SX8661 datasheet(55/88 Pages) SEMTECH

55 / 88 page

ADVANCED COMMUNICATIONS & SENSING

DATASHEET

Revision v3.2, January 2011

www.semtech.com

SX8661

Low Power, Capacitive Button Touch and Proximity Controller

(8 sensors) with LED Drivers and Analog Output

Figure 53

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 53 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 SX8661 button and proximity interface has three modes of operation:

•

Report All:

reports all touches of multiple fingers and proximity detection.

•

Report Single:

reports only a single touch and/or proximity. Subsequent touches are ignored until the

first touch is released. On the AOI proximity is implicit in case of a button touch.

•

Report Strongest:

reports the strongest touch. When the signal from another sensor rises above the

first sensor’s signal, the second sensor is then reported instead. On the AOI proximity is implicit in

case of a button touch.

Table 21 resumes the relation of reporting modes and information on the interfaces.

Reporting

Mode

I2C

AOI

GPIOs (LEDs)

Buzzer

All

Buttons and Proximity

Forced to Idle

Buttons and

Proximity

Button

Single

Proximity or

1 Button and Proximity

Idle or 1 Button or

Proximity

Buttons and

Proximity

Button

Strongest

Proximity or

1 Button and Proximity

Idle or 1 Button or

Proximity

Buttons and

Proximity

Button

Table 21

Reporting modes

The user can select to have the interrupt signal (INTB) on touching a button (proximity detected), releasing a

button (out of proximity) or both.

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

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