Searching \ for '[EE] reverse battery protection?' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: techref.massmind.org/techref/power/batterys.htm?key=battery
Search entire site for: 'reverse battery protection?'.

Exact match. Not showing close matches.
PICList Thread
'[EE] reverse battery protection?'
2006\04\14@154522 by alan smith

picon face
OK...diode in series, but that causes a voltage drop.  I've also seen using a low Rds(on) fet.  Any other simple, cheap solutions?

               
---------------------------------
Love cheap thrills? Enjoy PC-to-Phone  calls to 30+ countries for just 2¢/min with Yahoo! Messenger with Voice.

2006\04\14@155307 by Mike Hord

picon face
Reverse biased diode across input.  Clamps reverse voltage to one diode
drop, but if (when) the diode smokes, the reverse voltage dumps to the
load in full.

If looking at the FET option, remember that for high-side protection, you
need a PFET, and you should install it "backwards" otherwise the inherent
substrate diode will conduct when the battery is reversed.  The FET method
is my personal favorite.

Mike H.

On 4/14/06, alan smith <spam_OUTmicro_eng2TakeThisOuTspamyahoo.com> wrote:
> OK...diode in series, but that causes a voltage drop.  I've also seen using a low Rds(on) fet.  Any other simple, cheap solutions?
>
>
> ---------------------------------
> Love cheap thrills? Enjoy PC-to-Phone  calls to 30+ countries for just 2¢/min with Yahoo! Messenger with Voice.
>

2006\04\14@155651 by David VanHorn

picon face
On 4/14/06, alan smith <.....micro_eng2KILLspamspam@spam@yahoo.com> wrote:
>
> OK...diode in series, but that causes a voltage drop.  I've also seen
> using a low Rds(on) fet.  Any other simple, cheap solutions?


Diode in series with a relay coil, relay connects power if polarity is good.

--
> Feel the power of the dark side!  Atmel AVR

2006\04\14@161447 by Harold Hallikainen

face picon face

> Reverse biased diode across input.  Clamps reverse voltage to one diode
> drop, but if (when) the diode smokes, the reverse voltage dumps to the
> load in full.
>
> If looking at the FET option, remember that for high-side protection, you
> need a PFET, and you should install it "backwards" otherwise the inherent
> substrate diode will conduct when the battery is reversed.  The FET method
> is my personal favorite.
>
> Mike H.


How about a PTC thermistor in series, then a reverse biased diode. Or, use
a reverse biased zener diode. This two part circuit then gives over
current, over voltage, and reverse voltage protection.

Harold
"The ideal design has zero parts"

--
FCC Rules Updated Daily at http://www.hallikainen.com

2006\04\14@170130 by Thomas C. Sefranek

face picon face
-----Original Message-----
From: piclist-bouncesspamKILLspammit.edu [.....piclist-bouncesKILLspamspam.....mit.edu] On Behalf Of
alan smith
Sent: Friday, April 14, 2006 3:45 PM
To: Microcontroller discussion list - Public.
Subject: [EE] reverse battery protection?

OK...diode in series, but that causes a voltage drop.  I've also seen using
a low Rds(on) fet.  Any other simple, cheap solutions?

               
---------------------------------
Love cheap thrills? Enjoy PC-to-Phone  calls to 30+ countries for just
2¢/min with Yahoo! Messenger with Voice.

2006\04\14@172323 by Mike Hord

picon face
I've considered this as a means of reverse battery protection, but
it seems to me that the fact that the return current also has to
pass through a diode could lead to a softer-than-average ground.

Maybe a problem, maybe not.

Mike H.

On 4/14/06, Thomas C. Sefranek <EraseMEtcsspam_OUTspamTakeThisOuTcmcorp.com> wrote:
> {Original Message removed}

2006\04\14@173519 by alan smith

picon face
well....this is a two AA cell design, so no need for over voltage, or high currents, just if the user puts the batteries in backwards....
 
 Generally not a good idea...but wonder how much damage might occur if they end up in backwards?
 
 Think we all have done that a time or two in some consumer device.

