>>On Tue, 20 Oct 2009 15:49:59 -0700, Joerg <inva...@invalid.invalid>
>>wrote:

>>>Jon Kirwan wrote:
>>>> On Tue, 20 Oct 2009 12:52:04 -0700, Joerg <inva...@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 @ 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 @ 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.

>>On Tue, 20 Oct 2009 16:16:48 -0700, Jon Kirwan
>><j...@infinitefactors.org> wrote:

>>>On Tue, 20 Oct 2009 15:49:59 -0700, Joerg <inva...@invalid.invalid>
>>>wrote:

>>>>Jon Kirwan wrote:
>>>>> On Tue, 20 Oct 2009 12:52:04 -0700, Joerg <inva...@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 @ 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 @ 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