SX8661I07AULTRT Semtech, SX8661I07AULTRT Datasheet - Page 15

• Manufacturer Part Number: SX8661I07AULTRT
• Description: IC, Capacitive Button Touch And Proximity Controller, 8 SENSOR, MLPQ-28
• Manufacturer: Semtech

Specifications of SX8661I07AULTRT

• Controller Type: Capacitive Touch Screen
• Ic Interface Type: I2C
• Supply Voltage Range: 2.7V To 3.6V
• Operating Temperature Range: -40°C To +85°C

SX8661
Low Power, Capacitive Button Touch and Proximity Controller
(8 sensors) with LED Drivers and Analog Output
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
are buttons, which GPIO is used for outputs, for the Analog Output Interfaces, the Buzzer or LEDs and which
GPIO is mapped to which button.
Sensitivity and detection thresholds of the sensors are part of these parameters. Assuming that overlay material
and sensors areas are identical then the sensitivities and thresholds will be the same for each sensor. In case
sensors are not of the same size then sensitivities or thresholds might be chosen individually per sensor.
So a smaller size sensor can have a larger sensitivity while a big size sensor may have the lower sensitivity.
3.2.6
Configuration
During a development phase the parameters can be determined and fine tuned by the users and downloaded
over the I2C in a dynamic way. The parameter set can be downloaded over the I2C by the host each time the
SX8661 boots up. This allows a flexible way of setting the parameters at the expense of I2C occupation.
In case the parameters are frozen they can be programmed in Multiple Time Programmable (MTP) Non Volatile
Memory (NVM) on the SX8661. The programming needs to be done once (over the I2C). The SX8661 will then
boot up from the NVM and additional parameters from the host are not required anymore.
In case the host desires to overwrite the boot-up NVM parameters (partly or even complete) this can be done by
additional I2C communications.
3.3 Scan Period
The basic operation Scan period of the SX8661 sensing interface can be split into three periods over time.
In the first period (Sensing) the SX8661 is sensing all enabled CAP inputs, from CAP0 towards CAP7.
In the second period (Processing) the SX8661 processes the sensor data, verifies and updates the GPIO and the
I2C.
In the third period (Timer) the SX8661 is set in a low power mode and waits until a new cycle starts.
Figure 8 shows the different SX8661 periods over time.
Scan Period
Figure 8
The scan period determines the minimum reaction time of the SX8661. 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 SX8661
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.
3.4 Operation modes
The SX8661 has 3 operation modes. The main difference is found in the reaction time (corresponding to the scan
period) and power consumption.
Revision v3.2, January 2011
© 2011 Semtech Corp.
www.semtech.com
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