CAP1128
8 Channel Capacitive Touch Sensor
with 2 LED Drivers
PRODUCT FEATURES
General Description
The CAP1128, which incorporates SMSC’s RightTouch
®
1
technology, is a multiple channel Capacitive Touch sensor
with multiple power LED drivers. It contains eight (8)
individual capacitive touch sensor inputs with
programmable sensitivity for use in touch sensor
applications. Each sensor input automatically recalibrates
to compensate for gradual environmental changes.
The CAP1128 also contains two (2) LED drivers that offer
full-on / off, variable rate blinking, dimness controls, and
breathing. Each of the LED drivers may be linked to one of
the sensor inputs to be actuated when a touch is detected.
As well, each LED driver may be individually controlled via
a host controller.
The CAP1128 includes Multiple Pattern Touch recognition
that allows the user to select a specific set of buttons to be
touched simultaneously. If this pattern is detected, then a
status bit is set and an interrupt generated.
Additionally, the CAP1128 includes circuitry and support for
enhanced sensor proximity detection.
The CAP1128 offers multiple power states operating at low
quiescent currents. In the Standby state of operation, one
or more capacitive touch sensor inputs are active and all
LEDs may be used. If a touch is detected, it will wake the
system using the WAKE/SPI_MOSI pin.
Deep Sleep is the lowest power state available, drawing
5uA (typical) of current. In this state, no sensor inputs are
active. Driving the WAKE/SPI_MOSI pin or communications
will wake the device.
Datasheet
Applications
Desktop and Notebook PCs
LCD Monitors
Consumer Electronics
Appliances
Features
Eight (8) Capacitive Touch Sensor Inputs
— Programmable sensitivity
— Automatic recalibration
— Individual thresholds for each button
Proximity Detection
Multiple Button Pattern Detection
Calibrates for Parasitic Capacitance
Analog Filtering for System Noise Sources
Press and Hold feature for Volume-like Applications
Multiple Communication Interfaces
—
—
—
—
SMBus / I
2
C compliant interface
SMSC BC-Link interface
SPI communications
Pin selectable communications protocol and multiple
slave addresses (SMBus / I
2
C only)
Low Power Operation
— 5uA quiescent current in Deep Sleep
— 50uA quiescent current in Standby (1 sensor input
monitored)
— Samples one or more channels in Standby
Two (2) LED Driver Outputs
— Open Drain or Push-Pull
— Programmable blink, breathe, and dimness controls
— Can be linked to Capacitive Touch Sensor inputs
1. SMSC, the SMSC logo and RightTouch are registered trademarks
and the RightTouch logo is a trademark of Standard Microsystems
Corporation (“SMSC”).
Dedicated Wake output flags touches in low power state
System RESET pin
Available in 20-pin 4mm x 4mm QFN RoHS compliant
package
Block Diagram
LED1
LED2
RESET
VDD
GND
WAKE / SPI_MOSI
SPI_CS#
LED Driver, Breathe,
and Dimness control
Capacitive Touch Sensing Algorithm
SMBus /
BC-Link /
SPI Slave
Protocol
SMCLK/ BC_CLK /
SPI_CLK
SMDATA / BC_DATA/ SPI_MSIO /
SPI_MISO
ALERT# / BC_IRQ#
ADDR_COMM
CS1
CS2
CS3
CS4
CS5
CS6
CS7
CS8
SMSC CAP1128
DATASHEET
Revision 1.32 (01-05-12)
SMSC [ SMSC CORPORATION ]
