SX8661I07AULTRT Semtech, SX8661I07AULTRT Datasheet - Page 14

• 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

ADVANCED COMMUNICATIONS & SENSING
3.2
3.2.1
The SX8661 is intended to be used in applications which require capacitive sensors covered by isolating overlay
material and which need to detect the proximity of a finger/hand though the air. A finger approaching the
capacitive sensors will change the charge that can be loaded on the sensors. The SX8661 measures the change
of charge and converts that into digital values (ticks). The larger the charge on the sensors, the larger the number
of ticks will be. The charge to ticks conversion is done by the SX8661 Analog Sensor Interface (ASI).
The ticks are further processed by the SX8661 and converted in a high level, easy to use information for the
user’s host.
The information between SX8661 and the user’s host is passed through the I2C interface with an additional
interrupt signal indicating that the SX8661 has new information. For buttons this information is simply touched or
released. The SX8661 can operate without the I2C and interrupt by using the analog output interface (GPIO7
and/or GPIO6) which voltage level indicates the button touched or GPO with the autolight function.
3.2.2
Feedback to the user is using General Purpose Input Output (GPIO) pins. The SX8661 offers up to eight
individual configurable GPIO pins. The GPIO can e.g. be set as a LED driver which slowly fade-in when a finger
touches a button or proximity is detected and slowly fade-out when the button is released or finger goes out of
proximity. Fading intensity variations can be logarithmic or linear. Interval speed and initial and final light intensity
can be selected by the user. The fading is done using a 256 step PWM. The SX8661 has eight individual PWM
generators, one for each GPIO pin.
The LED fading-in and fading-out mode is called the GPO (fading) mode.
The LED fading can be initiated automatically by the SX8661 by setting the SX8661 autolightening feature. A
simple touch on a sensor and the corresponding LED will fade-in without any host interaction over the I2C.
In case the autolightening feature is disabled then the host will decide to start a LED fading-in period, simply by
setting the GPO pin to ‘high’ using one I2C command. The SX8661 will then slowly fade-in the LED using the
PWM autonomously.
In case the host needs to have full control of the LED intensity then the host can set the GPIO in the PWM mode
(GPP). The host is then able to set the PWM pulse width freely at the expense of an increased I2C occupation.
The GPIOs can be set further in special purpose output (SPO) for the buzzer or analog output interface.
3.2.3
The Analog Output Interface (AOI) is a PWM output signal between ground and VDD. The duty cycle of the AOI
output will change depending on which button is touched. A host controller can then measure the mean voltage
delivered on the AOI output and determine which button is touched at any given time.
The AOI feature allows the SX8661 device to replace directly legacy mechanical button controllers in a quick and
effortless manner. The SX8661 supports up to two Analog Output Interfaces, AOI-A and AOI-B (on GPIO7 and
GPIO6 respectively). The SX8661 allows buttons to be mapped on either AOI-A or AOI-B. The button mapping as
well as the mean voltage level that each button produces on a AOI output can be configured by the user through a
set of parameters described in later chapters (see 5.6).
3.2.4
The SX8661 can drive a buzzer (on GPIO5) to provide audible feedback on button touches. The buzzer duration
is set to approximately 30ms per default (see 5.7).
3.2.5
The SX8661 has many low level built-in, fixed algorithms and procedures. To allow a lot of freedom for the user
and adapt the SX8661 for different applications these algorithms and procedures can be configured with a large
set of parameters which will be described in the following sections. Examples of parameters are which sensors
Revision v3.2, January 2011
Introduction
General
GPIOs
Analog Output Interface A and B (SPO mode)
Buzzer (SPO mode)
Parameters
Low Power, Capacitive Button Touch and Proximity Controller
© 2011 Semtech Corp.
14
(8 sensors) with LED Drivers and Analog Output
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