BU21051FS Datasheet, PDF (3/7 Pages) Rohm – Capacitive Sensor Switch Control IC

BU21051FS
●Block Diagram, Pin configuration
Technical Note
●Sensor I/F CV Conversion Circuit:
This part selects target sensor and converts its capacitance to a voltage signal. Specifically, alleight sensors are selected
one-by-one and their capacity is compared to a common referencecapacity. Each difference value is converted to a certain
voltage signal.
・AD Conversion
The voltage signal derived from CV conversion is further converted to digital value by this block.
・Conversion Sequence Control
This block controls the process of CV conversion and generates timing of selecting target sensors.
・Noise Filter
The GND level difference between appliance and human body will cause noises to the CV conversion
・Compare threshold
CV converted to sensor data On / Off compared with a threshold, the switch converts the signal.
・Calibration
When the capacitance change do not exceed the threshold for a certain period, this blockstarts-up calibration process.
・Reset Generation
This is internal reset circuit. Reset is initialized by external SDN signal.
・Clock Generation
Clock from internal RC oscillation circuit is used as system clock.
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2009.04 - Rev.B