I am using my MCU to drive select lines of ten 74HC series multiplexers connected in parallel. Each select line presents a maximum capacitance of 10pF as per the datasheet. Which means the MCU pin has to switch a maximum of 100pF. The select lines switch approximately every 250us. In this case, do I need to have a buffer to drive the select lines or just the MCU pins will be able to drive this load adequately?
100 pF is still in a regular range and shouldn't cause problem. To reduce pin peak currents and power supply bounce, it would be a good idea to place a 50 to 100 ohm series resistor.