battery chargers, again
in [Design]
|
From: Joerg on 1 Oct 2009 17:09 John Larkin wrote: > On Thu, 01 Oct 2009 13:48:49 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> John Larkin wrote: >>> On Thu, 01 Oct 2009 13:10:44 -0700, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> John Larkin wrote: >>>>> On Wed, 30 Sep 2009 14:40:06 -0700, Joerg <invalid(a)invalid.invalid> >>>>> wrote: >>>>> >>>>>> John Larkin wrote: >>>>>>> On Wed, 30 Sep 2009 16:04:00 -0500, Vladimir Vassilevsky >>>>>>> <nospam(a)nowhere.com> wrote: >>>>>>> >>>>>>>> John Larkin wrote: >>>>>>>> >>>>>>>> >>>>>>>>> I'm working on a smallish board that has four switchers in one corner >>>>>>>>> and an ADC that's looking for a 1 nV spectral line in the other, >>>>>>>> The 1nV over the background of how many nV/root(Hz) ? >>>>>>> About 1. That's our target noise floor. The existing system is >>>>>>> ballpark 100 nv/rtHz with huge birdies all over the place. >>>>>>> >>>>>>> Never let scientists design electronics. >>>>>>> >>>>>>>>> range >>>>>>>>> of interest straddling all the switcher frequencies. >>>>>>>> Synchronize the switchers away from the particular frequency of interest? >>>>>>> The signals can be all over the place. >>>>>>> >>>>>>>>> I'm planning on >>>>>>>>> spread-spectrum wobulating all the switchers, just in case. >>>>>>>> So the dirt will be in band for sure? >>>>>>> Yup. Operating range is audio to many MHz, all at once. We digitize at >>>>>>> 64 Ms/s and FFT and see what's there. >>>>>>> >>>>>> How many MHz is "many"? And how much power does the biggest of the >>>>>> switchers have to deliver? >>>>> 20-ish. And just a couple of watts. I need 5, 3.3, 2.5, 1.8, 1.2, and >>>>> -5. All from +12. >>>>> >>>> Theoretically you could run it at 27.12MHz but that's nasty. If you >>>> can't stomach the dissipation of linears then you may be stuck with some >>>> spectral dodging scheme like the one I described. We do that in >>>> ultrasound sometimes but there I could always get a few clock control >>>> lines from some a DSP or FPGA. If I bought the digital and SW guys some >>>> beers that night ... >>> I've got a couple of switcher eval boards around. Maybe I should fire >>> some up and experiment with FMing the switcher freqs and see what that >>> does to the spectrum and to the output voltage. >>> >> But first check the limit values. Or at least try them out with a >> potmeter for the frequency set resistor. Easiest would be to have PWM >> chips with a sync input. > > One of my guys wants to have the FPGA synthesize a bunch of FMd clocks > and dump that into the reg sync inputs. I was planning to make an > analog triangle and squirt a little of it into the pins where the freq > set resistors connect. > For a test your method would be faster. For production, not so much, because you'd have to have a servo'ed dual MOSFET in that path. Rohm makes them, cheap, if that's the plan at the end. >> >>> Or better yet have somebody do it for me. >>> >> Can't you get a student who is eager to learn and make a buck from the >> university? Maybe throw in free parking :-) > > We usually have an intern or two for the summer, but we seem to have > run out. > They should be rather hungry in this economy. Might just take one phone call ;-) -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Rich Grise on 1 Oct 2009 17:10 On Wed, 30 Sep 2009 20:38:29 -0400, Spehro Pefhany wrote: > On Tue, 29 Sep 2009 15:18:12 -0700, the renowned Rich Grise >>On Tue, 29 Sep 2009 10:24:57 -0700, John Larkin wrote: >>> ... >>> I guess several of the posters here, if they left their lights on and >>> killed their battery, will always have their car towed and the battery >>> replaced. They have no need for jumper cables, and are happy buying >>> chargers that only charge batteries that don't need to be charged. >>> >>Ouch! John, I've never heard you scathe before, but geez! This post >>singed my eyebrows! >> >>Keep it up. >:-> It helps dispel that "leprechaun" image. ;-D > > Something like this http://www.speff.com/jl.jpg ? > Eek! Heavens, no! John is cute as a button! It's just that he's about 5'6" or so, a bit wiry, and Irish. :-) (I met him face-to-face at a trade show in Long Beach a couple of years ago, and picked up some of his refrigerator magnets.) :-) Cheers! Rich
From: John Larkin on 1 Oct 2009 21:18 On Thu, 01 Oct 2009 14:09:56 -0700, Joerg <invalid(a)invalid.invalid> wrote: >John Larkin wrote: >> On Thu, 01 Oct 2009 13:48:49 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> John Larkin wrote: >>>> On Thu, 01 Oct 2009 13:10:44 -0700, Joerg <invalid(a)invalid.invalid> >>>> wrote: >>>> >>>>> John Larkin wrote: >>>>>> On Wed, 30 Sep 2009 14:40:06 -0700, Joerg <invalid(a)invalid.invalid> >>>>>> wrote: >>>>>> >>>>>>> John Larkin wrote: >>>>>>>> On Wed, 30 Sep 2009 16:04:00 -0500, Vladimir Vassilevsky >>>>>>>> <nospam(a)nowhere.com> wrote: >>>>>>>> >>>>>>>>> John Larkin wrote: >>>>>>>>> >>>>>>>>> >>>>>>>>>> I'm working on a smallish board that has four switchers in one corner >>>>>>>>>> and an ADC that's looking for a 1 nV spectral line in the other, >>>>>>>>> The 1nV over the background of how many nV/root(Hz) ? >>>>>>>> About 