SMSC CAP1088 8 channel capacitive touch sensor with 8 led driver Datasheet

CAP1088
8 Channel Capacitive Touch
Sensor with 8 LED Drivers
PRODUCT FEATURES
Datasheet
General Description
Applications
The CAP1088 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 automatically recalibrates to
compensate for gradual environmental changes.

Features

The CAP1088 also contains eight (8) 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 sensors to be actuated when a touch is
detected. As well, each LED driver may be individually
controlled via a host controller.
Desktop and Notebook PC’s
LCD Monitors
Printers
Appliances
Eight (8) Capacitive Touch Sensor Inputs
— Programmable sensitivity
— Automatic recalibration
— Individual thresholds for each button

Flexible Capacitive Touch Sense algorithm
Multiple Communication interfaces
—
—
—
—
The CAP1088 offers multiple power states operating at
low quiescent currents.
During the Standby mode of operation, one or more
Capacitive Touch Sensors are active and all LEDs may
be used. If a touch is detected, then it will wake the
system using the WAKE/SPI_MOSI pin.
The Deep Sleep mode of operation is the lowest power
state available drawing 3uA of current. During this
mode, no sensors are activethough all LEDs may be
u s e d . D r i v i n g t h e WA K E / S P I _ M O S I p i n o r
communications will wake the device.

SMBus / I2C compliant interface
SMSC BC-Link interface
SPI communications
Pin selectable communications protocol and multiple
slave addresses (SMBus / I2C only)
Low Power operation
— 3uA quiescent current in Deep Sleep
— Samples one or more channels in Standby

Eight (8) LED Driver Outputs
— Open Drain or Push-Pull
— Programmable blink, breathe, and dimness controls
— Can be linked to Capacitive Touch Sensors

