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Home > Products > 8 bit M8051 Core > Touch MCU

Touch MCU

Description

ABOV’s touch switch series are 8 bit MCU with internal capacitive touch sensor. There are two types of capacitive touch switch ‘Self-capacitive’ and ‘Mutual capacitive’.

Types of capacitive touch switch
Self-capacitive method uses a changing of capacitance of RC-oscillator by touch. When the capacitance of RC-oscilaotr is changed the oscilator’s frequence also changed. So it is possible to recognize the touch event by monitoring the frequency changing.
Mutual capacitive method uses a changing of mutual capacitance between closed tx/rx pads. When the human body is close to the tx/rx pads it changes local electronic field which reduces the mutual capacitance between tx/rx pads. And by reduced mutual capacitance the received pulse signal is also reduced when the pulse signal is transmitted from the tx pad to the rx pad. So it is possible to recognize the touch event by monitoring the voltage of pulse signal at the rx pad.

Sensitivity
Sensitivity of capacitive touch switch is directly affected by the touch PAD's size and the overlay-block’s (case’s) material and thickness. So it is important to choose those properties. And it is possible to tune the sensitivity by firmware. So bigger step size (of sensitivity) is an advantage to tune the sensitivity.

Rom type description

COMBI

FLASH

OTP

MASK

Calibration
Touch switch is very affective from ambient environment like operating voltage, temperature, humidity, closed conductor, noise and wet-surface (it directly changes the capacitance). So there is auto-calibration hardware what makes it can adapt to the changing of the ambient environment. But when the ambient environment is sharply changed it can’t adapt to the environment well. So in that case it is required to do the manual calibration by firmware.

Etc.
There are more considerable facts to choose a touch IC like number of channels, power consumption, noise tolerance and communication channel with host system.

Because of that it is a 8051 compatilbe MCU, every 8051 C compilers can be used such as Keil-C or SDCC.