Hardware waterproof capacitive touch key BUF circuit

Abstract

A capacitive touch key is a common user interface device. A sensor judges whether a finger touch action exists or not by detecting the capacitance of a human body. Compared with a mechanical key, thecapacitive sensor is attractive in appearance, easy to use and long in service life. However, if a water film or water drops exist on the touch interface, the capacitance of the sensor is changed, andmistaken touch induction may occur. The invention provides a hardware waterproof capacitive touch key BUF circuit. The BUF circuit has the advantages of being simple in structure, low in power consumption and high in speed.

Description

technical field [0001] The invention belongs to the field of integrated circuit design and is used for the waterproof application of capacitive touch keys. Background technique [0002] Capacitive touch button is a common user interface device. The sensor judges whether there is a finger touch action by detecting the capacitance of the human body; compared with mechanical buttons, the capacitive sensor is beautiful in appearance, easy to use, and has a long life; Or water droplets will change the capacitance of the sensor, and false touch sensing may occur; the invention provides a hardware waterproof capacitive touch button BUF circuit, which has the characteristics of simple structure, low power consumption and fast speed. [0003] figure 1 It is the input signal of the hardware waterproof BUF. When the CHAR signal is high, VIN is charged to VDD. When the CHAR signal is low, the VIN signal is between 0 and VDD / 2; that is, the input and output voltage range of BUF is 0 ~V...

AI Technical Summary

Problems solved by technology

[0002] Capacitive touch button is a common user interface device. The sensor judges whether there is a finger touch action by detecting the capacitance of the human body; compared with mechanical buttons, the capacitive sensor is beautiful in appearance, easy to use, and has a long life; Or water droplets will change the capacitance of the sensor, and false touch sensing may occur; the invention provides a hardware waterproof capacitive touch button BUF circuit, the BUF circuit has the characteristics of simple structure, low power consumption and fast speed

[0003] figure 1 It is the input signal of the hardware waterproof BUF. When the CHAR signal is high, VIN is charged to VDD. When the CHAR signal is low, the VIN signal is between 0 and VDD / 2; that is, the input and output voltage range of BUF is 0 ~VDD requires BUF input and output rail-to-rail; while the input and output rail-to-rail operational amplifier structure is complex; BUF is used to drive waterproof electrodes, the waterproof electrodes have a large area and large parasitic capacitance, in order to improve the output response speed of BUF, improve The detection speed of the capacitive touch button requires a large slew rate of the BUF with a conventional structure, and a large slew rate means high power consumption; therefore, if a conventional BUF structure is used, it is necessary to design a BUF with a large slew rate and input and output rail-to-rail, Complex structure, high power consumption

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