Hello,
to supply the -2.0 Volt termination voltage for 16 differential ECL channels from a 5 Volt supply, I dicided use a LT3479. The circuit is like the application sheet circuit "5V to ???5V/600mA Inverting DC/DC Converter", adapted to to -2.0Volt. However efficiency is bad, below 40 %. Simulation (scad data below) confirms this data.
What in the datasheet did I miss that this result dissapoints me? I must admit, I didn't simulate beforehand...
-- Uwe Bonnes snipped-for-privacy@elektron.ikp.physik.tu-darmstadt.de
Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ---------- Version 4 SHEET 1 1308 680 WIRE -192 80 -192 64 WIRE -192 176 -192 160 WIRE -128 64 -192 64 WIRE -80 160 -80 128 WIRE -80 304 -112 304 WIRE -80 304 -80 224 WIRE -64 304 -80 304 WIRE -48 384 -48 368 WIRE -48 480 -48 464 WIRE -16 64 -48 64 WIRE -16 128 -80 128 WIRE -16 128 -16 64 WIRE -16 176 -16 128 WIRE -16 240 -16 176 WIRE 16 176 -16 176 WIRE 16 240 -16 240 WIRE 16 304 0 304 WIRE 16 368 -48 368 WIRE 64 64 -16 64 WIRE 64 112 64 64 WIRE 176 112 176 64 WIRE 176 432 176 416 WIRE 192 64 176 64 WIRE 288 64 272 64 WIRE 288 112 288 64 WIRE 352 64 288 64 WIRE 352 368 336 368 WIRE 384 176 336 176 WIRE 384 192 384 176 WIRE 432 176 384 176 WIRE 432 240 336 240 WIRE 448 368 432 368 WIRE 448 384 448 368 WIRE 448 464 448 448 WIRE 464 64 416 64 WIRE 464 144 464 128 WIRE 480 176 432 176 WIRE 528 64 464 64 WIRE 592 176 544 176 WIRE 592 304 336 304 WIRE 592 304 592 176 WIRE 656 240 432 240 WIRE 656 288 656 240 WIRE 736 64 592 64 WIRE 736 80 736 64 WIRE 736 176 592 176 WIRE 736 176 736 160 WIRE 736 192 736 176 WIRE 736 288 656 288 WIRE 736 288 736 272 WIRE 848 64 736 64 WIRE 848 96 848 64 WIRE 848 192 848 160 WIRE 928 64 848 64 WIRE 928 80 928 64 WIRE 928 192 928 160 FLAG 448 464 0 FLAG 176 432 0 FLAG -112 304 0 FLAG -48 480 0 FLAG -192 176 0 FLAG 848 192 0 FLAG 928 192 0 FLAG 928 64 OUT FLAG -192 64 IN FLAG 464 144 0 FLAG 384 192 0 SYMBOL PowerProducts\\\\LT3479 176 256 R0 SYMATTR InstName U1 SYMBOL ind 176 80 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 5 56 VBottom 0 SYMATTR InstName L1 SYMATTR Value 4.7µ SYMBOL res 336 384 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 0 56 VBottom 0 SYMATTR InstName R1 SYMATTR Value 10K SYMBOL cap 432 384 R0 SYMATTR InstName C1 SYMATTR Value 1n SYMBOL cap 0 288 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C2 SYMATTR Value 10n SYMBOL res -64 368 R0 SYMATTR InstName R2 SYMATTR Value 17.8K SYMBOL voltage -192 64 R0 SYMATTR InstName V1 SYMATTR Value 5 SYMBOL schottky 592 48 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName D1 SYMATTR Value PMEG2020AEA SYMATTR Description Diode SYMATTR Type diode SYMBOL res 720 64 R0 SYMATTR InstName R3 SYMATTR Value 160k SYMBOL res 720 176 R0 SYMATTR InstName R4 SYMATTR Value 100k SYMBOL cap 832 96 R0 SYMATTR InstName C3 SYMATTR Value 10µ SYMBOL res 912 64 R0 SYMATTR InstName R5 SYMATTR Value 4 SYMBOL cap 416 48 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C4 SYMATTR Value 10µ SYMATTR SpiceLine Rser=0.01 SYMBOL schottky 448 64 R0 SYMATTR InstName D2 SYMATTR Value PMEG2020AEA SYMATTR Description Diode SYMATTR Type diode SYMBOL cap 416 176 R0 SYMATTR InstName C5 SYMATTR Value 100p SYMBOL schottky 480 192 R270 WINDOW 0 32 32 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName D3 SYMATTR Value BAT54 SYMBOL res -32 48 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R6 SYMATTR Value 0.1 SYMBOL cap -96 160 R0 SYMATTR InstName C6 SYMATTR Value 1m TEXT 518 346 Left 0 !.tran 10m startup TEXT 288 16 Bottom 0 ;LT3479 - 3A, 300KHz to 3.5MHz, Full Featured Step-up DC/DC Converter\\nInput: 5V Output: 12V at 0.8A TEXT -256 496 Left 0 ;Note:\\n If the simulation model is not found please update with the "Sync Release" command from the "Tools" menu.\\n It remains the customer's responsibility to verify proper and reliable operation in the actual application.\\n Component substitution and printed circuit board layout may significantly affect circuit performance or reliability\\n Contact your local sales representative for assistance. This circuit is distributed to customers only for use with LTC parts\\n Copyright © 2006 Linear Technology Inc. All rights reserved.