Dedicated Wake output flags touches in low power
mode
System RESET pin
Available in 24-pin 4mm x 4mm RoHS compliant
QFN package
Block Diagram
LED1 LED2 LED3 LED4
RESET
VDD GND
WAKE / SPI_MOSI
SPI_CS#
LED Driver, Breathe,
and Dimness control
Capacitive Sensing Algorithm
SMBus /
BC-Link
or SPI
Slave
Protocol
SMCLK / BC_CLK /
SPI_CLK
SMDATA / BC_DATA /
SPI_MSIO / SPI_MISO
ALERT# / BC_IRQ#
ADDR_COMM
LED5 LED6 LED7 LED8
Note:
SMSC CAP1088
CS1 CS2
CS3 CS4 CS5 CS6 CS7 CS8
I2C is a trademark of NXP semiconductor. BC-Link is a trademark of SMSC.
DATASHEET
Revision 1.1 (08-05-09)
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
ORDERING INFORMATION
ORDERING NUMBER
CAP1088-1-CP-TR
PACKAGE
24-pin QFN 4mm x 4mm
(Lead Free RoHS compliant)
FEATURES
Eight Capacitive Touch Sensors, Eight
LED drivers, Dedicated Wake, Reset,
SMBus / BC-Link / SPI interfaces
REEL SIZE IS 4,000 PIECES
80 ARKAY DRIVE, HAUPPAUGE, NY 11788 (631) 435-6000, FAX (631) 273-3123
Copyright © 2009 SMSC or its subsidiaries. All rights reserved.
Circuit diagrams and other information relating to SMSC products are included as a means of illustrating typical applications. Consequently, complete information sufficient for
construction purposes is not necessarily given. Although the information has been checked and is believed to be accurate, no responsibility is assumed for inaccuracies. SMSC
reserves the right to make changes to specifications and product descriptions at any time without notice. Contact your local SMSC sales office to obtain the latest specifications
before placing your product order. The provision of this information does not convey to the purchaser of the described semiconductor devices any licenses under any patent
rights or other intellectual property rights of SMSC or others. All sales are expressly conditional on your agreement to the terms and conditions of the most recently dated
version of SMSC's standard Terms of Sale Agreement dated before the date of your order (the "Terms of Sale Agreement"). The product may contain design defects or errors
known as anomalies which may cause the product's functions to deviate from published specifications. Anomaly sheets are available upon request. SMSC products are not
designed, intended, authorized or warranted for use in any life support or other application where product failure could cause or contribute to personal injury or severe property
damage. Any and all such uses without prior written approval of an Officer of SMSC and further testing and/or modification will be fully at the risk of the customer. Copies of
this document or other SMSC literature, as well as the Terms of Sale Agreement, may be obtained by visiting SMSC’s website at http://www.smsc.com. SMSC is a registered
trademark of Standard Microsystems Corporation (“SMSC”). Product names and company names are the trademarks of their respective holders.
SMSC DISCLAIMS AND EXCLUDES ANY AND ALL WARRANTIES, INCLUDING WITHOUT LIMITATION ANY AND ALL IMPLIED WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE, TITLE, AND AGAINST INFRINGEMENT AND THE LIKE, AND ANY AND ALL WARRANTIES ARISING FROM ANY COURSE
OF DEALING OR USAGE OF TRADE. IN NO EVENT SHALL SMSC BE LIABLE FOR ANY DIRECT, INCIDENTAL, INDIRECT, SPECIAL, PUNITIVE, OR CONSEQUENTIAL
DAMAGES; OR FOR LOST DATA, PROFITS, SAVINGS OR REVENUES OF ANY KIND; REGARDLESS OF THE FORM OF ACTION, WHETHER BASED ON CONTRACT;
TORT; NEGLIGENCE OF SMSC OR OTHERS; STRICT LIABILITY; BREACH OF WARRANTY; OR OTHERWISE; WHETHER OR NOT ANY REMEDY OF BUYER IS HELD
TO HAVE FAILED OF ITS ESSENTIAL PURPOSE, AND WHETHER OR NOT SMSC HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
Revision 1.1 (08-05-09)
2
DATASHEET
SMSC CAP1088
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Table of Contents
Chapter 1 Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Chapter 2 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Chapter 3 Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1
3.2
3.3
3.4
3.5
3.6
3.7
Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.1
SMBus (I2C) Communications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.2
SPI Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.3
BC-Link Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
System Management Bus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.1
SMBus Start Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.2
SMBus Address and RD / WR Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.3
SMBus Data Bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.4
SMBus ACK and NACK Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.5
SMBus Stop Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.6
SMBus Timeout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.7
SMBus and I2C Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SMBus Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.1
SMBus Write Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.2
Block Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.3
SMBus Read Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.4
Block Read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.5
SMBus Send Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.6
SMBus Receive Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SPI Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.1
SPI Normal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.2
SPI Bi-Directional Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.3
SPI_CS# Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.4
Address Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.5
SPI Timeout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Normal SPI Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5.1
Reset Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5.2
Set Address Pointer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5.3
Write Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5.4
Read Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bi-Directional SPI Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.1
Reset Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.2
Set Address Pointer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.3
Write Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.4
Read Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
BC-Link Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15
15
15
15
16
16
16
16
16
17
17
17
17
17
18
18
18
18
19
19
20
20
20
20
20
20
21
22
22
23
24
24
24
25
25
25
Chapter 4 General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.1
4.2
4.3
4.4
4.5
Power States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RESET Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
WAKE/SPI_MOSI Pin Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LED Drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4.1
Linking LEDs to Capacitive Touch Sensors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Capacitive Touch Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5.1
Sensing Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5.2
Recalibrating Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SMSC CAP1088
3
DATASHEET
28
29
29
29
30
30
30
30
Revision 1.1 (08-05-09)
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
4.6
ALERT# Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.6.1
Sensor Interrupt Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Chapter 5 Register Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.10
5.11
5.12
5.13
5.14
5.15
5.16
5.17
5.18
5.19
5.20
5.21
5.22
5.23
5.24
5.25
5.26
5.27
5.28
5.29
5.30
5.31
5.32
5.33
5.34
5.35
5.36
5.37
Main Status Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.1
Sensor Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.2
LED Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Noise Flag Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sensor Delta Count Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sensitivity Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sensor Enable Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sensor Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sensor Configuration 2 Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Averaging and Sampling Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Calibration Activate Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Interrupt Enable Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Repeat Rate Enable Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Multiple Touch Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recalibration Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sensor Threshold Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sensor Noise Threshold Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.17.1 Sensor Noise Threshold 1 Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.17.2 Sensor Noise Threshold 2 Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Standby Channel Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Standby Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Standby Sensitivity Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Standby Threshold Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sensor Base Count Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LED Output Type Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sensor LED Linking Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LED Polarity Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LED Output Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LED Behavior Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.27.1 LED Behavior 1 - 81h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.27.2 LED Behavior 2 - 82h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LED Pulse 1 Period Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LED Pulse 2 Period Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LED Breathe Period Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LED Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LED Duty Cycle Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LED Direct Ramp Rates Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LED Off Delay Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Product ID Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Manufacturer ID Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Revision Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
35
36
36
36
37
37
38
39
40
41
42
43
44
45
45
46
47
48
49
49
49
50
50
52
52
53
53
54
55
56
57
58
58
59
60
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66
66
66
Chapter 6 Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
6.1
6.2
CAP1088 Package Drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Package Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Chapter 7 Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Revision 1.1 (08-05-09)
4
DATASHEET
SMSC CAP1088
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
List of Figures
Figure 1.1
Figure 3.1
Figure 3.1
Figure 3.1
Figure 3.2
Figure 3.3
Figure 3.4
Figure 3.5
Figure 3.6
Figure 3.7
Figure 3.8
Figure 3.9
Figure 3.10
Figure 4.1
Figure 4.2
Figure 4.3
Figure 5.1
Figure 5.2
Figure 5.3
Figure 5.4
Figure 5.5
Figure 5.6
Figure 6.1
Figure 6.2
Figure 6.3
Figure 6.4
CAP1088 Pin Diagram (24-Pin QFN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
SMBus Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
SPI Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Example SPI Bus Communication - Normal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
SPI Reset Interface Command - Normal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
SPI Set Address Pointer Command - Normal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
SPI Write Command - Normal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
SPI Read Command - Normal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
SPI Read Command - Normal Mode - Full . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
SPI Reset Interface Command - Bi-directional Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
SPI Set Address Pointer Command - Bi-directional Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . 25
SPI Write Data Command - Bi-directional Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
SPI Read Data Command - Bi-directional Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
System Diagram for CAP1088 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Sensor Interrupt Behavior - Repeat Rate Enabled. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Sensor Interrupt Behavior - No Repeat Rate Enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Pulse Behavior with Non-Inverted Polarity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Pulse Behavior with Inverted Polarity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Pulse 2 Behavior with Non-Inverted Polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Pulse 2 Behavior with Inverted Polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Direct Mode Behavior for Non-Inverted Polarity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Direct Mode Behavior for Inverted Polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
CAP1088 Package Drawing - 24-Pin QFN 4mm x 4mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
CAP1088 Package Dimensions - 24-Pin QFN 4mm x 4mm . . . . . . . . . . . . . . . . . . . . . . . . . 68
CAP1088 PCB Footprint - 24-pin QFN 4mm x 4mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
CAP1088 Package Markings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
SMSC CAP1088
5
DATASHEET
Revision 1.1 (08-05-09)
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
List of Tables
Table 1.1 Pin Description for CAP1088 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Table 1.2 Pin Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Table 2.1 Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Table 2.2 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Table 3.1 ADDR_COMM Pin Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 3.2 Protocol Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Table 3.3 Write Byte Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Table 3.4 Block Write Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Table 3.5 Read Byte Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Table 3.6 Block Read Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Table 3.7 Send Byte Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Table 3.8 Receive Byte Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Table 5.1 Register Set in Hexadecimal Order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Table 5.2 Main Status Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Table 5.3 Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Table 5.4 Noise Flag Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Table 5.5 Sensor Delta Count Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Table 5.6 Sensitivity Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Table 5.7 DELTA_SENSE Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Table 5.8 BASE_SHIFT Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Table 5.9 Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Table 5.10 Sensor Enable Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Table 5.11 Sensor Configuration Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Table 5.12 MAX_DUR Bit Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Table 5.13 RPT_RATE Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Table 5.14 Sensor Configuration 2 Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Table 5.15 Averaging and Sampling Configuration Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Table 5.16 AVG Bit Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Table 5.17 CYCLE_TIME Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Table 5.18 Calibration Activate Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Table 5.19 Interrupt Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Table 5.20 Repeat Rate Enable Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Table 5.21 Multiple Touch Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Table 5.22 B_MULT_T Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Table 5.23 Recalibration Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Table 5.24 NEG_DELTA_CNT Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Table 5.25 CAL_CFG Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Table 5.26 Sensor Threshold Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Table 5.27 Sensor Noise Threshold Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Table 5.28 CSx_BN_TH Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Table 5.29 Standby Channel Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Table 5.30 Standby Configuration Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Table 5.31 STBY_AVG Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Table 5.32 STBY_CY_TIME Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Table 5.33 Standby Configuration Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Table 5.34 STBY_SENSE Bit Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Table 5.35 Standby Threshold Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Table 5.36 Sensor Base Count Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Table 5.37 LED Output Type Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Table 5.38 Sensor LED Linking Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Table 5.39 LED Polarity Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Table 5.40 LED Output Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Revision 1.1 (08-05-09)
6
DATASHEET
SMSC CAP1088
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Table 5.41 LED Polarity Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.42 LED Behavior Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.43 LEDx_CTL Bit Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.44 LED Pulse 1 Period Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.45 LED Pulse / Breathe Period Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.46 LED Pulse 2 Period Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.47 LED Breathe Period Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.48 LED Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.49 PULSEX_CNT Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.50 LED Duty Cycle Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.51 LED Duty Cycle Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.52 LED Direct Ramp Rates Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.53 Rise / Fall Rate and Off Delay Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.54 LED Off Delay Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.55 Product ID Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.56 Vendor ID Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.57 Revision Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 7.1 Customer Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SMSC CAP1088
7
DATASHEET
56
57
58
59
60
60
61
62
62
63
63
64
64
65
66
66
66
70
Revision 1.1 (08-05-09)
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
RESET
VDD
CS1
CS2
CS3
CS4
24
23
22
21
20
19
Chapter 1 Pin Description
SPI_CS#
1
18
CS5
WAKE / SPI_MOSI
2
17
CS6
16
CS7
15
CS8
SMDATA / BC_DATA /
SPI_MSIO / SPI_MISO
SMCLK / BC_CLK /
SPI_CLK
3
CAP1088
24 pin QFN
4
11
12
LED8
LED6
LED7
ALERT# / BC_IRQ#
10
13
9
6
LED5
LED2
8
ADDR_COMM
LED4
14
7
5
LED3
LED1
GND
Figure 1.1 CAP1088 Pin Diagram (24-Pin QFN)
Table 1.1 Pin Description for CAP1088
PIN
NUMBER
PIN NAME
PIN FUNCTION
PIN TYPE
1
SPI_CS#
Active low chip-select for SPI bus
DI (5V)
WAKE - Active high wake / interrupt output Standby power state
DO
WAKE - Active high wake input - requires pull-down resistor
Deep Sleep power state
DI
SPI_MOSI - SPI Master-Out-Slave-In port when used in
normal mode
DI (5V)
2
WAKE /
SPI_MOSI
Revision 1.1 (08-05-09)
8
DATASHEET
SMSC CAP1088
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Table 1.1 Pin Description for CAP1088 (continued)
PIN
NUMBER
3
4
5
6
7
8
9
10
11
12
13
PIN NAME
SMDATA /
BC_DATA /
SPI_MSIO /
SPI_MISO
SMCLK /
BC_CLK /
SPI_CLK
PIN FUNCTION
PIN TYPE
SMDATA - Bi-directional, open-drain SMBus data - requires
pull-up resistor
DIOD (5V)
BC_DATA - Bi-directional, open-drain BC-Link data requires pull-up resistor
DIO
SPI_MSIO - SPI Master-Slave-In-Out bidirectional port
when used in bi-directional mode
DIO
SPI_MISO - SPI Master-In-Slave-Out port when used in
normal mode
DO
SMCLK - SMBus clock input - requires pull-up resistor
DI (5V)
BC_CLK - BC-Link clock input
DI (5V)
SPI_CLK - SPI clock input
DI (5V)
Open drain LED 1 driver (default)
OD (5V)
Push-pull LED 1 driver
DO
Open drain LED 2 driver (default)
OD (5V)
Push-pull LED 2 driver
DO
Open drain LED 3 driver (default)
OD (5V)
Push-pull LED 3 driver
DO
Open drain LED 4 driver (default)
OD (5V)
Push-pull LED 4 driver
DO
Open drain LED 5 driver (default)
OD (5V)
Push-pull LED 5 driver
DO
Open drain LED 6 driver (default)
OD (5V)
Push-pull LED 6 driver
DO
Open drain LED 7 driver (default)
OD (5V)
Push-pull LED 7 driver
DO
Open drain LED 8 driver (default)
OD (5V)
Push-pull LED 8 driver
DO
LED1
LED2
LED3
LED4
LED5
LED6
LED7
LED8
ALERT# /
BC_IRQ#
ALERT# - Active low alert / interrupt output for SMBus alert
or SPI interrupt
OD (5V)
BC_IRQ# - Active low interrupt / optional for BC-Link
OD (5V)
14
ADDR_COMM
Address / communications select pin - pull-down resistor
determines address / communications mechanism
AI
15
CS8
Capacitive Touch Sensor 8
AIO
16
CS7
Capacitive Touch Sensor 7
AIO
17
CS6
Capacitive Touch Sensor 6
AIO
SMSC CAP1088
9
DATASHEET
Revision 1.1 (08-05-09)
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Table 1.1 Pin Description for CAP1088 (continued)
PIN
NUMBER
PIN NAME
PIN FUNCTION
PIN TYPE
18
CS5
Capacitive Touch Sensor 5
AIO
19
CS4
Capacitive Touch Sensor 4
AIO
20
CS3
Capacitive Touch Sensor 3
AIO
21
CS2
Capacitive Touch Sensor 2
AIO
22
CS1
Capacitive Touch Sensor 1
AIO
23
VDD
Positive Power supply
Power
24
RESET
Active high soft reset for system - resets all registers to
default values. This pin contains an internal 50uA pull-down
current.
DI (5V)
Bottom Pad
GND
Ground
Power
The pin types are described in detail below. All pins labeled with (5V) are 5V tolerant.
APPLICATION NOTE: For the 5V tolerant pins that have a pull-up resistor, the pull-up voltage must not exceed 3.6V
when the CAP1088 is unpowered.
APPLICATION NOTE: The SPI_CS# pin should be grounded when SMBus, I2C, or BC-Link communications are
used.
Table 1.2 Pin Types
PIN TYPE
DESCRIPTION
Power
Revision 1.1 (08-05-09)
This pin is used to supply power or ground to the
device.
DI
Digital Input - This pin is used as a digital input. This
pin is 5V tolerant.
AIO
Analog Input / Output -This pin is used as an I/O for
analog signals.
DIOD
Digital Input / Open Drain Output- This pin is used as a
digital I/O. When it is used as an output, it is open drain
and requires a pull-up resistor. This pin is 5V tolerant.
OD
Open Drain Digital Output - this pin is used as a digital
output. It is open drain and requires a pull-up resistor.
This pin is 5V tolerant.
DO
Push-pull Digital Output - This pin is used as a digital
output and can sink and source current.
DIO
Push-pull Digital Input / Output - This pin is used as an
I/O for digital signals.
10
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SMSC CAP1088
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Chapter 2 Electrical Specifications
Table 2.1 Absolute Maximum Ratings
Voltage on 5V tolerant pins (V5VT_PIN)
-0.3 to 5.5
V
Voltage on 5V tolerant pins (|V5VT_PIN - VDD|) Note 2.2
0 to 3.6
V
Voltage on VDD pin
-0.3 to 4
V
Voltage on any other pin to GND
-0.3 to VDD + 0.3
V
Package Power Dissipation up to TA = 85°C for 24 pin QFN
(see Note 2.3)
0.9
W
Junction to Ambient (θJA) (see Note 2.4)
58
°C/W
Operating Ambient Temperature Range
-40 to 125
°C
Storage Temperature Range
-55 to 150
°C
ESD Rating, All Pins, HBM
8000
V
Note 2.1
Stresses above those listed could cause permanent damage to the device. This is a stress
rating only and functional operation of the device at any other condition above those
indicated in the operation sections of this specification is not implied.
Note 2.2
For the 5V tolerant pins that have a pull-up resistor, the voltage difference between
V5VT_PIN and VDD must never exceed 3.6V.
Note 2.3
The Package Power Dissipation specification assumes a recommended thermal via design
consisting of a 3x3 matrix of 0.3mm (12mil) vias at 1.0mm pitch connected to the ground
plane with a 2.5 x 2.5mm thermal landing.
Note 2.4
Junction to Ambient (θJA) is dependent on the design of the thermal vias. Without thermal
vias and a thermal landing, the θJA is approximately 60°C/W including localized PCB
temperature increase.
Table 2.2 Electrical Specifications
VDD = 3V to 3.6V, TA = 0°C to 100°C, all Typical values at TA = 27°C unless otherwise noted.
CHARACTERISTIC
SYMBOL
MIN
TYP
MAX
UNIT
CONDITIONS
DC Power
Supply Voltage
SMSC CAP1088
VDD
3.0
3.3
3.6
11
DATASHEET
V
Revision 1.1 (08-05-09)
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Table 2.2 Electrical Specifications (continued)
VDD = 3V to 3.6V, TA = 0°C to 100°C, all Typical values at TA = 27°C unless otherwise noted.
CHARACTERISTIC
SYMBOL
Supply Current
MIN
TYP
MAX
UNIT
CONDITIONS
ISTBY
160
210
uA
Standby state active
1 sensor monitored
No LED active
Default conditions (8 avg, 70ms
cycle time)
IDSLEEP
3
10
uA
Deep Sleep state active
LEDs at 100% or 0% Duty Cycle
No communications
TA < 85°C
IDD
300
500
uA
Average current
Capacitive Sensing Active
LEDs enabled
pF
Pad untouched
2
pF
Pad touched
100
%
Programmable
Capacitive Touch Sensor
Maximum Base
Capacitance
Detectable
Capacitive Shift
CBASE
ΔCTOUCH
50
0.1
LED Drivers
Duty Cycle
DUTYLED
Sinking Current
ISINK
24
mA
VOL = 0.4
Sourcing Current
ISOURCE
24
mA
VOH = VDD - 0.4
0
I/O Pins - SPI_CS#, RESET, WAKE / SPI_MOSI, and ALERT# pins
Output Low Voltage
VOL
Output High Voltage
VOH
Input High Voltage
VIH
Input Low Voltage
VIL
0.8
V
Leakage Current
ILEAK
±5
uA
0.4
V
ISINK_IO = 4mA
VDD 0.4
V
WAKE pin only
ISOURCE_IO = 4mA
2.0
V
powered or unpowered
TA < 85°C
SMDATA / BC_DATA / SPI_MSIO / SPI_MISO and SMCLK / BC_CLK / SPI_CLK pins
Output Low Voltage
VOL
Output High Voltage
VOH
Input High Voltage
VIH
Input Low Voltage
VIL
0.8
V
Leakage Current
ILEAK
±5
uA
Revision 1.1 (08-05-09)
0.4
V
ISINK_IO = 8mA
VDD 0.4
V
ISOURCE_IO = 8mA
2.0
V
12
DATASHEET
powered or unpowered
TA < 85°C
pull-up voltage < 3.6V
SMSC CAP1088
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Table 2.2 Electrical Specifications (continued)
VDD = 3V to 3.6V, TA = 0°C to 100°C, all Typical values at TA = 27°C unless otherwise noted.
CHARACTERISTIC
SYMBOL
SMBus First
Communication
tSMB
MIN
TYP
MAX
UNIT
15
ms
CONDITIONS
SMBus Timing
Input Capacitance
CIN
5
pF
Clock Frequency
fSMB
Spike Suppression
tSP
Bus free time Start to
Stop
tBUF
1.3
us
Setup Time: Start
tSU:STA
0.6
us
Setup Time: Stop
tSU:STP
0.6
us
Data Hold Time
tHD:DAT
0.6
6
us
Data Setup Time
tSU:DAT
0.6
72
us
Clock Low Period
tLOW
1.3
us
Clock High Period
tHIGH
0.6
us
Clock/Data Fall time
tFALL
300
ns
Min = 20+0.1CLOAD ns
Clock/Data Rise time
tRISE
300
ns
Min = 20+0.1CLOAD ns
Capacitive Load
CLOAD
400
pF
per bus line
10
400
kHz
50
ns
BC-Link Timing
Clock Period
tCLK
250
ns
Data Hold Time
tHD:DAT
0
ns
Data Setup Time
tSU:DAT
30
ns
Clock Duty Cycle
Duty
40
50
60
Data must be valid before clock
%
SPI Timing
Clock Period
tP
250
Clock Low Period
tLOW
0.4 x tP
0.6 x tP
ns
Clock High Period
tHIGH
0.4 x tP
0.6 x tP
ns
Clock Rise / Fall
time
tRISE /
tFALL
0.1 x tP
ns
Data Output Delay
tD:CLK
10
ns
Data Setup Time
tSU:DAT
20
ns
Data Hold Time
tHD:DAT
20
ns
SMSC CAP1088
ns
13
DATASHEET
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Table 2.2 Electrical Specifications (continued)
VDD = 3V to 3.6V, TA = 0°C to 100°C, all Typical values at TA = 27°C unless otherwise noted.
CHARACTERISTIC
SYMBOL
MIN
SPI_CS# to
SPI_CLK setup time
tSU:CS
0
Wake Time
tWAKE
10
Revision 1.1 (08-05-09)
TYP
MAX
UNIT
CONDITIONS
ns
20
14
DATASHEET
us
SPI_CS# asserted to CLK assert
SMSC CAP1088
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Chapter 3 Communications
3.1
Communications
The CAP1088 communicates using the 2-wire SMBus or I2C bus, the 2-wire proprietary BC-Link, or
the SPI bus. Regardless of communication mechanism, the device functionality remains unchanged.
The communications mechanism as well as the SMBus (or I2C) slave address is determined by the
resistor connected between the ADDR_COMM pin and ground as shown in Table 3.1.
Table 3.1 ADDR_COMM Pin Decode
PULL-DOWN RESISTOR (+/- 5%)
PROTOCOL USED
SMBUS ADDRESS
<= 47k
SPI Communications using
Normal 4-wire Protocol Used
n/a
56k
SPI Communications using BiDirectional 3-wire Protocol Used
n/a
68k
BC-Link Communications
n/a
82k
SMBus / I2C
0101_100(r/w)
100k
SMBus / I2C
0101_011(r/w)
120k
SMBus / I2C
0101_010(r/w)
150k
SMBus /
I2C
0101_001(r/w)
VDD
SMBus / I2C
0101_000(r/w)
3.1.1
SMBus (I2C) Communications
When configured to communicate via the SMBus, the CAP1088 supports the following protocols: Send
Byte, Receive Byte, Read Byte, and Write Byte. In addition, the device supports I2C formatting for block
read and block write protocols.
APPLICATION NOTE: For SMBus/I2C communications, the SPI_CS# pin is not used and should be grounded; any
data presented to this pin will be ignored.
See Section 3.2 and Section 3.3 for more information on the SMBus bus and protocols respectively.
3.1.2
SPI Communications
When configured to communicate via the SPI bus, the CAP1088 supports both bi-directional 3-wire
and normal 4-wire protocols and uses the SPI_CS# pin to enable communications.
See Section 3.4 and Section 3.5 for more information on the SPI bus and protocols respectively.
3.1.3
BC-Link Communications
When BC-Link communications are used, the CAP1088 supports the read byte protocol and the write
byte protocol.
APPLICATION NOTE: For BC-Link communications, the SPI_CS# pin is not used and should be grounded; any
data presented to this pin will be ignored.
See Section 3.7 for more information on the BC-Link Bus and protocols respectively.
SMSC CAP1088
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APPLICATION NOTE: Upon power up, the CAP1088 will not respond to any communications for up to 15ms. After
this time, full functionality is available.
3.2
System Management Bus
The CAP1088 communicates with a host controller, such as an SMSC SIO, through the SMBus. The
SMBus is a two-wire serial communication protocol between a computer host and its peripheral
devices. A detailed timing diagram is shown in Figure 3.1. Stretching of the SMCLK signal is supported;
however, the CAP1088 will not stretch the clock signal.
TLOW
THIGH
THD:STA
TSU:STO
TRISE
SMCLK
THD:STA
THD:DAT
TFALL
TSU:STA
TSU:DAT
SMDATA
TBUF
P
S
S
S - Start Condition
P - Stop Condition P
Figure 3.1 SMBus Timing Diagram
3.2.1
SMBus Start Bit
The SMBus Start bit is defined as a transition of the SMBus Data line from a logic ‘1’ state to a logic
‘0’ state while the SMBus Clock line is in a logic ‘1’ state.
3.2.2
SMBus Address and RD / WR Bit
The SMBus Address Byte consists of the 7-bit client address followed by the RD / WR indicator bit. If
this RD / WR bit is a logic ‘0’, then the SMBus Host is writing data to the client device. If this RD / WR
bit is a logic ‘1’, then the SMBus Host is reading data from the client device.
See Table 3.1 for available SMBus addresses.
3.2.3
SMBus Data Bytes
All SMBus Data bytes are sent most significant bit first and composed of 8-bits of information.
3.2.4
SMBus ACK and NACK Bits
The SMBus client will acknowledge all data bytes that it receives. This is done by the client device
pulling the SMBus Data line low after the 8th bit of each byte that is transmitted. This applies to both
the Write Byte and Block Write protocols.
The Host will NACK (not acknowledge) the last data byte to be received from the client by holding the
SMBus data line high after the 8th data bit has been sent. For the Block Read protocol, the Host will
ACK each data byte that it receives except the last data byte.
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3.2.5
SMBus Stop Bit
The SMBus Stop bit is defined as a transition of the SMBus Data line from a logic ‘0’ state to a logic
‘1’ state while the SMBus clock line is in a logic ‘1’ state. When the CAP1088 detects an SMBus Stop
bit, and it has been communicating with the SMBus protocol, it will reset its client interface and prepare
to receive further communications.
3.2.6
SMBus Timeout
The CAP1088 includes an SMBus timeout feature. Following a 30ms period of inactivity on the SMBus
where the SMCLK pin is held low, the device will timeout and reset the SMBus interface.
The timeout function defaults to disabled. It can be enabled by setting the TIMEOUT bit in the
Configuration register (see Section 5.6).
3.2.7
SMBus and I2C Compliance