               
---------------------------------
Love cheap thrills? Enjoy PC-to-Phone  calls to 30+ countries for just 2¢/min with Yahoo! Messenger with Voice.

2006\04\14@175555 by Mike Hord

picon face
> well....this is a two AA cell design, so no need for over voltage, or
> high currents, just if the user puts the batteries in backwards....

You might be surprised how much current two AA batteries can put
out.

>   Generally not a good idea...but wonder how much damage might
> occur if they end up in backwards?

What are they feeding?  Some regulators have built-in reverse protection.
If they are feeding a PIC directly (say, a 12F675), you'll have a bad day.

Check the absolute maximum ratings of the devices on your battery
power bus.  If the absolute max of reverse inserted batteries (say,
-3.2V to -3.4V relative to nominal ground) doesn't exceed the absolute max
of the devices hooked to that node, you're okay.

Most devices are comfortable with about one diode drop below ground
before smoke leakage occurs.

Mike H.

2006\04\14@182211 by alan smith

picon face
Good point....hadn't thought of that.  Thanks.

Mike Hord <mike.hordspamspam_OUTgmail.com> wrote:   are feeding a PIC directly (say, a 12F675), you'll have a bad day.

Check the absolute maximum ratings of the devices on your battery
power bus. If the absolute max of reverse inserted batteries (say,
-3.2V to -3.4V relative to nominal ground) doesn't exceed the absolute max
of the devices hooked to that node, you're okay.

Most devices are comfortable with about one diode drop below ground
before smoke leakage occurs.

Mike H.

2006\04\14@200340 by Jinx

face picon face
> I've also seen using a low Rds(on) fet

Hi Alan, I came across an example of this the other day

http://pdfserv.maxim-ic.com/en/ds/MAX6791-MAX6796.pdf (532kB)

"The MAX6791-MAX6796 include an over-voltage protection
circuit that is capable of driving a p-channel MOSFET to protect
against reverse-battery conditions. This MOSFET eliminates the
need for external diodes, thus minimizing the input voltage drop.
See the Typical Application Circuit. The low p-channel MOSFET
onresistance of 30m? or less yields a forward-voltage drop of only
a few millivolts versus hundreds of millivolts for a diode, thus
improving efficiency in battery-operated devices. Connecting a
positive battery voltage to the drain of Q1 (see the Typical Application
Circuit) forward biases its body diode. When the source voltage
exceeds Q1's threshold voltage, Q1 turns on. Once the FET is on,
the battery is fully connected to the system and can deliver power to
the device and the load. An incorrectly inserted battery reverse-biases
the FET's body diode. The gate remains at the ground potential. The
FET remains off and disconnects the reversed battery from the system.
The internal zener diode and resistor combination at GATEP prevent
damage to the p-channel MOSFET during an overvoltage condition.
See the Functional Diagrams."

2006\04\17@180843 by alan smith

picon face
If only....someone else BESIDES maxim was making it.  I will never design in a maxim part, even tho qty of this might be in the 100K/yr

Jinx <@spam@joecolquittKILLspamspamclear.net.nz> wrote:  > I've also seen using a low Rds(on) fet

Hi Alan, I came across an example of this the other day

http://pdfserv.maxim-ic.com/en/ds/MAX6791-MAX6796.pdf (532kB)

"The MAX6791-MAX6796 include an over-voltage protection
circuit that is capable of driving a p-channel MOSFET to protect
against reverse-battery conditions. This MOSFET eliminates the
need for external diodes, thus minimizing the input voltage drop.
See the Typical Application Circuit. The low p-channel MOSFET
onresistance of 30m? or less yields a forward-voltage drop of only
a few millivolts versus hundreds of millivolts for a diode, thus
improving efficiency in battery-operated devices. Connecting a
positive battery voltage to the drain of Q1 (see the Typical Application
Circuit) forward biases its body diode. When the source voltage
exceeds Q1's threshold voltage, Q1 turns on. Once the FET is on,
the battery is fully connected to the system and can deliver power to
the device and the load. An incorrectly inserted battery reverse-biases
the FET's body diode. The gate remains at the ground potential. The
FET remains off and disconnects the reversed battery from the system.
The internal zener diode and resistor combination at GATEP prevent
damage to the p-channel MOSFET during an overvoltage condition.
See the Functional Diagrams."

