quick max232 question

[jrz126]

Is it possible to obtain a -12V supply (or close to it) from a max232?
Alex_rcpilot posted this image here where he obtained a +13V supply to use for programming PIC's.


Is it possible to get a -12v output? I'm trying to build a PID controller and there is an opamp that requires a +/-12 supply.

 

[Nigel Goodwin]

The output from a MAX232 is usually about +/-10V or so, the circuit above looks to have an extra voltage-doubler to give it more.

The current availability from a MAX232 is only low, how much do you need?, and how critical is the voltage?. Is your only available supply rail 5V?, if you have a higher rail it would be easier to generate a -12V rail.

 

[jrz126]

I only have a +12V supply and I need a +/-12V and a +5V.
I dont think there will be that much of a draw on the -12V supply. Its only used for the neg. supply rail of an op amp. So I have alittle play in the voltage levels (I think)

 

[jrz126]

Looking over the schematic some more, they do pull the -12V supply from the max232. Comes off of pin 6.

 

[Oznog]

I only have a +12V supply and I need a +/-12V and a +5V.
I dont think there will be that much of a draw on the -12V supply. Its only used for the neg. supply rail of an op amp. So I have alittle play in the voltage levels (I think)

Depends on what the op amp is driving. The output current comes from the - supply when the output is below ground.