105.html

Vin 9V-38V  Vout 5V. Iout 1.5A. 3pin SIP package with pinout similar to a
TO-220, but a bit wider package.  Vertical or horizontal mounting.

I've used these and the 3.3v variant with great success.  A real nice part.

Hope this helps.

Dave Challis

{Original Message removed}

2004\12\19@152732 by csb

flavicon
face
> This brings up a question I have been meaning to ask here - I have
> been looking for a Switching Regulator which will replace a 7805
> product in a TO-200 package. It's not that I need the full 1Amp
> output - I do need to drop 12V to 24V down to 5V to power a
> card which will pull about 150mA MAX.  Worst case is dropping
> 19volts @ 150mA which is 2.85 Watts - that's a lot of power to
> throw away to get 0.75 watts.
>
> The board was designed with a TO-220 standing up and thus
> taking very little PCB realestate.  While there are small switching
> regulators which will do this, they are invariably in DIP packages.
> There is simply no way to get a 16-pin DIP in the place of a
> TO-220.
>
> Has anyone seen such a device?  A switcher in a TO-200 which
> can deliver 5.0 volts @ 150mA from 12V - 24V? It certainly seems
> like a product many people would have a use for.

If there aren't too many to build: solder the switching regulator
on a small circuit, with 3 leads soldered on one side with 100mil
spacing, you would then have a homemade TO220. It would probably
be possible to make something small, needing no heatsinking, maybe.

Christian

____________________________________________

2004\12\19@154835 by PicDude

flavicon
face
This will probably meet your needs...

       http://www.datel.com/data/meters/dms-78xxsr.pdf

Cheers,
-Neil.


On Sunday 19 December 2004 01:47 pm, Roy J. Gromlich scribbled:
{Quote hidden}

> {Original Message removed}

2004\12\19@161111 by Jinx

face picon face
John, can you jack up reference pin with a diode instead ?
This will give you an o/p V of 5V+diode and allow you to use
a 9V battery as the i/p limit has also been raised by a diode V

This is something I do with zeners (k to pin, a to 0V) or trimpot
to raise o/p to non-standard voltages. With a zener you need to
have a couple of mA back from the o/p to the cathode to stabilise
it, but I "think" you can insert a signal diode (eg 1N4148) in the
reference pin path to ground, with cathode to 0V and anode to
pin without needing any feedback as above. This would give you
an o/p voltage of ~ 5.6V and an i/p range up to 9.6V

____________________________________________

2004\12\19@165404 by David Duffy

flavicon
face
Olin Lathrop wrote:

>Roy J. Gromlich wrote:
>  
>
>>Has anyone seen such a device?  A switcher in a TO-200 which
>>can deliver 5.0 volts @ 150mA from 12V - 24V? It certainly seems
>>like a product many people would have a use for.
>>    
>>
>
>Your unlikely to find that because an inductor needs to be in there
>somewhere.  If you only want a 3 terminal device, this implies the inductor
>is internal.  I don't imagine anyone has put an inductor and the associated
>electronics into a TO-220 package.  If they did, it would be a lot more
>expensive than a 7805.
>  
>

The PowerTrends ones are 3 pin but larger than a TO-220 case.
It is just "in - ground - out" like a 7805 though.
David...

____________________________________________

2004\12\19@171852 by William Chops Westfield

face picon face

On Dec 19, 2004, at 11:47 AM, Roy J. Gromlich wrote:

> This brings up a question I have been meaning to ask here - I have
> been looking for a Switching Regulator which will replace a 7805
> product in a TO-200 package.

There are some products like that on the market.  They tend to be
pretty expensive ($10+)

I did a PCB layout for the Piclist's "Black regulator" designed to
plug into a 3-terminal regulator pattern.  It hasn't been tested (or
even built yet), but you're welcome to what I've got.  I don't know
how the cost comparison with a $15 commercial regulator module would
work out in a commercial endeavor, and I don't recall the restrictions
on the IP for the Black regulator, but it might be a start.

(surely MANY of the itsy-bitsy modern switching regulators can go onto
an appropriately sized PCB.  I wonder why that isn't a more common
app-note ?)

BillW
____________________________________________

2004\12\19@172800 by Roy J. Gromlich

picon face
Actually, thanks to two of the posters here, I now know that there are two
devices
I can use - one by TI and the other from Datel.  The datel part is a bit
closer to the
TO-220 package size, but after checking the data sheets I see that both
could be
used  on the PCB in question.  I need to get some samples to test, to
determine
which is best.  Right now it looks like the Datel part will have slightly
better efficiency
at the lower currents I need, but maybe not in actual practice.

