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 Posted: Thu Oct 22, 2009 3:14 pm |
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Guest
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On Oct 21, 11:54 pm, Jon Elson <el... at (no spam) pico-systems.com> wrote:
[quote]michael nikolaou wrote:
Hi to newsgroup
I'm making a mcu based device which i want to be very small and low cost
The design consumes 100..120 ma at (no spam) 3.3V
The problem is the installation that requires 12 or 24 volts to operate.
Check out the LM2575 series of regulator. There
should be a 3.3 V version
of it, I use the 5 V version in one of my
products. It needs a Schottky diode
and an inductor as the only additional parts other
than input and output
capacitors. No need for post regulators, it is
very clean.
Jon
[/quote]
That's a nice part, but the OP wants a tiny inductor, so the slow
(52KHz) switching frequency's a problem for him.
This part switches up to 1MHz and costs even less--only a dollar at (no spam) 1k
compared to $1.13 for the LM2575T-3.3.
http://www.national.com/pf/LM/LM2694.html
It's PFM rather than PWM, so careful calculations are in order. I did
none--just skimmed it.
--
Cheers,
James Arthur |
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| Nico Coesel... |
| Posted: Thu Oct 22, 2009 4:14 pm |
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Guest
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"michael nikolaou" <michaelnikolaou_remove_me_ at (no spam) yahoo.com> wrote:
[quote]I need to make clear so we avoid confusions
The device uses a 2.2" tft lcd . This thing has a backlight and no matter
what
draws 60 ma at (no spam) 3.3V .That i can't avoid . So with 60 ma Arm7 consumption
i end up to 120 ma.
Now as i see whether i have a small switcher with huge inductor and
capacitor
so my board space is too large .
The other solution is super fast switcher that has everything small but
needs 2 euros
at least .
I imagine every engineer designing devices has faced this question .
I'm sure though that a simple cpu controlled switcher could cope with the
large dropout
from 24V to 4-5 volts and then a simple linear regulator could take you to
3.3V so you play
it safe.If things go wrong (cpu malfunction ) thermal shutdown from the
linear regulator would
reset the cpu and that would restart the system
As i see it a simple fet switch with cpu pwm control should satisfy that .
Any opinions or experience on that subject???
[/quote]
You mean some sort of pre-regulator before the linear? That might
work, expecially if you make the the backlight is off until the
pre-regulated voltage is withing range.
--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
"If it doesn't fit, use a bigger hammer!"
-------------------------------------------------------------- |
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| michael nikolaou... |
| Posted: Sat Oct 24, 2009 11:15 am |
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Guest
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Dagmar
that is pretty good IC .Only the 150 uH spoils the picture . That
needs 8x 8 mm minimum board size .
The capacitors are fine. i think i will stick to that
dagmargoodboat at (no spam) yahoo.com wrote:
[quote]On Oct 21, 11:54 pm, Jon Elson <el... at (no spam) pico-systems.com> wrote:
michael nikolaou wrote:
Hi to newsgroup
I'm making a mcu based device which i want to be very small and low cost
The design consumes 100..120 ma at (no spam) 3.3V
The problem is the installation that requires 12 or 24 volts to operate.
Check out the LM2575 series of regulator. There
should be a 3.3 V version
of it, I use the 5 V version in one of my
products. It needs a Schottky diode
and an inductor as the only additional parts other
than input and output
capacitors. No need for post regulators, it is
very clean.
Jon
That's a nice part, but the OP wants a tiny inductor, so the slow
(52KHz) switching frequency's a problem for him.
This part switches up to 1MHz and costs even less--only a dollar at (no spam) 1k
compared to $1.13 for the LM2575T-3.3.
http://www.national.com/pf/LM/LM2694.html
It's PFM rather than PWM, so careful calculations are in order. I did
none--just skimmed it.
--
Cheers,
James Arthur[/quote] |
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| who where... |
| Posted: Sat Oct 24, 2009 7:07 pm |
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Guest
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On Sat, 24 Oct 2009 20:15:47 +0300, michael nikolaou
<michaelnikolaou_remove_ at (no spam) yahoo.com> wrote:
[quote]Dagmar
that is pretty good IC .Only the 150 uH spoils the picture . That
needs 8x 8 mm minimum board size .
The capacitors are fine. i think i will stick to that
[/quote]
Unfortunately your design requirements create a conundrum -
"cost/size/efficiency - choose any two" works but wanting all three
makes it well nigh impossible.
