sx8639 Semtech Corporation, sx8639 Datasheet - Page 45

• Manufacturer Part Number: sx8639
• Description: Low Power, Capacitive Button And Wheel Touch Controller 8 Sensors With Enhanced Led Drivers And Proximity Sensing
• Manufacturer: Semtech Corporation

ADVANCED COMMUNICATIONS & SENSING
CapSensitivity0_1, CapSensitivity2_3, CapSensitivity4_5, CapSensitivity6_7, CapProxEnable:
Revision 7_8, September 10
The minimum position of the wheel is associated to the CAP pin, attributed to the wheel, with the lowest index
(in Figure 48 this is CAP2).
The maximum position of the wheel is associated to the CAP pin, attributed to the wheel, with the highest
index (in Figure 48 this is CAP6).
The sensitivity of the sensors can be set between 8 values. The higher the sensitivity is set the larger the value
of the ticks will be.
The minimum sensitivity can be used for thin overlay materials and large sensors, while the maximum
sensitivity is required for thicker overlay and smaller sensors or proximity sensing.
The required sensitivity needs to be determined during a product development phase. Too low sensitivity
settings result in missing touches. Too high sensitivity settings will result in fault detection of fingers hovering
above the touch sensors.
The sensitivity is identical for all sensors in common sensitivity mode using the bits CapSensitivity0_1[7:4] and
can be set individually using register CapModeMisc[2:0].
The maximum number of ticks that can be obtained depends on the selected sensitivity and if proximity
sensing is enabled. This is illustrated in Table 17.
Sensitivity
Figure 48
0
1
2
3
4
5
6
7
Button and Wheel good/bad configuration examples (II)
Table 17
(8 sensors) with Enhanced LED Drivers and Proximity Sensing
(CapProxEnable = OFF)
Maximum Tick Level
© 2010 Semtech Corp.
Low Power, Capacitive Button and Wheel Touch Controller
Approximate
ASI Maximum Tick Levels
1000
2000
3000
4000
5000
6000
7000
8000
45
(CapProxEnable = ON)
Maximum Tick Level
Approximate
32000
12000
16000
20000
24000
28000
4000
8000
DATASHEET
www.semtech.com
SX8639