getting -5V

[Arakon]

are there voltage regulators or circuits that can get -5V out of +5V?
that way the jamenco PSU could work for i.e. midway boards too.

 

[Electroman]

Absolutely. What kind of current do you require?

There are a few ways to develop a -5V.

1.) Charge pump. Any 7660 can do that for you. You may find numbers like LM7660, ICL7660, TC7660, they are all the same. 7661, 7662 are just like them but accept higher voltages.
Each 7660 require 2 capacitors. Good for currents < 20mA.

<a href="http://www.digikey.com/scripts/us/dksus.dll?Detail?Ref=141764&Row=349224" target="_blank">http://www.digikey.com/scripts/us/dksus.dll?Detail?Ref=141764&Row=349224</a>

2.) Inductive inverting switching regulator. You would use this if you needed > 20mA of current. These are often more complicated but work well and easily enough.

3.) If you have a clock pulse (preferably 50/50% duty cycle) you can handmake a charge pump with 2 diodes and 2 capacitors.

I use devices like this all the time, its part of what I do. Hell I can prob just draw you a schematic and hook you up something for ya if you want.

 

[Arakon]

the jamenco PSU outputs 4A on the 5V line.. I'd need -5V at 0.5-0.8A, while of course keeping enough power for the 5V line to run the PCBs too.

 

[RiotoftheBlood]

Look into NTE957. I picked up a few of these for one of my coworkers earlier this week - he is using it in a circuit to supply -2V, although it can supply a wide range of negative output voltages. It can supply 1.5 A. Sounds ideal for what you need, although I'm not certain of exactly what is supposed to be on each pin. I'll ask him on Monday...

<a href="http://www.nteinc.com/specs/900to999/pdf/nte957.pdf" target="_blank">http://www.nteinc.com/specs/900to999/pdf/nte957.pdf</a>

 

[ttooddddyy]

Easiest way to do it, on the jamenco smps 5 volt secondary connect a rec diode "backwards" to derive the negative voltage.


Im assuming the 4 amps +5 volts on the psu is more than adequate for that supply rail ???

<small>[ September 06, 2003, 06:01 PM: Message edited by: ttooddddyy ]</small>

 

[ttooddddyy]

bump

 

[Arakon]

I don't know that much about voltage generation.. could you give some more details?
the 4A are plenty to drive most arcade boards.