Favorite reverse bias protection for battery circuits

[Joerg]

Yikes! $4.50 each at digikey! ouch...

And over $2 in production qties, which is why I never used a solution
like that and kept designing with discretes instead. LTC is a great
company but the pricing on the more mundane parts such as this one is
IMHO a wee bit out of touch.

 

[D Yuniskis]

Hi Jan,

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)

 

[Joerg]

[snip]

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: <[email protected]>

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


...Jim Thompson

An additional Joerg-ian caution: Micrel's website has no E-mail
contact info, you have to call... probably get someone who doesn't
know shit :-(

And then you have large companies where you write to a provided email
link, asking a question where it's obvious that major sales volume could
result, get no response, ask at another email address, get no response.
Recently happened at ON Semi, a manufacturer whose parts I otherwise
really like. Sad. All the while everyone laments about the economy :-(

 

[Charlie E.]

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

 

[legg]

Charlie E. wrote:

I like LTC4358.

They took care of a lot of problems typical for trivial DIY reverse
battery protection circuits.

Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

Cowards: No V/I characteristics around zero.

Hides a potential can of worms.

...... the normally-off synchronous rectifier has been a bee in my
bonnet for a long time.

RL

 

[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

 

[Spehro Pefhany]

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/FDMA410NZ.pdf

50m ohm at 1.5V Vgs.

Does n-channel still offer a cost advantage over p-channel for very
low voltage devices?

Here's a p-channel device with 113m ohm at 1.2V Vgs.
http://www.vishay.com/docs/74620/sia419dj.pdf

Apparently a SC-70 can dissipate 19W if you can hold the case to
25°C...

 

[Joerg]

Where do you get a discrete NMOSFET that will be thoroughly on at 1.8V
VGS?

The Micrel part _may_ work.

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

 

[Joerg]

[email protected] wrote:
Hammy 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?

The Micrel part _may_ work.

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?"

[...]

 

[Joerg]

[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.

 

[Joerg]

[email protected] 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/FDMA410NZ.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

 

[Joerg]

On Thu, 18 Mar 2010 14:11:36 -0400, Spehro Pefhany

On Thu, 18 Mar 2010 10:53:31 -0700, Jim Thompson

[email protected] 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/FDMA410NZ.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.

 

[Joerg]

Jim Thompson 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 ;-)

 

[JosephKK]

Jim Thompson wrote:
Jim Thompson 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 whenthey
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?

 

[Joerg]

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.

That's exactly what I was explaining, to include batteries in the
rotating scheme.

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.

We had some stuff like that in the army. As for flavor, that was rather
debatable even when "fresh"

 

[D Yuniskis]

Hi Joerg,

We had some stuff like that in the army. As for flavor, that was rather
debatable even when "fresh"

<grin> As a kid, I spent a few months living on C-rations (research).
It's hard to imagine doing that for a prolonged period. Even the
"chocolate" was abysmal!

I am surprised, though, that things *can* stay preserved, canned,
for such a long period of time. I imagine it depends on the
foodstuffs involved, the materials from which the cans are made,
any *coatings* applied to the insides of the cans and the
mechanical integrity of those cans.

I would imagine vacuum packing something like beans in glass
(or metal) would also have a very long shelf life -- but I'm
not a big fan of legumes! :-(

 

[Charlie E.]

Hi Joerg,


<grin> As a kid, I spent a few months living on C-rations (research).
It's hard to imagine doing that for a prolonged period. Even the
"chocolate" was abysmal!

I am surprised, though, that things *can* stay preserved, canned,
for such a long period of time. I imagine it depends on the
foodstuffs involved, the materials from which the cans are made,
any *coatings* applied to the insides of the cans and the
mechanical integrity of those cans.

I would imagine vacuum packing something like beans in glass
(or metal) would also have a very long shelf life -- but I'm
not a big fan of legumes! :-(

I had a similiar experience. Visiting a friend, I noticed a bunch of
boxes of C-rations sitting in the garage. Asked about them, and found
they were expired rations from a fallout shelter. I asked if I could
have some, and soon found myself in possession of about six cases of
them. Over the next few months, tried them out, and found which were
tolerable, and which were really, really bad! A couple of years
later, at ROTC summer camp, when we were issued C-rations, I knew
which ones to get, and which ones to trade... ;-)

Charlie

 

[Joerg]

Michael A. Terrell wrote:

[...]

We had some stuff like that in the army. As for flavor, that was rather
debatable even when "fresh"

It wasn't intened to be 'good', it was meant to keep you alive.

Well, we sometimes had helpful friends around to kill the stale taste.
What were their names .... oh yeah, now I remember. Jack Daniels, Jim
Beam ...

 

[D Yuniskis]

I had a similiar experience. Visiting a friend, I noticed a bunch of
boxes of C-rations sitting in the garage. Asked about them, and found
they were expired rations from a fallout shelter. I asked if I could
have some, and soon found myself in possession of about six cases of
them. Over the next few months, tried them out, and found which were

Ah, I wasn't as lucky. That's *all* I had to eat! :-/
(though I could have "as much as I wanted" -- small consolation
that! :> )

tolerable, and which were really, really bad! A couple of years

I think the franks and beans were tolerable (and I *hate* beans -- so
that tells you how bad I considered most of it!). The pasta (?)
defied description. :< The little "fruit cakes" doubled as
hockey pucks :-/

later, at ROTC summer camp, when we were issued C-rations, I knew
which ones to get, and which ones to trade... ;-)

Ones to trade: ALL
Ones to get: see above

;-)

But, remember to save the TP packet! (and the P38, of course!!)

 

[JosephKK]

Hi Joerg,


<grin> As a kid, I spent a few months living on C-rations (research).
It's hard to imagine doing that for a prolonged period. Even the
"chocolate" was abysmal!

I am surprised, though, that things *can* stay preserved, canned,
for such a long period of time. I imagine it depends on the
foodstuffs involved, the materials from which the cans are made,
any *coatings* applied to the insides of the cans and the
mechanical integrity of those cans.

I would imagine vacuum packing something like beans in glass
(or metal) would also have a very long shelf life -- but I'm
not a big fan of legumes! :-(

Most often the things that matter are cleanliness of the containers and
the sterility after closing. After the previous coatings and pH of the
preserved food play.