The major difference between SMBus and I2C devices is highlighted here. For complete compliance
information refer to the SMBus 2.0 specification.
1. Minimum frequency for SMBus communications is 10kHz.
2. The client protocol will reset if the clock is held low longer than 30ms.
3. The client protocol will reset if both the clock and the data line are high for longer than 150us (idle
condition).
4. I2C devices do not support the Alert Response Address functionality (which is optional for SMBus).
5. I2C devices support block read and write differently. I2C protocol allows for unlimited number of
bytes to be sent in either direction. The SMBus protocol requires that an additional data byte
indicating number of bytes to read / write is transmitted. The CAP1088 supports I2C formatting only.
3.3
SMBus Protocols
The CAP1088 is SMBus 2.0 compatible and supports Send Byte, Read Byte, Block Read, Receive
Byte as valid protocols as shown below. The CAP1088 also supports the I2C block read and block
write protocols. Finally, it will respond to the Alert Response Address protocol but is not in full
compliance.
All of the below protocols use the convention in Table 3.2.
Table 3.2 Protocol Format
DATA SENT
TO DEVICE
Data sent
3.3.1
DATA SENT TO
THE HOST
Data sent
SMBus Write Byte
The Write Byte is used to write one byte of data to a specific register as shown in Table 3.3.
Table 3.3 Write Byte Protocol
START
SLAVE
ADDRESS
WR
ACK
REGISTER
ADDRESS
ACK
REGISTER
DATA
ACK
STOP
1 ->0
YYYY_YYY
0
0
XXh
0
XXh
0
0 -> 1
SMSC CAP1088
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
3.3.2
Block Write
The Block Write is used to write multiple data bytes to a group of contiguous registers as shown in
Table 3.4. It is an extension of the Write Byte Protocol.
APPLICATION NOTE: When using the Block Write protocol, the internal address pointer will be automatically
incremented after every data byte is received. It will wrap from FFh to 00h.
Table 3.4 Block Write Protocol
START
SLAVE
ADDRESS
WR
ACK
REGISTER
ADDRESS
ACK
REGISTER
DATA
ACK
1 ->0
YYYY_YYY
0
0
XXh
0
XXh
0
REGISTER
DATA
ACK
REGISTER
DATA
ACK
...
REGISTER
DATA
ACK
STOP
XXh
0
XXh
0
...
XXh
0
0 -> 1
3.3.3
SMBus Read Byte
The Read Byte protocol is used to read one byte of data from the registers as shown in Table 3.5.
Table 3.5 Read Byte Protocol
START
1->0
SLAVE
ADDRESS
YYYY_YYY
3.3.4
WR
ACK
REGISTER
ADDRESS
ACK
START
CLIENT
ADDRESS
0
0
XXh
0
1 ->0
YYYY_YYY
RD
1
ACK
0
REGISTER
DATA
XXh
NACK
1
STOP
0 -> 1
Block Read
The Block Read is used to read multiple data bytes from a group of contiguous registers as shown in
Table 3.6. It is an extension of the Read Byte Protocol.
APPLICATION NOTE: When using the Block Read protocol, the internal address pointer will be automatically
incremented after every data byte is received. It will wrap from FFh to 00h.
Table 3.6 Block Read Protocol
START
SLAVE
ADDRESS
WR
ACK
REGISTER
ADDRESS
ACK
START
SLAVE
ADDRESS
RD
ACK
REGISTER
DATA
1->0
YYYY_YYY
0
0
XXh
0
1 ->0
YYYY_YYY
1
0
XXh
ACK
REGISTER
DATA
ACK
REGISTER
DATA
ACK
REGISTER
DATA
ACK
...
REGISTER
DATA
NACK
STOP
0
XXh
0
XXh
0
XXh
0
...
XXh
1
0 -> 1
3.3.5
SMBus Send Byte
The Send Byte protocol is used to set the internal address register pointer to the correct address
location. No data is transferred during the Send Byte protocol as shown in Table 3.7.
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Datasheet
Table 3.7 Send Byte Protocol
START
SLAVE
ADDRESS
WR
ACK
REGISTER
ADDRESS
ACK
STOP
1 -> 0
YYYY_YYY
0
0
XXh
0
0 -> 1
3.3.6
SMBus Receive Byte
The Receive Byte protocol is used to read data from a register when the internal register address
pointer is known to be at the right location (e.g. set via Send Byte). This is used for consecutive reads
of the same register as shown in Table 3.8.
Table 3.8 Receive Byte Protocol
START
SLAVE
ADDRESS
RD
ACK
REGISTER DATA
NACK
STOP
1 -> 0
YYYY_YYY
1
0
XXh
1
0 -> 1
3.4
SPI Interface
The SMBus has a predefined packet structure, the SPI does not. The SPI Bus can operate in two
modes of operation, normal 4-wire mode and bi-directional 3-wire mode. All SPI commands consist of
8-bit packets set to a specific slave device (identified by the CS pin).
The SPI bus will latch data on the rising edge of the clock and the clock and data both idle high.
All commands are supported via both operating modes. The supported commands are: Reset Serial
interface, set address pointer, write command and read command. Note that all other codes received
during the command phase are ignored and have no effect on the operation of the device.
tP
tHIGH
tLOW
SPI_CLK
tFALL
tRISE
SPI_MSIO or
SPI_MOSI or
SPI_MISO
tSU:DAT
tD:CLK
tHD:DAT
Figure 3.1 SPI Timing
SMSC CAP1088
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
3.4.1
SPI Normal Mode
The SPI Bus can operate in two modes of operation, normal and bi-directional mode. In the normal
mode of operation, there are dedicated input and output data lines. The host communicates by sending
a command along the CAP1088 SPI_MOSI data line and reading data on the SPI_MISO data line.
Both communications occur simultaneously which allows for larger through put of data transactions.
All basic transfers consist of two 8 bit transactions from the Master device while the slave device is
simultaneously sending data at the current address pointer value.
Data writes consist of two or more 8-bit transactions. The host sends a specific write command
followed by the data to write the address pointer. Data reads consist of one or more 8-bit transactions.
The host sends the specific read data command and continues clocking for as many data bytes as it
wishes to receive.
3.4.2
SPI Bi-Directional Mode
In the bi-directional mode of operation, the SPI data signals are combined into the SPI_MSIO line,
which is shared for data received by the device and transmitted by the device. The protocol uses a
simple handshake and turn around sequence for data communications based on the number of clocks
transmitted during each phase.
All basic transfers consist of two 8 bit transactions. The first is an 8 bit command phase driven by the
Master device. The second is by an 8 bit data phase driven by the Master for writes, and by the
CAP1088 for read operations.
The auto increment feature of the address pointer allows for successive reads or writes. The address
pointer will return to 00h after reaching FFh.
3.4.3
SPI_CS# Pin
The SPI Bus is a single master, multiple slave serial bus. Each slave has a dedicated CS pin (chip
select) that the master asserts low to identify that the slave is being addressed. There are no formal
addressing options.
3.4.4
Address Pointer
All data writes and reads are accessed from the current address pointer. In both Bi-directional mode
and Full Duplex mode, the Address pointer is automatically incremented following every read
command or every write command.
The address pointer will return to 00h after reaching FFh.
3.4.5
SPI Timeout
The CAP1088 does not detect any timeout conditions on the SPI bus.
3.5
Normal SPI Protocols
When operating in normal mode, the SPI bus internal address pointer is incremented depending upon
which command has been transmitted. Multiple commands may be transmitted sequentually so long
as the SPI_CS# pin is asserted low. Figure 3.1 shows an example of this operation.
Revision 1.1 (08-05-09)
20
DATASHEET
SMSC CAP1088
SPI_MOSI
7Ah
7Ah
7Dh
41h
7Eh
66h
7Dh
41h
7Fh
7Fh
7Fh
7Fh
7Fh
7Fh
7Dh
40h
7Fh
7Fh
SPI_MISO
XXh
(invalid)
XXh
(invalid)
YYh
(invalid)
YYh
(invalid)
XXh
(invalid)
45h
AAh
(invalid)
AAh
(invalid)
55h
(invalid)
66h
AAh
AAh
55h
80h
43h
78h
XXh
(invalid)
56h
SPI Address Pointer
SPI Data output buffer
Register Address /
Data
41h
45h
00h
XXh
40h / 56h
41h / 45h
42h / AAh
43h / 55h
44h / 80h
45h / 43h
46h / 78h
42h
AAh
41h
55h
41h
66h
42h
AAh
43h
55h
44h
80h
45h
43h
46h
78h
40h
80h
40h
56h
40h / 56h
41h / 45h
42h / AAh
43h / 55h
44h / 80h
45h / 43h
40h / 56h
41h / 66h
42h / AAh
43h / 55h
44h / 80h
45h / 43h
40h / 56h
41h / 66h
42h / AAh
43h / 55h
44h / 80h
45h / 43h
40h / 56h
41h / 66h
42h / AAh
43h / 55h
44h / 80h
45h / 43h
40h / 56h
41h / 66h
42h / AAh
43h / 55h
44h / 80h
45h / 43h
40h / 56h
41h / 66h
42h / AAh
43h / 55h
44h / 80h
45h / 43h
40h / 56h
41h / 66h
42h / AAh
43h / 55h
44h / 80h
45h / 43h
40h / 56h
41h / 66h
42h / AAh
43h / 55h
44h / 80h
45h / 43h
40h / 56h
41h / 66h
42h / AAh
43h / 55h
44h / 80h
45h / 43h
46h / 78h
46h / 78h
46h / 78h
46h / 78h
46h / 78h
46h /78h
46h /78h
46h / 78h
46h /78h
Indicates SPI Address pointer incremented
21
DATASHEET
Figure 3.1 Example SPI Bus Communication - Normal Mode
3.5.1
Reset Interface
Resets the Serial interface whenever two successive 7Ah codes are received. Regardless of the current phase of the transaction - command or data,
the receipt of the successive reset commands resets the Serial communication interface only. All other functions are not affected by the reset operation.
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SPI_CS#
SMSC CAP1088
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
SPI_CS#
SPI_CLK
Master SPDOUT
SPI_MOSI
‘0’
‘1’
‘1’
‘1’
‘1’
‘0’
‘1’
‘0’
‘0’
Reset - 7Ah
‘1’
‘1’
‘1’
‘0’
‘1’
‘0’
Reset - 7Ah
Invalid register data
SPI_MISO
‘1’
00h – Internal Data buffer empty
Master Drives
Slave Drives
Figure 3.2 SPI Reset Interface Command - Normal Mode
3.5.2
Set Address Pointer
The Set Address Pointer command sets the Address pointer for subsequent reads and writes of data.
The pointer is set on the rising edge of the final data bit. At the same time, the data that is to be read
is fetched and loaded into the internal output buffer but is not transmitted.
SPI_CS#
SPI_CLK
Master SPDOUT
SPI_MOSI
‘0’
‘1’
‘1’
‘1’
‘1’
‘1’
‘0’
Register Address
‘1’
Set Address Pointer – 7Dh
Unknown, Invalid Data
Unknown, Invalid Data
SPI_MISO
Master Drives
Slave Drives
Address pointer set
Figure 3.3 SPI Set Address Pointer Command - Normal Mode
3.5.3
Write Data
The Write Data protocol updates the contents of the register referenced by the address pointer. As the
command is processed, the data to be read is fetched and loaded into the internal output buffer but
not transmitted. Then, the register is updated with the data to be written. Finally, the address pointer
is incremented.
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Datasheet
SPI_CS#
SPI_CLK
Master SPDOUT
SPI_MOSI
Write Command – 7Eh
SPI_MISO
Unknown, Invalid Data
Data to Write
Old Data at Current Address Pointer
Master Drives
Slave Drives
1. Data written at current
address pointer
2. Address pointer incremented
Figure 3.4 SPI Write Command - Normal Mode
3.5.4
Read Data
The Read Data protocol is used to read data from the device. During the normal mode of operation,
while the device is receiving data, the CAP1088 is simultaneously transmitting data to the host. For
the Set Address commands and the Write Data commands, this data may be invalid and it is
recommended that the Read Data command is used.
SPI_CS#
SPI_CLK
Master SPDOUT
SPI_MOSI
‘0’
‘1’
‘1’
‘1’
‘1’
‘1’
‘1’
‘1’
SPI_MISO
Invalid, Unknown Data *
Master Drives
‘0’
‘1’
‘1’
‘1’
‘1’
‘1’
‘1’
‘1’
Subsequent Read
Commands – 7F
First Read Command – 7Fh
Data at Current Address Pointer
Address Pointer
Incremented **
Slave Drives
* The first read command after any other command will return invalid data for the first
byte. Subsequent read commands will return the data at the Current Address Pointer
** The Address Pointer is incremented 8 clocks after the Read Command has been
received. Therefore continually sending Read Commands will result in each command
reporting new data. Once Read Commands have been finished, the last data byte will be
read during the next 8 clocks for any command
Figure 3.5 SPI Read Command - Normal Mode
SMSC CAP1088
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1. Register Read Address
updated to Current SPI Read
Address pointer.
2. Register Read Address
incremented = current address
pointer +1 – end result =
register address pointer doesn’t
change
1. Register Read Address
incremented = current address
pointer + 1
1. Register Read Address
updated to Current SPI Read
Address pointer
SPI_CS#
SPI_MISO
‘0’
‘1’
‘1’
‘1’
‘1’
‘1’
‘1’
‘1’
‘0’
XXh
Read Command – 7Fh
Master SPDOUT
SPI_MOSI
‘1’
‘1’
‘1’
‘1’
‘1’
‘1’
‘1’
Subsequent Read Commands – 7Fh
Data at previously set register address = current
SPI_CLK
address pointer
Data at previously set register address = current
address pointer (SPI)
Master Drives
1. Output buffer transmitted =
data at previous address
1. Register data loaded into
pointer + 1 = current address
output buffer = data at current
pointer
address pointer
Data at previously set register address = current
address pointer (SPI)
Slave Drives
Register Data loaded into
1. Register data loaded into
Output buffer = data at current
output buffer = data at current
address pointer + 1
address pointer
1. SPI Read Address
Incremented = new current
1. Output buffer transmitted =
address pointer
data at current address pointer
2. Register Read Address
+1
Incremented = current address 1. Output buffer transmitted =
2. Flag set to increment SPI
data at previous register
pointer +1
Read Address at end of next 8
address pointer + 1 = current
clocks
address pointer
1. Output buffer transmitted =
data at current address pointer
+1
2. Flag set to increment SPI
Read Address at end of next 8
clocks
Figure 3.6 SPI Read Command - Normal Mode - Full
3.6
3.6.1
Bi-Directional SPI Protocols
Reset Interface
Resets the Serial interface whenever two successive 7Ah codes are received. Regardless of the
current phase of the transaction - command or data, the receipt of the successive reset commands
resets the Serial communication interface only. All other functions are not affected by the reset
operation.
SPI_CS#
SPI_CLK
Master SPDOUT
SPI_MSIO
‘0’
‘1’
‘1’
‘1’
‘1’
‘0’
‘1’
‘0’
‘0’
‘1’
‘1’
‘1’
‘1’
‘0’
‘1’
‘0’
Reset - 7Ah
Reset - 7Ah
Figure 3.7 SPI Reset Interface Command - Bi-directional Mode
3.6.2
Set Address Pointer
Sets the address pointer to the register to be accessed by a read or write command. This command
overrides the auto-incrementing of the address pointer.
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SPI_CS#
SPI_CLK
Master SPDOUT
SPI_MSIO
‘0’
‘1’
‘1’
‘1’
‘1’
‘1’
‘0’
Register Address
‘1’
Set Address Pointer – 7Dh
Figure 3.8 SPI Set Address Pointer Command - Bi-directional Mode
3.6.3
Write Data
Writes data value to the register address stored in the address pointer. Performs auto increment of
address pointer after the data is loaded into the register.
SPI_CS#
SPI_CLK
Master SPDOUT
SPI_MSIO
‘0’
‘1’
‘1’
‘1’
‘1’
‘1’
‘1’
‘0’
Register Write Data
Write Command – 7Eh
Figure 3.9 SPI Write Data Command - Bi-directional Mode
3.6.4
Read Data
Reads data referenced by the address pointer. Performs auto increment of address pointer after the
data is transferred to the Master.
SPI_CS#
SPI_CLK
Master SPDOUT
SPI_MSIO
‘0’
‘1’
‘1’
‘1’
‘1’
‘1’
‘1’
Register Read Data
‘1’
Read Command – 7Fh
Master Drives
Slave Drives
Indeterminate
Figure 3.10 SPI Read Data Command - Bi-directional Mode
3.7
BC-Link Interface
The BC-Link is a proprietary bus developed to allow communication between a host controller device
to a companion device. This device uses this serial bus to read and write registers and for interrupt
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processing. The interface uses a data port concept, where the base interface has an address register,
data register and a control register, defined in the SMSC’s 8051’s SFR space.
Refer to documentation for the BC-Link comptabile host controller for details on how to access the
CAP1088 via the BC-Link Interface.
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Chapter 4 General Description
The CAP1088 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 automatically recalibrates to compensate for gradual
environmental changes.
The CAP1088 also contains eight (8) low side (or push-pull) 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
sensors to be actuated when a touch is detected. As well, each LED driver may be individually
controlled via a host controller.
Finally, the device contains a dedicated RESET pin to act as a soft reset by the system.
The CAP1088 offers multiple power states operating at low quiescent currents during its Deep Sleep
state. The device also contains a wake pin (WAKE/SPI_MOSI) output to wake the system when a
touch is detected in Standby and to wake the device from Deep Sleep. It can monitor one or more
channels while in a lower power state and respond to communications normally.
The device communicates with a host controller using the SPI bus, SMSC BC-Link bus, or via SMBus
/ I2C. The host controller may poll the device for updated information at any time or it may configure
the device to flag an interrupt whenever a touch is detected on any sensor.
A typical system diagram is shown in Figure 4.1.
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LED1
Touch
Button
Touch
Button
Touch
Button
Touch
Button
SPI_CS#
RESET
WAKE / SPI_MOSI
ALERT# / BC_IRQ#
SMCLK / BC_CLK / SPI_CLK
3.3V – 5V
SMDATA / BC_DATA / SPI_MSIO / SPI_MISO
Embedded Controller
VDD
ADDR_COMM
3.3V – 5V
CAP1088
LED8
CS1
CS8
LED2
LED7
CS2
CS7
LED3
LED6
CS3
CS6
LED4
LED5
CS4
CS5
Touch
Button
Touch
Button
Touch
Button
Touch
Button
Figure 4.1 System Diagram for CAP1088
4.1
Power States
The CAP1088 has three operating states depending on the status of the STBY and DSLEEP bits.
When the device transitions between power states, previously detected touches (for inactive channels)
are cleared and the status bits reset.
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1. Fully Active - The device is fully active. It is monitoring all active Capacitive Sensor channels and
driving all LED channels as defined.
2. Standby - The device is in a lower power state. It will measure a programmable number of channels
(as determined by the Standby Channel register - default none). Interrupts will still be generated
based on the active channels. The device will still respond to communications normally and can
be returned to the Fully Active state of operation by clearing the STBY bit.
3. Deep Sleep - The device is in its lowest power state. It is not monitoring any Capacitive Sensor
channels. It can be awakened by SMBus or SPI communications targeting the device (which will
cause the DSLEEP bit to be automatically cleared).
If the device is not communicating via the 4-wire SPI bus, then during this state of operation, if the
WAKE/SPI_MOSI pin is driven high by an external source, the device will clear the DSLEEP bit
and return to Fully Active.
APPLICATION NOTE: The Deep Sleep state does not change LED drive behavior so it is It is the user’s
responsibility to ensure that the LEDs are driven to the desired state prior to entering Deep
Sleep. This is best achieved by unlinking the LEDs from the sensors and driving the LEDs
to the desired state using the LED Output Control register.
APPLICATION NOTE: If the CAP1088 is configured to communicate using the BC-Link protocol, the device does
not support Deep Sleep.
4.2
RESET Pin
The RESET pin is an active high reset that is driven from an external source. While it is asserted high,
all the internal blocks will be held in reset including the communications protocol used. No Capacative
Touch sensors will be sampled and the LEDs will not be driven.
All configuration settings will be reset to default states (thus waking the device from Deep Sleep) and
all readings will be cleared. Once the RESET pin is pulled low, the CAP1088 will begin operation as
if a power-on-reset had occurred.
4.3
WAKE/SPI_MOSI Pin Operation
When the CAP1088 is placed in Standby, and is not communicating using the 4-wire SPI protocol,it
will assert the WAKE/SPI_MOSI pin when a touch is detected on one of its sampled sensors. The pin
will remain asserted until the INT bit has been cleared and then it will be de-asserted.
When the CAP1088 is placed in Deep Sleep and it is not commuicating using the 4-wire SPI protocol,
the WAKE/SPI_MOSI pin is monitored by the device as an input. If the WAKE/SPI_MOSI pin is driven
high by an external source, the CAP1088 will clear the DSLEEP bit.
When the device is placed in Deep Sleep, this pin is a High-Z input and must have a pull-down resistor
to GND for proper operation.
4.4
LED Drivers
The CAP1088 contains eight (8) LED Drivers. Each LED driver can be configured to operate in one of
the following modes with either push-pull or open drain drive. Additionally, each LED driver can be
linked to the respective Capacitive Touch sensor input.
1. Direct - The LED is configured to be on or off when the corresponding input stimulus is on or off
(or inverted). The brightness of the LED can be programmed from full off to full on (default).
Additionally, the LED contains controls to individually configure ramping on, off, and turn-off delay.
2. Pulse 1 - The LED is configured to fade ON-OFF-ON a programmable number of times with
programmable rate and min / max brightness. This behavior may be actuated when a press is
detected, or when a release is detected.
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3. Pulse 2 - The LED is configured to “Breathe” while actuated and then “Pulse” when the sensor is
released.
4. Breathe - The LED is configured to fade continuously ON-OFF-ON (i.e. to "Breathe”) with a
programmable rate and min / max brightness.
In addition to these four behaviors, all LED drivers support host initiated LED actuation. All LEDs also
have an option to assert the ALERT# pin when the initated behavior has reached its maximum or
minimum brightness levels.
4.4.1
Linking LEDs to Capacitive Touch Sensors
All LEDs can be linked to the corresponding Capacitive Touch Sense input channel so that when the
sensor detects a touch, the corresponding LED will be actuated at one of the programmed responses.
4.5
Capacitive Touch Sensing
The CAP1088 contains eight (8) independent Capacitive Touch Sensor inputs. Each sensor has
dynamic range to detect a change of capacitance due to a touch. Additionally, each sensor can be
configured to be automatically and routinely re-calibrated.
4.5.1
Sensing Cycle
Each Capacitive Touch Sensor has controls to be activated and included in the sensing cycle. When
the device is active, it automatically initiates a sensing cycle and repeats the cycle every time it
finishes. The cycle polls through each active Sensor starting with CS1 and extending through CS8. As
each Capacitive Touch Sensor is polled, its measurement is compared against a baseline “not touched”
measurement. If the delta measurement is large enough, then a touch is detected and an interrupt
generated.
The sensing cycle time is programmable (see Section 5.10).
4.5.2
Recalibrating Sensors
Each sensor is regularly recalibrated at an adjustable rate. By default, the recalibration routine stores
the average 256 previous measurements and periodically updates the base “Not Touched” setting for
the Capacitive Touch Sensor input.
It is possible that the device loses sensitivity to a touch. This may happen as a result of a noisy
environment, an accidental recalibration during a touch, or other environmental changes. When this
occurs, then the base untouched sensor may generate negative delta count values. The device will
detect this condition based on a programmable number of consecutive negative delta readings. When
it detects the condition, the CAP1088 will automatically re-calibrate the base-count settings. During this
recalibration, the device will not respond to touches.
4.6
ALERT# Pin
The ALERT# pin is an active low output that is driven when an interrupt event is detected.
Whenever an interrupt is generated, the INT bit (see Section 5.1) is set. The ALERT# pin is cleared
when INT bit is cleared by the user. Additionally, when the INT bit is cleared by the user, status bits
are only cleared if no touch is detected.
4.6.1
Sensor Interrupt Behavior
The sensor interrupts are generated in one of two ways:
1. An interrupt is generated when a touch is detected and when a release is detected (see Figure 4.3).
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2. If the repeat rate is enabled (see Section 5.6), then, so long as the touch is held, another interrupt
will be generated based on the programmed repeat rate (see Figure 4.2).
When the repeat rate is enabled, the device uses an additional control called MPRESS that determines
whether a touch is flagged as a simple “touch” or a “press and hold”. The MPRESS[3:0] bits set a
minimum press timer. When the button is touched the timer begins. If the sensor is released before
the minimum press timer expires, then it is flagged as a touch and an interrupt is generated upon the
release. If the sensor detects a touch for longer than this timer value, then it is flagged as a “press
and hold” event. So long as the touch is held, interrupts will be generated at the programmed repeat
rate and upon a release.
Interrupt on
Touch
Polling Cycle
(35ms)
Interrupt on
Release
Button Repeat Rate
(175ms)
Touch Detected
Button Repeat Rate
(175ms)
Button Repeat Rate
(175ms)
ALERT Pin / INT bit
Button Status
SMBus Write to INT bit
Figure 4.2 Sensor Interrupt Behavior - Repeat Rate Enabled
APPLICATION NOTE: The host may need to poll the device twice to determine that a release has been detected.
Interrupt on
Touch
Polling Cycle
(35ms)
Interrupt on
Release
Touch Detected
ALERT Pin /
INT bit
Button Status
SMBus Write to
INT bit
Figure 4.3 Sensor Interrupt Behavior - No Repeat Rate Enabled
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Chapter 5 Register Description
The registers shown in Table 5.1 are accessible through the communications protocol. An entry of ‘-’
indicates that the bit is not used and will always read ‘0’.
Table 5.1 Register Set in Hexadecimal Order
REGISTER
ADDRESS
R/W
REGISTER NAME
FUNCTION
DEFAULT
VALUE
PAGE
00h
R/W
Main Status Control
Controls general power states and
power dissipation
00h
Page 35
03h
R
Sensor Status
Returns the state of the sampeld
Capacative Touch Sensor
00h
Page 36
04h
R
LED Status
Stores status bits for LEDs
00h
Page 36
0Ah
R
Noise Flag Status
Stores the noise flags for sensors
00h
Page 37
10h
R
Sensor 1 Delta Count
Stores the delta count for CS1
00h
Page 37
11h
R
Sensor 2 Delta Count
Stores the delta count for CS2
00h
Page 37
12h
R
Sensor 3 Delta Count
Stores the delta count for CS3
00h
Page 37
13h
R
Sensor 4 Delta Count
Stores the delta count for CS4
00h
Page 37
14h
R
Sensor 5 Delta Count
Stores the delta count for CS5
00h
Page 37
15h
R
Sensor 6 Delta Count
Stores the delta count for CS6
00h
Page 37
16h
R
Sensor 7 Delta Count
Stores the delta count for CS7
00h
Page 37
17h
R
Sensor 8 Delta Count
Stores the delta count for CS8
00h
Page 37
1Fh
R/W
Sensitivity Control
Controls the sensitivity of the
threshold and delta counts and data
scaling of the base counts
2Fh
Page 38
20h
R/W
Configuration
Controls general functionality and
LED controls
20h
Page 39
21h
R/W
Sensor Enable
Controls whether the Capacitive
Touch Sensor inputs are sampled
FFh
Page 40
22h
R/W
Sensor Configuration
Controls reset delay and auto-repeat
delay for sensors operating in the full
power state
A4h
Page 41
23h
R/W
Sensor Configuration
2
Controls the MPRESS controls for all
sensors
07h
Page 42
24h
R/W
Averaging and
Sampling Config
Controls averaging and sampling
window
1Dh
Page 43
26h
R/W
Calibration Activate
Activates manual re-calibration for
Capacative Touch Sensors
FFh
Page 44
27h
R/W
Interrupt Enable
Enables Interrupts associated with
Capacative Touch Sensors
FFh
Page 45
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Table 5.1 Register Set in Hexadecimal Order (continued)
REGISTER
ADDRESS
R/W
REGISTER NAME
FUNCTION
DEFAULT
VALUE
PAGE
28h
R/W
Repeat Rate Enable
Enables repeat rate for Capacative
Touch Sensors
FFh
Page 45
2Ah
R/W
Multiple Press
Configuration
Determines the number of
simultaneous touches to flag a
multiple touch condition
80h
Page 46
2Fh
R/W
Recalibration
Configuration
Determines re-calibration timing and
sampling window
8Bh
Page 47
30h
R/W
Sensor 1 Threshold
Stores the delta count threshold to
determine a touch for Capacitive
Touch Sensor 1
40h
Page 48
31h
R/W
Sensor 2 Threshold
Stores the delta count threshold to
determine a touch for Capacitive
Touch Sensor 2
40h
Page 48
32h
R/W
Sensor 3 Threshold
Stores the delta count threshold to
determine a touch for Capacitive
Touch Sensor 3
40h
Page 48
33h
R/W
Sensor 4 Threshold
Stores the delta count threshold to
determine a touch for Capacitive
Touch Sensor 4
40h
Page 48
34h
R/W
Sensor 5 Threshold
Stores the delta count threshold to
determine a touch for Capacitive
Touch Sensor 5
40h
Page 48
35h
R/W
Sensor 6 Threshold
Stores the delta count threshold to
determine a touch for Capacitive
Touch Sensor 6
40h
Page 48
36h
R/W
Sensor 7 Threshold
Stores the delta count threshold to
determine a touch for Capacitive
Touch Sensor 7
40h
Page 48
37h
R/W
Sensor 8 Threshold
Stores the delta count threshold to
determine a touch for Capacitive
Touch Sensor 8
40h
Page 48
38h
R/W
Sensor Noise
Threshold 1
Stores controls for selecting the
noise threshold for sensors 1 - 4
55h
Page 49
39h
R/W
Sensor Noise
Threshold 2
Stores controls for selecting the
noise threshold for sensors 5 - 8
55h
Page 49
Standby Configuration Registers
40h
R/W
Standby Channel
Controls which sensors are enabled
while in standby
00h
Page 50
41h
R/W
Standby Configuration
Controls averaging and cycle time
while in standby
1Dh
Page 50
42h
R/W
Standby Sensitivity
Controls sensitivity settings used
while in standby
02h
Page 52
43h
R/W
Standby Threshold
Stores the touch detection threshold
for active sensors in standby
40h
Page 52
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Table 5.1 Register Set in Hexadecimal Order (continued)
REGISTER
ADDRESS
R/W
REGISTER NAME
FUNCTION
DEFAULT
VALUE
PAGE
50h
R
Sensor 1 Base Count
Stores the reference count value for
sensor 1
C8h
Page 53
51h
R
Sensor 2 Base Count
Stores the reference count value for
sensor 2
C8h
Page 53
52h
R
Sensor 3 Base Count
Stores the reference count value for
sensor 3
C8h
Page 53
53h
R
Sensor 4 Base Count
Stores the reference count value for
sensor 4
C8h
Page 53
54h
R
Sensor 5 Base Count
Stores the reference count value for
sensor 5
C8h
Page 53
55h
R
Sensor 6 Base Count
Stores the reference count value for
sensor 6
C8h
Page 53
56h
R
Sensor 7 Base Count
Stores the reference count value for
sensor 7
C8h
Page 53
57h
R
Sensor 8 Base Count
Stores the reference count value for
sensor 8
C8h
Page 53
71h
R/W
LED Output Type
Controls the output type for the LED
outputs
00h
Page 53
72h
R/W
Sensor LED Linking
Controls linking of sensors to LED
channels
00h
Page 56
73h
R/W
LED Polarity
Controls the output polarity of LEDs
00h
Page 57
74h
R/W
LED Output Control
Controls the output state of the LEDs
00h
Page 54
81h
R/W
LED Behavior 1
Controls the behavior and response
of LEDs 1 - 4
00h
Page 57
82h
R/W
LED Behavior 2
Controls the behavior and response
of LEDs 5 - 8
00h
Page 57
84h
R/W
LED Pulse 1 Period
Controls the period of each breathe
during a pulse
20h
Page 59
85h
R/W
LED Pulse 2 Period
Controls the period of the breathing
during breathe and pulse operation
14h
Page 60
86h
R/W
LED Breathe Period
Controls the period of an LED
breathe operation
5Dh
Page 61
88h
R/W
LED Config
Controls LED configuration
04h
Page 62
90h
R/W
LED Pulse 1 Duty
Cycle
Determines the min and max duty
cycle for the pulse operation
F0h
Page 63
91h
R/W
LED Pulse 2 Duty
Cycle
Determines the min and max duty
cycle for breathe and pulse
operation
F0h
Page 63
92h
R/W
LED Breathe Duty
Cycle
Determines the min and max duty
cycle for the breathe operation
F0h
Page 63
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Table 5.1 Register Set in Hexadecimal Order (continued)
REGISTER
ADDRESS
R/W
REGISTER NAME
FUNCTION
DEFAULT
VALUE
PAGE
93h
R/W
LED Direct Duty Cycle
Determines the min and max duty
cycle for Direct mode LED operation
F0h
Page 63
94h
R/W
LED Direct Ramp
Rates
Determines the rising and falling
edge ramp rates of the LEDs
00h
Page 64
95h
R/W
LED Off Delay
Determines the off delay for all LED
behaviors
00h
Page 65
FDh
R
Product ID
Stores a fixed value that identifies
each product
40h
Page 66
FEh
R
Manufacturer ID
Stores a fixed value that identifies
SMSC
5Dh
Page 66
FFh
R
Revision
Stores a fixed value that represents
the revision number
81h
Page 66
During Power-On-Reset (POR), the default values are stored in the registers. A POR is initiated when
power is first applied to the part and the voltage on the VDD supply surpasses the POR level as
specified in the electrical characteristics. Any reads to undefined registers will return 00h. Writes to
undefined registers will not have an effect.
5.1
Main Status Control Register
Table 5.2 Main Status Control Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
00h
R/W
Main Status
Control
-
-
STBY
DSLEEP
-
-
-
INT
00h
The Main Status and Control register controls the primary power state of the device.
Bit 5 - STBY - Enables Standby.