If cost is ignored, then a TO-220-ish integrated switcher like
http://www.recom-international.com/pdf/Innoline/R-78AAxx-0.5_SMD.pdf
would possibly fit the bill. |
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| JosephKK... |
| Posted: Fri Oct 30, 2009 6:06 pm |
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Guest
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On Tue, 20 Oct 2009 16:16:48 -0700, Jon Kirwan
<jonk at (no spam) infinitefactors.org> wrote:
[quote]On Tue, 20 Oct 2009 15:49:59 -0700, Joerg <invalid at (no spam) invalid.invalid
wrote:
Jon Kirwan wrote:
On Tue, 20 Oct 2009 12:52:04 -0700, Joerg <invalid at (no spam) invalid.invalid
wrote:
michael nikolaou wrote:
Guys
Thanks for all your replies
My small research has found that switcher solutions are.
1. simple and small sized switcher solutions are expensive.
2. Mc33063 are ok in terms of price but the inductor plus the capacitors are
too much board estate
3. Small size means high frequency and so you start with selective
components etc.
Not really, the passive parts are easy. But the challenge will be to
find a mainstream (meaning inexpensive) small switcher chip. The cheap
ones are all old and slow, 300kHz or less. This will take some time
because you must always check pricing. You could start by looking at
chips for the Power over Ethernet (PoE) market.
I NEED ONLY 120 ma is there nothing low cost and simple ?.
One switcher i located used 10 uH inductor , 47 uF output capacitor at (no spam) 6.3V
and 2.2uF input capacitor
but total cost was 1.8 euros. I's using one ARM7 mcu that costs 3 euro and
i don't want to spend as much for the PSU.
Some lower consumption devices at (no spam) 50 mA were using uA78M33 regulator with a
zener if 24 volts was used.
Joerg do you have schematic to study about the idea you are proposing ?
No, that would be a little R&D project. Requires tight reigns on the
firmware because the switcher must never skip a beat. But if you have a
free timer in your ARM MCU it can be done.
Any other simple ideas ???
Another option would be to use a CD40106 or something similar as a
Schmitt oscillator, with its VCC capped/zenered around 6-8V. This can
drive a little FET, a simple logic level device like a 2N7002 as long as
doesn't cost much. Pipe Vref out of your MCU (hoping it has that ....)
and use a cheap opamp to pull the Schmitt oscillator input "to the side"
when the target voltage is reached. That reduces the duty cycle as much
as needed to maintain regulation, pretty much like the throttle on a
gasoline-powered generator. If the target voltage doesn't have to be
very precise you could also use a NPN plus zener for that, without a
reference source. Probably a TL431-type device would work as well and
those are quite cheap, in the penny range.
This has been an interesting discussion. What is bothering me a lot,
in reading it, is the "ONLY 120mA" thing! 120mA? Only? Cripes. If
I were imagining being as space-constrained as the OP suggests, I'd IN
THE FIRST PLACE start asking myself why I actually need 120mA! Is it
the processor, itself? If so, look to get rid of it and find
something else. Doing so may put constraints on the application
itself (doing logarithms on a PIC16 is quite different in speed than
doing them on an ARM9, for example), but it may greatly relax the
power supply design issues. Everything is trade-off. But I'm
bothered by the casual acceptance of a 120mA spec as gospel when there
is a serious space and cost issue here.
What is sucking that power? Can it be changed? If not, why not?
I sure hope it's not the MCU alone because that would spell trouble.
It sounds familiar. I've looked at these 'low power' ARM chips,
noticed that many seem to average 20-50mA, with the lower figure only
on a good day and many requiring more. It was NOT a shock to me to
see 120mA with ARMs. In fact, I'm just fine with that. But when the
OP writes, "I'm making a mcu based device which i want to be very
small and low cost" and then out the other side of the mouth says
"only 120mA" then I'm truly wondering.
One of the BIG tradeoffs is power __AND__ heat. And by the time you
get anywhere near 120mA, you've often got both problems in spades.
It's a fundamentally different domain.
I guess that's why I just went _white_ when I read those figures and
the OP's language in the same context. The only way 120mA is a
little, these days, is if you are used to x86 processors running at
GHz and requiring multiple power supply rails to help contain heat
problems better.
If you live in that world, I can see it. But that sure isn't MY
embedded world perspective. I consider moving into the 120mA domain
as being akin to a "damn-the-torpedoes, devil-may-care" world. At
that point, you are already spending dollars, not pennies, and have
board room to spare. And if you are chugging 120mA, you NEED space,
anyway.
Often there are other things like ADCs, analog stuff etc. 120mA is
really a piece of cake from a power converter point of view. After all,
that's only 600mW if his VCC is 5V. Low enough for an energy star :-)
Hehe. Yeah. If we are talking washing machines, 120mA is no problem.
