SX8663 datasheet(11/64 Pages) SEMTECH

11 / 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

Figure 6

Scan Period

The scan period determines the minimum reaction time of the SX8663. The scan period can be configured by the

host from 15ms to values larger than a second.

The reaction time is defined as the interval between a touch on the sensor and the moment that the SX8663

generates the interrupt on the INTB pin. The shorter the scan period the faster the reaction time will be.

Very low power consumptions can be obtained by setting very long scan periods with the expense of having

longer reaction times.

All external events like GPIO, I2C and the interrupt are updated in the processing period, so once every scan

period.

3.3

Operation modes

The SX8663 has 3 operation modes. The main difference is found in the reaction time (corresponding to the scan

period) and power consumption.

Active mode offers fast scan periods. The typical reaction time is 30ms. All enabled sensors are scanned and

information data is processed within this interval.

Doze mode increases the scan period time which increases the reaction time to 195ms typical and at the same

time reduces the operating current.

Sleep mode turns the SX8663 OFF, except for the I2C peripheral, minimizing operating current while maintaining

the power supplies. In Sleep mode the SX8663 does not do any sensor scanning. The Sleep mode will be exited

by any I2C access.

The user can specify other scan periods for the Active and Doze mode and decide for other compromises

between reaction time and power consumption.

In most applications the reaction time needs to be fast when fingers are present, but can be slow when no person

uses the application. In case the SX8663 is not used for a specific time it will go from Active mode into Doze

mode and power will be saved. This time-out is determined by the Passive Timer which can be configured by the

user or turned OFF if not required.

To leave Doze mode and enter Active mode this can be done by a simple touch on any button.

The host can decide to force the operating mode by issuing commands over the I2C (using register

CompOpMode) and take fully control of the SX8663. The diagram in Figure 7 shows the available operation

modes and the possible transitions.

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