Thanks lots, guys.

RJG
{Original Message removed}

2004\12\19@175614 by Martin Klingensmith

flavicon
face
Roy J. Gromlich wrote:

>Actually, thanks to two of the posters here, I now know that there are two
>devices
>I can use - one by TI and the other from Datel.  The datel part is a bit
>closer to the
>TO-220 package size, but after checking the data sheets I see that both
>could be
>used  on the PCB in question.  I need to get some samples to test, to
>determine
>which is best.  Right now it looks like the Datel part will have slightly
>better efficiency
>at the lower currents I need, but maybe not in actual practice.
>
>Thanks lots, guys.
>
>RJG
>  
>

National "simple switchers" are TO-220 but require a small inductor
right? I think they run at either 50 or 70-some KHz, making the required
inductor pretty small.

--
Martin K
____________________________________________

2004\12\19@193853 by Mark Rages

face picon face
What regulator is this, BTW?

Regards,
Mark,
markrages@gmail

On Sun, 19 Dec 2004 10:23:13 -0800, John Pearson <spam_OUTxeroTakeThisOuTspamcmc.net> wrote:
> I have a 5v voltage regulator where the data sheet states the absolute maximum input voltage is 9v DC. I want to use transistor batteries on it and the voltage that the regulator sees on the input side, with the full circuit operating, with a new battery, is about 9.2 - 9.3 volts.
>
> I don't want to slip-in a diode because I want to get the maximum life out of the battery without a voltage drop penalty.
>
> What do you think. Am I looking for trouble?
>
> Thanks
> John
> ______________________________________________

2004\12\19@201852 by Keelan Lightfoot

picon face
The National Semiconductor LM2674 looks pretty attractive, and it's
available in an 8 pin DIP or SOIC8. It needs 3 external capacitors, an
inductor and a diode. It runs at 260 kHz, so the inductor is very
small.
____________________________________________

2004\12\19@212045 by John Pearson

flavicon
face
Jinx, that sounds good but I need 5.0volts.

This is an mpu circuit, so I use a diode to drop off .7v, then when the mpu
sees the battery voltage has dropped to around 5.75v, the mpu turns on a
mosfet that shunts the diode. This would also be a good time to signal a low
battery condition. Would I need an n or p channel mosfet to shunt the diode
from the battery plus post, and what signal, high or low?


{Original Message removed}

2004\12\19@234858 by Russell McMahon

face
flavicon
face
> Jinx, that sounds good but I need 5.0volts.
>
> This is an mpu circuit, so I use a diode to drop off .7v, then when the
> mpu
> sees the battery voltage has dropped to around 5.75v, the mpu turns on a
> mosfet that shunts the diode. This would also be a good time to signal a
> low
> battery condition. Would I need an n or p channel mosfet to shunt the
> diode
> from the battery plus post, and what signal, high or low?

If you tell us what regulator you are using, what sort of current drain you
need and any other critical constraints (board exists, ....) we can probably
provide more help. If you don't want to add extra components there are low
drop out low quiesecent current regulators that easily withstand 9v in and
have very little input-output drop at the end of battery life.

An essentially flat 9v battery will have about 5.4 volts terminal voltage (6
x 0.9) so a regulator with 0.4 volts or less dropout at maximum rated
current will do the job. Arguably you can get SOME energy down to 4.8v (6 x
0.8) but there is vv little energy difference between the two.

Switching series diodes sounds like massive overkill for such an
application. If you are able to go to those lengths there are better ways to
get an *approximately* zero dropout linear regulator. (eg a FET with 50
milliohm Rdson will give you 50 mV dropout at 1 amp. Such FETs are not too
hard to find.


       RM



--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.296 / Virus Database: 265.6.0 - Release Date: 17/12/2004

____________________________________________

2004\12\20@040006 by James Newtons Massmind

face picon face
I would very much like to publish that layout on the PICList site. I can get
you some free PCBs in return.

---
James.



> {Original Message removed}

2004\12\20@063035 by Russell McMahon

face
flavicon
face
>I would very much like to publish that layout on the PICList site. I can
>get
> you some free PCBs in return.

>> I did a PCB layout for the Piclist's "Black regulator"
>> designed to plug into a 3-terminal regulator pattern.  It
>> hasn't been tested (or even built yet), but you're welcome to
>> what I've got.

>> ...I don't recall the restrictions on
>> the IP for the Black regulator, but it might be a start.

AFAIK Roman's design is public domain - maybe postcardware. (fwiw it's hard
to do otherwise with a circuit topography).

