Power supply question

[Lowly Engineer]

I need to build a supply that puts out 750mA at 5V. The problem is
that it must accept an input from 2.5 to 12V. I can find lots of
step-up and step-down designs, but nothing that will handle this
range.

Any ideas?

 

[Richard Henry]

I need to build a supply that puts out 750mA at 5V. The problem is
that it must accept an input from 2.5 to 12V. I can find lots of
step-up and step-down designs, but nothing that will handle this
range.

Step up to 15V. Then step down to 5V.

 

[Active8]

I need to build a supply that puts out 750mA at 5V. The problem is
that it must accept an input from 2.5 to 12V. I can find lots of
step-up and step-down designs, but nothing that will handle this
range.

Any ideas?

i think if you check this group or maybe it was the microchip site- i
think that's where it is, you'll find a switcher that goes from buck to
boost and back, but i don't know if it'll deal with that range.

brs,
mike

 

[The real Andy]

i think if you check this group or maybe it was the microchip site- i
think that's where it is, you'll find a switcher that goes from buck to
boost and back, but i don't know if it'll deal with that range.

Try doing a search for SEPIC topology convertors.

 

[piero]

it is possible with a flyback topology. The inductor must have two
coils, I'm sure I've seen an application, don't remeber where, probably
Linear Technology, give it a try. The matter is how to manage such a low
input voltage.
Regards. piero

 

[Active8]

Try doing a search for SEPIC topology convertors.

one return synopsis says:

A step-up converter followed by an LDO regulator offers better battery
life
than a classic SEPIC design when operating from one lithium-ion cell.
....

it's a maxim article. they put the LDO in with the boost converter.

or

Sepic
(a.) Of or pertaining to sepia; done in sepia; as, a sepic drawing.

Sepia
(a.) Of a dark brown color, with a little red in its composition; also,
made of, or done in, sepia.
(n.) The common European cuttlefish.
(n.) A genus comprising the common cuttlefish and numerous similar
species. See Illustr. under Cuttlefish.
(n.) A pigment prepared from the ink, or black secretion, of the sepia,
or cuttlefish. Treated with caustic potash, it has a rich brown color;
and this mixed with a red forms Roman sepia. Cf. India ink, under India.

http://www.brainydictionary.com

brs,
mike

 

[budgie]

one return synopsis says:

A step-up converter followed by an LDO regulator offers better battery
life
than a classic SEPIC design when operating from one lithium-ion cell.

That's great IF (and it's a big if) the input range is less than the
required LDO min Vin. In the O/P's case, the LDO is going to be ~5v15
min input, so "step-up followed by LDO" isn't going to fit. If he
wanted 15v output, it would.

it's a maxim article. they put the LDO in with the boost converter.

because it fits their application/load_requirement. It doesn't fit
the O/P's.

 

[Active8]

That's great IF (and it's a big if) the input range is less than the
required LDO min Vin. In the O/P's case, the LDO is going to be ~5v15
min input,

what in the hell are you talking about? the LDO follows the boost
converter. step up to 15 and down to 12 as another poster put it.

it's 2.5 - 12 input for the OP's spec.

if you step up to Vout plus *no less than* the LDO's dropout, then you
can get the 5V out *if* the chip will do it and it does. it's the
MAX1800 *input* spec that doesn't meet the OP's spec. and i bet it could
be rigged to do it with a little creative circuitry.

MAX669 does meet the spec. and it's linked to from the same page as the
article that google returned. so you just turned him away from a
possible solution.

so "step-up followed by LDO" isn't going to fit. If he
wanted 15v output, it would.

why not? a boost converter followed by a 7805 will do it, too.

tell it to the guy who suggested stepping up to 15 and down to 12.

because it fits their application/load_requirement. It doesn't fit
the O/P's.

did you read the whole data sheet? i get the impression you didn't. i
qualified my statements with "might not*s and all.

i was commenting to andy on something i found interesting.

never said that it would meet the OP's requirement. and when i first
mentioned what andy pointed out was called SEPIC, i clearly implied that
it *might not* meet the spec, either. it's was a suggestion. i'm not
going to read the spec for the OP, we were pointing him in the right
direction. hell, just searching on SEPIC found the part. luckily Maxim
has a quick view so you don't have to eat lunch waiting for a spec to
download.

andy, thanks. budgie...

