CAPACITANCE SENSING CIRCUIT
First Claim
1. A capacitance sensing circuit, comprising:
- an analog capacitance-detecting circuit configured to detect a touch capacitance of a touch panel when a touch action occurs according to a charging current and convert a detected value of the touch capacitance into a pulse width modulation (PWM) control signal;
a PWM-to-digital circuit configured to convert the PWM control signal into a sensing count value according to a clock signal; and
a self-calibration counter configured to adjust the charging current or the clock signal according to a difference between the sensing count value and a predetermined detecting range, thereby adjusting the predetermined detecting range for matching a range of the sensing count value.
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Accused Products
Abstract
A capacitance sensing circuit for a touch panel includes an analog capacitance-detecting circuit, a PWM-to-digital circuit and a self-calibration circuit. The analog capacitance-detecting circuit detects the capacitance of the touch panel based on a charging current, and converts the detected capacitance into a PWM control signal. The PWM-to-digital circuit converts the PWM control signal into a sensing count value based on a clock signal. The self-calibration circuit adjusts the value of the charging current or the frequency of the clock signal according to the difference between the range of the sensing count value and a predetermined detecting range. The predetermined detecting range can thus be adjusted for matching the range of the sensing count value.
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Citations
10 Claims
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1. A capacitance sensing circuit, comprising:
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an analog capacitance-detecting circuit configured to detect a touch capacitance of a touch panel when a touch action occurs according to a charging current and convert a detected value of the touch capacitance into a pulse width modulation (PWM) control signal; a PWM-to-digital circuit configured to convert the PWM control signal into a sensing count value according to a clock signal; and a self-calibration counter configured to adjust the charging current or the clock signal according to a difference between the sensing count value and a predetermined detecting range, thereby adjusting the predetermined detecting range for matching a range of the sensing count value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification