BU21009MUV Datasheet, PDF (12/14 Pages) Rohm – Capacitive Sensor Switch Control IC

BU21009MUV
Technical Note
【FDh : Switch ON -> OFF Threshold Value】
Name:
TH_OFF
Address:
FDh
Description: This register provides a threshold value for transitioning from ON to OFF.
This is relative value from reference value (128d). So absolute value of threshold is128d + OFF[6:0].
It makes a threshold value between TH_ON and TH_OFF.
TH_OFF must be smaller than TH_ON (TH_OFF =< TH_ON)
Maximum value is 256d and minimum value is 128d.
Bit7
FDh
-
R/W
-
Initial val.
-
Bit6
OFF[6]
W
0
Bit5
OFF[5]
W
0
Bit4
OFF[4]
W
0
Bit3
OFF[3]
W
0
Bit2
OFF[2]
W
0
Bit1
OFF[1]
W
0
Bit0
OFF[0]
W
1
【FEh : LED Port Data】
Name:
DLED
Address:
FEh
Description: When LED is not linked with the sensor, it becomes a simple digital output that controls the LED.
1 : Light. 0 : Turned off.
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
FEh
D7
D6
D5
D4
D3
D2
D1
D0
R/W
W
W
W
W
W
W
W
W
Initial val.
0
0
0
0
0
0
0
0
●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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12/13
2009.04 - Rev.B