LDO

John Larkin · 2016-10-12T05:09:59+00:00

I need to make 1.5 volts (for DDR3 ram) from a 1.8 rail, and it was easier to just do it from available parts than find a new regulator to buy. Loop comp is the first wild guess, but it looks fine. At 0.3 volts drain-source, the mosfet is acting like a variable resistor. Version 4 SHEET 1 1080 680 WIRE -48 -32 -144 -32 WIRE 336 -32 256 -32 WIRE 512 -32 336 -32 WIRE -144 -16 -144 -32 WIRE -48 0 -48 -32 WIRE 512 16 512 -32 WIRE -240 128 -272 128 WIRE -112 128 -176 128 WIRE 0 128 -32 128 WIRE 256 128 256 -32 WIRE 512 128 512 96 WIRE -144 176 -144 64 WIRE -432 192 -464 192 WIRE -384 192 -432 192 WIRE -272 192 -272 128 WIRE -272 192 -304 192 WIRE -176 192 -272 192 WIRE 0 208 0 128 WIRE 0 208 -112 208 WIRE 48 208 0 208 WIRE 208 208 128 208 WIRE -176 224 -272 224 WIRE -432 272 -464 272 WIRE -384 272 -432 272 WIRE -272 272 -272 224 WIRE -272 272 -304 272 WIRE 256 288 256 224 WIRE 400 288 256 288 WIRE 448 288 400 288 WIRE 496 288 448 288 WIRE 656 288 576 288 WIRE 800 288 656 288 WIRE 848 288 800 288 WIRE 880 288 848 288 WIRE -272 304 -272 272 WIRE -144 304 -144 240 WIRE 656 320 656 288 WIRE 448 336 448 288 WIRE 800 336 800 288 WIRE -272 448 -272 384 WIRE 448 464 448 400 WIRE 656 464 656 400 WIRE 800 464 800 416 FLAG 448 464 0 FLAG 400 288 OUT FLAG 512 128 0 FLAG -48 0 0 FLAG -432 192 OUT FLAG -272 448 0 FLAG 800 464 0 FLAG 656 464 0 FLAG 848 288 LOAD FLAG -144 304 0 FLAG 336 -32 1.8 FLAG -432 272 1.8 SYMBOL cap 432 336 R0 WINDOW 0 -77 13 Left 2 WINDOW 3 -79 45 Left 2 SYMATTR InstName C2 SYMBOL voltage 512 0 R0 WINDOW 0 56 41 Left 2 WINDOW 3 54 80 Left 2 SYMATTR InstName V1 SYMATTR Value 1.8 SYMBOL Opamps\UniversalOpamp2 -144 208 R0 WINDOW 0 73 45 Left 2 SYMATTR InstName U1 SYMATTR Value2 Avol=1Meg GBW=8Meg Slew=10Meg SYMBOL res 144 192 R90 WINDOW 0 76 52 VBottom 2 WINDOW 3 84 52 VTop 2 SYMATTR InstName R2 SYMATTR Value 22 SYMBOL voltage -144 80 R180 WINDOW 0 55 81 Left 2 WINDOW 3 56 50 Left 2 SYMATTR InstName V2 SYMATTR Value 5 SYMBOL res -288 176 R90 WINDOW 0 -51 51 VBottom...

Oct 12, 2016 42 Replies

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Jim Thompson 9 years ago

In LTspice the "solver" is an extra issue besides choosing a time-step. ...Jim Thompson

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John Larkin 9 years ago

I just got an eval board for the Linear LT8602, which is a cute quad synchronous switcher. It seems to work fine. It's interesting that they intend two of the outputs to run off the prime DC source, and two others to run off one of the switcher outputs.

My production people dislike QFN leadless packages, so the TI TPS54302 is still appealing.

John Larkin Highland Technology, Inc lunatic fringe electronics

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Tim Wescott 9 years ago

I worked with a pretty good control engineer (helped to hire her, actually) who started out in economics, got interested in control (they teach control theory in economics degree programs), and finished up her PhD in applied math.

Tim Wescott Wescott Design Services http://www.wescottdesign.com I'm looking for work -- see my website!

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