switching regulator with mcu
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From: Joerg on 21 Oct 2009 13:34 John Devereux wrote: > Joerg <invalid(a)invalid.invalid> writes: > >> John Devereux wrote: >>> Joerg <invalid(a)invalid.invalid> writes: >>> >>>> John Devereux wrote: > > [...] > >>> Of course, neat. Finally the famed Jeorgian discrete SMPS is starting to >>> take shape :) >>> >> My first one took shape about 15 years ago, tons of them in use by >> consumers right now, still coming off the conveyor belt (in China). I >> don't know if it will outlast the VW Beetle in production but it >> might. It has already survived the client company's president :-( >> >> Back then I learned a valuable lesson: Inductor prices in the western >> world must be taken with a grain of salt. A custom mfg place in Taiwan >> outbid a catalog (!) part from a western manufacturer, big time. And >> we even got an EMI-savvy toroid for our money versus the cheap open >> cores from mainstream distributors. Of course it does help not to have >> a middleman in the game. >> >> > > [...] > >>> Anyone know how to do this for smaller quantities (<~1k, say?). I've got >>> plenty of Asian suppliers trying to get our PCB business, but nobody >>> trying to sell me inductors :(. >>> >> <1k? No, I don't think they'd even talk to you. > > I should have said "single reel" since there are typically more than > that on a reel. I guess we could probably make a "strategic" buy of ~5k > if needed. If they're *really* cheap 10k! :) > You could talk to companies like this: http://www.xfmrs.com/ But since 10k is a small qty mostly you'll have to start here: http://www.globalsources.com/gsol/I/Power-inductor-manufacturers/b/2000000003844/3000000184262/22705.htm >> However, Asia is all about one thing: Connections. Ask the PCB >> stuffing places what sort of deals they can get locally. They might be >> able to swing it, with a supplier they already buy lots of other stuff >> from. >> >> If you have reputable places there that do <1k qty board runs with >> decent quality let me (and others here) know. I bet lots of us are >> interested. > > Sorry, I meant bare PCB not stuffed. They advertise stuffing too - down > to any quantity - but they said once they buy non-free issued parts from > Digikey... :) > That won't give you much of an upside. I recently had a proto-run fabbed in the US (Aurora, Colorado), full turn-key, and was pleasantly surprised: http://www.aapcb.com/ > I just thought it strange that I can get small qtys of PCBs at 1/2 the > price of local suppliers, but nobody does the same for parts. (Which > ought to be much easier to supply). > They do, in places like Shenzen, if you let them purchase. But be careful that they don't substitute, say, an electrolytic for a more "economical" part. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: John Devereux on 21 Oct 2009 14:48 Joerg <invalid(a)invalid.invalid> writes: > John Devereux wrote: [...] >> >> I should have said "single reel" since there are typically more than >> that on a reel. I guess we could probably make a "strategic" buy of ~5k >> if needed. If they're *really* cheap 10k! :) >> > > You could talk to companies like this: > > http://www.xfmrs.com/ > > But since 10k is a small qty mostly you'll have to start here: > > http://www.globalsources.com/gsol/I/Power-inductor-manufacturers/b/2000000003844/3000000184262/22705.htm > [...] >> Sorry, I meant bare PCB not stuffed. They advertise stuffing too - down >> to any quantity - but they said once they buy non-free issued parts from >> Digikey... :) >> > > That won't give you much of an upside. I recently had a proto-run > fabbed in the US (Aurora, Colorado), full turn-key, and was pleasantly > surprised: > > http://www.aapcb.com/ > Thanks for the links; bookmarked. Will look into it further. >> I just thought it strange that I can get small qtys of PCBs at 1/2 the >> price of local suppliers, but nobody does the same for parts. (Which >> ought to be much easier to supply). >> > > They do, in places like Shenzen, if you let them purchase. But be > careful that they don't substitute, say, an electrolytic for a more > "economical" part. -- John Devereux
From: Nico Coesel on 21 Oct 2009 17:26 Joerg <invalid(a)invalid.invalid> wrote: >Nico Coesel wrote: >> "michael nikolaou" <michaelnikolaou_remove_me_(a)yahoo.com> 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 @ 3.3V >>> The problem is the installation that requires 12 or 24 volts to operate. >>> I don't want to use a switching regulator to make the voltage drop since its >>> to much >>> circuit involved and also not a zener since its to much heat involved . >> >> Too much circuitry? Look at devices from TI like the TPS5410. Very >> small and it will run at a wide variety of input voltages. >> > >But mucho Dolares. I'd try using the MCU if possible if this is a high >volume product. But it'll require lots of nifty engineering. For low >volume, yeah, don't bother and use a chip. Then I'd use the MC34063 >which costs under 20 cents. None of those high-faluting newfangled ritzy >ones ;-) Yes, but the decrease in costs of the chip is compensated by a large inductor and capacitors. -- 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!" --------------------------------------------------------------
From: Joerg on 21 Oct 2009 17:36 Nico Coesel wrote: > Joerg <invalid(a)invalid.invalid> wrote: > >> Nico Coesel wrote: >>> "michael nikolaou" <michaelnikolaou_remove_me_(a)yahoo.com> 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 @ 3.3V >>>> The problem is the installation that requires 12 or 24 volts to operate. >>>> I don't want to use a switching regulator to make the voltage drop since its >>>> to much >>>> circuit involved and also not a zener since its to much heat involved . >>> Too much circuitry? Look at devices from TI like the TPS5410. Very >>> small and it will run at a wide variety of input voltages. >>> >> But mucho Dolares. I'd try using the MCU if possible if this is a high >> volume product. But it'll require lots of nifty engineering. For low >> volume, yeah, don't bother and use a chip. Then I'd use the MC34063 >> which costs under 20 cents. None of those high-faluting newfangled ritzy >> ones ;-) > > Yes, but the decrease in costs of the chip is compensated by a large > inductor and capacitors. > If you have the space those are cheap. Unfortunately Michael doesn't have the space. But he also doesn't have the BOM budget for a modern switcher chip :-( IOW he is between a rock and a hard spot so the MCU or homebrew may be his only options. I don't know if his ARM7 MCU has good timers left in there. If not he's going to have to roll his own around a Schmitt inverter. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jon Elson on 22 Oct 2009 00:54
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 @ 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 |