Dual Vout Supply Chip

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NV185864
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Dual Vout Supply Chip

Post by NV185864 » Tue Mar 21, 2006 2:46 pm

I've sucessfully built a video amplifier using the
LT1193. Now I want to put the +5V and the -5V on the same board with a ~12VDC input. Does anyone have a good transformerless buck circuit for this task?
Oh by the way I just used the circuit shown in the application information part of the LT1193 data sheet.

Engineer1138
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Re: Dual Vout Supply Chip

Post by Engineer1138 » Tue Mar 21, 2006 3:07 pm

Can you use a 7805 and a charge pump (7660) to get the -5V?

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Chris Smith
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Re: Dual Vout Supply Chip

Post by Chris Smith » Tue Mar 21, 2006 4:20 pm

You can use a voltage divider to get your plus and minus voltages as long as its not tied to the rails.

Robert Reed
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Re: Dual Vout Supply Chip

Post by Robert Reed » Tue Mar 21, 2006 5:35 pm

Geo
Digikey and Mouser carry a variety of DC-DC converter chips. If your power requirements are lo, you might want to browse thru their listings. Small and simple but may be a little pricey for your project The nice thing is they require no external components.

NV185864
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Re: Dual Vout Supply Chip

Post by NV185864 » Wed Mar 22, 2006 6:26 am

I couldn't find any DC-DC converters with enough output current. I need + 100mA - 100mA.
The 7805 / 7660 looks like it will work. That is if I can figure out how to use the 7660. At first blush it looks very simple. With two 10uF caps and +5V in I get -5V out? What about the switch to ground from pin 6?

Engineer1138
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Re: Dual Vout Supply Chip

Post by Engineer1138 » Wed Mar 22, 2006 12:23 pm

It looks like the pin 6 connection is only if your input voltage is below 3.5V. I don't remember it being there from my use of the older versions of the 7660, but the Maxim version at http://pdfserv.maxim-ic.com/en/ds/ICL7660-MAX1044.pdf shows it.

I don't think you can get 100mA from a 7660 though. I believe they are limited to about 25mA since they're designed for opamp supplies and the like.

cato
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Re: Dual Vout Supply Chip

Post by cato » Wed Mar 22, 2006 2:21 pm

Ask the guy that sold you the LT1193. Linear Tech makes lots of power supply chips. 1054 sounds like one that will flip a 5V input to -5V...

<small>[ March 22, 2006, 02:22 PM: Message edited by: cato ]</small>

sagitarius867
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Re: Dual Vout Supply Chip

Post by sagitarius867 » Sat Mar 25, 2006 8:01 am

u can use 7812 and 7912 to get +/- 12V DC output
yours shiva

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Re: Dual Vout Supply Chip

Post by sagitarius867 » Sat Mar 25, 2006 8:05 am

or u can use a clamping network to convert 12 to 5v, simple few resistors
yours shiva

NV185864
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Re: Dual Vout Supply Chip

Post by NV185864 » Tue Mar 28, 2006 1:29 am

LT1193 looks good. I'll post my finished design when complete. Thanks for the help.

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