Be aware that the Black regulator, while superb on component count, is not
especially good on several performance parameters. The 3 transistor "God's
switching regulator" circuit that I published is far more tolerant of
inductor value and has substantially better regulation with input and load
variations, despite it's less unusual use of the zener diode reference.
(This isn't just sour grapes on my part - this conclusion was arrived at
independently by a friend who was evaluating all known designs for use in a
lowest reasonable cost, volume application). He improved the usually
somewhat chaotic switching of the circuit by a series RC feedback network
(hot side of buck inductor to drive transistor base from memory). This makes
the circuit appear more conventional in operation, for those who like 'nice'
waveforms, but doen't necessarily make the circuit perform any better.

A 3 terminal regulator replacement pcb layout is an excellent idea. If
people are going to spend time on this they may wish to try both designs to
see which is most applicable. Roman's certainly wins if absolute minimum
component count is vital




       Russell McMahon







--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.296 / Virus Database: 265.6.0 - Release Date: 17/12/2004

____________________________________________

2004\12\20@095530 by Mark Rages

face picon face
instead of adding extra components and software, why not get a
regulator that's good for more than 9V input? I'll bet you can find
one.

Regards,
Mark
markrages@gmail


On Sun, 19 Dec 2004 18:32:51 -0800, John Pearson <.....xeroKILLspamspam@spam@cmc.net> wrote:
> Jinx, that sounds good but I need 5.0volts.
>
> This is an mpu circuit, so I use a diode to drop off .7v, then when the mpu
> sees the battery voltage has dropped to around 5.75v, the mpu turns on a
> mosfet that shunts the diode. This would also be a good time to signal a low
> battery condition. Would I need an n or p channel mosfet to shunt the diode
> from the battery plus post, and what signal, high or low?
>
>
> {Original Message removed}

2004\12\20@102108 by John Pearson

flavicon
face
Because, unforunately, it is not an option I have.

----- Original Message -----
From: "Mark Rages" <markragesspamKILLspamgmail.com>
To: "Microcontroller discussion list - Public." <.....piclistKILLspamspam.....mit.edu>
Sent: Monday, December 20, 2004 6:55 AM
Subject: Re: [EE:] Is this going to die?


{Quote hidden}

mpu
> > sees the battery voltage has dropped to around 5.75v, the mpu turns on a
> > mosfet that shunts the diode. This would also be a good time to signal a
low
> > battery condition. Would I need an n or p channel mosfet to shunt the
diode
{Quote hidden}

>

2004\12\20@105429 by Mike Hord

picon face
> OK, stop typing and trying thinking instead.  Whether there is a diode in
> there dropping the input voltage to the regulator or the regulator drops the
> additional voltage itself, you still have the same current drawn and
> therefore the same efficiency.  At 9.3V in and 5V out, the efficiency is
> only 54%, assuming the regulator ground current is minimal compared to the
> load current (probably the case).  The only difference the diode will make
> is raise the minimum battery voltage that will still produce regulated
> output.  Let's say the regulator needs 500mV headroom.  Without a diode,
> this voltage would be 5.5V.  With a 700mV diode drop, it would be 6.2V.
> 6.2V is still "dead" for a 9V battery.
>
> If efficiency is really important, use a switching regulator.

There are limits to this; I just went through design for a long-term datalogger
which needed to run for months on batteries.

After much hemming, hawing, experimenting and recalculating, I came to
the conclusion that using a low Iq linear regulator with a 9V battery was in
almost all respects a superior solution to switching regulator solutions
because:

1.  It was very tough to get the level of Iq desired (<20 uA) from a switcher.
2.  Switchers require much more fancy circuitry than the two caps needed
for the linear regulator.
3.  A 9V battery is (usually) far easier to integrate into the power system,
thanks to its built-on snaps.  Yes, I know about the AA and AAA cases
with wires attached and a power switch and screw to hold them together,
but ask yourself, is that REALLY simpler than a 9V's snaps?
4.  If you integrate over life of the battery, the efficiency picture improves.
While it's true that at 9V in and 5V out, efficiency is only a dismal 54%,
down around 6V, efficiency goes up to 83%, which ain't half bad.
5.  Switchers produce more noise in the circuit; removing them makes
noise control that much easier.

The moral of this story is that for low current, low noise applications,
using a 9V with a linear regulator isn't the worst option.  If you don't need
low noise, low Iq, however, a switcher is definitely the way to go.

Mike H.
____________________________________________

2004\12\20@125501 by olin_piclist

face picon face
John Pearson wrote:
> Because, unforunately, it is not an option I have.

This doesn't make sense.  If you can add other circuitry, how can you not
spec a different regulator?


