BU21008MUV Datasheet, PDF (15/17 Pages) Rohm – Capacitive Sensor Switch Control IC

BU21008MUV
Technical Note
●Operation mode
This IC has a normal mode, idle mode and a shutdown mode as states of operation.
【Normal mode】
This is the normal operation of the device. Output pin INT="L".
【Idle mode】
This is the mode when the normal mode times out due to inactivity on the keys. In this mode the control interface is still alive.
*Usually time-out is aimed at about 200msec or less.
*Transition between normal and idle modes is automatic and without software control.
【Shutdown mode】
In this mode the device is completely stopped-and reset. This is achieved by making the terminal SDN L.
All analog circuits and the logic circuits are stopped. The return from the shutdown mode returns by making the terminal SDN H.
*After shut-down all registers have their default values.
●Interface and system clock selection
I/F selection with MODE [1:0] pin. System clock selection by RXD.
【Using 2wires serial bus mode (MODE［1:0］＝00b)】
The 2wires serial bus is used for host I/F.
RXD=0 in the system clock: Built-in oscillator is used.
RXD=1 in the system clock: The clock input from CLK_EXT is used.
●Initialization procedure
A normal power on sequence is:
(1) Power on
(2) Setup the registers
(3) Write ‘1’ to 0xEF (done register)
<sensing operation begins after auto-calibration occurs>
●Power supply turning on procedure
You should always power on DVDD at the same time as AVDD or before AVDD.
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2009.04 - Rev.B