‘0’ (default) - Sensor scanning is active and LEDs are functional.

‘1’ - Capacitive Touch Sensor scanning is limited to the sensors set in the Standby Channel register
(see Section 5.18). The status registers will not be cleared until read. LEDs that are linked to
Capacitive Touch sensors will remain linked and active. Sensors that are no longer sampled will
flag a release and then remain in a non-touched state. LEDs that are manually controlled will be
unaffected.
Bit 4 - DSLEEP - Enables Deep Sleep by deactivating all functions. This bit will be cleared when the
WAKE pin is driven high or when SPI or SMBus are received targeting the CAP1088. If the CAP1088
is configured to communicate using the BC-Link protocol, then this bit is ignored.

‘0’ (default) - Sensor scanning is active and LEDs are functional.

‘1’ - All sensor scanning is disabled and all LEDs are disabled. The status registers are
automatically cleared and the INT bit is cleared.
Bit 0 - INT - Indicates that there is an interrupt. This bit is only set if the ALERT# pin has been asserted.
If a channel detects a touch and its associated interrupt enable bit is not set to a logic ‘1’ then no
action is taken.
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This bit is cleared by writing a logic ‘0’ to it. When this bit is cleared, the ALERT# pin will be deasserted
and all status registers will be cleared if the condition has been removed. If the WAKE/SPI_MOSI pin
is asserted as a result of a touch detected while in Standby, it will likewise be deasserted when this
bit is cleared.
Note that this pin is not driven when communicating via the 4-wire SPI protocol
5.2

‘0’ - No interrupt pending.

