sx8643 Semtech Corporation, sx8643 Datasheet - Page 17

• Manufacturer Part Number: sx8643
• Description: Ultra Low Power, Capacitive Button Touch Controller 12 Sensors With Enhanced Led Drivers
• Manufacturer: Semtech Corporation

ADVANCED COMMUNICATIONS & SENSING
3.9 Processing
The first processing step of the raw ticks, coming out of the ASI, is low pass filtering to obtain an estimation of the
average capacitance: tick-ave (see Figure 12).
This slowly varying average is important in the detection of slowly changing environmental changes.
The difference of the tick average and the raw ticks, tick-diff, is a good estimation of rapid changing input
capacitances.
The tick-diff, tick-ave and the configuration parameters in the SPM are then processed and determines the sensor
information, I2C registers status and PWM control.
3.10 Configuration
Figure 13 shows the building blocks used for configuring the SX8643.
The default configuration parameters of the SX8643 are stored in the Quick Start Memory (QSM). This
configuration data is setup to a very common application for the SX8643 with eight buttons. Without any
programming or host interaction the SX8643 will startup in the Quick Start Application.
Revision 7_5, February 10
ASI
processing
compensation DCV
ticks (raw)
low pass
© 2010 Semtech Corp.
Figure 13
Figure 12
Ultra Low Power, Capacitive Button Touch Controller
tick-ave
tick-diff
Configuration
17
Processing
(12 sensors) with Enhanced LED Drivers
processing
SPM
PWM LED
controller
controller
GPIO
I2C
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SX8643