Favorite reverse bias protection for battery circuits [Design]

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From: Jim Thompson on 17 Mar 2010 12:23

On Wed, 17 Mar 2010 08:49:33 -0700, Charlie E. <edmondson(a)ieee.org>
wrote:

>On Tue, 16 Mar 2010 17:57:01 -0500, Vladimir Vassilevsky
><nospam(a)nowhere.com> wrote:
>
>>LTC4358
>
>Yikes! $4.50 each at digikey! ouch...
>
>Charlie

It's a power NMOS plus a charge pump.

Gate drive requires no power in your application (slow).

Could you use discrete power MOS plus a 12V button cell? (Can't quote
the part number, CR...., but there's one in my Q45 remote)

Jazzy would be push and release button, flyback inductor powers NMOS
gate ;-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

The only thing bipartisan in this country is hypocrisy

From: Jim Thompson on 17 Mar 2010 12:32

On Wed, 17 Mar 2010 08:42:42 -0700, Charlie E. <edmondson(a)ieee.org>
wrote:

>On Tue, 16 Mar 2010 18:40:22 -0400, "Martin Riddle"
><martin_rid(a)verizon.net> wrote:
>
>>
>>
>>"Joerg" <invalid(a)invalid.invalid> wrote in message
>>news:80a0b7F5q1U2(a)mid.individual.net...
>>> Hammy wrote:
>>>> On Tue, 16 Mar 2010 10:56:46 -0700, Charlie E. <edmondson(a)ieee.org>
>>>> wrote:
>>>>
>>>>> Hi All,
>>>>> Still working on my color reader, and getting close. Biggest
>>>>> problem
>>>>> is that now I have almost TOO much drive on my LEDs, but that I can
>>>>> deal with!
>>>>>
>>>>> Now, to the latest problem. My system is for the visually impaired.
>>>>> I
>>>>> just put the batteries in one of my prototypes backwards, and it
>>>>> didn't last very long. While I expect this device to have very long
>>>>> battery life, since it normally doesn't operate but for a second or
>>>>> two, it looks like the MC1253's don't like getting reversed biased
>>>>> very long. So, for my design question of the day - What is your
>>>>> favorite circuit for preventing reverse bias from the batteries?
>>>>> The
>>>>> old diode trick drops too much voltage, so wondered if there are any
>>>>> clever FET tricks to block backwards voltages.
>>>>>
>>>>> Thanks!
>>>>>
>>>>> Charlie
>>>> I usually use #2 on this page a shorting shottky.
>>>>
>>>> http://www.recom-international.com/press/Reverse%20Polarity%20Protection%20for%20DC/DC%20Converters.html
>>>
>>>
>>> That renders the unit dead and a blind or almost blind person will
>>> have a hard time finding or buying the proper fuse and installing it.
>>>
>>> Charlie: Solution #3 is the ticket (look on Hammy's link). But make
>>> sure that the FET is guaranteed to be fully turned on at the lowest
>>> allowed battery voltage, IOW the point where an UVLO comes on.
>>>
>>> --
>>> Regards, Joerg
>>>
>>
>>
>>You can replace the fuse with a PTC, batteries might not like it, but it
>>would still function when the batteries are inserted correctly.
>>
>>Cheers
>>
>
>Presently looking at http://www.micrel.com/_PDF/mic94052-53.pdf which
>seems to fit the bill. Any one used these, and know the gotchas?
>
>Thanks,
>Charlie

If source/body orientation is as shown, it can't handle reverse
battery :-(

Ooops! Yes it will... Apply battery at terminal "D", load at terminal
"VIN"... just as I showed in...

Message-ID: <om20q55rp2gcfo182497qclispunbe61or(a)4ax.com>

Caution... who knows where "real" substrate is, so buy one and test
:-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

The only thing bipartisan in this country is hypocrisy

From: D Yuniskis on 17 Mar 2010 13:24

Hi Jan,

Jan Panteltje wrote:
> On a sunny day (Tue, 16 Mar 2010 17:13:43 -0700) it happened D Yuniskis
> <not.going.to.be(a)seen.com> wrote in <hnp642$l9s$1(a)speranza.aioe.org>:
>
>> Hi Jan,
>>
>> Jan Panteltje wrote:
>>> Use a bigger batteriy and a bridge rectifier,
>>> then it does not matter how they are put in.
>> The device ends up larger. And weighs more, etc.
>>
>> For *one* device, this is no big deal. But, folks with
>> disabilities tend to have *lots* of "special devices".
>> Each is typically larger than it's counterpart (for
>> the mainstream population).
>
> I was joking!
> But on a more serious note:
> Most visually impaired have great sense in their fingers,
> they will have no problem feeling what side of an AA of AAA goes where.

This typically depends on the cause of the vision loss.
E.g., those suffering from diabetic retinopathy will tend
to have diminished sensitivity in extremities. (i.e., Braille
is a non-starter)

> I can do it too wit heyes closed :-)

From: Jim Thompson on 17 Mar 2010 13:26

On Tue, 16 Mar 2010 10:56:46 -0700, Charlie E. <edmondson(a)ieee.org>
wrote:

>Hi All,
>Still working on my color reader, and getting close. Biggest problem
>is that now I have almost TOO much drive on my LEDs, but that I can
>deal with!
>
>Now, to the latest problem. My system is for the visually impaired. I
>just put the batteries in one of my prototypes backwards, and it
>didn't last very long. While I expect this device to have very long
>battery life, since it normally doesn't operate but for a second or
>two, it looks like the MC1253's don't like getting reversed biased
>very long. So, for my design question of the day - What is your
>favorite circuit for preventing reverse bias from the batteries? The
>old diode trick drops too much voltage, so wondered if there are any
>clever FET tricks to block backwards voltages.
>
>Thanks!
>
>Charlie

WHAT is an MC1253? Maybe local protection?

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

The only thing bipartisan in this country is hypocrisy

From: Charlie E. on 17 Mar 2010 13:51

On Wed, 17 Mar 2010 10:26:37 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote:

>On Tue, 16 Mar 2010 10:56:46 -0700, Charlie E. <edmondson(a)ieee.org>
>wrote:
>
>>Hi All,
>>Still working on my color reader, and getting close. Biggest problem
>>is that now I have almost TOO much drive on my LEDs, but that I can
>>deal with!
>>
>>Now, to the latest problem. My system is for the visually impaired. I
>>just put the batteries in one of my prototypes backwards, and it
>>didn't last very long. While I expect this device to have very long
>>battery life, since it normally doesn't operate but for a second or
>>two, it looks like the MC1253's don't like getting reversed biased
>>very long. So, for my design question of the day - What is your
>>favorite circuit for preventing reverse bias from the batteries? The
>>old diode trick drops too much voltage, so wondered if there are any
>>clever FET tricks to block backwards voltages.
>>
>>Thanks!
>>
>>Charlie
>
>WHAT is an MC1253? Maybe local protection?
>
> ...Jim Thompson

It's a Microchip charge pump regulator. Using two, one to provide
3.3VDC for most of the circuit, and one to boost the LED drive to a
constant current of 20mA. Although, I am thinking of lowering that to
12mA to give more life...

Charlie