‘1’ - A touch has been detected on one or more channels and the interrupt has been asserted.
Status Registers
Table 5.3 Status Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
03h
R
Sensor Status
CS8
CS7
CS6
CS5
CS4
CS3
CS2
CS1
00h
04h
R
LED Status
LED8_
DN
LED7_
DN
LED6_
DN
LED5_
DN
LED4_
DN
LED3_
DN
LED2_
DN
LED1_
DN
00h
The Sensor Status Registers store status bits that indicate a touch has been detected. A value of ‘0’
in any bit indicates that no touch has been detected. A value of ‘1’ in any bit indicates that a touch
has been detected.
All status bits are cleared when the device enters the Deep Sleep (DSLEEP = ‘1’ - see Section 5.1).
All status bits are cleared when the INT bit is cleared and if a touch on the respective Capacitive Touch
Sensor is no longer present. If a touch is still detected, then the bits will not be cleared (but this will
not cause the interrupt to be asserted - see Section 5.6).
5.2.1
Sensor Status
Bit 7 - CS8 - Indicates that a touch was detected on Sensor 8. This sensor can be linked to LED8.
Bit 6 - CS7 - Indicates that a touch was detected on Sensor 7. This sensor can be linked to LED7.
Bit 5 - CS6 - Indicates that a touch was detected on Sensor 6. This sensor can be linked to LED6.
Bit 4 - CS5 - Indicates that a touch was detected on Sensor 5. This sensor can be linked to LED5.
Bit 3 - CS4 - Indicates that a touch was detected on Sensor 4. This sensor can be linked to LED4.
Bit 2 - CS3 - Indicates that a touch was detected on Sensor 3. This sensor can be linked to LED3.
Bit 1 - CS2 - Indicates that a touch was detected on Sensor 2. This sensor can be linked to LED2.
Bit 0 - CS1 - Indicates that a touch was detected on Sensor 1. This sensor can be linked to LED1.
5.2.2
LED Status
Bit 7 - LED8_DN - Indicates that LED8 has finished its ramping behavior as determined by the
LED8_CTL bits.
Bit 6 - LED7_DN - Indicates that LED7 has finished its ramping behavior as determined by the
LED7_CTL bits.
Bit 5 - LED6_DN - Indicates that LED6 has finished its ramping behavior as determined by the
LED6_CTL bits.
Bit 4 - LED5_DN - Indicates that LED5 has finished its ramping behavior as determined by the
LED5_CTL bits.
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Bit 3 - LED4_DN - Indicates that LED4 has finished its ramping behavior as determined by the
LED4_CTL bits.
Bit 2 - LED3_DN - Indicates that LED3 has finished its ramping behavior as determined by the
LED3_CTL bits.
Bit 1 - LED2_DN - Indicates that LED2 has finished its ramping behavior as determined by the
LED2_CTL bits.
Bit 0 - LED1_DN - Indicates that LED1 has finished its ramping behavior as determined by the
LED1_CTL bits.
5.3
Noise Flag Status Registers
Table 5.4 Noise Flag Status Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
0Ah
R
Noise Flag Status
CS8_
NOISE
CS7_
NOISE
CS6_
NOISE
CS5_
NOISE
CS4_
NOISE
CS3_
NOISE
CS2_
NOISE
CS1_
NOISE
00h
The Noise Flag Status registers store status bits that are generated from the analog block if the
detected noise is above the operating region of the analog detector. These bits indicate that the most
recently received data from the sensor is invalid and should not be used for touch detection.
Furthermore, so long as the bit is set for a particular channel, no decisions are made with the data. A
touch is not detected, and a release is not detected.
These bits are not sticky and will be cleared automatically if the analog block does not report a noise
error.
5.4
Sensor Delta Count Registers
Table 5.5 Sensor Delta Count Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
10h
R
Sensor 1 Delta
Count
Sign
64
32
16
8
4
2
1
00h
11h
R
Sensor 2 Delta
Count
Sign
64
32
16
8
4
2
1
00h
12h
R
Sensor 3 Delta
Count
Sign
64
32
16
8
4
2
1
00h
13h
R
Sensor 4 Delta
Count
Sign
64
32
16
8
4
2
1
00h
14h
R
Sensor 5 Delta
Count
Sign
64
32
16
8
4
2
1
00h
15h
R
Sensor 6 Delta
Count
Sign
64
32
16
8
4
2
1
00h
16h
R
Sensor 7 Delta
Count
Sign
64
32
16
8
4
2
1
00h
17h
R
Sensor 8 Delta
Count
Sign
64
32
16
8
4
2
1
00h
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
The Sensor Delta Count registers store the delta count that is compared against the threshold used to
determine if a touch has been detected. The count value represents a change in input due to the
capacitor associated with a touch on one of the sensors and is referenced to a calibrated base “Not
touched” count value. The delta is an instantaneous change and is updated once per sensor per
sensing cycle (see Section 4.5.1 - sensor cycle).
The value presented is a standard 2’s complement number. In addition, the value is capped at a value
of 7Fh. A reading of 7Fh indicates that the sensitivity settings are too high and should be adjusted
accordingly (see Section 5.5).
The value is also capped at a negative value of FFh for negative delta counts which may result upon
a release.
5.5
Sensitivity Control Register
Table 5.6 Sensitivity Control Register
ADDR
R/W
REGISTER
B7
1Fh
R/W
Sensitivity Control
-
B6
B5
B4
DELTA_SENSE[2:0]
B3
B2
B1
B0
DEFAULT
BASE_SHIFT[3:0]
The Sensitivity Control register controls the sensitivity of a touch detection.
Bits 6- 4 DELTA_SENSE[2:0] - Controls the sensitivity of a touch detection. The sensitivity settings act
to scale the relative delta count value higher or lower based on the system parameters. A setting of
000b is the most sensitive while a setting of 111b is the least sensitive. At the more sensitive settings,
touches are detected for a smaller delta C corresponding to a “lighter” touch. These settings are more
sensitive to noise however and a noisy environment may flag more false touches than higher sensitivity
levels.
APPLICATION NOTE: A value of 128x is the most sensitive setting available. At the most sensitivity settings, the
MSB of the Delta Count register represents 64 out of ~25,000 which corresponds to a touch
of approximately 0.25% of the base capacitance (or a ΔC of 25fF from a 10pF base
capacitance). Conversely a value of 1x is the least sensitive setting available. At these
settings, the MSB of the Delta Count register corresponds to a delta count of 8192 counts
out of ~25,000 which corresponds to a touch of approximately 33% of the base capacitance
(or a ΔC of 3.33pF from a 10pF base capacitance).
Table 5.7 DELTA_SENSE Bit Decode
DELTA_SENSE[2:0]
2
1
0
SENSITIVITY MULTIPLIER
0
0
0
128x (most sensitive)
0
0
1
64x
0
1
0
32x (default)
0
1
1
16x
1
0
0
8x
1
0
1
4x
1
1
0
2x
1
1
1
1x - (least sensitive)
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2Fh
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Bits 3 - 0 - BASE_SHIFT[3:0] - Controls the scaling and data presentation of the Base Count registers.
The higher the value of these bits, the larger the range and the lower the resolution of the data
presented. The scale factor represents the multiplier to the bit-weighting presented in these register
descriptions.
APPLICATION NOTE: The BASE_SHIFT[3:0] bits normally do not need to be updated. These settings will not affect
touch detection or sensitivity. These bits are sometimes helpful in analyzing the Cap Sensing
board performance and stability.
Table 5.8 BASE_SHIFT Bit Decode
BASE_SHIFT[3:0]
3
2
1
0
DATA SCALING
FACTOR
0
0
0
0
1x
0
0
0
1
2x
0
0
1
0
4x
0
0
1
1
8x
0
1
0
0
16x
0
1
0
1
32x
0
1
1
0
64x
0
1
1
1
128x
1
0
0
0
256x
256x
(default = 1111b)
All others
5.6
Configuration Register
Table 5.9 Configuration Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
20h
R/W
Configuration
TIMEOUT
WAKE_
CFG
BLK_ DIG_
NOISE
BLK_ ANA_
NOISE
MAX_DUR_
EN
-
-
-
20h
The Configuration register controls general global functionality that affects the entire device.
Bit 7 - TIMEOUT - Enables the timeout and idle functionality of the SMBus protocol.

‘0’ (default) - The SMBus timeout and idle functionality are disabled. The SMBus interface will not
time out if the clock line is held low. Likewise, it will not reset if both the data and clock lines are
held high for longer than 150us. This is used for I2C compliance.

‘1’ - The SMBus timeout and idle functionality are enabled. The SMBus interface will time out if the
clock line is held low for longer than 30ms. Likewise, it will reset if both the data and clock lines
are held high for longer than 150us.
Bit 6 - WAKE_CFG - Configures the operation of the WAKE pin.

SMSC CAP1088
‘0’ (default) - The WAKE pin is not asserted when a touch is detected while the device is in Standby.
It will still be used to wake the device from Deep Sleep when driven high.
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‘1’ - The WAKE pin will be asserted high when a touch is detected while the device is in Standby.
It will also be used to wake the device from Deep Sleep when driven high.
Bit 5 - BLK_DIG_NOISE - Determines whether the digital noise threshold is used by the device.

‘0’ - The digital noise threshold is used. If a delta count value exceeds the noise threshold but does
not exceed the touch threshold, then the sample is discarded and not used for the automatic recalibration routine.

‘1’ (default) - The noise threshold is not used. Any delta count that is less than the touch threshold
is used for the automatic re-calibration routine.
Bit 4 - BLK_ANA_NOISE - Determines whether the analog noise flag setting will block a touch
detection as well as the analog calibration routine.

‘0’ (default) - If the analog noise bit is set, then a touch is blocked on the corresponding channel
and will force the analog calibration routine to retry.

‘1’ - A touch is not blocked even if the analog noise bit is set. Likewise, the analog calibration
routine will not retry if the analog noise bit is set.
Bit 3 - MAX_DUR_EN - Determines whether the maximum duration recalibration is enabled for nongrouped sensors.
5.7

‘0’ (default) - The maximum duration recalibration functionality is disabled. A touch may be held
indefinitely and no re-calibration will be performed on any sensor.

‘1’ - The maximum duration recalibration functionality is enabled. If a touch is held for longer than
the MAX_DUR bit settings, then the re-calibration routine will be restarted (see Section 5.8).
Sensor Enable Registers
Table 5.10 Sensor Enable Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
21h
R/W
Sensor Enable
CS8_EN
CS7_EN
CS6_EN
CS5_EN
CS4_EN
CS3_EN
CS2_EN
CS1_EN
FFh
The Sensor Enable registers determine whether a Capacitive Touch Sensor input is included in the
sampling cycle. The length of the sampling cycle is not affected by the number of sensors measured.
Bit 7 - CS8_EN - Enables the CS8 input to be included during the sampling cycle.

‘0’ - The CS8 input is not included in the sampling cycle.

‘1’ (default) - The CS8 input is included in the sampling cycle.
Bit 6 - CS7_EN - Enables the CS7 input to be included during the sampling cycle.
Bit 5 - CS6_EN - Enables the CS6 input to be included during the sampling cycle.
Bit 4 - CS5_EN - Enables the CS5 input to be included during the sampling cycle.
Bit 3 - CS4_EN - Enables the CS4 input to be included during the sampling cycle.
Bit 2 - CS3_EN - Enables the CS3 input to be included during the sampling cycle.
Bit 1 - CS2_EN - Enables the CS2 input to be included during the sampling cycle.
Bit 0 - CS1_EN - Enables the CS1 input to be included during the sampling cycle.
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
5.8
Sensor Configuration Register
Table 5.11 Sensor Configuration Register
ADDR
R/W
REGISTER
22h
R/W
Sensor
Configuration
B7
B6
B5
B4
B3
MAX_DUR[3:0]
B2
B1
B0
DEFAULT
RPT_RATE[3:0]
A4h
The Sensor Configuration Register controls timings associated with the Capacitive Sensor channels 1
- 8.
Bits 7 - 4 - MAX_DUR[3:0] - (default 1010b) - Determines the maximum time that a sensor is allowed
to be touched until the Capacitive Touch sensor is recalibrated as shown in Table 5.12.
Table 5.12 MAX_DUR Bit Decode
MAX_DUR[3:0]
3
2
1
0
TIME BEFORE RECALIBRATION
0
0
0
0
560ms
0
0
0
1
840ms
0
0
1
0
1120ms
0
0
1
1
1400ms
0
1
0
0
1680ms
0
1
0
1
2240ms
0
1
1
0
2800ms
0
1
1
1
3360ms
1
0
0
0
3920ms
1
0
0
1
4480ms
1
0
1
0
5600ms
1
0
1
1
6720ms
1
1
0
0
7840ms
1
1
0
1
8906ms
1
1
1
0
10080ms
1
1
1
1
11200ms
Bits 3 - 0 - RPT_RATE[3:0] - (default 0100b) Determines the time duration between interrupt assertions
when auto repeat is enabled. The resolution is 35ms the range is from 35ms to 560ms as shown in
Table 5.13.
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Table 5.13 RPT_RATE Bit Decode
RPT_RATE[3:0] OR M_PRESS[3:0]
3
2
1
0
INTERRUPT REPEAT RATE
OR M_PRESS TIME
0
0
0
0
35ms
0
0
0
1
70ms
0
0
1
0
105ms
0
0
1
1
140ms
0
1
0
0
175ms
0
1
0
1
210ms
0
1
1
0
245ms
0
1
1
1
280ms
1
0
0
0
315ms
1
0
0
1
350ms
1
0
1
0
385ms
1
0
1
1
420ms
1
1
0
0
455ms
1
1
0
1
490ms
1
1
1
0
525ms
1
1
1
1
560ms
5.9
Sensor Configuration 2 Register
Table 5.14 Sensor Configuration 2 Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
23h
R/W
Sensor
Configuration 2
-
-
-
-
B3
B2
B1
M_PRESS[3:0]
B0
DEFAULT
07h
Bits 3- 0 - M_PRESS[3:0] - (default 0111b) - Determines the minimum amount of time that sensors
configured to use auto repeat must detect a sensor touch to detect a “press and hold” event. If the
sensor detects a touch for longer than the M_PRESS[3:0] settings, then a “press and hold” event is
detected.
This is the maximum amount of time that sensors can detect a sensor touch to differentiate between
a “touch” and a “press and hold”. If a sensor detects a touch for less than or equal to the
M_PRESS[3:0] settings, then a touch event is detected.
The resolution is 35ms the range is from 35ms to 560ms as shown in Table 5.13.
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
5.10
Averaging and Sampling Configuration Register
Table 5.15 Averaging and Sampling Configuration Register
ADDR
R/W
REGISTER
24h
R/W
Averaging and
Sampling Config
B7
B6
B5
B4
B3
B2
SAMP_
TIME
AVG[2:0]
B1
B0
DEFAULT
CYCLE_TIME
[1:0]
1Dh
The Averaging and Sampling Configuration register controls the number of samples taken and the total
sensor cycle time for all active sensors while the device is functioning normally.
Bits 5 - 3 - AVG[2:0] - Determines the number of samples that are taken for all active channels during
the sensor cycle as shown in Table 5.16. All samples are taken consecutively on the same channel
before the next channel is sampled and the result is averaged over the number of samples measured
before updating the measured results.
For example, if CS1, CS2, and CS3 are sampled during the sensor cycle, and the AVG[2:0] bits are
set to take 4 samples per channel, then the full sensor cycle will be: CS1, CS1, CS1, CS1, CS2, CS2,
CS2, CS2, CS3, CS3, CS3, CS3.
Table 5.16 AVG Bit Decode
AVG[2:0]
2
1
0
NUMBER OF SAMPLES TAKEN
PER MEASUREMENT
0
0
0
1
0
0
1
2
0
1
0
4
0
1
1
8 (default)
1
0
0
16
1
0
1
32
1
1
0
64
1
1
1
128
Bit 2 - SAMP_TIME - Determines the time to take a single sample.

‘0’ - The sampling time is ~2.56ms.

‘1’ (default) - The sampling time is ~1.28ms.
Bits 1 - 0 - CYCLE_TIME[1:0] - Determines the overall cycle time for all measured channels during
normal operation as shown in Table 5.17. All measured channels are sampled at the beginning of the
cycle time. If additional time is remaining, then the device is placed into a lower power state for the
remaining duration of the cycle.
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Table 5.17 CYCLE_TIME Bit Decode
CYCLE_TIME[1:0]
1
0
OVERALL CYCLE TIME
0
0
35ms
0
1
70ms (default)
1
0
105ms
1
1
140ms
APPLICATION NOTE: The programmed cycle time is only maintained if the total averaging time for all samples is
less than the programmed cycle. The AVG[2:0] bits will take priority so that if more samples
are required than would normally be allowed during the cycle time, the cycle time will be
extended as necessary to accommodate the number of samples to be measured.
5.11
Calibration Activate Registers
Table 5.18 Calibration Activate Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
26h
R/W
Calibration
Activate
CS8_CAL
CS7_CAL
CS6_CAL
CS5_CAL
CS4_CAL
CS3_CAL
CS2_CAL
CS1_CAL
FFh
The Calibration Activate register force the respective sensors to be re-calibrated. When a bit is set,
the corresponding Capacitive Touch Sensor will be re-calibrated and the bit will be automatically
cleared once the re-calibration routine has finished. During the re-calibration routine, the sensors will
not detect a press for up to 600ms and the Sensor Base Count register values will be invalid. During
this time, any press on the corresponding sensors will invalidate the re-calibration.
Bit 7 - CS8_CAL - When set, the CS8 input is re-calibrated. This bit is automatically cleared once the
sensor has been re-calibrated successfully.
Bit 6 - CS7_CAL - When set, the CS7 input is re-calibrated. This bit is automatically cleared once the
sensor has been re-calibrated successfully.
Bit 5 - CS6_CAL - When set, the CS6 input is re-calibrated. This bit is automatically cleared once the
sensor has been re-calibrated successfully.
Bit 4 - CS5_CAL - When set, the CS5 input is re-calibrated. This bit is automatically cleared once the
sensor has been re-calibrated successfully.
Bit 3 - CS4_CAL - When set, the CS4 input is re-calibrated. This bit is automatically cleared once the
sensor has been re-calibrated successfully.
Bit 2 - CS3_CAL - When set, the CS3 input is re-calibrated. This bit is automatically cleared once the
sensor has been re-calibrated successfully.
Bit 1 - CS2_CAL - When set, the CS2 input is re-calibrated. This bit is automatically cleared once the
sensor has been re-calibrated successfully.
Bit 0 - CS1_CAL - When set, the CS1 input is re-calibrated. This bit is automatically cleared once the
sensor has been re-calibrated successfully.
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
5.12
Interrupt Enable Register
Table 5.19 Interrupt Enable Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
27h
R/W
Interrupt
Enable
CS8_
INT_EN
CS7_
INT_EN
CS6_
INT_EN
CS5_
INT_EN
CS4_
INT_EN
CS3_
INT_EN
CS2_
INT_EN
CS1_
INT_EN
FFh
The Interrupt Enable registers determine whether a sensor touch or release causes the interrupt pin
to be asserted.
Bit 7 - CS8_INT_EN - Enables the interrupt pin to be asserted if a touch is detected on CS8
(associated with the CS8 status bit).

‘0’ - The interrupt pin will not be asserted if a touch is detected on CS8 (associated with the CS8
status bit).

‘1’ (default) - The interrupt pin will be asserted a touch is detected on CS8 (associated with the
CS8 status bit).
Bit 6 - CS7_INT_EN - Enables the interrupt pin to be asserted if a touch is detected on CS7
(associated with the CS7 status bit).
Bit 5 - CS6_INT_EN - Enables the interrupt pin to be asserted if a touch is detected on CS6
(associated with the CS6 status bit).
Bit 4 - CS5_INT_EN - Enables the interrupt pin to be asserted if a touch is detected on CS5
(associated with the CS5 status bit).
Bit 3 - CS4_INT_EN - Enables the interrupt pin to be asserted if a touch is detected on CS4
(associated with the CS4 status bit).
Bit 2 - CS3_INT_EN - Enables the interrupt pin to be asserted if a touch is detected on CS3
(associated with the CS3 status bit).
Bit 1 - CS2_INT_EN - Enables the interrupt pin to be asserted if a touch is detected on CS2
(associated with the CS2 status bit).
Bit 0 - CS1_INT_EN - Enables the interrupt pin to be asserted if a touch is detected on CS1
(associated with the CS1 status bit).
5.13
Repeat Rate Enable Register
Table 5.20 Repeat Rate Enable Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
28h
R/W
Repeat Rate
Enable
CS8_
RPT_EN
CS7_
RPT_EN
CS6_
RPT_EN
CS5_
RPT_EN
CS4_
RPT_EN
CS3_
RPT_EN
CS2_
RPT_EN
CS1_
RPT_EN
FFh
The Repeat Rate Enable register determines the interrupt behavior of the buttons as described in
Section 4.6.1.
Bit 7 - CS8_RPT_EN - Enables the repeat rate for Capacitive Touch Sensor 8.