1. That's our target noise floor. The existing system is >>>>>>>> ballpark 100 nv/rtHz with huge birdies all over the place. >>>>>>>> >>>>>>>> Never let scientists design electronics. >>>>>>>> >>>>>>>>>> range >>>>>>>>>> of interest straddling all the switcher frequencies. >>>>>>>>> Synchronize the switchers away from the particular frequency of interest? >>>>>>>> The signals can be all over the place. >>>>>>>> >>>>>>>>>> I'm planning on >>>>>>>>>> spread-spectrum wobulating all the switchers, just in case. >>>>>>>>> So the dirt will be in band for sure? >>>>>>>> Yup. Operating range is audio to many MHz, all at once. We digitize at >>>>>>>> 64 Ms/s and FFT and see what's there. >>>>>>>> >>>>>>> How many MHz is "many"? And how much power does the biggest of the >>>>>>> switchers have to deliver? >>>>>> 20-ish. And just a couple of watts. I need 5, 3.3, 2.5, 1.8, 1.2, and >>>>>> -5. All from +12. >>>>>> >>>>> Theoretically you could run it at 27.12MHz but that's nasty. If you >>>>> can't stomach the dissipation of linears then you may be stuck with some >>>>> spectral dodging scheme like the one I described. We do that in >>>>> ultrasound sometimes but there I could always get a few clock control >>>>> lines from some a DSP or FPGA. If I bought the digital and SW guys some >>>>> beers that night ... >>>> I've got a couple of switcher eval boards around. Maybe I should fire >>>> some up and experiment with FMing the switcher freqs and see what that >>>> does to the spectrum and to the output voltage. >>>> >>> But first check the limit values. Or at least try them out with a >>> potmeter for the frequency set resistor. Easiest would be to have PWM >>> chips with a sync input. >> >> One of my guys wants to have the FPGA synthesize a bunch of FMd clocks >> and dump that into the reg sync inputs. I was planning to make an >> analog triangle and squirt a little of it into the pins where the freq >> set resistors connect. >> > >For a test your method would be faster. For production, not so much, >because you'd have to have a servo'ed dual MOSFET in that path. Rohm >makes them, cheap, if that's the plan at the end. I don't follow that. If I make a simple triangle wave, maybe 0.5 volts p-p, a few KHz maybe, and run it through a big resistor into the regulator pin that the timing resistor connects to, it should FM the switcher's frequency. I'll check all the regs to make sure, but the Fset pins are usually at DC, and the Fset resistor usually sets a DC current that the chip uses to make frequency. If I have, say, a 1 MHz switcher and push it +-1%, that's 20 KHz p-p, so I should reduce the amplitude of a 1 MHz birdie by about 20,000:1 in a 1 Hz BW situation. Not that much in real life, but even 100:1 is a good number. John
From: John Larkin on 1 Oct 2009 21:33 On Thu, 01 Oct 2009 14:06:36 -0700, Joerg <invalid(a)invalid.invalid> wrote: >> The layout is tedious, because we're optimizing the BGA FPGA routing >> as we go along... can't just draw the schematic and go forward to the >> board. >> > >Ouch. > > >> This *is* rev 30. >> > >Double-Ouch. I am firing up rev 1 of a really unorthodox cicuit this >afternoon. Wish me luck, and if you hear a muffled boom north-east from >you guys ... Was that an earthquake or was the Joerg? To calarify, this is rev 30 of the working layout. We haven't fabbed any boards yet. The PCB file will be formally released as 26D150A.PCB, to make rev A of the product. During layout, we number every iteration. If we change a net or add a resistor or whatever, we start with schematic 26S150A29.SCH, change it to 26S150A30.SCH and save that, make the differences file ECO30, apply that onto pcb 26D150A29.PCB, and save as 26D150A30.PCB. So we have all the iterations and all the ECO files, all organized. When we release the schematic and pcb as rev A, we delete all that working junk. Since we're iterating on the BGA pinout, we're spinning a lot of ECOs. If we go A to B, we start the sequence all over, 26S150B1.SCH etc. John
From: John Larkin on 1 Oct 2009 22:40
On Thu, 01 Oct 2009 14:10:05 -0700, Rich Grise <richgrise(a)example.net> wrote: >On Wed, 30 Sep 2009 20:38:29 -0400, Spehro Pefhany wrote: >> On Tue, 29 Sep 2009 15:18:12 -0700, the renowned Rich Grise >>>On Tue, 29 Sep 2009 10:24:57 -0700, John Larkin wrote: >>>> ... >>>> I guess several of the posters here, if they left their lights on and >>>> killed their battery, will always have their car towed and the battery >>>> replaced. They have no need for jumper cables, and are happy buying >>>> chargers that only charge batteries that don't need to be charged. >>>> >>>Ouch! John, I've never heard you scathe before, but geez! This post >>>singed my eyebrows! >>> >>>Keep it up. >:-> It helps dispel that "leprechaun" image. ;-D >> >> Something like this http://www.speff.com/jl.jpg ? >> > >Eek! Heavens, no! John is cute as a button! It's just that he's about >5'6" or so, a bit wiry, and Irish. :-) (I met him face-to-face at a trade >show in Long Beach a couple of years ago, and picked up some of his >refrigerator magnets.) :-) > That's what we give out these days, instead of pots of gold. John |