triple switcher
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From: langwadt on 15 Nov 2009 15:37 On 15 Nov., 19:41, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Sat, 14 Nov 2009 13:40:27 -0800 (PST), MooseFET > > > > <kensm...(a)rahul.net> wrote: > >On Nov 14, 10:40 am, 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 > > >How about LT3507? > > Lots of external parts, schottkies and inductors. > > > > >LT3564 seems to get a lot of switcher into a small package. > > We already stock the LTC3407, 3411, and 3412, all similar. But it > would be great if somebody did a minimal-parts, minimal-size triple > synchronous switcher, ideally with internal inductors. I *told* LTC to > do this, and, incredibly, they haven't got around to it. It's not as > if FPGAs are losing popularity. > > The Spartan 6 parts will run from two supplies (Vccint can run from > 3.3) but we want to use a DDR dram, at 1.8 volts, so we're back up to > three. > something like a ISL65426 and an ldo? -Lasse
From: dagmargoodboat on 15 Nov 2009 16:01 On Nov 15, 12:20 pm, MooseFET <kensm...(a)rahul.net> wrote: > On Nov 14, 5:35 pm, dagmargoodb...(a)yahoo.com wrote: > > > On Nov 14, 4:40 pm, MooseFET <kensm...(a)rahul.net> wrote: > > > > I haven't been able to find a way to do it with either a PIC or a 555 > > > but I'll keep thinking about it. > > > Either's fine. > > > (view in fixed font) > > > U1 U2 ... U11 > > .-------. .-------. .-------. > > +12v >--|gnd Vdd|--|gnd Vdd|-...-|gnd Vdd|--> +5v > > '-------' '-------' '-------' > > > U1-U11 = 555 or PIC. > > That isn't 3 voltages per chip as the OP asked for. It also doesn't > really regulate. John asked for a switcher with 3 regulated outputs, to save space. You wanted a 555 or a PIC. So, like our health care bill, I blended the two sets of requirements and came up with a solution that costs more, uses more parts & space, doesn't regulate, but does use either a 555 or a PIC. That's called compromise. > I have made a booster regulator with the LM555 that worked just fine. > I have figured out the design for a bucker that looks like it would > work but so far without adding a lot of external parts I haven't come > up with a way to regulate more than one voltage. The classic way is a flyback with multiple secondaries, close the loop on the main voltage, LDOs on the others. But of course we all knew that. -- Cheers, James Arthur
From: John Larkin on 15 Nov 2009 16:09 On Sun, 15 Nov 2009 12:37:31 -0800 (PST), "langwadt(a)fonz.dk" <langwadt(a)fonz.dk> wrote: >On 15 Nov., 19:41, John Larkin ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> On Sat, 14 Nov 2009 13:40:27 -0800 (PST), MooseFET >> >> >> >> <kensm...(a)rahul.net> wrote: >> >On Nov 14, 10:40�am, 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 >> >> >How about LT3507? >> >> Lots of external parts, schottkies and inductors. >> >> >> >> >LT3564 seems to get a lot of switcher into a small package. >> >> We already stock the LTC3407, 3411, and 3412, all similar. But it >> would be great if somebody did a minimal-parts, minimal-size triple >> synchronous switcher, ideally with internal inductors. I *told* LTC to >> do this, and, incredibly, they haven't got around to it. It's not as >> if FPGAs are losing popularity. >> >> The Spartan 6 parts will run from two supplies (Vccint can run from >> 3.3) but we want to use a DDR dram, at 1.8 volts, so we're back up to >> three. >> > >something like a ISL65426 and an ldo? > >-Lasse The LTM4615 has all that inside, including the inductors and LDO. That may be the most compact solution, for $24. Still no magic bullet. John
From: Jan Panteltje on 15 Nov 2009 16:48 On a sunny day (Sun, 15 Nov 2009 13:09:30 -0800) it happened John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in <abr0g5pgk26nsabqgu2jr9q6r1rmcrmmv4(a)4ax.com>: >>> I *told* LTC to >>> do this, and, incredibly, they haven't got around to it. It's not as >>> if FPGAs are losing popularity. Voltages and how many change all the time, better have separate switchers, Havin ga 3 in 1 would reduce the market by a factor 9 :-) >>> The Spartan 6 parts will run from two supplies (Vccint can run from >>> 3.3) but we want to use a DDR dram, at 1.8 volts, so we're back up to >>> three. >>> >> >>something like a ISL65426 and an ldo? >> >>-Lasse > >The LTM4615 has all that inside, including the inductors and LDO. That >may be the most compact solution, for $24. You make small series with high profits. No reason not to use 3 switchers.
From: John Larkin on 15 Nov 2009 17:08
On Sun, 15 Nov 2009 21:48:22 GMT, Jan Panteltje <pNaonStpealmtje(a)yahoo.com> wrote: >On a sunny day (Sun, 15 Nov 2009 13:09:30 -0800) it happened John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in ><abr0g5pgk26nsabqgu2jr9q6r1rmcrmmv4(a)4ax.com>: > >>>> I *told* LTC to >>>> do this, and, incredibly, they haven't got around to it. It's not as >>>> if FPGAs are losing popularity. > > >Voltages and how many change all the time, better have separate switchers, >Havin ga 3 in 1 would reduce the market by a factor 9 :-) The LTC switcher voltages are usually programmed with one or two resistors per output. An SPI interface to a nonvolatile memory would be even better. > > >>>> The Spartan 6 parts will run from two supplies (Vccint can run from >>>> 3.3) but we want to use a DDR dram, at 1.8 volts, so we're back up to >>>> three. >>>> >>> >>>something like a ISL65426 and an ldo? >>> >>>-Lasse >> >>The LTM4615 has all that inside, including the inductors and LDO. That >>may be the most compact solution, for $24. > >You make small series with high profits. >No reason not to use 3 switchers. We're space constrained by the fixed size of a VME module. The current project is a 16 channel differential-input digitizer with BIST and a 32-bit interface (requiring two DIN connectors and lots of buffers to the backplane.) It's very tight, and the more features we include the more we can sell. Wasting 2 or 3 square inches on voltage regs is silly. We commonly build products with 8 or 9 separate power rails, with the power regulators over a third of the board area. This is getting silly. SIPs would be useful, to use available height instead of valuable board surface area. The thermals might be better, too. John |