On a sunny day (Sun, 15 Nov 2009 18:43:06 -0800 (PST)) it happened MooseFET wrote in :
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.
How about:
D1 -------!
ET
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.
On a sunny day (Mon, 16 Nov 2009 06:45:06 -0800 (PST)) it happened MooseFET wrote in :
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.
.3,
5,P8...
BTW re: LTM4625 -- 22uF cap required per output.
-- Cheers, James Arthur
ET
seF=3D
links shows.
To get the reactive elements small the PWM needs to go at a few MHz. The PIC doesn't have enough drive for that.
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
Dude, you've got the lab, and a marketing department - or at least, customers - why not just do it?
Good Luck! Rich]
how much current do you need?
seen the ADP2121?
the adp2109 looks similar but is available with 1.0,1.2,1.5,1.8V output
-Lasse
8...
ADP2121.pdf
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
We use LTC3411's a lot, tiny little MSOP-10 synchronous switchers. They are rated for 1.6 amps and are happy doing that. But they only work up to 5.5 volts in, so we use the LTM thing to get down from +12 to +3.3 and then let the tiny switchers take over for the lower stuff.
John
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