 

[budgie]

what in the hell are you talking about? the LDO follows the boost
converter. step up to 15 and down to 12 as another poster put it.

it's 2.5 - 12 input for the OP's spec.

Yes, and the O/P wanted 5v out. LDO = LOW dropout. If you're going
from 15 down to 5v, LDO is neither a requirement nor a beneift.

if you step up to Vout plus *no less than* the LDO's dropout, then you
can get the 5V out *if* the chip will do it and it does. it's the
MAX1800 *input* spec that doesn't meet the OP's spec. and i bet it could
be rigged to do it with a little creative circuitry.

MAX669 does meet the spec. and it's linked to from the same page as the
article that google returned. so you just turned him away from a
possible solution.


why not? a boost converter followed by a 7805 will do it, too.

Of course it will. But some fool in this thread posted a line
(quoted):

"A step-up converter followed by an LDO regulator offers better
battery life"

and stepping up from x to 15 and then an LDo to 5v isn't at all
efficient or conducive to decent battery life.

tell it to the guy who suggested stepping up to 15 and down to 12.

He's obviously talking about something different to the O/P task.

did you read the whole data sheet? i get the impression you didn't. i
qualified my statements with "might not*s and all.

I certainly didn't, because your post was riddled with nonsense, and I
was commenting on your post not the Maxim spec sheet.

i was commenting to andy on something i found interesting.

never said that it would meet the OP's requirement. and when i first
mentioned what andy pointed out was called SEPIC, i clearly implied that
it *might not* meet the spec, either. it's was a suggestion. i'm not
going to read the spec for the OP, we were pointing him in the right
direction. hell, just searching on SEPIC found the part. luckily Maxim
has a quick view so you don't have to eat lunch waiting for a spec to
download.

It sounds like you didn't read the O/P spec either.

 

[Active8]

Of course it will. But some fool in this thread posted a line
(quoted):

"A step-up converter followed by an LDO regulator offers better
battery life"

the fool already told you that he was commenting to his replier
regarding something interesting that came up in the SEPIC search. then
some jackass butted in with bullshit. next time i'll make sure that it's
just an interesting OT side note so i don't have to listen to shit from
you. will that make you happy?

and stepping up from x to 15 and then an LDo to 5v isn't at all
efficient or conducive to decent battery life.

never said it was.
a typo. i meant 5V. if you read the thread, you'd know what was going
on.

He's obviously talking about something different to the O/P task.

no, he was talking about what the OP could do to complete his task which
was going from 2.5 to 12V in to 5V out.

I certainly didn't, because your post was riddled with nonsense, and I
was commenting on your post not the Maxim spec sheet.

so you butt into conversations without even knowing WTF is going on.

It sounds like you didn't read the O/P spec either.

sure i did. now you admit *you* didn't. i only said that you didn't read
the Maxim spec. i figured andy would know i wasn't suggesting that
something involving a single Li-ion batt had anything to do with OP's
task. notice he didn't say anything? but you, OTOH, are just ignorant
enough to think i was talking to the OP.

OP's solution was the SEPIC link at the bottom of that spec. it's the
same solution Richard gave except he didn't specify how the step down
should be implemented.

have a nice day

 

[budgie]

the fool already told you that he was commenting to his replier
regarding something interesting that came up in the SEPIC search. then
some jackass butted in with bullshit.

Care to explain which part was bullshit?

next time i'll make sure that it's
just an interesting OT side note so i don't have to listen to shit from
you. will that make you happy?

Fark, what a case you are. Trying to crawl out of it.

never said it was.

Andy suggested SEPIC. You chose to quote a SEPIC-related item which
stated that the above approach was more efficient than a SEPIC
approach. Trying to crawl out of it.

a typo. i meant 5V. if you read the thread, you'd know what was going
on.

