Proximity Detection

Abstract

In certain embodiments, an apparatus includes a sensing element having a capacitance to a first reference voltage. The capacitance is variable as a function of a proximity of an object to the sensing element. The apparatus further includes a sample capacitor connected to the sensing element and control circuitry connected to the sample capacitor. The control circuitry is configured to supply a charge to the sample capacitor and the sensing element and discharge the sensing element. The control circuitry is further configured to provide, in response to the discharge of the sensing element, a signal indicative of the capacitance to the first reference voltage of the sensing element. The control circuitry is further configured to process the signal to detect a change in the capacitance to the first reference voltage as indicative of the proximity of the object to the sensing element.

1 . An apparatus, comprising:
 a sensing element having a capacitance to a first reference voltage, the capacitance being variable as a function of a proximity of an object to the sensing element;   a sample capacitor connected to the sensing element; and   control circuitry connected to the sample capacitor, the control circuitry configured to:
 supply a charge to the sample capacitor and the sensing element; 
 discharge the sensing element; 
 provide, in response to the discharge of the sensing element, a signal indicative of the capacitance to the first reference voltage of the sensing element; 
 process the signal to detect a change in the capacitance to the first reference voltage as indicative of the proximity of the object to the sensing element, 
   wherein the control circuitry comprises a first switching element, a second switching element, and a third switching element, each switching element having a respective open state and a respective closed state, the control circuitry further comprising an analog comparator, wherein:   the first switching element is configured to connect the sample capacitor to the first reference voltage in the closed state;