Patent ID: 8896325

Claim:
A capacitance sensing circuit, comprising a capacitive device having a capacitance; said capacitance sensing circuit being capable of applying in an initialization phase a pull-up current to said capacitive device, said capacitive device initially being at a first voltage level; measuring an initialization period of time for changing said first voltage level into a second voltage level by means of said pull-up current; determining a pull-up voltage level as a voltage level present at said capacitive device after a fraction of said initialization period of time; applying in a measurement phase said pull-up current to said capacitive device, said capacitive device initially being at said first voltage level, during a pull-up period of time, for changing said first voltage level into said pull-up voltage level; applying a measurement current to said capacitive device, said capacitive device being at said pull-up voltage level; and measuring a measurement period of time, during which said pull-up voltage level changes into said second voltage level by means of said measurement current.