US 7,843,249 B2Granted

Adaptive capacitive touch sense control circuit

AssigneeChiphomer Technology Limited

InventorsZhong Zhang, Jiantao Cheng, Ke Wu, Chaoqun Wu

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Abstract

An adaptive capacitive touch sense control circuit includes a voltage buffer, a current setting resistor, a current mirror, a capacitor, a start comparator, an end comparator and a time-to-digital converter. The capacitor is connected with the current setting resistor. The circuit further includes a latch with a first control switch and a second control switch. The current setting resistor is switched between the ground and a voltage source through a switching element, so that when the current setting resistor is grounded, the first control switch is closed and the second control switch is opened, and when the current setting resistor is connected with the voltage source, the second control switch is closed and the first control switch is opened. An adaptive charging mode is adopted to sense a capacitance variation with a great ability of interference recognition, a simple structure, low power consumption and real time processing.

Claims12

Dependent claims

An adaptive capacitive touch sense control circuit, comprising a voltage buffer, a current setting resistor, a current mirror, two capacitors, a start comparator, an end comparator and a time-to-digital converter, with the voltage buffer being connected with the current setting resistor and the current mirror, the two capacitors being connected with the current mirror, the start comparator and the end comparator, and the start comparator and the end comparator being connected with the time-to-digital converter, wherein one of the two capacitors is connected with the current setting resistor;

the control circuit further comprises a latch provided with a first control switch between the capacitor and the current mirror and between the voltage buffer and the current setting resistor and a second control switch between one of the two capacitors and the current setting resistor, the latch is connected with the first control switch;
and the current setting resistor is switched between ground and a voltage source through a switching element, so that when the current setting resistor is grounded, the first control switch is closed and the second control switch is opened, and when the current setting resistor is connected with the voltage source, the second control switch is closed and the first control switch is opened.

Dependencies are inferred from the claim text.