Question about MAX232

Hi, I have some questions about a IC i'm trying to connect to my standalone Arduino. (No Arduino board)

This is the datasheet: http://www.ti.com/lit/ds/symlink/max232.pdf

My question is to do with the pins. Please can someone confirm if I have the pins correct, and inform me on some of the pins I don't know.

Pin 16: This is the power that provides 5 Volts with a capacitor to help with power issues on the line.
Pin 1 & 3: Capacitor
Pin 3 & 5: Capacitor
Pin 11: Arduino TX pin (outbound data)
Pin 10: Ground - I only need 1 serial for this project.
Pin 12: Arduino RX pin (inbound data)
Pin 9: Ground - I only need 1 serial for this project.
Pin 2: ??? On the datasheet it says the chip can run on 5volts - what is this for?
Pin 6: ??? On the datasheet it says the chip can run on 5volts - what is this for?
Pin 14: Computer RX line (inbound data for computer)
Pin 13: Computer TX line (outbound data from computer)
Pin 15: Ground.

Please can you guys check if this looks correct, and let me know what you think?

Cheers,

Cameron.

chip.png

Positive output supply voltage range, VS+ . . . . VCC ? 0.3 V to 15 V
Negative output supply voltage range, VS? . . . . ?0.3 V to ?15 V

Pins 2 & 6 are the output of charge pump that makes the +/-8.5 to +/-10V supply voltage for input & output buffers. RS232 signals can swing from +/-3V to +/-25V.

Maxim's MAX232 datasheet explains it much better than TI's - TI seems to have gone really minimalistic compared to what they put out in the mid 80's when I started work with a fresh BSEE.

http://datasheets.maximintegrated.com/en/ds/MAX220-MAX249.pdf

Hi, CrossRoads,

Thank you for your response. I have a few questions (sorry for being dumb I just don't know enough about EE)

Pin 16 the input voltage? So, it can take anything from -0.3 volts to 15 volts. So 5 volts would be okay?

I'm lost on what a charge pump is? Does that mean I have to have 8.5 volts running to that chip?

Sorry for all the questions,

Cameron.

16 is 5V input, yes.
Pins 2 & 6, are not inputs - they are internal voltages that need an external cap.
Do not connect anything but a cap on these pins.

You can read more about charge pumps here

Hi, CrossRoads,

Thank you for your reply. So how would you wire the physical connections for pin 2 and pin 6? I know now (thanks to your help) that they need capacitors, but would I wire them together with capacitor each? (the diagram is not that clear)

Also, did my other pins look correct? And should I connect the GROND from my computers serial cable to my ground on my Arduino?

Thank you so much for your help.

Yes, capacitor on pin 2 to Gnd, and capacitor on pin 6 to Gnd. Pin 2 and 6 do not connect tp each other.
PC Gnd connects to Arduino Gnd.
Rest looks good.

You'd da man, CrossRoads.

Thank you so much!

Cameron.

No problem. Good luck.

You can see how I wired up a MAX232 to communicate with 2 ATmega328Ps here


I added some jumpers to allow disconnect of the Rx to the '328Ps in case I wanted to use the input for something else.

The max232 includes a capacitive "voltage doubler" circuit to get approximately 2Vcc, and a capacitive "voltage inverter" to get approximately -(2Vcc) from that. C1 and C2 (from your diagram) are the capacitors "inside" the voltage doubler/inverter, and C3 and C4 are essentially the "output smoothing capacitors" for those two supplies (so they go between the "outputs" of the converters and Gnd.)

Pin 16 is the POWER SUPPLY for the chip (up to 6V, but 5V "nominal"), which is not the same as the inputs (spec'ed at -0.3 - 15V)

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