Problem with using MAX3222 as UART to RS232 converter

[girish_wabale]

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.....

 

[Gorgon]

max3222, 1uf

Have you tied the /shutdown pin to Vcc? If left floating you can get different results based on the small variations from component to component.

The charge pumps is shut down when this input is low.

TOK

 

[girish_wabale]

Re: PROBLEM IN MAX3222

I have tied shutdown to VCC but still it is not working

 

[Gorgon]

Re: PROBLEM IN MAX3222

What sort of power do you use for supplying 5V to the circuit? If it is not low impedance, it may work against the charge pump.

Have you tried to prototype this circuit, and did it work then? If it did and the circuit is the same, what else is changed in the transfer to a pcb?

TOK

 

[girish_wabale]

Re: PROBLEM IN MAX3222

I am using 3 V Batteries ....I have tried with same board I made 15 Boards in that 5 are working and only problem is -ve Reg voltage is not generating

 

[siongboon]

Re: PROBLEM IN MAX3222

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.


**broken link removed**