Presence of body sensing method for touch sensitive control panel of mobile phone, involves controlling drive part, signal and noise measurement parts to provide charge sensing circuit with measurement of signal in which noise is cancelled

摘要

The method involves coupling a signal measurement capacitor to a key during a signal measurement part of the measurement cycle to the effect that the charge induced on the key during the drive part of the measurement cycle is transferred to the signal measurement capacitor. An amount of charge induced on the key is determined from a noise measurement part. The drive part, the signal measurement part and the noise measurement parts are controlled to provide the charge sensing circuit with a measurement of the signal from which the noise induced on the key is cancelled. Independent claims are also included for the following: (1) an apparatus for sensing the presence of a body from a change in an amount of charge present on a capacitively charged key (2) a touch sensitive control panel including a key matrix.