‘0’ - The repeat rate for CS8 is disabled. It will only generate an interrupt when a touch is detected
and when a release is detected no matter how long the touch is held for.

‘1’ (default) - The repeat rate for CS8 is enabled. In the case of a “touch” event, it will generate an
interrupt when a touch is detected and a release is detected. In the case of a “press and hold”
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Datasheet
event, it will generate an interrupt when a touch is detected and at the repeat rate so long as the
touch is held. It will not generate an interrupt when a release is detected.
Bit 6 - CS7_RPT_EN - Enables the repeat rate for Capacitive Touch Sensor 7.
Bit 5 - CS6_RPT_EN - Enables the repeat rate for Capacitive Touch Sensor 6.
Bit 4 - CS5_RPT_EN - Enables the repeat rate for Capacitive Touch Sensor 5.
Bit 3 - CS4_RPT_EN - Enables the repeat rate for Capacitive Touch Sensor 4.
Bit 2 - CS3_RPT_EN - Enables the repeat rate for Capacitive Touch Sensor 3.
Bit 1 - CS2_RPT_EN - Enables the repeat rate for Capacitive Touch Sensor 2.
Bit 0 - CS1_RPT_EN - Enables the repeat rate for Capacitive Touch Sensor 1.
5.14
Multiple Touch Configuration Register
Table 5.21 Multiple Touch Configuration
ADDR
R/W
REGISTER
B7
B6
B5
B4
2Ah
R/W
Multiple Touch
Config
MULT_
BLK_EN
-
-
-
B3
B2
B_MULT_T[1:0]
B1
B0
DEFAULT
-
-
80h
The Multiple Touch Configuration register controls the settings for the multiple touch detection circuitry.
These settings determine the number of simultaneous buttons that may be pressed before action is
taken.
Bit 7 - MULT_BLK_EN - Enables the multiple button blocking circuitry.

‘0’ - The multiple touch circuitry is disabled. The device will not block multiple touches.

‘1’ (default)- The multiple touch circuitry is enabled. The device will accept the number of touches
equal to programmed multiple touch threshold and block all others. It will remember which sensor
is valid and block all others until that sensor has been released.
Bits 3 - 2 - B_MULT_T[1:0] - Determines the number of simultaneous touches on all sensors before a
Multiple Touch Event is detected and sensors are blocked. The bit decode is given by Table 5.22.
Table 5.22 B_MULT_T Bit Decode
B_MULT_T[1:0]
1
0
NUMBER OF SIMULTANEOUS TOUCHES
0
0
1 (default)
0
1
2
1
0
3
1
1
4
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DATASHEET
SMSC CAP1088
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
5.15
Recalibration Configuration Register
Table 5.23 Recalibration Configuration Registers
ADDR
R/W
REGISTER
B7
B6
B5
2Fh
R/W
Recalibration
Configuration
BUT_
LD_TH
-
-
B4
B3
B2
NEG_DELTA_
CNT[1:0]
B1
B0
DEFAULT
CAL_CFG[2:0]
8Bh
The Recalibration Configuration register controls the automatic re-calibration routine settings as well
as advanced controls to program the Sensor Threshold register settings.
Bit 7 - BUT_LD_TH - Enables setting all Sensor Threshold registers by writing to the Sensor 1
Threshold register.

‘0’ - Each Sensor X Threshold register is updated individually.

‘1’ (default) - Writing the Sensor 1 Threshold register will automatically overwrite the Sensor
Threshold registers for all sensors (Sensor Threshold 1 through Sensor Threshold 8). The
individual Sensor X Threshold registers (Sensor 2 Threshold through Sensor 8 Threshold) can be
individually updated at any time.
Bits 4 - 3 - NEG_DELTA_CNT[1:0] - Determines the number of negative delta counts necessary to
trigger a digital re-calibration as shown in Table 5.24.
Table 5.24 NEG_DELTA_CNT Bit Decode
NEG_DELTA_CNT[1:0]
1
0
NUMBER OF CONSECUTIVE NEGATIVE DELTA
COUNT VALUES
0
0
8
0
1
16 (default)
1
0
32
1
1
None (disabled)
Bits 2 - 0 - CAL_CFG[2:0] - Determines the update time and number of samples of the automatic recalibration routine. The settings applies to all sensors universally (though individual sensors can be
configured to support re-calibration - see Section 5.11).
Table 5.25 CAL_CFG Bit Decode
CAL_CFG[2:0]
2
1
0
RECALIBRATION
SAMPLES (SEE
Note 5.1)
0
0
0
16
16
0
0
1
32
32
0
1
0
64
64
0
1
1
256
256 (default)
1
0
0
256
1024
SMSC CAP1088
47
DATASHEET
UPDATE TIME (SEE
Note 5.2)
Revision 1.1 (08-05-09)
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Table 5.25 CAL_CFG Bit Decode (continued)
CAL_CFG[2:0]
2
1
0
RECALIBRATION
SAMPLES (SEE
Note 5.1)
1
0
1
256
2048
1
1
0
256
4096
1
1
1
256
7936
5.16
UPDATE TIME (SEE
Note 5.2)
Note 5.1
Recalibration Samples refers to the number of samples that are measured and averaged
before the Base Count is updated however does not control the base count update period.
Once this target number of update cycles is reached, the device may wait additional time
as determined by the Update Time before the base count is updated as determiend by the
settings.
Note 5.2
Update Time refers to the amount of time (in polling cycle periods) that elapses before the
Base Count is updated. For those settings that have the Update Time greater than the
Recalibration Samples value, the device will wait (and continue to average the updated
base count) until the Update Time has elapsed before the base count is updated.
Sensor Threshold Registers
Table 5.26 Sensor Threshold Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
30h
R/W
Sensor 1
Threshold
-
64
32
16
8
4
2
1
40h
31h
R/W
Sensor 2
Threshold
-
64
32
16
8
4
2
1
40h
32h
R/W
Sensor 3
Threshold
-
64
32
16
8
4
2
1
40h
33h
R/W
Sensor 4
Threshold
-
64
32
16
8
4
2
1
40h
34h
R/W
Sensor 5
Threshold
-
64
32
16
8
4
2
1
40h
35h
R/W
Sensor 6
Threshold
-
64
32
16
8
4
2
1
40h
36h
R/W
Sensor 7
Threshold
-
64
32
16
8
4
2
1
40h
37h
R/W
Sensor 8
Threshold
-
64
32
16
8
4
2
1
40h
The Sensor Threshold registers store the delta threshold that is used to determine if a touch has been
detected. When a touch occurs, the input signal of the corresponding sensor changes due to the
capacitance associated with a touch. If the sensor input change exceeds the threshold settings, then
a touch is detected.
When the BUT_LD_TH bit is set (see Section 5.15 - bit 7), writing data to the Sensor 1 Threshold
register will update all of the sensor threshold registers (31h - 37h inclusive).
Revision 1.1 (08-05-09)
48
DATASHEET
SMSC CAP1088
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
5.17
Sensor Noise Threshold Registers
Table 5.27 Sensor Noise Threshold Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
38h
R/W
Sensor Noise
Threshold 1
CS4_BN_TH
[1:0]
CS3_BN_TH
[1:0]
CS2_BN_TH
[1:0]
CS1_BN_TH
[1:0]
55h
39h
R/W
Sensor Noise
Threshold 2
CS8_BN_TH
[1:0]
CS7_BN_TH
[1:0]
CS6_BN_TH
[1:0]
CS5_BN_TH
[1:0]
55h
The Sensor Noise Threshold registers control the value of a secondary internal threshold to detect
noise and improve the automatic recalibration routine. If a Capacitive Touch Sensor output exceeds
the Sensor Noise Threshold but does not exceed the sensor threshold, then it is determined to be
caused by a noise spike. That sample is not used by the automatic re-calibration routine.
The Sensor Noise Threshold is proportional to the programmed threshold as shown in Table 5.28.
Table 5.28 CSx_BN_TH Bit Decode
CSX_BN_TH[1:0]
5.17.1
1
0
THRESHOLD DIVIDE SETTING
0
0
25%
0
1
37.5% (default)
1
0
50%
1
1
62.5%
Sensor Noise Threshold 1 Register
The Sensor Noise Threshold 1 register controls the noise threshold for Capacitive Touch Sensors 1-4.
Bits 7-6 - CS4_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 4.
Bits 5-4 - CS3_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 3.
Bits 3-2 - CS2_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 2.
Bits 1-0 - CS1_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 1.
5.17.2
Sensor Noise Threshold 2 Register
The Sensor Noise Threshold 2 register controls the noise threshold for Capacitive Touch Sensors 5 - 8.
Bits 7-6 - CS8_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 8.
Bits 5-4 - CS7_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 7.
Bits 3-2 - CS6_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 6.
Bits 1-0 - CS5_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 5.
SMSC CAP1088
49
DATASHEET
Revision 1.1 (08-05-09)
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
5.18
Standby Channel Register
Table 5.29 Standby Channel Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
40h
R/W
Standby
Channel
CS8_
STBY
CS7_
STBY
CS6_
STBY
CS5_
STBY
CS4_
STBY
CS3_
STBY
CS2_
STBY
CS1_
STBY
00h
The Standby Channel register controls which (if any) Capacitive Touch Sensors are active during
Standby.
Bit 7 - CS8_STBY - Controls whether the CS8 channel is active in Standby.

‘0’ (default) - The CS8 channel not be sampled during Standby.

‘1’ - The CS8 channel will be sampled during Standby. It will use the Standby threshold setting, and
the standby averaging and sensitivity settings.
Bit 6 - CS7_STBY - Controls whether the CS7 channel is active in Standby.
Bit 5 - CS6_STBY - Controls whether the CS6 channel is active in Standby.
Bit 4 - CS5_STBY - Controls whether the CS5 channel is active in Standby.
Bit 3 - CS4_STBY - Controls whether the CS4 channel is active in Standby.
Bit 2 - CS3_STBY - Controls whether the CS3 channel is active in Standby.
Bit 1 - CS2_STBY - Controls whether the CS2 channel is active in Standby.
Bit 0 - CS1_STBY - Controls whether the CS1 channel is active in Standby.
5.19
Standby Configuration Register
Table 5.30 Standby Configuration Register
ADDR
R/W
REGISTER
B7
B6
41h
R/W
Standby
Configuration
AVG_
SUM
-
B5
B4
STBY_AVG[2:0]
B3
B2
STBY_
SAMP_
TIME
B1
B0
STBY_CY_TIME
[1:0]
DEFAULT
1Dh
The Standby Configuration register controls averaging and cycle time for those sensors that are active
in Standby.
Bit 7 - AVG_SUM - Determines whether the active sensors will average the programmed number of
samples or whether they will accumulate for the programmed number of samples.

‘0’ - (default) - The active sensor delta count values will be based on the average of the
programmed number of samples when compared against the threshold.

‘1’ - The active sensor delta count values will be based on the summation of the programmed
number of samples when compared against the threshold.
Bits 5 - 3 - STBY_AVG[2:0] - Determines the number of samples that are taken for all active channels
during the sensor cycle as shown in Table 5.31. All samples are taken consecutively on the same
channel before the next channel is sampled and the result is averaged over the number of samples
measured before updating the measured results.
Revision 1.1 (08-05-09)
50
DATASHEET
SMSC CAP1088
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Table 5.31 STBY_AVG Bit Decode
STBY_AVG[2:0]
2
1
0
NUMBER OF SAMPLES TAKEN
PER MEASUREMENT
0
0
0
1
0
0
1
2
0
1
0
4
0
1
1
8 (default)
1
0
0
16
1
0
1
32
1
1
0
64
1
1
1
128
Bit 2 - STBY SAMP_TIME - Determines the time to take a single sample when the device is in Standby.

‘0’ - The sampling time is ~2.56ms.

‘1’ (default) - The sampling time is ~1.28ms.
Bits 1 - 0 - STBY_CY_TIME[2:0] - Determines the overall cycle time for all measured channels during
normal operation as shown in Table 5.17. All measured channels are sampled at the beginning of the
cycle time. If additional time is remaining, then the device is placed into a lower power state for the
remaining duration of the cycle.
Table 5.32 STBY_CY_TIME Bit Decode
STBY_CY_TIME[1:0]
1
0
OVERALL CYCLE TIME
0
0
35ms
0
1
70ms (default)
1
0
105ms
1
1
140ms
APPLICATION NOTE: The programmed cycle time is only maintained if the total averaging time for all samples is
less than the programmed cycle. The STBY_AVG[2:0] bits will take priority so that if more
samples are required than would normally be allowed during the cycle time, the cycle time
will be extended as necessary to accommodate the number of samples to be measured.
SMSC CAP1088
51
DATASHEET
Revision 1.1 (08-05-09)
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
5.20
Standby Sensitivity Register
Table 5.33 Standby Configuration Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
42h
R/W
Standby
Sensitivity
-
-
-
-
-
B2
B1
B0
DEFAULT
STBY_SENSE[2:0]
02h
The Standby Sensitivity register controls the sensitivity for sensors that are active in Standby.
Bits 2 - 0 - STBY_SENSE[2:0] - Controls the sensitivity for sensors that are active in Standby. The
sensitivity settings act to scale the relative delta count value higher or lower based on the system
parameters. A setting of 000b is the most sensitive while a setting of 111b is the least sensitive. At the
more sensitive settings, touches are detected for a smaller delta C corresponding to a “lighter” touch.
These settings are more sensitive to noise however and a noisy environment may flag more false
touches than higher sensitivity levels.
APPLICATION NOTE: A value of 128x is the most sensitive setting available. At the most sensitivity settings, the
MSB of the Delta Count register represents 64 out of ~25,000 which corresponds to a touch
of approximately 0.25% of the base capacitance (or a ΔC of 25fF from a 10pF base
capacitance). Conversely a value of 1x is the least sensitive setting available. At these
settings, the MSB of the Delta Count register corresponds to a delta count of 8192 counts
out of ~25,000 which corresponds to a touch of approximately 33% of the base capacitance
(or a ΔC of 3.33pF from a 10pF base capacitance).
Table 5.34 STBY_SENSE Bit Decode
STBY_SENSE[2:0]
5.21
2
1
0
SENSITIVITY MULTIPLIER
0
0
0
128x (most sensitive)
0
0
1
64x
0
1
0
32x (default)
0
1
1
16x
1
0
0
8x
1
0
1
4x
1
1
0
2x
1
1
1
1x - (least sensitive)
Standby Threshold Register
Table 5.35 Standby Threshold Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
43h
R/W
Standby
Threshold
-
64
32
16
8
4
2
1
40h
Revision 1.1 (08-05-09)
52
DATASHEET
SMSC CAP1088
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
The Standby Threshold registers stores the delta threshold that is used to determine if a touch has
been detected. When a touch occurs, the input signal of the corresponding sensor changes due to the
capacitance associated with a touch. If the sensor input change exceeds the threshold settings, then
a touch is detected.
5.22
Sensor Base Count Registers
Table 5.36 Sensor Base Count Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
50h
R
Sensor 1 Base
Count
128
64
32
16
8
4
2
1
C8h
51h
R
Sensor 2 Base
Count
128
64
32
16
8
4
2
1
C8h
52h
R
Sensor 3 Base
Count
128
64
32
16
8
4
2
1
C8h
53h
R
Sensor 4 Base
Count
128
64
32
16
8
4
2
1
C8h
54h
R
Sensor 5 Base
Count
128
64
32
16
8
4
2
1
C8h
55h
R
Sensor 6 Base
Count
128
64
32
16
8
4
2
1
C8h
56h
R
Sensor 7 Base
Count
128
64
32
16
8
4
2
1
C8h
57h
R
Sensor 8 Base
Count
128
64
32
16
8
4
2
1
C8h
The Sensor Base Count registers store the calibrated “Not Touched” input value from the Capacitive
Touch Sensor inputs. These registers are periodically updated by the re-calibration routine.
The routine uses an internal adder to add the current count value for each reading to the sum of the
previous readings until sample size has been reached. At this point, the upper 16 bits are taken and
used as the Sensor Base Count. The internal adder is then reset and the re-calibration routine
continues.
The data presented is determined by the BASE_SHIFT[3:0] bits (see Section 5.5).
5.23
LED Output Type Register
Table 5.37 LED Output Type Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
71h
R/W
LED Output
Type
LED8_
OT
LED7_
OT
LED6_
OT
LED5_
OT
LED4_
OT
LED3_
OT
LED2_
OT
LED1_
OT
00h
The LED Output Type register controls the type of output for the LED pins. Each pin is controlled by
a single bit.
SMSC CAP1088
53
DATASHEET
Revision 1.1 (08-05-09)
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Bit 7 - LED8_OT - Determines the output type of the LED8 pin.