But room isn't a problem, then, either. There's always a corner, plus
one HUGE heat sink, too. ;)
Michael may have to go with a SEPIC if he wants the FET to switch to GND
but that's not a big deal either, just two parts more. Since the advent
of PoE he's got plenty of options.
I'd recommend that Michael rethink 120mA. I mean, jeeez! If you
nearing a watt already, with overhead, you need space and you expect
to spend something on the power supply, too. Or some serious, crafted
time. Or both.
Almost two decades ago, I was worrying over a thermal cooling stack
with two Peltier stages and the bottom stage was consuming half a
watt. I was worried about that much heat. And the tiny micro device
plus analog circuits at the top was burning some 30mW. Now that's the
kind of thing you get with 120mA! 2-stage Peltier coolers AND a
micro. 20 years ago.
This is crazy-making to think about 120mA! Yeah, if you are making an
iPhone or internet interface device with RF and all. I mean, you need
to actually broadcast maybe 1/4 watt or so. So yeah. But "I'm making
a mcu based device which i want to be very small and low cost?"
The OP and I must come from different universes!
Jon
[/quote]
You may be on to something. OP seems to also be considering a linear
regulator from 24 V to 3.3. Talk about power waste. |
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| Jon Kirwan... |
| Posted: Fri Oct 30, 2009 6:13 pm |
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Guest
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On Fri, 30 Oct 2009 17:06:28 -0700,
"JosephKK"<quiettechblue at (no spam) yahoo.com> wrote:
[quote]On Tue, 20 Oct 2009 16:16:48 -0700, Jon Kirwan
jonk at (no spam) infinitefactors.org> wrote:
On Tue, 20 Oct 2009 15:49:59 -0700, Joerg <invalid at (no spam) invalid.invalid
wrote:
Jon Kirwan wrote:
On Tue, 20 Oct 2009 12:52:04 -0700, Joerg <invalid at (no spam) invalid.invalid
wrote:
michael nikolaou wrote:
Guys
Thanks for all your replies
My small research has found that switcher solutions are.
1. simple and small sized switcher solutions are expensive.
2. Mc33063 are ok in terms of price but the inductor plus the capacitors are
too much board estate
3. Small size means high frequency and so you start with selective
components etc.
Not really, the passive parts are easy. But the challenge will be to
find a mainstream (meaning inexpensive) small switcher chip. The cheap
ones are all old and slow, 300kHz or less. This will take some time
because you must always check pricing. You could start by looking at
chips for the Power over Ethernet (PoE) market.
I NEED ONLY 120 ma is there nothing low cost and simple ?.
One switcher i located used 10 uH inductor , 47 uF output capacitor at (no spam) 6.3V
and 2.2uF input capacitor
but total cost was 1.8 euros. I's using one ARM7 mcu that costs 3 euro and
i don't want to spend as much for the PSU.
Some lower consumption devices at (no spam) 50 mA were using uA78M33 regulator with a
zener if 24 volts was used.
Joerg do you have schematic to study about the idea you are proposing ?
No, that would be a little R&D project. Requires tight reigns on the
firmware because the switcher must never skip a beat. But if you have a
free timer in your ARM MCU it can be done.
Any other simple ideas ???
Another option would be to use a CD40106 or something similar as a
Schmitt oscillator, with its VCC capped/zenered around 6-8V. This can
drive a little FET, a simple logic level device like a 2N7002 as long as
doesn't cost much. Pipe Vref out of your MCU (hoping it has that ...)
and use a cheap opamp to pull the Schmitt oscillator input "to the side"
when the target voltage is reached. That reduces the duty cycle as much
as needed to maintain regulation, pretty much like the throttle on a
gasoline-powered generator. If the target voltage doesn't have to be
very precise you could also use a NPN plus zener for that, without a
reference source. Probably a TL431-type device would work as well and
those are quite cheap, in the penny range.
This has been an interesting discussion. What is bothering me a lot,
in reading it, is the "ONLY 120mA" thing! 120mA? Only? Cripes. If
I were imagining being as space-constrained as the OP suggests, I'd IN
THE FIRST PLACE start asking myself why I actually need 120mA! Is it
the processor, itself? If so, look to get rid of it and find
something else. Doing so may put constraints on the application
itself (doing logarithms on a PIC16 is quite different in speed than
doing them on an ARM9, for example), but it may greatly relax the
power supply design issues. Everything is trade-off. But I'm
bothered by the casual acceptance of a 120mA spec as gospel when there
is a serious space and cost issue here.
