this is just a quick and dirty question. I don't understand the purpose of the 1 \$\mu\$F caps in the MAX232 circuit. What do they do, exactly? Can they be skipped? Can they be swapped with 10 \$\mu\$F caps?
Electronic – use 10\$\mu\$F caps in a MAX232
max232rs232
Related Topic
- Electronic – Why MAX232 works without any capacitors
- Electronic – arduino – Voltage level too low for MAX232
- Electronic – arduino – Problems with homemade RS232-to-TTL converter board based on TI’s MAX232
- Electronic – RX/TX LED for MAX232
- Electrical – use a MAX232 to communicate between a PIC and a Raspberry Pi
- Electronic – Can a MAX232 IC be used for RS-232C standard
Best Answer
They're definitely required! For their function look at the block diagram
You'll see that they're connected to the voltage doubler and voltage inverter. These create +10V from the 5V power supply and -10V resp. This is done by charge pumps.
An oscillator will control the switches so that either S1 and S3 are closed or S2 and S4. When S1 and S3 are closed C1 is connected to ground and V+ and charged to V+. When S2 and S4 are closed the top of C2, which is V+ higher than the bottom is connected to ground, so that the bottom now is V+ below ground. Via the switches the charge flows to C2, which will then have a negative voltage. So that's for the inverter. The same principle is used to double the incoming voltage.
C1 and C2 are the external 1\$\mu\$F capacitors. If they're omitted there won't be any +10V or -10V and no signal at the drivers' outputs.
In its datasheet Maxim recommends 1\$\mu\$F for the MAX232, 100nF for the MAX232A. I wouldn't recommend using 10\$\mu\$F instead of the 1\$\mu\$F. The switches might have some resistance and the capacitor may not get fully charged in the time one pair of switches is closed.
edit
In a comment to another answer which said 10\$\mu\$F will probably be OK someone said:
He didn't say, but it looks like he used 10\$\mu\$F. If you use the recommended value of 1\$\mu\$F you should get \$\pm\$10V. The 7V seems to confirm my doubts about the charging of the larger capacitors.