MAX3232CPWR waveform issue

Jacky,

The ripple is normal.

The cause of the VOL ripple is based that the nominal target for the charge pump voltage (for the DOUT drivers) is -5.5V and two times VCC is 6.6V, therefore one cycle of boost gains significant voltage which is the sudden increase seen in the saw tooth ripple. Over time the voltage on the storage capacitor V- drains until a new cycle of boost is needed.

The same thing happens on V+, but it's a little worse because power needed for V- flows though V+ first.

If you would like to reduce the ripple, you can increase value of V+, C2, and V- capacitors. With V+ being the most important change. The idea is that less voltage is gained per cycle reduces ripple. 330nF is a good starting point.

Yes.