best quick&cheap power supply inverter

Question

I have a +5V power supply and need to invert to a -5V supply sourcing about 25mA. I've got an LMC7660 running now. It's ok for the short term, it outputs -4.4V with 100mV p-p switching noise, but that's unacceptible for my long-term needs.

Anyone have any experience with LMC7660 / ICL7660 - like switched capacitor inverters? There must be some better parts on the market nowadays, we've had those LMC7660's in a drawer for at least 12 years. I can probably hunt something down, but figured I'd ask here.

Answer 1

I use the Analog Devices ADM660 which does about 100mA. Wasn't concerned with the switching noise in my application since I followed it with an LDO.

You could check out the LT1046 which also does 100mA. The ICL7660S looked interesting.

Your best bet is probably the Linear Technology site. If you can get one of the 100mA devices you may able to get an adjustable LDO to remove the switching noise. For the LTC660 the graph show -4.8V at 30mA. That gives you a few hundred mV of dropout at 30mA.

Answer 2

After looking around I think I'm going to use a TPS60403, it's got a higher switching frequency (250kHz) than the LMC7660.

Answer 3

You can do it with a 4009 and a few capacitors and diodes. I have to do this when using the ICL7107 chip - I've copied the circuit to here for you. http://www.flickr.com/photos/tronixstuff/4474249137/ However, you might get a bit less than -5V