SX8663 datasheet(43/64 Pages) SEMTECH

43 / 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

Buttons Parameters

Address

Name

Bits Description

0x64: 100%

0x27

BtnStuckAtTimeout

7:0

Defines the stuck at timeout for buttons.

0x00: OFF (default)

0x01: 1 second

…

0xFF: 255 seconds

Table 13

Button Parameters

A reliable button operation requires a coherent setting of the registers.

Figure 45 shows an example of a touch and a release. The ticks will vary slightly around the zero idle state.

When the touch occurs the ticks will rise sharply. At the release of the button the ticks will go down rapidly and

converge to the idle zero value.

Figure 45

Touch and Release Example

As soon as the ticks become larger than the CAP thresholds (see registers of the previous section) plus the

hysteresis (defined in register BtnHysteresis ) the debounce counter starts.

In the example of Figure 45 the touch is validated after 2 ticks (BtnCfg [2:0] = 1).

The release is detected immediately (BtnCfg [3] = 0) at the first tick which is below the threshold minus the

hysteresis.

BtnCfg

The user can select to have the interrupt signal (INTB) on touching a button, releasing a button or both.

In noisy environments it may be required to debounce the touch and release detection decision.

In case the debounce is enabled the SX8663 will count up to the number of debounce samples BtnCfg [1:0],

BtnCfg [3:2] before taking a touch or release decision. The sample period is identical to the scan period.

BtnAvgPosThresh

Small environmental and system noise cause the ticks to vary slowly around the zero idle mode value.

In case the ticks get slightly positive this is considered as normal operation. Very large positive tick values

indicate a valid touch. The averaging filter is disabled as soon as the average reaches the value defined by

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