2006\04\17@191312 by Jinx

face picon face
> If only....someone else BESIDES maxim was making it.  I will
> never design in a maxim part, even tho qty of this might be in the
> 100K/yr

Hi Alan, I was actually citing Maxim's demonstration of the FET as
reverse-polarity protection. That the part is also a regulator is purely
coincidental

2006\04\17@193252 by Bob Axtell

face picon face
alan smith wrote:
> If only....someone else BESIDES maxim was making it.  I will never design in a maxim part, even tho qty of this might be in the 100K/yr
>  
Lord, yes. Maxim has been disappointing this old timer for a LONG time.

{Quote hidden}

2006\04\18@024759 by Steve Smith

flavicon
face
The answer is in the maxim data sheet! Use the concept a Pfet resistor and
zener.

The body diode conducts if correctly polarised and then the zener and
resistor take over turning on the fet shorting the body diode and reducing
the diode losses to a few 10s of mV at the expense of the couple of uA taken
to turn the fet on without the expense of the supervisor ic.........

Rgds
Steve

{Original Message removed}

2006\04\19@121258 by alan smith

picon face
Ahh..ok.  Sorry, didnt mean to imply I was not gratefull for the info.

Jinx <RemoveMEjoecolquittTakeThisOuTspamclear.net.nz> wrote:  > If only....someone else BESIDES maxim was making it. I will
> never design in a maxim part, even tho qty of this might be in the
> 100K/yr

Hi Alan, I was actually citing Maxim's demonstration of the FET as
reverse-polarity protection. That the part is also a regulator is purely
coincidental

2006\04\19@194015 by Zik Saleeba

face picon face
Why the dislike of Maxim? I was just about to design a couple of their
parts into something I'm working on...

Cheers,
Zik

On 18/04/06, alan smith <spamBeGonemicro_eng2spamBeGonespamyahoo.com> wrote:
{Quote hidden}

>

2006\04\19@195733 by David VanHorn

picon face
On 4/19/06, Zik Saleeba <RemoveMEzikspamTakeThisOuTzikzak.net> wrote:
>
> Why the dislike of Maxim? I was just about to design a couple of their
> parts into something I'm working on...


You can buy 10, and you can buy 1,000,000.  Try buying 1000.


--
> Feel the power of the dark side!  Atmel AVR

2006\04\19@201231 by Mike Hord

picon face
> Why the dislike of Maxim? I was just about to design a couple of their
> parts into something I'm working on...

Maxim is okay, and they have a lot of really cool and useful parts, but
that usefulness is a direct result of the large amounts of unobtanium
that goes into their production.  This has several results:
1.  When world supplies of unobtanium dip, the part you need suddenly
has a seven-month lead time.
2.  Maxim's rep as being a less-than-dependable source, especially
in the mid-low quantity range, has led to counterfeit Maxim parts
being commonly available.  You won't get them if you buy from
Digi-Key, but if your contract manufacturer has to second-source and
they go to their cousin Chet in his VW Micro Bus, you may be left
holding the bag at the end of the day.  After all, counterfeiting ICs is
much less serious an offense than counterfeiting money!
3.  Maxim keeps a large supply of unobtainium on hand so they can,
on short order, fabricate a sample of almost any device they sell.  Once
the samples have been inextricably worked into your design, point 1
comes into play.  When questioned about procuring parts fabricated
from their unobtainium stock, a Maxim rep will say "Can't do that, I'd
be out of stock then!"  When asked why they have such a long lead
time, they'll then say "Because we have all this extra unobtainium
here, so we don't need to order any yet."

In fact, some engineers hold that the troubles associated with using
Maxim parts can be so confounding that 999 times out of 1000, it is
easier, cheaper, and less frustrating just to do without the part in
the first place.

Mike H.

2006\04\19@202521 by Zik Saleeba

face picon face
Wow - great information. Thanks for that.

