Favorite reverse bias protection for battery circuits [Design]

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From: Joerg on 18 Mar 2010 19:46

Jim Thompson wrote:
> On Thu, 18 Mar 2010 13:50:58 -0700, Joerg <invalid(a)invalid.invalid>
> wrote:
>
>> Jim Thompson wrote:
>>> On Thu, 18 Mar 2010 14:11:36 -0400, Spehro Pefhany
>>> <speffSNIP(a)interlogDOTyou.knowwhat> wrote:
>>>
>>>> On Thu, 18 Mar 2010 10:53:31 -0700, Jim Thompson
>>>> <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote:
>>>>
>>>>> On Thu, 18 Mar 2010 10:25:17 -0700, Joerg <invalid(a)invalid.invalid>
>>>>> wrote:
>>>>>
>>>>>> dagmargoodboat(a)yahoo.com wrote:
>>> [snip]
>>>>>>>> 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
>>>>>>> Joerg, you big spender! Use an n-FET--they're better and cheaper--in
>>>>>>> the ground lead.
>>>>>>>
>>>>>> Yup, that's what I'd do in this case :-)
>>>>> Where do you get a discrete NMOSFET that will be thoroughly on at 1.8V
>>>>> VGS?
>>>> Here's one:
>>>> http://www.fairchildsemi.com/ds/FD%2FFDMA410NZ.pdf
>>>>
>>>> 50m ohm at 1.5V Vgs.
>>>>
>>>> Does n-channel still offer a cost advantage over p-channel for very
>>>> low voltage devices?
>>> I don't think so...
>>>
>> Young buck say to old buck: N-channel mostly less bucks for same bang :-)
>>
>> I don't have much in examples anymore because the notes about p-channel
>> candidates where used to kindle the wood stove. But it happened time and
>> again when I thought about push-pull drivers and two n-channels plus
>> bootstrap was the better deal (financially).
>>
>>
>>>> Here's a p-channel device with 113m ohm at 1.2V Vgs.
>>>> http://www.vishay.com/docs/74620/sia419dj.pdf
>>> It appears that the N-channel part is made on an P-substrate and
>>> vice-versa.
>>>
>>>> Apparently a SC-70 can dissipate 19W if you can hold the case to
>>>> 25�C...
>>>>
>>> [snip]
>>>
>>> Nice devices!
>>>
>>> ...Jim Thompson
>
> That was true in the past. Now-a-days I see no rationale for a price
> difference except for "what the market will bear" :-)
>

There really is a penalty. Yeah, initially the difference may seem tiny
or zilch but if you want a P-channel with the same performance as the
N-channel and not just 70%, very different thing.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

From: Joerg on 18 Mar 2010 19:47

Jim Thompson wrote:
> On Thu, 18 Mar 2010 13:31:57 -0700, Joerg <invalid(a)invalid.invalid>
> wrote:
>
>> Jim Thompson wrote:
>>> On Thu, 18 Mar 2010 12:26:57 -0700, Joerg <invalid(a)invalid.invalid>
>>> wrote:
>>>
>>>> Jim Thompson wrote:
>>>>> On Thu, 18 Mar 2010 11:57:26 -0700, Joerg <invalid(a)invalid.invalid>
>>>>> wrote:
>>> [snip]
>>>>>> Plenty of others. If it has to be cheap (and somehow it always has to
>>>>>> be...), here's an example at around 15 cents, Rdson guaranteed down to 1.5V:
>>>>>>
>>>>>> http://www.diodes.com/datasheets/ds31186.pdf
>>>>>>
>>>>>> You need to get out into the world of discretes some more :-)
>>>>> Nope! I avoid markets that are priced like popcorn.
>>>>>
>>>> Oh, it's not always that way. Roughly half of my designs aren't required
>>>> to be rock-bottom in BOM cost. Although I can't help it, the calculator
>>>> in my head is always running. Sometimes clients are surprised when they
>>>> see the (working) circuit. "You mean, that's it?"
>>>>
>>>> [...]
>>> I get that all the time. I really enjoy finding clever solutions to
>>> difficult problems. If I ever lose that capability I'll simply
>>> self-dispatch :-)
>>>
>> That's squarely against my religious beliefs. Life doesn't end with
>> Alzheimers and the like. In fact, our new canine addition (former guide
>> dog trainee, hopefully passes therapy dog cert after Easter) will have
>> one such case very soon. And already has served in that area.
>
> I only believe in myself, so I have no such problem :-)
>

Then you'll have a (huge) problem after you die ;-)

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

From: Jim Thompson on 18 Mar 2010 19:58

On Thu, 18 Mar 2010 16:47:25 -0700, Joerg <invalid(a)invalid.invalid>
wrote:

