max232 heating problem

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niranjan23

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hello ....

I have some weird problem...that is my 8051 programmer board max232 ic is heating when I connect serially to PC to check serial communication by using hyper terminal......when I connect to my PC COM port(COM1) and when I try to type any thing on terminal window
I couldn't type any thing...and at the same time max232 IC is get heated extremely high.


I dont know what is the problem. I checked Voltage and they are same as below....also I checked my serial COM port pin and c51 serial pins ....
So please help me...in this...!!!

VCC: 5.09V
V+ : 9.3V
V- : -8.71V
 

The most probable cause is that you are not cross connecting the Tx/Rx lines and you have two outputs connected together.

Is it connected like

 

But my serial cable is ok...I tested and used many times....then how it is possible..??
 

niranjan23 said:
But my serial cable is ok
Click to expand...

What do you mean by that , what cable is that?
Was the MAX232 already connected to it or you made the connection now?

Basically I'm asking you that you have connected the correct pin of MAX 232 to the correct pins of the MCU and the RS232 plug.
A schematic of the connection you have used would help.
 

The charge pump must be working because it is boosting the +5V and generating the negative supply. That only leaves the data connections to check. Most likely you have the TX of the MAX232 connected to the TX of the RS232 lines. As both are drivers, if one is positive and the other negative, a high current will flow between them and cause heating. You should have the TX of one crossed over to the RX of the other. Also check the TX pins have not been shorted to ground.

Brian.
 

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