‘0’ (default) - The LED8 pin is an open-drain output with an external pull-up resistor. When the
appropriate pin is set to the “active“ state (logic ‘1’) then the pin will be driven low. Conversely,
when the pin is set to the “inactive” state (logic ‘0’), then the pin will be left in a High Z state and
pulled high via an external pull-up resistor.

‘1’ - The LED8 pin is a push-pull output. When driving a logic ‘1’ the pin is driven high. When driving
a logic ‘0’ the pin is driven low.
Bit 6 - LED7_OT - Determines the output type of the LED7 pin.
Bit 5 - LED6_OT - Determines the output type of the LED6 pin.
Bit 4 - LED5_OT - Determines the output type of the LED5 pin.
Bit 3 - LED4_OT - Determines the output type of the LED4 pin.
Bit 2 - LED3_OT - Determines the output type of the LED3 pin.
Bit 1 - LED2_OT - Determines the output type of the LED2 pin.
Bit 0 - LED1_OT - Determines the output type of the LED1 pin.
5.24
Sensor LED Linking Register
Table 5.38 Sensor LED Linking Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
72h
R/W
Sensor LED
Linking
CS8_
LED8
CS7_
LED7
CS6_
LED6
CS5_
LED5
CS4_
LED4
CS3_
LED3
CS2_
LED2
CS1_
LED1
00h
The Sensor LED Linking registers control whether a Capacitive Touch Sensor is linked to an LED
output or not. If the corresponding bit is set, then the appropriate LED output will change states defined
by the LED Behavior controls (see Section 5.27) in response to the Capacitive Touch sensor.
Bit 7 - CS8_LED8 - Links the LED8 output to a detected touch on the CS8 sensor. When a touch is
detected, the LED is actuated and will behave as determined by the LED Behavior controls.

‘0’ (default) - The LED8 output is not associated with a the CS8 input. If a touch is detected on the
CS8 input, then the LED will not automatically be actuated. The LED is enabled and controlled via
the LED Output Configuration register (see Section 5.24) and the LED Behavior registers (see
Section 5.27).

‘1’ - The LED8 output is associated with the CS8 input. If a touch is detected on the CS8 input
then the LED will be actuated and behave as defined in Table 5.43.
Bit 6 - CS7_LED7 - Links the LED7 output to a detected touch on the CS7 sensor. When a touch is
detected, the LED is actuated and will behave as determined by the LED Behavior controls.
Bit 5 - CS6_LED6 - Links the LED6 output to a detected touch on the CS6 sensor. When a touch is
detected, the LED is actuated and will behave as determined by the LED Behavior controls.
Bit 4 - CS5_LED5 - Links the LED5 output to a detected touch on the CS5 sensor. When a touch is
detected, the LED is actuated and will behave as determined by the LED Behavior controls.
Bit 3 - CS4_LED4 - Links the LED4 output to a detected touch on the CS4 sensor. When a touch is
detected, the LED is actuated and will behave as determined by the LED Behavior controls.
Bit 2 - CS3_LED3 - Links the LED3 output to a detected touch on the CS3 sensor. When a touch is
detected, the LED is actuated and will behave as determined by the LED Behavior controls.
Revision 1.1 (08-05-09)
54
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Bit 1 - CS2_LED2 - Links the LED2 output to a detected touch on the CS2 sensor. When a touch is
detected, the LED is actuated and will behave as determined by the LED Behavior controls.
Bit 0 - CS1_LED1 - Links the LED1 output to a detected touch on the CS1 sensor. When a touch is
detected, the LED is actuated and will behave as determined by the LED Behavior controls.
5.25
LED Polarity Register
Table 5.39 LED Polarity Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
73h
R/W
LED Polarity
LED8_
POL
LED7_
POL
LED6_
POL
LED5_
POL
LED4_
POL
LED3_
POL
LED2_
POL
LED1_
POL
00h
The LED Polarity registers control the logical polarity of the LED outputs.
APPLICATION NOTE: The polarity controls determine the final LED pin drive. A touch on a linked Capacitive Touch
Sensor is treated in the same way as the LED Output Control bit being set to a logic ‘1’.
APPLICATION NOTE: For LED operation, the duty cycle settings determine the % of time that the LED pin will be
driven to a logic ‘1’ state in a non-inverted system or to a logic ‘0’ state in an inverted system.
The duty cycle settings operate independently of the polarity controls. Therefore, the Max
Duty Cycle settings define the maximum % of time that the LED pin will be driven high in a
non-inverted system while the Min Duty Cycle settings determine the minimum % of time that
the LED pin will be driven high in a non-inverted system.
The LED drive assumes that the LEDs are configured such that if the LED pin is driven to
a logic ‘0’ then the LED will be on and that the CAP1088 LED pin is sinking the LED current.
Conversely, if the LED pin is driven to a logic ‘1’ then the LED will be off and there is no
current flow.
Finally, the breathe operations will always ramp the duty cycle from the minimum duty cycle
to the maximum duty cycle and then back down to the minimum duty cycle.
The LED Polarity controls lead to two conditions that have the apparent effect of changing
the duty cycle settings. If an LED output is non-inverted then the Maximum Duty Cycle
settings will define the maximum % of time that the LED is off. Conversely the Minimum
Duty Cycle settings will define the minimum % of time that the LED is off. As well, when
there is no touch detected or the LED Output Control register bit is at a logic ‘0’ then the
LED output will be driven at the minimum duty cycle setting. The relative brightness will then
ramp from maximum to minimum and back.
If an LED output is inverted, then the Maximum Duty Cycle settings will define the maximum
% of time that the LED is on and the Minimum Duty Cycle settings will determine the
minimum % of time that the LED is on. As well, when there is no touch detected, or the LED
Output Control register bit is at a logic ‘0’, then the LED output will be driven at the minimum
duty cycle setting. The relative brightness will then ramp from minimum to maximum and
back.
Bit 7 - LED8_POL - Determines the polarity of the LED8 output.

‘0’ (default) - The LED8 output is inverted. A setting of ‘1’ in the LED Output Control register will
cause the output to be driven to a logic ‘0’ as determined by the LED behavior. Similarly, the duty
cycles corresponding to Pulse and Breathe operations will indicate the amount of time that the LED
is driven to a logic ‘0’ state (corresponding to “active”).

‘1’ - The LED8 output is non-inverted. A setting of ‘1’ in the LED Output Control register will cause
the output to be driven to a logic ‘1’ or left in the high-z state as determined by its output type and
LED behavior. Similarly, the duty cycles corresponding to Pulse and Breathe operations will indicate
to the amount of time that the LED is driven to a logic ‘1’ state (corresponding to “inactive”).
SMSC CAP1088
55
DATASHEET
Revision 1.1 (08-05-09)
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Bit 6 - LED7_POL - Determines the polarity of the LED7 output.
Bit 5 - LED6_POL - Determines the polarity of the LED6 output.
Bit 4 - LED5_POL - Determines the polarity of the LED5 output.
Bit 3 - LED4_POL - Determines the polarity of the LED4 output.
Bit 2 - LED3_POL - Determines the polarity of the LED3 output.
Bit 1 - LED2_POL - Determines the polarity of the LED2 output.
Bit 0 - LED1_POL - Determines the polarity of the LED1 output.
5.26
LED Output Control Register
Table 5.40 LED Output Control Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
74h
R/W
LED Output
Control
LED8_
DR
LED7_
DR
LED6_
DR
LED5_
DR
LED4_
DR
LED3_
DR
LED2_
DR
LED1_
DR
00h
The LED Output Control Register controls the output state of the LED pins.
All LEDs that are associated with a Capacitive Touch Sensor channel are automatically enabled and
will be actuated per the LED Behavior.
For those LEDs that are not linked with a Capacitive Touch Sensor channel, then the bit state
determines whether the LED is actuated or not actuated.
The LED Polarity Control register will determine the non actuated state of the LED pins.
Table 5.41 shows the interaction between the polarity controls, output controls and relative brightness.
Table 5.41 LED Polarity Behavior
LED
OUTPUT
CONTROL
REGISTER
POLARITY
MAX DUTY
MIN DUTY
0
inverted
maximum % of
time that the LED
is on (logic 0)
minimum % of
time that the LED
is on (logic 0)
1
inverted
maximum % of
time that the LED
is on (logic 0)
0
noninverted
1
noninverted
BRIGHTNESS
LED
APPEARANCE
off
maximum brightness at
minimum duty cycle
on at minimum
duty cycle
minimum % of
time that the LED
is on (logic 0)
on
maximum brightness at
max duty cycle. Brightness
ramps from min to max
according to
LED behavior
maximum % of
time that the LED
is off (logic 1)
minimum % of
time that the LED
is off (logic 1)
off
maximum brightness at 100
- min duty cycle
on at 100 - min
duty cycle
(Note 5.3)
maximum % of
time that the LED
is off (logic 1)
minimum % of
time that the LED
is off (logic 1)
on
maximum brightness at 100
- min duty cycle. Brightness
ramps from max to min
according to
LED behavior
Note 5.3
Revision 1.1 (08-05-09)
LED
BEHAVIORS
For example: when polarity is non-inverted, if min duty cycle is 0, then the LED would be
at logic 1 (off) 0% of the time. It will be at logic 0 (on), 100% of the time (100 - min duty
cycle).
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Bit 7 - LED8_DR - Determines whether the LED8 output is driven high or low.

‘0’ (default) - The LED8 output is driven at the minimum duty cycle or not actuated.

‘1’ - The LED8 output is driven at the maximum duty cycle or is actuated.
Bit 6 - LED7_DR - Determines whether LED7 output is driven high or low.
Bit 5 - LED6_DR - Determines whether LED6 output is driven high or low.
Bit 4 - LED5_DR - Determines whether LED5 output is driven high or low.
Bit 3 - LED4_DR - Determines whether LED4 output is driven high or low.
Bit 2 - LED3_DR - Determines whether LED3 output is driven high or low.
Bit 1 - LED2_DR - Determines whether LED2 output is driven high or low.Bit 0 - LED1_DR Determines whether LED1 output is driven high or low.
5.27
LED Behavior Registers
Table 5.42 LED Behavior Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
81h
R/W
LED Behavior 1
LED4_CTL[1:0]
LED3_CTL[1:0]
LED2_CTL[1:0]
LED1_CTL[1:0]
00h
82h
R/W
LED Behavior
LED8_CTL[1:0]
LED7_CTL[1:0]
LED6_CTL[1:0]
LED5_CTL[1:0]
00h
The LED Behavior registers control the operation of LEDs. Each LED pin is controlled by a 2-bit field
and the behavior is determined by whether the LED is linked to a Capacitive Touch Sensor or not.
If the corresponding LED output is linked to a Capacitive Touch Sensor than the Start and Stop triggers
are used. The defined behavior will activate when the Start Trigger is met and will stop when the Stop
Trigger is met.
If the LED output is not associated with a a Capacitive Touch Sensor, then the appropriate behavior
will be enabled / disabled by the LED Output Control register. If the respective LEDx_DR bit is set to
a logic ‘1’ then this will be associated as a “touch” and if the LEDx_DR bit is set to a logic ‘0’ then this
will be associated as a “release”.
The LED Polarity Control register will determine the non actuated state of the LED outputs. If the LED
Polarity Control register is set to be inverted (default), then an non actuated LED pin will be driven to
a logic ‘1’ state and the LED will be off. If the LED Polarity Control register is set to be non-inverted,
then the non actuated LED pin will be driven to the logic ’0’ state and the LED will be on.
APPLICATION NOTE: If an LED is not linked to a Capacitive Touch Sensor and is breathing (via the Breathe or
Pulse behaviors), it will finish its current “breath” before any changes to behavior are
processed.
APPLICATION NOTE: If an LED is not linked to the Capacitive Touch Sensor and configured to operate using Pulse
1 Behavior, then the circuitry will only be actuated when the corresponding bit is set. It will
not check the bit condition until the Pulse 1 behavior is finished. The device will not
remember if the bit was cleared and reset while it was actuated.
APPLICATION NOTE: If an LED is actuated and it is switched from linked to a Capacitive Touch Sensor to unlinked
(or vice versa), then the LED will respond to the new command source immediately. For
example, if a linked LED was actuated by a touch and the control is changed so that it is
unlinked, it will check the status of the corresponding LED Output Control bit. If that bit is ‘0’,
then the LED will behave as if a release was detected. LIkewise, if an unlinked LED was
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
actuated by the LED Output Control register and the control is changed so that it is linked
and no touch is detected, then the LED will behave as if a release was detected.
APPLICATION NOTE: If the period for any breathe operation is changed while the LED is actuated, then the LED
output will be reset to 0% drive and any breathing will re-initiate at the new settings. For
Pulse 1 and Pulse 2 behaviors, the number of pulses will be retained.
5.27.1
LED Behavior 1 - 81h
Bits 7 - 6 - LED4_CTL[1:0] - Determines the behavior of LED4 as shown in Table 5.43.
Bits 5 - 4 - LED3_CTL[1:0] - Determines the behavior of LED3 as shown in Table 5.43.
Bits 3 - 2 - LED2_CTL[1:0] - Determines the behavior of LED2 as shown in Table 5.43.
Bits 1 - 0 - LED1_CTL[1:0] - Determines the behavior of LED1 as shown in Table 5.43.
5.27.2
LED Behavior 2 - 82h
Bits 7 - 6 - LED8_CTL[1:0] - Determines the behavior of LED8 as shown in Table 5.43.
Bits 5 - 4 - LED7_CTL[1:0] - Determines the behavior of LED7 as shown in Table 5.43.
Bits 3 - 2 - LED6_CTL[1:0] - Determines the behavior of LED6 as shown in Table 5.43.
Bits 1 - 0 - LED5_CTL[1:0] - Determines the behavior of LED5 as shown in Table 5.43.
Table 5.43 LEDx_CTL Bit Decode
LEDX_CTL
[1:0]
1
0
0
START
TRIGGER
STOP
TRIGGER
Direct
The LED is driven to the programmed state
(active or inactive). See Figure 5.5
Touch Detected
or LED Control
bit set
Release
Detected or
LED Control
bit cleared
Touch or
Release
Detected (See
Section 5.31) or
LED Control bit
set
n/a
OPERATION
DESCRIPTION
0
0
1
Pulse 1
The LED will “Pulse” a programmed
number of times. During each “Pulse” the
LED will breathe up to the maximum
brightness and back down to the minimum
brightness so that the total “Pulse” period
matches the programmed value.
1
0
Pulse 2
The LED will Breathe when the start trigger
is detected. When the stop trigger is
detected, it will “Pulse” a number of times
then return to its minimum brightness.
Touch Detected
or LED Control
bit set
Release
Detected or
LED Control
bit cleared
Breathe
The LED will breathe. It will be driven with
a duty cycle that ramps up from the
programmed minimum duty cycle (default
0%) to the programmed maximum duty
cycle duty cycle (default 100%) and then
back down. Each ramp takes up 50% of the
programmed period. The total period of
each “breath” is determined by the LED
Breathe Period controls - see Section 5.30.
Touch Detected
or LED Control
bit set
Release
Detected or
LED Control
bit cleared
1
1
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
APPLICATION NOTE: The PWM frequency is determined based on the selected LED behavior, the programmed
breathe period, and the programmed min and max duty cycles. For the Direct Mode, the
PWM frequency is calculated based on the programmed Rise and Fall times. If these are
set at 0, then the maximum PWM frequency will be used based on the programmed duty
cycle settings.
5.28
LED Pulse 1 Period Register
Table 5.44 LED Pulse 1 Period Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
84h
R/W
LED Pulse 1
Period
ST_
TRIG
P1_
PER6
P1_
PER5
P1_
PER4
P1_
PER3
P1_
PER2
P1_
PER1
P1_
PER0
20h
The LED Pulse Period 1 register determines the overall period of a pulse operation as determined by
the LED_CTL registers (see Table 5.43 - setting 01b). Each LSB represents 32ms so that a setting of
14h (20d) would represent a period of 640ms. The total range is from 32ms to 4.06 seconds as shown
in Table 5.45.
APPLICATION NOTE: Due to constraints on the LED Drive PWM operation, any Breathe Period less than 160ms
(05h) may not be achievable. The device will breathe at the minimum period possible as
determined by the period and min / max duty cycle settings.
Bit 7 - ST_TRIG - Determines the start trigger for the LED Pulse behavior.

‘0’ (default) - The LED will Pulse when a touch is detected.

