Vasile Surducan wrote...
>Yes, but not with only one doubler !
>I had working with a family member of 232, max 3232
>and have unpleasant surprise to have only -5V and +8V at outputs.
>This means, a doubler is not enough for +20V

Interesting. I decided it might be worth doing some quick
measurements.

I have an Analog Devices ADM202 in a PIC circuit right here beside
me. With a 5.00V supply, 0.1uF caps and absolutely no load it is
producing +9.83V and -9.62V (19.45V between outputs).

When I connect it to the RS232 port of a PC it drops to +9.00V and
-7.90V (total 16.90V) with a 4.90V supply. No comms taking place.

The supply dropped to 4.90V because on this board I have a 22R
resistor and 100uF cap decoupling the 5V rail to (hopefully) prevent
noise from the charge pump getting into a radio receiver on the
same supply rail.

Brent Brown
Electronic Design Solutions
16 English Street
Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile/text: 025 334 069
eMail:  brent.brown@clear.net.nz

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