triple switcher
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From: MooseFET on 17 Nov 2009 22:23 On Nov 16, 6:55 am, Jan Panteltje <pNaonStpealm...(a)yahoo.com> wrote: > On a sunny day (Mon, 16 Nov 2009 06:45:06 -0800 (PST)) it happened MooseFET > <kensm...(a)rahul.net> wrote in > <828b5506-8b03-490c-a0ab-291210be8...(a)b25g2000prb.googlegroups.com>: > > > > >On Nov 16, 3:15 am, Jan Panteltje <pNaonStpealm...(a)yahoo.com> wrote: > >> On a sunny day (Sun, 15 Nov 2009 18:43:06 -0800 (PST)) it happened MooseF= > >ET > >> <kensm...(a)rahul.net> wrote in > >> <cb721d88-65d3-4d08-95a2-3e96c826c...(a)m7g2000prd.googlegroups.com>: > > >> >The ADC on the PIC isn't fast enough to do cycle by cycle voltage > >> >checking so you would have to close the servo loop at way less than > >> >Nyquist. Unfortunately this would also make the filter capacitors > >> >big. > > >> You can use the PIC comparator and hysteretic control. > >> You can also use cycle by cycle current mode, and by > >> adding 1 or 2 extra transistors control the current, so > >> make a true current mode switcher. > >> http://panteltje.com/panteltje/pic/pwr_pic/index.html > >> Have not tried the 2 transistor thingy yet, but published > >> a circuit for it here a while back. > > >The added stuff to make it work is as big as just making the whole > >switcher. The PIC can't directly drive the pass elements. > > If you mean power MOSFET by pass-elements, then yes it can, as the above links shows. > You are a bit limited in frequency then of course, say 76 kHz. To get the reactive elements small the PWM needs to go at a few MHz. The PIC doesn't have enough drive for that.
From: John Larkin on 18 Nov 2009 16:18 On Sat, 14 Nov 2009 10:40:44 -0800, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > > >We keep running into the requirement to turn +12 or +5 volts into 3.3, >1.2 (fpga core), and usually a third voltage, 1.8 (for drams) or 2.5 >(fpga Vccint). We'd like to consolidate this to save board area and >general complexity. Any suggestions? > >LTM4615 looks interesting, a bit expensive but very small. > >http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1424,P89092 > > >And other ideas? > >John > Well, the resolution was to use two LTM8023's, which we have in this case, to make 3.3 and 1.2 from available +5, and an LM1117 to make 1.8 from 3.3. Clumsy. Somebody should make a tiny triple switcher module to run FPGAs; they'd sell a lot of them. John
From: Rich Grise on 19 Nov 2009 16:57 On Wed, 18 Nov 2009 13:18:36 -0800, John Larkin wrote: > On Sat, 14 Nov 2009 10:40:44 -0800, John Larkin >> >>We keep running into the requirement to turn +12 or +5 volts into 3.3, >>1.2 (fpga core), and usually a third voltage, 1.8 (for drams) or 2.5 >>(fpga Vccint). We'd like to consolidate this to save board area and >>general complexity. Any suggestions? >> >>LTM4615 looks interesting, a bit expensive but very small. >> >>http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1424,P89092 >> >>And other ideas? > > Well, the resolution was to use two LTM8023's, which we have in this case, > to make 3.3 and 1.2 from available +5, and an LM1117 to make 1.8 from 3.3. > Clumsy. Somebody should make a tiny triple switcher module to run FPGAs; > they'd sell a lot of them. > Dude, you've got the lab, and a marketing department - or at least, customers - why not just do it? Good Luck! Rich]
From: langwadt on 19 Nov 2009 18:18 On 18 Nov., 22:18, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Sat, 14 Nov 2009 10:40:44 -0800, John Larkin > > > > <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > > >We keep running into the requirement to turn +12 or +5 volts into 3.3, > >1.2 (fpga core), and usually a third voltage, 1.8 (for drams) or 2.5 > >(fpga Vccint). We'd like to consolidate this to save board area and > >general complexity. Any suggestions? > > >LTM4615 looks interesting, a bit expensive but very small. > > >http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1424,P8... > > >And other ideas? > > >John > > Well, the resolution was to use two LTM8023's, which we have in this > case, to make 3.3 and 1.2 from available +5, and an LM1117 to make 1.8 > from 3.3. Clumsy. Somebody should make a tiny triple switcher module > to run FPGAs; they'd sell a lot of them. > > John how much current do you need? seen the ADP2121? http://www.analog.com/static/imported-files/data_sheets/ADP2121.pdf has an example layout, 2.5x3.4mm one layer for 600mA 1.8V though it looks like it only available with 1.8V out the adp2109 looks similar but is available with 1.0,1.2,1.5,1.8V output -Lasse
From: dagmargoodboat on 20 Nov 2009 14:37
On Nov 19, 6:18 pm, "langw...(a)fonz.dk" <langw...(a)fonz.dk> wrote: > On 18 Nov., 22:18, John Larkin > > > > <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > > On Sat, 14 Nov 2009 10:40:44 -0800, John Larkin > > > <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > > > >We keep running into the requirement to turn +12 or +5 volts into 3.3, > > >1.2 (fpga core), and usually a third voltage, 1.8 (for drams) or 2.5 > > >(fpga Vccint). We'd like to consolidate this to save board area and > > >general complexity. Any suggestions? > > > >LTM4615 looks interesting, a bit expensive but very small. > > > >http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1424,P8... > > > >And other ideas? > > > >John > > > Well, the resolution was to use two LTM8023's, which we have in this > > case, to make 3.3 and 1.2 from available +5, and an LM1117 to make 1.8 > > from 3.3. Clumsy. Somebody should make a tiny triple switcher module > > to run FPGAs; they'd sell a lot of them. > > > John > > how much current do you need? > > seen the ADP2121?http://www.analog.com/static/imported-files/data_sheets/ADP2121.pdf > has an example layout, 2.5x3.4mm one layer for 600mA 1.8V > though it looks like it only available with 1.8V out > > the adp2109 looks similar but is available with 1.0,1.2,1.5,1.8V > output > > -Lasse That's a gorgeous part. $0.80 @ 1,000, production availability: 11/20/2009. 2x2mm layout if you use one of the smaller inductors. -- Cheers, James Arthur |