Oh, so now we are supposed to second-guess your every word in case
it's a typo. Trying to crawl out of it.

no, he was talking about what the OP could do to complete his task which
was going from 2.5 to 12V in to 5V out.

I was referring to the fool cited in the previous comment, not Richard
or Andy.

so you butt into conversations without even knowing WTF is going on.

It would appear I have more of a clue what is going on, and what the
O/P wanted, than you.

sure i did. now you admit *you* didn't.
Que?

i only said that you didn't read
the Maxim spec. i figured andy would know i wasn't suggesting that
something involving a single Li-ion batt had anything to do with OP's
task. notice he didn't say anything? but you, OTOH, are just ignorant
enough to think i was talking to the OP.

No, you were poo-pooing the SEPIC approach with your quote.

OP's solution was the SEPIC link at the bottom of that spec. it's the
same solution Richard gave except he didn't specify how the step down
should be implemented.

have a nice day

Likewise.

 

[Active8]

Care to explain which part was bullshit?

your conception

Fark, what a case you are. Trying to crawl out of it.

what do you want me to do, flog myself?

Andy suggested SEPIC. You chose to quote a SEPIC-related item which
stated that the above approach was more efficient than a SEPIC
approach. Trying to crawl out of it.

i didn't state an opinion, i just pasted in a bit from a synopsis.

you can't read. the article synopsis specifically stated that the
approach was more efficient "when operating from one lithium-ion cell".
i didn't assume anything. i just threw it out there as an interesting
"find".

now if you insist on second guessing me... trying to tell me what my
intentions are... **** off. you don't know me.

Oh, so now we are supposed to second-guess your every word in case
it's a typo. Trying to crawl out of it.

well you obviously are trying to second guess me, jackass. you've just
implied that by pasting that quote in that you could perceive what my
opinion was.

It would appear I have more of a clue what is going on, and what the
O/P wanted, than you.

so you feel he wants to read this back and forth between us, then.

Que?

you snipped out the exact words where you admit it, weasel.

No, you were poo-pooing the SEPIC approach with your quote.

there you go again second guessing me, jackass. i didn't comment on the
quote other than to state that it was from a Maxim spec.

BTW, i was the one who suggested SEPIC in the first place (unless that's
what richard meant) based on something i'd recently picked up on. Andy
gave me the proper term to search on and i did.

huh... you definitly rank as one of the biggest UseNET jackasses i've
run into so far. you've distorted as much as possible and started a
fight. i think you're a troll. i've never seen you or your sorry ass
moniker in this group or any other group i frequent so you obviously
have nothing to contribute.

don't bother replying, dickhead.

 

[budgie]

your conception

pathetic, really.

what do you want me to do, flog myself?

i didn't state an opinion, i just pasted in a bit from a synopsis.

you can't read. the article synopsis specifically stated that the
approach was more efficient "when operating from one lithium-ion cell".
i didn't assume anything. i just threw it out there as an interesting
"find".

now if you insist on second guessing me... trying to tell me what my
intentions are... **** off. you don't know me.

I don't second-guess. That was the point.

well you obviously are trying to second guess me, jackass. you've just
implied that by pasting that quote in that you could perceive what my
opinion was.

I don't second guess. But I do read TUVM.

so you feel he wants to read this back and forth between us, then.

you snipped out the exact words where you admit it, weasel.

Fucking liar. Show us.

there you go again second guessing me, jackass. i didn't comment on the
quote other than to state that it was from a Maxim spec.

I don't second guess. But I DO read.

BTW, i was the one who suggested SEPIC in the first place (unless that's
what richard meant) based on something i'd recently picked up on. Andy
gave me the proper term to search on and i did.

huh... you definitly rank as one of the biggest UseNET jackasses i've
run into so far. you've distorted as much as possible and started a
fight. i think you're a troll. i've never seen you or your sorry ass
moniker in this group or any other group i frequent so you obviously
have nothing to contribute.

The biggest problem with usenet is that even idiots like you are
aloowed to express a view. Shame really.

don't bother replying, dickhead.

Sorry, you don't get to rule usenet any time soon.