‘1’ - The LED will Pulse when a release is detected.
The Pulse 1 operation is shown in Figure 5.1 when the LED output is configured for non-inverted
polarity and in Figure 5.2 for inverted polarity.
.
Touch Detected or
Release Detected
X pulses after touch or after release
Normal – untouched
operation
(100% - Pulse 1 Min Duty Cycle) * Brightness
Normal – untouched
operation
LED
Brightness
(100% - Pulse 1 Max Duty Cycle) * Brightness
Pulse 1 Period
(P1_PER)
Figure 5.1 Pulse Behavior with Non-Inverted Polarity
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Touch Detected or
Release Detected
X pulses after touch or after release
Pulse 1 Max Duty Cycle * Brightness
LED
Brightness
Normal – untouched
operation
Normal – untouched
operation
Pulse 1 Min Duty Cycle * Brightness
Pulse Period
(P1_PER)
Figure 5.2 Pulse Behavior with Inverted Polarity
Table 5.45 LED Pulse / Breathe Period Example
5.29
SETTING
(HEX)
SETTING (DECIMAL)
TOTAL BREATHE / PULSE
PERIOD (MS)
00h
0
32
01h
1
32
02h
2
64
03h
3
96
04h
4
128
...
...
...
7Ch
124
3,968
7Dh
125
4,000
7Eh
126
4,032
7Fh
127
4.064
LED Pulse 2 Period Register
Table 5.46 LED Pulse 2 Period Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
85h
R/W
LED Pulse 2
Period
-
P2_
PER6
P2_
PER5
P2_
PER4
P2_
PER3
P2_
PER2
P2_
PER1
P2_
PER0
14h
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
The LED Pulse 2 Period register determines the overall period of a pulse operation as determined by
the LED_CTL registers (see Table 5.43 - setting 10b). Each LSB represents 32ms so that a setting of
14h (20d) would represent a period of 640ms. The total range is from 32ms to 4.06 seconds (see
Table 5.45).
APPLICATION NOTE: Due to constraints on the LED Drive PWM operation, any Breathe Period less than 160ms
(05h) may not be achievable. The device will breathe at the minimum period possible as
determined by the period and min / max duty cycle settings.
The Pulse 2 Behavior is shown in Figure 5.3 for non-inverted polarity and in Figure 5.4 for inverted
polarity.
Normal – untouched
operation
Release Detected
Touch Detected
Normal – untouched
operation
X additional pulses after release
(100% - Pulse 2 Min Duty Cycle) *
Brightness
LED
Brightness
...
Breathe
and Pulse
Period
(P2_PER)
(100% - Pulse 2 Max Duty Cycle) * Brightness
Figure 5.3 Pulse 2 Behavior with Non-Inverted Polarity
Normal – untouched
operation
Release Detected
Touch Detected
Normal – untouched
operation
X additional pulses after release
Pulse 2 Max Duty Cycle * Brightness
LED
Brightness
...
Breathe
and Pulse
Period
Pulse 2 Min Duty Cycle * Brightness
Figure 5.4 Pulse 2 Behavior with Inverted Polarity
5.30
LED Breathe Period Register
Table 5.47 LED Breathe Period Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
86h
R/W
LED Breathe
Period
-
BR_
PER6
BR_
PER5
BR_
PER4
BR_
PER3
BR_
PER2
BR_
PER1
BR_
PER0
5Dh
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
The LED Breathe Period register determines the overall period of a breathe operation as determined
by the LED_CTL registers (see Table 5.43 - setting 11b). Each LSB represents 32ms so that a setting
of 14h (20d) would represent a period of 640ms. The total range is from 32ms to 4.06 seconds (see
Table 5.45).
APPLICATION NOTE: Due to constraints on the LED Drive PWM operation, any Breathe Period less than 160ms
(05h) may not be achievable. The device will breathe at the minimum period possible as
determined by the period and min / max duty cycle settings.
5.31
LED Configuration Register
Table 5.48 LED Configuration Register
ADDR
R/W
REGISTER
B7
B6
B5
88h
R/W
LED Config
-
RAMP_
ALERT
B4
B3
PULSE2_CNT[2:0]
B2
B1
B0
DEFAULT
PULSE1_CNT[2:0]
The LED Configuration register controls general LED behavior as well as the number of pulses that
are sent for the PULSE LED output behavior.
Bit 6 - RAMP_ALERT - Determines whether the device will assert the ALERT# pin when LEDs
actuated by the LED Output Control register bits have finished their respective behaviors.

‘0’ (default) - The ALERT# pin will not be asserted when LEDs actuated by the LED Output Control
register have finished their programmed behaviors.

‘1’ - The ALERT# pin will be asserted whenever any LED that is actuated by the LED Output
Control register has finished its programmed behavior.
Bits 5 - 3 - PUSLE2_CNT[2:0] - Determines the number of pules used for the Pulse 2 behavior as
shown in Table 5.49.
Bits 2 - 0 - PULSE1_CNT[2:0] - Determines the number of pulses used for the Pulse 1 behavior as
shown in Table 5.49.
Table 5.49 PULSEX_CNT Decode
PULSEX_CNT[2:0]
2
1
0
NUMBER OF BREATHS
0
0
0
1 (default - Pulse 2)
0
0
1
2
0
1
0
3
0
1
1
4
1
0
0
5 (default - Pulse 1)
1
0
1
6
1
1
0
7
1
1
1
8
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04h
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
5.32
LED Duty Cycle Registers
Table 5.50 LED Duty Cycle Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
90h
R/W
LED Pulse 1
Duty Cycle
P1_MAX_DUTY[3:0]
P1_MIN_DUTY[3:0]
F0h
91h
R/W
LED Pulse 2
Duty Cycle
P2_MAX_DUTY[3:0]
P2_MIN_DUTY[3:0]
F0h
92h
R/W
LED Breathe
Duty Cycle
BR_MAX_DUTY[3:0]
BR_MIN_DUTY[3:0]
F0h
93h
R/W
Direct Duty
Cycle
DR_MAX_DUTY[3:0]
DR_MIN_DUTY[3:0]
F0h
The LED Duty Cycle registers determine the minimum and maximum duty cycle settings used for the
LED for each LED behavior. These settings affect the brightness of the LED when it is fully off and
fully on.
The LED driver duty cycle will ramp up from the minimum duty cycle (see Section 5.32) to the
maximum duty cycle and back down again.
APPLICATION NOTE: Changes to the Duty Cycle settings will be applied immediately. When the respective register
is written, the LED output will be reset to the minimum (or maximum) setting and restarted
at the updated settings.
APPLICATION NOTE: Upon power on reset (or upon release of the RESET pin), the first breath will breathe from
100% (or 0% duty cycle as determined by the polarity registers) to the programmed minimum
(or maximum as determined by the polarity registers) and then proceed normally.
APPLICATION NOTE: If the min duty cycle and the max duty cycle are set to the same % then the minimum duty
cycle will automatically be changed to the next lower setting. For example, if the maximum
duty cycle were set at 1100b (35%) and the minimum duty cycle were set at 1101b (35%),
the device will automatically use the minimum value at 1100b (25%).
Bits 7 - 4 - X_MAX_DUTY[3:0] - Determines the maximum PWM duty cycle for the LED drivers as
shown in Table 5.51
Bits 3 - 0 - X_MIN_DUTY[3:0] - Determines the minimum PWM duty cycle for the LED drivers as
shown in Table 5.51.
Table 5.51 LED Duty Cycle Decode
X_MAX/MIN_DUTY [3:0]
3
2
1
0
MAXIMUM DUTY CYCLE
MINIMUM DUTY CYCLE
0
0
0
0
1%
0%
0
0
0
1
2%
1%
0
0
1
0
3%
2%
0
0
1
1
4%
3%
0
1
0
0
5%
4%
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Table 5.51 LED Duty Cycle Decode (continued)
X_MAX/MIN_DUTY [3:0]
3
2
1
0
MAXIMUM DUTY CYCLE
MINIMUM DUTY CYCLE
0
1
0
1
6%
5%
0
1
1
0
7%
6%
0
1
1
1
9%
7%
1
0
0
0
11%
9%
1
0
0
1
14%
11%
1
0
1
0
18%
14%
1
0
1
1
25%
18%
1
1
0
0
35%
25%
1
1
0
1
50%
35%
1
1
1
0
70%
50%
1
1
1
1
100%
70%
5.33
LED Direct Ramp Rates Register
Table 5.52 LED Direct Ramp Rates Register
ADDR
R/W
REGISTER
B7
B6
94h
R/W
LED Direct
Ramp Rates
-
-
B5
B4
B3
RISE_RATE[2:0]
B2
B1
B0
DEFAULT
FALL_RATE[2:0]
00h
The LED Direct Ramp Rates register control the rising and falling edge time of an LED that is
configured to operate in Direct mode. The rising edge time corresponds to the amount of time the LED
takes to transition from its minimum duty cycle to its maximum duty cycle. Conversely, the falling edge
time corresponds to the amount of time that the LED takes to transition from its maximum duty cycle
to its minimum duty cycle.
Bits 5 - 3 - RISE_RATE[2:0] - Determines the rising edge time of an LED when it transitions from its
minimum drive state to its maximum drive state as shown in Table 5.53.
Bits 2 - 0 - FALL_RATE[2:0] - Determines the falling edge time of an LED when it transitions from its
maximum drive state to its minimum drive state as shown in Table 5.53.
Table 5.53 Rise / Fall Rate and Off Delay Decode
RISE_RATE/ FALL_RATE / DIR_OFF_DLY [2:0]
2
1
0
RISE / FALL TIME (TRISE / TFALL), OFF DELAY
(TOFF)
0
0
0
0
0
0
1
250ms
Revision 1.1 (08-05-09)
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SMSC CAP1088
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Table 5.53 Rise / Fall Rate and Off Delay Decode (continued)
RISE_RATE/ FALL_RATE / DIR_OFF_DLY [2:0]
2
1
0
RISE / FALL TIME (TRISE / TFALL), OFF DELAY
(TOFF)
0
1
0
500ms
1
1
1
750ms
1
0
0
1s
1
0
1
1.25s
1
1
0
1.5s
1
1
1
2s
5.34
LED Off Delay Register
Table 5.54 LED Off Delay Register
ADDR
R/W
REGISTER
B7
B6
95h
R/W
LED Off Delay
Register
-
-
B5
B4
B3
-
-
B2
B1
B0
DEFAULT
DIR_OFF_DLY [2:0]
00h
The LED Off Delay register determines the amount of time an LED In Direct Mode remains active after
it is no longer actuated (such as after a release has been detected or the drive state has been
changed).
Bits 2 - 0 - DIR_OFF_DLY[2:0] - Determines the turn-off delay for all LEDs that are configured to
operate in Direct Mode as shown in Table 5.53.
The Direct Mode operation is determined by the combination of programmed Rise Time, Fall Time, Min
and Max Duty cycles, Off Delay, and polarity. Figure 5.5 shows the behavior for Non-Inverted polarity
while Figure 5.6 shows the behavior for inverted polarity.
N orm al –
untouched
operation
LE D
Brightness
Touch
Detected
R elease
Detected
Norm al –
untouched
operation
(100% - M in D uty Cycle) *
Brightness
RISE _RATE
Setting (t RISE )
(100% - M ax Duty
Cycle) * Brightness
O ff D elay
(t OFF _DLY )
FALL_RA TE
Setting (t FA LL )
Figure 5.5 Direct Mode Behavior for Non-Inverted Polarity
SMSC CAP1088
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
R elease
D etected
Touch
D etected
M ax D uty Cycle * B rightness
LE D
B rightness
N orm al –
untouched
operation
M in D uty C ycle * B rightness
N orm al –
untouched
operation
R IS E_R A TE
Setting (t R IS E )
O ff D elay
(t O FF_D LY )
FA LL_R A TE
S etting (t FA LL )
Figure 5.6 Direct Mode Behavior for Inverted Polarity
5.35
Product ID Register
Table 5.55 Product ID Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
FDh
R
Product ID
0
1
0
0
0
0
0
0
40h
The Product ID register stores a unique 8-bit value that identifies the device.
5.36
Manufacturer ID Register
Table 5.56 Vendor ID Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
FEh
R
Manufacturer ID
0
1
0
1
1
1
0
1
5Dh
The Vendor ID register stores an 8-bit value that represents SMSC.
5.37
Revision Register
Table 5.57 Revision Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
FFh
R
Revision
1
0
0
0
0
0
0
1
81h
The Revision register stores an 8-bit value that represents the part revision.
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Chapter 6 Package Information
6.1
CAP1088 Package Drawings
Figure 6.1 CAP1088 Package Drawing - 24-Pin QFN 4mm x 4mm
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Figure 6.2 CAP1088 Package Dimensions - 24-Pin QFN 4mm x 4mm
Figure 6.3 CAP1088 PCB Footprint - 24-pin QFN 4mm x 4mm
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8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
6.2
Package Marking
TOP
0.41
LINE: 1 – SMSC Logo without circled (R) symbol
LINE: 2 – Device ID, Version
LINE: 3 – Last 7 digits of Lot Number
LINE: 4 – Revision and Country Code (RCC)
C 1 0 8 8 - 1
1 2 3 4 5 6 a
R C C
e3
3x 0.56
PB-FREE/GREEN SYMBOL
(Matte Sn)
PIN 1
LINES 1 to 3: CENTER HORIZONTAL ALIGNMENT
LINE 4: LEFT HORIZONTAL ALIGNMENT
BOTTOM
BOTTOM MARKING NOT ALLOWED
Figure 6.4 CAP1088 Package Markings
SMSC CAP1088
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DATASHEET
Revision 1.1 (08-05-09)
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Chapter 7 Revision History
Table 7.1 Customer Revision History
REVISION LEVEL & DATE
Rev. 1.1 (08-05-09)
SECTION/FIGURE/ENTRY
CORRECTION
Features
“TBD” replaced with “3uA” under Low Power
Operation
General Description
Deep sleep drawing “5uA” of current changed to
“3uA”
Chapter 1, Pin Description
Application Note added: “The SPI_CS# pin should
be grounded when SMBus, I2C, or BC-Link
communications are used.”
Pin description table updated: Added to pin
function description for RESET pin: “This pin
contains an internal 50uA pull-down current.”
Table 2.2, "Electrical
Specifications"
Table updated:
- Current Measurement, ISTBY - changed the
typical column to 160, max to 210. Changed the
conditions to read: " Standby state active, one
sensor monitored, no LED active, default
conditions (8 avg, 70ms cycle time)"
- Current Measurement, IDSLEEP -changed the
TYP column value to 3 and max to 10.
- Base Capacitance Line - changed the name to
"Maximum Base Capacitance". Removed the value
in the MIN column and MAX column. Added 50 in
the TYP column.
Section 3.1.1, "SMBus (I2C)
Communications"
The following text deleted: “The SPI_CS# pin is not
used and any data presented to this pin will be
ignored.”
and replaced with an application note: “For
SMBus/I2C communications, the SPI_CS# pin is
not used and should be grounded; any data
presented to this pin will be ignored.”
Section 3.1.3, "BC-Link
Communications"
The following application note added: “For BC-Link
communications, the SPI_CS# pin is not used and
should be grounded; any data presented to this pin
will be ignored.”
Table 3.1, "ADDR_COMM
Pin Decode"
Modified table heading, “Pull-Down Resistor” by
adding “(+/- 5%)”
Section 5.28, "LED Pulse 1
Period Register",
Added note describing limitation on operation
Section Table 5.45, "LED
Pulse / Breathe Period
Example" and
Section 5.30, "LED Breathe
Period Register"
Table 5.51, "LED Duty Cycle
Decode"
Revision 1.1 (08-05-09)
Updated table for Min and Max columns
70
DATASHEET
SMSC CAP1088
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Table 7.1 Customer Revision History (continued)
REVISION LEVEL & DATE
SECTION/FIGURE/ENTRY
Section 6.2, "Package
Marking"
Rev. 1.0 (06-16-09)
CORRECTION
Updated package markings per new standards
Document title modified;
reel size added to ordering information;
updates to pinout, general description and register set.
Chapter 1, Pin Description
Pin tables modified adding SPI to “ALERT# /
BC_IRQ#” pin
Updated pin description for WAKE/SPI_MOSI pin
to identify that it can be an input during Deep
Sleep.
Table 2.1, "Absolute
Maximum Ratings"
Table and notes following table modified
Section 3.1,
"Communications"
Updated paragraph to describe proper
ADDR_COMM pin function
Table 3.1, "ADDR_COMM
Pin Decode"
“/I2C” added “SMBus” in “Protocol Used” column
Figure 3.1, "SPI Timing"
Updated figure
Section 3.7, "BC-Link
Interface"
Removed “8051” from 2nd paragraph
Chapter 4, General
Description
Second to last paragraph removed, not needed as
clarification follows
Section 4.1, "Power States"
Removed mention of LED driver outputs
Figure 4.1, "System
Diagram for CAP1088"
Updated system diagram for proper ADDR_COMM
pin usage. Changed from pull-up to VDD to pulldown to GND
Section 4.2, "RESET Pin"
Modified to indicate all communication buses
Section 4.3,
"WAKE/SPI_MOSI Pin
Operation"
Updated text for wake pin during Deep Sleep
Section 4.4, "LED Drivers"
“Pulse 1” modified
Section 4.4, "LED Drivers"
Updated text for # of LEDs
Table 5.1, "Register Set in
Hexadecimal Order"
Updated text and register descriptions for incorrect
#’s Cap Sense channels
Rev. 0.56 (5/1/09)
General
Fixed typos and updated text as necessary.
Cleaned up system diagrams
Rev. 0.54 (4/24/09)
Figure 4.1, "System
Diagram for CAP1088"
Updated figures for pin names
Section 5.5, "Sensitivity
Control Register"
Renamed bit fields
Section 5.6, "Configuration
Register"
Renamed bits 5 and 6
Section 3.4, "SPI Interface"
Updated section to describe Normal operation
Rev. 0.53 (4/23/09)
SMSC CAP1088
71
DATASHEET
Revision 1.1 (08-05-09)
8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Table 7.1 Customer Revision History (continued)
REVISION LEVEL & DATE
Rev. 0.52 (4/17/09)
Revision 1.1 (08-05-09)
SECTION/FIGURE/ENTRY
General
CORRECTION
Initial document creation
72
DATASHEET
SMSC CAP1088

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