SX8663 datasheet(41/64 Pages) SEMTECH

41 / 64 page

ADVANCED COMMUNICATIONS & SENSING

Rev5 4

th August 2011

www.semtech.com

SX8663

Capacitive Button Matrix (up to 36) and Proximity Controller

with Individual LED Drivers and Buzzer Output

Capacitive Sensors Parameters

Address

Name

Bits Description

3:0

Periodic Offset Compensation

Defines the periodic offset compensation.

0x0: OFF (default)

0x1: 1 second

0x2: 2 seconds

…

0x7: 7 seconds

0x8: 16 seconds

0x9: 18 seconds

…

0xE: 28 seconds

0xF: 60 seconds

Table 12

Capacitive Sensors Parameters

CapSenseProtect

If needed, ASI activity can be protected against LED interference by automatically disabling GPIOs during

sensing periods. At the end of the sensing activity, GPIOs activity resume normally.

CapModeMisc

By default the ASI uses common sensitivity for all capacitive sensors in the case overlay material and sensors

sizes are about equal. The register bits CapSensitivity0_1[7:4] determine the sensitivity for all sensors in

common sensitivity mode.

The ASI can use an individual sensitivity for each CAP pin The individual sensitivity mode results in longer

sensing periods than required in common sensitivity mode.

CapSensitivity0_1,

CapSensitivity2_3,

CapSensitivity4_5,

CapSensitivity6_7,

CapSensitivity8_9,

CapSensitivity10_11

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.

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].

CapThresh0, CapThresh1, CapThresh2, CapThresh3, CapThresh4, CapThresh5, CapThresh6, CapThresh7,

CapThresh8, CapThresh9, CapThresh10, CapThresh11:

For each CAP pin a threshold level can be set individually.

The threshold levels are used by the SX8663 for making touch and release decisions.

The details are explained in the sections for buttons.

CapPerComp

The SX8663 offers a periodic offset compensation for applications which are subject to substantial

environmental changes. The periodic offset compensation is done at a defined interval and only if buttons are

released.

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