WIRELESS & SENSING

DATASHEET

Revision 1.6

June 27, 2012

© 2012 Semtech Corporation

www.semtech.com

11

SX9500

Ultra Low Power, Capacitive

Four (4) - Channel Proximity/Button

Controller

3

3.1

Introduction

3.1.1

General

The SX9500 is a low-cost, very low-power 4-channel capacitive controller that can operate either as a proximity

or button sensor.

The SX9500 includes sophisticated on-chip auto-calibration circuitry to regularly perform

sensitivity adjustments, maintaining peak performance over a wide variation of temperature, humidity and noise

environments, providing simplified product development and enhanced performance.

3.1.2

Parameters and Configuration

The SX9500 allows the user full parameter customization for Sensor sensitivity, hysteresis, and detection

thresholds. If custom parameters are used by the customer, these parameters must be uploaded by the host

immediately following boot-up or after a reset.

3.1.3

Sensor Touch/Proximity Adjustment

Capacitive touch/proximity detection is directly proportional to the SX9500 internal gain and threshold settings,

and external sensor area to optimize proximity detection distance. A longer touch/proximity detection range can

be accomplished without changing the capacitive sensor size, by using a high sensitivity setting and/or lower

signal threshold setting for touch/proximity detection.

3.2

Scan Period

The Scan period determines the minimum touch/proximity detection reaction time of the SX9500 and can be

varied by the host from 30ms to approximately 400ms. Touch/proximity detection reaction time is proportional to

the Scan period and inversely proportional to power consumption, so longer Scan periods corresponds to lower

power, but also to longer detection reaction times.

The Scan period of the SX9500 is defined by two periods: Sensing and Idle. During the Sensing period, all

enabled CS inputs, from CS0 to CS3 are sampled and any detection reported via the I2C bus (via I2C register

polling or NIRQ). The Sensing period is variable and is proportional to the Scan Frequency and Resolution

settings in the Cap Sensing Control Registers. During the Idle period, the SX9500 the analog circuits are placed

in standby and the idle timer is initiated. Upon expiry of the idle timer, a new Scan period cycle begins.

Figure 6 Scan Period