What is sucking that power? Can it be changed? If not, why not?
I sure hope it's not the MCU alone because that would spell trouble.
It sounds familiar. I've looked at these 'low power' ARM chips,
noticed that many seem to average 20-50mA, with the lower figure only
on a good day and many requiring more. It was NOT a shock to me to
see 120mA with ARMs. In fact, I'm just fine with that. But when the
OP writes, "I'm making a mcu based device which i want to be very
small and low cost" and then out the other side of the mouth says
"only 120mA" then I'm truly wondering.
One of the BIG tradeoffs is power __AND__ heat. And by the time you
get anywhere near 120mA, you've often got both problems in spades.
It's a fundamentally different domain.
I guess that's why I just went _white_ when I read those figures and
the OP's language in the same context. The only way 120mA is a
little, these days, is if you are used to x86 processors running at
GHz and requiring multiple power supply rails to help contain heat
problems better.
If you live in that world, I can see it. But that sure isn't MY
embedded world perspective. I consider moving into the 120mA domain
as being akin to a "damn-the-torpedoes, devil-may-care" world. At
that point, you are already spending dollars, not pennies, and have
board room to spare. And if you are chugging 120mA, you NEED space,
anyway.
Often there are other things like ADCs, analog stuff etc. 120mA is
really a piece of cake from a power converter point of view. After all,
that's only 600mW if his VCC is 5V. Low enough for an energy star :-)
Hehe. Yeah. If we are talking washing machines, 120mA is no problem.
But room isn't a problem, then, either. There's always a corner, plus
one HUGE heat sink, too. ;)
Michael may have to go with a SEPIC if he wants the FET to switch to GND
but that's not a big deal either, just two parts more. Since the advent
of PoE he's got plenty of options.
I'd recommend that Michael rethink 120mA. I mean, jeeez! If you
nearing a watt already, with overhead, you need space and you expect
to spend something on the power supply, too. Or some serious, crafted
time. Or both.
Almost two decades ago, I was worrying over a thermal cooling stack
with two Peltier stages and the bottom stage was consuming half a
watt. I was worried about that much heat. And the tiny micro device
plus analog circuits at the top was burning some 30mW. Now that's the
kind of thing you get with 120mA! 2-stage Peltier coolers AND a
micro. 20 years ago.
This is crazy-making to think about 120mA! Yeah, if you are making an
iPhone or internet interface device with RF and all. I mean, you need
to actually broadcast maybe 1/4 watt or so. So yeah. But "I'm making
a mcu based device which i want to be very small and low cost?"
The OP and I must come from different universes!
Jon
You may be on to something. OP seems to also be considering a linear
regulator from 24 V to 3.3. Talk about power waste.
[/quote]
OMG! Are you kidding? (I must have missed reading and/or connecting
the dots on posts you saw.)
Jon |
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| JosephKK... |
| Posted: Tue Nov 03, 2009 12:26 am |
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Guest
|
On Fri, 30 Oct 2009 17:13:07 -0700, Jon Kirwan
<jonk at (no spam) infinitefactors.org> wrote:
[quote]On Fri, 30 Oct 2009 17:06:28 -0700,
"JosephKK"<quiettechblue at (no spam) yahoo.com> wrote:
On Tue, 20 Oct 2009 16:16:48 -0700, Jon Kirwan
jonk at (no spam) infinitefactors.org> wrote:
On Tue, 20 Oct 2009 15:49:59 -0700, Joerg <invalid at (no spam) invalid.invalid
wrote:
Jon Kirwan wrote:
On Tue, 20 Oct 2009 12:52:04 -0700, Joerg <invalid at (no spam) invalid.invalid
wrote:
michael nikolaou wrote:
Guys
Thanks for all your replies
My small research has found that switcher solutions are.
1. simple and small sized switcher solutions are expensive.
2. Mc33063 are ok in terms of price but the inductor plus the capacitors are
too much board estate
3. Small size means high frequency and so you start with selective
components etc.
Not really, the passive parts are easy. But the challenge will be to
find a mainstream (meaning inexpensive) small switcher chip. The cheap
ones are all old and slow, 300kHz or less. This will take some time
because you must always check pricing. You could start by looking at
chips for the Power over Ethernet (PoE) market.
I NEED ONLY 120 ma is there nothing low cost and simple ?.
One switcher i located used 10 uH inductor , 47 uF output capacitor at (no spam) 6.3V
and 2.2uF input capacitor
but total cost was 1.8 euros. I's using one ARM7 mcu that costs 3 euro and
i don't want to spend as much for the PSU.
