Patent ID: 7830158

Claim:
For use in a device for measuring capacitance provided at an electrode, relative to a reference node, by applying electrical charge to the electrode to ramp voltage signals between first and second reference voltage levels over multiple ramp cycles initiated in synchronization with clock cycles, the capacitance being proportionate to the cumulative whole number of clock cycles counted during voltage signal ramping over the multiple ramp cycles, a method comprising, upon reaching one of the reference voltages during a present ramp cycle at a time t 1 during a terminal clock cycle: relative to one of the first and second reference voltage levels, adjusting a starting voltage level for a subsequent ramp cycle by an amount to compensate for incremental voltage ramping that occurs from the time t 1 to the end of the terminal clock cycle; and adjusting the number of clock cycles counted during the present ramp cycle depending on the adjusted starting voltage of the subsequent ramp cycle.