LT1010 rail splitter not splitting

Fibo · 2014-09-17T14:52:06+00:00

Hello, I'm trying to use the LT1010 to make a +/- 2.5V rail out of a 5V sup ply. There's a simple circuit for this in the datasheet, but I wired it up, two 100K resistors in series and the center going into the LT1010... In this configuration the input is 4.3V (where I expected 2.5V)??? I spiced it and got a 3.28V at my input? Thanks! I'm using a small RECOM for my 5V supply LTSPICE: Version 4 SHEET 1 880 680 WIRE 64 16 -80 16 WIRE 144 16 64 16 WIRE 64 64 64 16 WIRE -80 128 -80 16 WIRE 144 160 144 16 WIRE 64 192 64 144 WIRE 128 192 64 192 WIRE 288 192 192 192 WIRE 384 192 288 192 WIRE 288 224 288 192 WIRE 64 240 64 192 WIRE 384 240 384 192 WIRE -80 336 -80 208 WIRE 64 336 64 320 WIRE 64 336 -80 336 WIRE 160 336 160 224 WIRE 160 336 64 336 WIRE 288 336 288 304 WIRE 288 336 160 336 WIRE 384 336 384 304 WIRE 384 336 288 336 WIRE 64 352 64 336 FLAG 64 352 0 SYMBOL Opamps\LT1010 160 128 R0 SYMATTR InstName U1 SYMBOL res 48 224 R0 SYMATTR InstName R1 SYMATTR Value 100k SYMBOL res 48 48 R0 SYMATTR InstName R2 SYMATTR Value 100k SYMBOL voltage -80 112 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 5V SYMBOL res 272 208 R0 SYMATTR InstName R3 SYMATTR Value 10k SYMBOL cap 368 240 R0 SYMATTR InstName C1 TEXT -114 376 Left 2 !.tran 1

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rickman 11 years ago

I looked at the numbers and even the TLE2426 would have been shoehorned into the existing board. The present circuit is a zener and resistor (both 0603 I believe) without a cap because there is no room. The TLE2426 could actually be a 3 pin part so maybe a plain jane SOT-23 would be better or preferably a SC-70. Jeeze, sometimes I have nightmares about having to rework that board. It was like a jigsaw puzzle with *extra* pieces and I had to make them all fit!

Adding an SO16 would mean I'd have to replace the FPGA!

I did a bit of a search and I don't see where anyone else makes such a part. Interesting. I guess it was a niche that just one maker could fill well enough.

Rick

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Phil Hobbs 11 years ago

I think that's right. It's really a convenience part more than anything. (And of course the TCA0372 runs warm to the touch just from its quiescent current.)

Cheers

Phil Hobbs

Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net

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John Larkin 11 years ago

What? WHAT? Speak up, young man!

John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com

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bloggs.fredbloggs.fred 11 years ago

Nobody said the part was an unqualified ridiculous, the original statement was that as a standalone part it's ridiculous.

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josephkk 11 years ago

I wasn't aware that it may be a mooo'ving target.

?-)

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John S 11 years ago

When the nurse finished giving me a hearing test a couple of weeks ago, she made a comment that I did not understand. I said What? and she looked at me in disgust. I suddenly realized what she was thinking.

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Phil Hobbs 11 years ago

I understood, but didn't entirely agree. One wouldn't design a product that way, for sure, but from the OP's choice of parts, I expect this is a one-off and they're what he has in his drawer. For that sort of thing I wouldn't hesitate to use it myself--the LT1010 would work fine for many applications.

I still use a bunch of LF356es in one-offs, because they work fine and I have a couple of hundred of them.

Cheers

Phil Hobbs

Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net

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Phil Hobbs 11 years ago

Well, he and I do a lot of physicsy stuff, so it's important to choose the right sleazy approximations.

Cheers

Phil Hobbs

Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net

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John Larkin 11 years ago

Your new diet is threatening the calibration of the LPMU.

John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com

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Phil Hobbs 11 years ago

My local gravity decreased by about 12% to date. Gravitas is still mostly absent, and my Bubba impression has gone all to hell. ;)

I call it the P. G. Wodehouse diet--laying off the starchy foods.

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Cheers

Phil Hobbs

Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net

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John Larkin 11 years ago

Fabulous stuff. Nobody could write like Wodehouse.

Another good diet book is "Something New"

John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com

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rickman 11 years ago

Was the name Ratched by any chance?

Rick

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LT1010 rail splitter not splitting

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