I am using MAX3222 as UART -RS232 convertor ..
I am using stanserd ckt given in the datasheet but it is not generating -ve ref voltage .
I have made lot of boards some of them are working but not everyone.
I am using charge pump caps of 100nf ihave tried with 1uf non polarised cap but not geiitng same board working..
for ESD i have taken precausions but still it is not working...
Can enybody tell me possible causes.....
Since you have successfully fabrication board using MAX232,
You might want to test if it is the problem of IC or PCB board.
Sometimes, IC can be faulty.