Some lower consumption devices at (no spam) 50 mA were using uA78M33 regulator with a
zener if 24 volts was used.
Joerg do you have schematic to study about the idea you are proposing ?
No, that would be a little R&D project. Requires tight reigns on the
firmware because the switcher must never skip a beat. But if you have a
free timer in your ARM MCU it can be done.
Any other simple ideas ???
Another option would be to use a CD40106 or something similar as a
Schmitt oscillator, with its VCC capped/zenered around 6-8V. This can
drive a little FET, a simple logic level device like a 2N7002 as long as
doesn't cost much. Pipe Vref out of your MCU (hoping it has that ....)
and use a cheap opamp to pull the Schmitt oscillator input "to the side"
when the target voltage is reached. That reduces the duty cycle as much
as needed to maintain regulation, pretty much like the throttle on a
gasoline-powered generator. If the target voltage doesn't have to be
very precise you could also use a NPN plus zener for that, without a
reference source. Probably a TL431-type device would work as well and
those are quite cheap, in the penny range.
This has been an interesting discussion. What is bothering me a lot,
in reading it, is the "ONLY 120mA" thing! 120mA? Only? Cripes. If
I were imagining being as space-constrained as the OP suggests, I'd IN
THE FIRST PLACE start asking myself why I actually need 120mA! Is it
the processor, itself? If so, look to get rid of it and find
something else. Doing so may put constraints on the application
itself (doing logarithms on a PIC16 is quite different in speed than
doing them on an ARM9, for example), but it may greatly relax the
power supply design issues. Everything is trade-off. But I'm
bothered by the casual acceptance of a 120mA spec as gospel when there
is a serious space and cost issue here.
What is sucking that power? Can it be changed? If not, why not?
I sure hope it's not the MCU alone because that would spell trouble.
It sounds familiar. I've looked at these 'low power' ARM chips,
noticed that many seem to average 20-50mA, with the lower figure only
on a good day and many requiring more. It was NOT a shock to me to
see 120mA with ARMs. In fact, I'm just fine with that. But when the
OP writes, "I'm making a mcu based device which i want to be very
small and low cost" and then out the other side of the mouth says
"only 120mA" then I'm truly wondering.
One of the BIG tradeoffs is power __AND__ heat. And by the time you
get anywhere near 120mA, you've often got both problems in spades.
It's a fundamentally different domain.
I guess that's why I just went _white_ when I read those figures and
the OP's language in the same context. The only way 120mA is a
little, these days, is if you are used to x86 processors running at
GHz and requiring multiple power supply rails to help contain heat
problems better.
If you live in that world, I can see it. But that sure isn't MY
embedded world perspective. I consider moving into the 120mA domain
as being akin to a "damn-the-torpedoes, devil-may-care" world. At
that point, you are already spending dollars, not pennies, and have
board room to spare. And if you are chugging 120mA, you NEED space,
anyway.
Often there are other things like ADCs, analog stuff etc. 120mA is
really a piece of cake from a power converter point of view. After all,
that's only 600mW if his VCC is 5V. Low enough for an energy star :-)
Hehe. Yeah. If we are talking washing machines, 120mA is no problem.
But room isn't a problem, then, either. There's always a corner, plus
one HUGE heat sink, too. ;)
Michael may have to go with a SEPIC if he wants the FET to switch to GND
but that's not a big deal either, just two parts more. Since the advent
of PoE he's got plenty of options.
I'd recommend that Michael rethink 120mA. I mean, jeeez! If you
nearing a watt already, with overhead, you need space and you expect
to spend something on the power supply, too. Or some serious, crafted
time. Or both.
Almost two decades ago, I was worrying over a thermal cooling stack
with two Peltier stages and the bottom stage was consuming half a
watt. I was worried about that much heat. And the tiny micro device
plus analog circuits at the top was burning some 30mW. Now that's the
kind of thing you get with 120mA! 2-stage Peltier coolers AND a
micro. 20 years ago.
This is crazy-making to think about 120mA! Yeah, if you are making an
iPhone or internet interface device with RF and all. I mean, you need
to actually broadcast maybe 1/4 watt or so. So yeah. But "I'm making
a mcu based device which i want to be very small and low cost?"
The OP and I must come from different universes!
Jon
You may be on to something. OP seems to also be considering a linear
regulator from 24 V to 3.3. Talk about power waste.
OMG! Are you kidding? (I must have missed reading and/or connecting
the dots on posts you saw.)
Jon
[/quote]
And it is possible that i misread instead. YMMV. |
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