Patent ID: 7075523

Claim:
Apparatus for use with a first number of sensing electrodes of a human-input touch pad, the apparatus comprising: a sampling capacitor having first and second leads; potential measurement means electrically connected with the sampling capacitor; and a multiplexer; the multiplexer comprising: a first switching stage comprising switches fewer in number than the first number, and comprising more than one switch, the switches having first ends electrically connected with the first lead of the sampling capacitor; a second switching stage comprising groups of switches, each group corresponding to a respective second end of a switch in the first stage, each group comprising more than one switch, the switches in each group having first ends electrically connected with the respective second end; a third switching stage comprising groups of switches, each group corresponding to a respective second end of a switch in the second switching stage, each group comprising more than one switch, the switches in each group having first ends electrically connected with the respective second end; each switch in the third switching stage having a second end electrically connected with one of the sensing electrodes.