Cheers,
Zik

On 20/04/06, Mike Hord <mike.hordEraseMEspam.....gmail.com> wrote:
{Quote hidden}

> -

2006\04\19@203345 by David VanHorn

picon face
>
>
> In fact, some engineers hold that the troubles associated with using
> Maxim parts can be so confounding that 999 times out of 1000, it is
> easier, cheaper, and less frustrating just to do without the part in
> the first place.



And you'd think that they would pay attention to this sort of comment.



--
> Feel the power of the dark side!  Atmel AVR

2006\04\19@204342 by Gerhard Fiedler

picon face
Zik Saleeba wrote:

> Wow - great information. Thanks for that.

Just for fun... check the availability of, say, 1000 of the devices you
just thought of using once a month over the next year. If you haven't had
to do that yet, this might provide some insight :)

Gerhard

2006\04\20@000402 by Bob Barr

flavicon
face
On Wed, 19 Apr 2006 20:33:45 -0400, "David VanHorn" wrote:

>>
>>
>> In fact, some engineers hold that the troubles associated with using
>> Maxim parts can be so confounding that 999 times out of 1000, it is
>> easier, cheaper, and less frustrating just to do without the part in
>> the first place.
>
>
>
>And you'd think that they would pay attention to this sort of comment.
>

As long as Maxim's high-volume customers keep buying their parts, they
really have little need to worry about the little sub-10K unit buyers.


Regards, Bob

2006\04\24@152016 by alan smith

picon face
Just as long as you dont need production qty.......even among the distributors...maxim are bad news

Zik Saleeba <EraseMEzikspamzikzak.net> wrote:  Why the dislike of Maxim? I was just about to design a couple of their
parts into something I'm working on...

Cheers,
Zik

On 18/04/06, alan smith wrote:
{Quote hidden}

>

2006\04\24@161326 by Bob Axtell

face picon face
alan smith wrote:
> Just as long as you dont need production qty.......even among the distributors...maxim are bad news
>
> Zik Saleeba <RemoveMEzikEraseMEspamEraseMEzikzak.net> wrote:  Why the dislike of Maxim? I was just about to design a couple of their
> parts into something I'm working on...
>
>  
Zik, the problems with maxim are two-fold:

1. They never have parts. They ALWAYS have samples. They never have
parts when your client will need to buy them...unless your client is buying
100K. They will certainly promise in good faith, but simply can't
deliver. You
will spend your next year designing OUT maxim parts, because your client
is angry with you. This didn't happen to me ONCE, it happened many times,
until finally, having lost all my front teeth, I having given up on MAXIM.

2. They advertise components that have not been thoroughly "vetted" (tested
under all conditions). This list includes, but is not limited to: parts
that generate
so much EMI that the product cannot pass FCC radiation specs; parts that
have a squirrelly oscillator that causes the part to lose some internal
clocks;
"AC MAINS" pass regulators that can't pass  UL/CE regulations (I had a
drawer full of these, NOT ONE ever worked). The OSC problem  killed
almost 3 weeks of my design time.

Try to design around reliable, honest vendors, such as TI, LT, National,
and
(tentatively) ON Semi.

While I am at it there are a couple of others you need to watch
carefully: Atmel
(drops product lines much too easily); and ST (drops SOME product lines-
such as video overlay generators- even when they cornered the world market!
go figure!).

--Bob

{Quote hidden}

>> -

2006\04\29@195108 by andrew kelley

picon face
Use a AA cell holder that has built in reversal protection: most
commonly, it is a bit of plastic around the + side terminal that
prevents the flat end from contacting, but the nub fits right in.

andrew

On 4/14/06, alan smith <RemoveMEmicro_eng2spam_OUTspamKILLspamyahoo.com> wrote:
> well....this is a two AA cell design, so no need for over voltage, or high currents, just if the user puts the batteries in backwards....
>
>  Generally not a good idea...but wonder how much damage might occur if they end up in backwards?
>
>  Think we all have done that a time or two in some consumer device.

More... (looser matching)
- Last day of these posts
- In 2006 , 2007 only
- Today
- New search...