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com
____________________________________________

2004\12\20@130044 by olin_piclist

face picon face
Mike Hord wrote:
> 3.  A 9V battery is (usually) far easier to integrate into the power
> system, thanks to its built-on snaps.  Yes, I know about the AA and AAA
> cases
> with wires attached and a power switch and screw to hold them together,
> but ask yourself, is that REALLY simpler than a 9V's snaps?

No, but that's a complicated way to hold AA or AAA batteries.  For those
types, I like to use the battery clips from Keystone.  These mount directly
on the circuit board, one for each end of the battery.  The circuit board
becomes part of the battery holder.  The batteries snap in but are held
firmly in place.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com
____________________________________________

2004\12\20@130440 by William Chops Westfield

face picon face
>
>>> I did a PCB layout for the Piclist's "Black regulator"
>>> designed to plug into a 3-terminal regulator pattern.

Ok, I'll test it and see if it works :-)  It's designed to be somewhat
flexible WRT switching transistor, inductor, and output cap selection
(packagewise.)  But perhaps not enough (I wonder if everything fits.)

In what way is the circuit sensitive to the inductor?  My selection of
inductors with known parameters is somewhat limitted :-(

BillW
____________________________________________

2004\12\20@131138 by William Chops Westfield

face picon face
On Dec 20, 2004, at 7:54 AM, Mike Hord wrote:

> 3.  A 9V battery is (usually) far easier to integrate into the power
> system,
> thanks to its built-on snaps.  Yes, I know about the AA and AAA cases
> with wires attached and a power switch and screw to hold them together,
> but ask yourself, is that REALLY simpler than a 9V's snaps?
>
But 2 AAs contain significantly more energy than a 9V battery...

BillW
____________________________________________

2004\12\20@155026 by Mike Hord

picon face
> No, but that's a complicated way to hold AA or AAA batteries.  For those
> types, I like to use the battery clips from Keystone.  These mount directly
> on the circuit board, one for each end of the battery.  The circuit board
> becomes part of the battery holder.  The batteries snap in but are held
> firmly in place.

True, but if he can't find a way to integrate a different regulator, I think
finding a place to put different batteries also might be hard!

And BillW pointed out...
> But 2 AAs contain significantly more energy than a 9V battery...

Which is also very true, but I discovered that when all is said and done,
the aforementioned reasons outweighed the benefits of switching to AA
or AAA batteries.

In the future, we plan to (probably) switch to AA by remachining the
chassis the product is mounted in to function like a maglite case, where
one end is unscrewed and the batteries slide in.  Until then, the 9V
remains the weapon of choice.

YMMV.

Mike H.
____________________________________________

2004\12\20@175621 by Russell McMahon

face
flavicon
face
> instead of adding extra components and software, why not get a
> regulator that's good for more than 9V input? I'll bet you can find
> one.

LM2936 up to 50 mA - excellent low quiescent and low dropout. Expensive.
LM2931 (1A but higher quiesecent)
LT3020, LT1086 (from memory),
KA76L05Z
...

       RM



--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.296 / Virus Database: 265.6.2 - Release Date: 20/12/2004

____________________________________________

2004\12\20@175621 by Russell McMahon

face
flavicon
face
>> instead of adding extra components and software, why not get a
>> regulator that's good for more than 9V input? I'll bet you can find
>> one.

All this sounds rather cryptic - can you provide more details so we can
understand the real nature of the problem?


       RM



--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.296 / Virus Database: 265.6.2 - Release Date: 20/12/2004

____________________________________________

2004\12\20@181019 by Russell McMahon

face
flavicon
face
> In what way is the circuit sensitive to the inductor?  My selection of
> inductors with known parameters is somewhat limited :-(

Based on comments by my friend who did comparative tests. He reports that
the Black regulator needs a much larger inductor than the GSR for equivalent
functionality. This does not make sense if you opine that all buck
converters in a given situation are essentially identical. However, the GSR
seems to be rather less than normal in all sorts of ways. (A circuit that
isn't easy to analyse by normal means annoys some people and the tendency is
to try and fit it into another category. Obviously the operation can be well
described formally, but it hasn't been done fully yet AFAIK). Using a
smaller inductor implies a higher effective switching frequency, all other
things being equal. GSR switching waveform tends to look like noise in
original version. (Liable to do a good job of reducing emissions at any one
frequency).

The GSR will generally work with any sensible inductor (and quite a few
nonsensical ones :-) ).

He also reports that adding the series RC feedback circuit improved
efficiency by about 10% in his particular application (mid 60's to mid 70's
AFAIR). Efficiency achieved will depend on many parameters (incl eg
inductor, switch, Vin, Vout, power level, ...). I imagine that without
extension the circuit will never approach the efficiency levels of modern
highly optimised IC based solutions, which can exceed 90% in the right
conditions.




