Cytron Technical Forum

According to datasheet, it states that the charge pump capacitor of max232 circuit are 1uF. Just wondering does the capacitance affect the performance of the IC i.e capacitance would give a voltage level of +-10V instead of +-12V, or affects the baud rate (gives problem at high baud rate), or problems at high frequency?

just a noob question

Does this question has any connection with your "ZigBee communication" problems?

Allen

I have Zigbee in my project but this is for the barcode scanner. And this is more to understand the operation and performance of the max232. So does is affect? Because bigger capacitance will take a longer time to charge.

In the datasheet, it's shows 1uF. I'm use 10uF, since now no problem yet. I have tried to high baudrate also, it's still ok. I'm not testing for the performance, since it's working.

I tried using 0.1uF C-Cap as well and got no problem

nicholaswsw WROTE:I have Zigbee in my project but this is for the barcode scanner. And this is more to understand the operation and performance of the max232. So does is affect? Because bigger capacitance will take a longer time to charge.

MAX232 was designed to replace the older 74188 & 74189 chips. If using 74188/189 pair, the +/-12V is supplied by the circuit designer which complicates the power supply design. MAX232 came out to simplify RS232 (V24I) for the MCU user. So performance wise, I would guess it is a compromise of the older design.

All the RS232 interface cards in my office equipments uses 74188/189 pairs because our terminals (PC) and the RS232 servers racks are very far apart. If I remembered correctly, I have connected a RS232 terminal 50M away from the RS232 server card and still worked.

I am not sure how far can a MAX232 serial interface work at 9600 bauds.

Allen