Favorite reverse bias protection for battery circuits [Design]

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From: Jim Thompson on 18 Mar 2010 15:35

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 :-)

...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: Joerg on 18 Mar 2010 16:31

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.

--
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 16:50

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

--
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 19:29

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 :-)

...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 18 Mar 2010 19:31

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" :-)

...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