>Jim Thompson wrote:
>> On Thu, 18 Mar 2010 13:31:57 -0700, Joerg <invalid(a)invalid.invalid>
>> wrote:
>>
>>> Jim Thompson wrote:
>>>> On Thu, 18 Mar 2010 12:26:57 -0700, Joerg <invalid(a)invalid.invalid>
>>>> wrote:
>>>>
>>>>> Jim Thompson wrote:
>>>>>> On Thu, 18 Mar 2010 11:57:26 -0700, Joerg <invalid(a)invalid.invalid>
>>>>>> wrote:
>>>> [snip]
>>>>>>> Plenty of others. If it has to be cheap (and somehow it always has to
>>>>>>> be...), here's an example at around 15 cents, Rdson guaranteed down to 1.5V:
>>>>>>>
>>>>>>> http://www.diodes.com/datasheets/ds31186.pdf
>>>>>>>
>>>>>>> You need to get out into the world of discretes some more :-)
>>>>>> Nope! I avoid markets that are priced like popcorn.
>>>>>>
>>>>> Oh, it's not always that way. Roughly half of my designs aren't required
>>>>> to be rock-bottom in BOM cost. Although I can't help it, the calculator
>>>>> in my head is always running. Sometimes clients are surprised when they
>>>>> see the (working) circuit. "You mean, that's it?"
>>>>>
>>>>> [...]
>>>> I get that all the time. I really enjoy finding clever solutions to
>>>> difficult problems. If I ever lose that capability I'll simply
>>>> self-dispatch :-)
>>>>
>>> That's squarely against my religious beliefs. Life doesn't end with
>>> Alzheimers and the like. In fact, our new canine addition (former guide
>>> dog trainee, hopefully passes therapy dog cert after Easter) will have
>>> one such case very soon. And already has served in that area.
>>
>> I only believe in myself, so I have no such problem :-)
>>
>
>Then you'll have a (huge) problem after you die ;-)

I promise to not be "greasy" :-)

...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: JosephKK on 18 Mar 2010 22:07

On Thu, 18 Mar 2010 16:58:14 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote:

>On Thu, 18 Mar 2010 16:47:25 -0700, Joerg <invalid(a)invalid.invalid>
>wrote:
>
>>Jim Thompson wrote:
>>> On Thu, 18 Mar 2010 13:31:57 -0700, Joerg <invalid(a)invalid.invalid>
>>> wrote:
>>>
>>>> Jim Thompson wrote:
>>>>> On Thu, 18 Mar 2010 12:26:57 -0700, Joerg <invalid(a)invalid.invalid>
>>>>> wrote:
>>>>>
>>>>>> Jim Thompson wrote:
>>>>>>> On Thu, 18 Mar 2010 11:57:26 -0700, Joerg <invalid(a)invalid.invalid>
>>>>>>> wrote:
>>>>> [snip]
>>>>>>>> Plenty of others. If it has to be cheap (and somehow it always has to
>>>>>>>> be...), here's an example at around 15 cents, Rdson guaranteed down to 1.5V:
>>>>>>>>
>>>>>>>> http://www.diodes.com/datasheets/ds31186.pdf
>>>>>>>>
>>>>>>>> You need to get out into the world of discretes some more :-)
>>>>>>> Nope! I avoid markets that are priced like popcorn.
>>>>>>>
>>>>>> Oh, it's not always that way. Roughly half of my designs aren't required
>>>>>> to be rock-bottom in BOM cost. Although I can't help it, the calculator
>>>>>> in my head is always running. Sometimes clients are surprised when they
>>>>>> see the (working) circuit. "You mean, that's it?"
>>>>>>
>>>>>> [...]
>>>>> I get that all the time. I really enjoy finding clever solutions to
>>>>> difficult problems. If I ever lose that capability I'll simply
>>>>> self-dispatch :-)
>>>>>
>>>> That's squarely against my religious beliefs. Life doesn't end with
>>>> Alzheimers and the like. In fact, our new canine addition (former guide
>>>> dog trainee, hopefully passes therapy dog cert after Easter) will have
>>>> one such case very soon. And already has served in that area.
>>>
>>> I only believe in myself, so I have no such problem :-)
>>>
>>
>>Then you'll have a (huge) problem after you die ;-)
>
>I promise to not be "greasy" :-)
>
> ...Jim Thompson

So there is going to be past passing party where there will be JT chops and
sausages and handouts of smoked JT?

From: Michael A. Terrell on 22 Mar 2010 22:11

Joerg wrote:
>
> D Yuniskis wrote:
> > Joerg wrote:
> >>> I just want something for my bugout-bag that I can rely on
> >>> *without* having to worry that some component (e.g., a
> >>> battery *buried* inside the "emergency light") has died
> >>> because it's been in storage for 10 years... I *think*
> >>> this thing will work good as there are no "components"
> >>> that I'd have to worry about crapping out (just the little
> >>> DC "motor/generator" and a bunch of mechanical bits)
> >>>
> >>> What good are emergency devices if you can't rely on
> >>> them in an emergency?? :>
> >>
> >> That's what preventive maintenance is for :-)
> >
> > Bug out bag isn't something that sits in a prominent
> > position in the house. I.e., you've got to go *looking*
> > for it. And, hopefully, *never* need it. (out of sight,
> > out of mind)
> >
>
> Ahm, what about the food items in there? Just imagine, you and your
> family have successfully evacuated. Now dad does the manly thing and
> starts the fire. Mom pulls out a can of Progresso, says 'Best before
> 1998' on there, puts in can opener ... *POOF* .. *SPLAT* ... a horrid
> stench wafts through the area ... "Oh, maybe that's why the can was
> bulging" :-)

Didn't they teach you about stock rotation in Europe? Once a year
the emergency food and batteries are replaced with fresh stock, and the
old stock is put into the regular stock.

BTW, some canned goods were found in 'Old West' ghost towns that were
about 100 years old. Other than loss of flavor, they were supposed to
still be safe to eat.

--
Lead free solder is Belgium's version of 'Hold my beer and watch this!'