The TMUX7208 and TMUX7209 have a transmission gate topology, as shown in Figure 8-1. Any mismatch in the stray capacitance associated with the NMOS and PMOS causes an output level change whenever the switch is opened or closed.

Figure 8-1 Transmission Gate Topology

The TMUX720x contains specialized architecture to reduce charge injection on the Drain (D). To further reduce charge injection in a sensitive application, a compensation capacitor (Cp) can be added on the Source (Sx). This will ensure that excess charge from the switch transition will be pushed into the compensation capacitor on the Source (Sx) instead of the Drain (D). As a general rule of thumb, Cp should be 20x larger than the equivalent load capacitance on the Drain (D). Figure 8-2 shows charge injection variation with different compensation capacitors on the Source side. This plot was captured on the TMUX7219 as part of the TMUX720x family with a 100pF load capacitance.

Figure 8-2 Charge Injection Compensation