MAX3221: whether we have 200kHz charge pump

Amelie,

The charge pump circuitry used for our RS232 devices has a charge pump switching frequency of about 100kHz ~ 200kHz. 

If you look at the blue markings on this oscilloscope capture, you can see the switching effect occurring between the flying capacitor dumping charge into the storage capacitor to generate higher voltage potentials. This switching rate occurs at around 100kHz ~ 200kHz. 

The red is the regulator period where charge on the storage capacitor dissipates through the load. The regulator period is determined by capacitance and loading on the output.

For more in depth information about this topic, please see the charge pump blog post here.

Regards,

Tyler