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toalan
- 15th February 2005, 20:00
hi guys I need to get a -5V power rail from a +5V rail, any ideas as to which IC can do the job cheaply?

Regards,

Alan To

mister_e
- 15th February 2005, 20:17
why you need it? for an op-amp or else. Some dc to dc converter will do the job but they're not cheap. you can build something with one 555 ... that's working.

see those links
http://www.electronics-lab.com/projects/power/023/

OR with a simple circuit modification, if your PIC have a extra PWM output you can use it as pulse generator instead of the 555 ;)

NavMicroSystems
- 15th February 2005, 20:51
toalan

an ICL7660 would do the job @ low cost & minimal part count.

see: Datasheet (http://www.intersil.com/data/fn/fn3072.pdf)

If you have a MAX232 on Board and there is a driver spare (like it would be with the BootLoader)
you could even use this spare driver to generate +/- 12V

toalan
- 15th February 2005, 21:23
Sweet that is exactly the IC I am looking for, cheap and minimal parts. yes it is for OPAMPs, I was using an external battery to provide the negative voltage, this make my circuit much less ugly.
You guys rock. Thanks a bundle.

NavMicroSystems
- 16th February 2005, 02:13
Yet another problem solved ;-)

toalan
- 23rd February 2005, 18:35
I also used the Max232 to generate the -ve voltage I need. Thanks again Nav for pointing me to 2 possible solutions.