I'm having a heck of a time getting the MAX3232 on my board to operate correctly. I've attached a snippet of my schematic and screen shots of all the relevant pins. I'm not sure what the C+/- pins are supposed to look like, but I can certainly see a lot of ripple on the V+ and especially V-. The RS232 output has the data I expect basically modulated with this ripple. My terminal will display the correct character about 80% of the time but the other 20% is garbage.
I've checked and replaced the 0.1UF capacitors
I've checked the ground connection to the PC
I've checked that VCC looks pretty clean
I've| checked my schematic and layout symbol for errors.
I've checked multiple boards (I doubt the part is bad)
The one thing that I did see was that in my layout the V+ and V- caps are connected through fairly small vias which may be causing series inductance. However I was able to solder on caps to the pins on the chip to bypass these inductors and the same problem occurred.
Note that the images I'm supplying are with the serial connection connected. If I open it up I still see the ripple, but it's a lower frequency (maybe a clue)
I've used these types of chips plenty of times before without any problem, I'm pretty stumped here.
Thanks,
Oops, when I originally posted I though I could update files. I'll just describe what I'm seeing: On my V- line a see -6 volts with about 2 volts of saw-tooth on top of it. I also see this saw-tooth on my data.
Hello,
I would verify your capacitor values, they depend on the level of your Vcc. On page 7 of the data sheet it specifies the different capacitor values you should use.
Regards,
Robert Regojo.