       Russell McMahon



--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.296 / Virus Database: 265.6.2 - Release Date: 20/12/2004

____________________________________________

2004\12\20@182830 by Spehro Pefhany

picon face
At 10:23 AM 12/19/2004 -0800, you wrote:
>I have a 5v voltage regulator where the data sheet states the absolute
>maximum input voltage is 9v DC. I want to use transistor batteries on it
>and the voltage that the regulator sees on the input side, with the full
>circuit operating, with a new battery, is about 9.2 - 9.3 volts.
>
>I don't want to slip-in a diode because I want to get the maximum life out
>of the battery without a voltage drop penalty.
>
>What do you think. Am I looking for trouble?
>
>Thanks
>John

Don't you need a series diode anyway for reverse-battery protection?

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
KILLspamspeffKILLspamspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com




____________________________________________

2004\12\20@184657 by Marcel Duchamp

picon face
This so-called "GSR" thingy has been getting kicked around a lot
recently...  does anyone have a link to a schematic for it?
MD



Russell McMahon wrote:
>
> The GSR will generally work with any sensible inductor (and quite a few
> nonsensical ones :-) ).
>
____________________________________________

2004\12\20@210106 by Dwayne Reid

flavicon
face
At 03:28 PM 12/20/2004, Russell McMahon wrote:

>LM2936 up to 50 mA - excellent low quiescent and low dropout. Expensive.
>LM2931 (1A but higher quiesecent) LT3020, LT1086 (from memory), KA76L05Z

LP2950A - reasonably inexpensive, darned reliable, accurate.  But Iq is
rather high at ~ 75 uA.

dwayne

--
Dwayne Reid   <RemoveMEdwaynerTakeThisOuTspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 20 years of Engineering Innovation (1984 - 2004)
 .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-
    `-'   `-'   `-'   `-'   `-'   `-'   `-'   `-'   `-'
Do NOT send unsolicited commercial email to this email address.
This message neither grants consent to receive unsolicited
commercial email nor is intended to solicit commercial email.

____________________________________________

2004\12\21@023811 by Russell McMahon

face
flavicon
face
> This so-called "GSR" thingy has been getting kicked around a lot
> recently...  does anyone have a link to a schematic for it?

See new thread "[EE] Low cost switching regulators".



--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.296 / Virus Database: 265.6.2 - Release Date: 20/12/2004

____________________________________________

2004\12\21@095659 by Mike Hord

picon face
> Don't you need a series diode anyway for reverse-battery protection?
>
> Best regards,
>
> Spehro Pefhany --"it's the network..."            "The Journey is the reward"

Not necessarily.  I haven't used a diode for reverse protection since
Russell turned me on the the reverse PMOSFET method.  I prefer it
greatly because it doesn't require such a high drop as the diode
method.  I don't know if there are any disadvantages; it seems to be
pretty sturdy to me.  It is a bit pricier, so in 10000 uber-cheap devices,
it's probably not worth it, but in a higher quality device where an extra
$0.10-$0.25 per unit won't make much difference, it's pretty appealing.

Mike H.
____________________________________________

2004\12\21@104815 by Bob Axtell

face picon face
The 9V battery clip is a serious source of semiconductor damage, because the
customer ALWAYS touches the battery to the WRONG clip direction before he
locates (by feel) the correct direction- and the damage is already done.

My standard way of doing that is to use a Schottky diode, like a 1N5818
in series
with the positive lead. The drop is usually less than 100mV, and
negligible at
100uA. It seems to be about $0.10 USD max.

--Bob


Mike Hord wrote:

{Quote hidden}

>_____________________________________________

2004\12\21@110249 by Mike Hord
picon face
> The 9V battery clip is a serious source of semiconductor damage, because the
> customer ALWAYS touches the battery to the WRONG clip direction before he
> locates (by feel) the correct direction- and the damage is already done.

The gate is connected to the negative terminal through a 1 MOhm resistor to
provide some protection on it.  I don't know how good it is, though, but I
suspect pretty good.

> My standard way of doing that is to use a Schottky diode, like a 1N5818
> in series
> with the positive lead. The drop is usually less than 100mV, and
> negligible at
> 100uA. It seems to be about $0.10 USD max.

Schottky diodes can allow much more reverse current than a MOSFET will;
datasheet says 1 mA at 25 deg C.  But I suspect even 1 mA should be
tolerable.  I may experiment with that some.

Mike H.
____________________________________________

More... (looser matching)
- Last day of these posts
- In 2004 , 2005 only
- Today
- New search...