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CAP1298
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Datasheet CAP1298 Datasheet

8-Channel Capacitive Touch Sensor with
SMBus
Protocol
SMCLK SMDATA
VDD GND
ALERT#
Capacitive Touch Sensing Algorithm
CS1CS2CS3CS4CS6CS7 CS8
CS5 /
SG
Proximity Detection & Signal Guard
CAP1298
PRODUCT FEATURES
General Description
The CAP1298 which incorporates RightTouch® technology, is a multiple channel capacitive touch sensor. It contains eight (8) individual capacitive touch sensor inputs with programmable sensitivity for use in touch sensor applications. Each sensor input is calibrated to compensate for system parasitic capacitance and automatically recalibrated to compensate for gradual environmental changes.
In addition, the CAP1298 can be configured to detect proximity on one or more channels with an optional signal guard to reduce noise sensitivity and to isolate the proximity antenna from nearby conductive surfaces that would otherwise attenuate the e-field.
The CAP1298 includes Multiple Pattern Touch recognition that allows the user to select a specific set of buttons to be touched simultaneously. If this pattern is detected, a status bit is set and an interrupt is generated.
The CAP1298 has Active and Standby states, each with its own sensor input configuration controls. The Combo state allows a combination of sensor input controls to be used which enables one or more sensor inputs to operate as buttons while another sensor input is operating as a proximity detector. Power consumption in the Standby and Combo states is dependent on the number of sensor inputs enabled as well as averaging, sampling time, and cycle time. Deep Sleep is the lowest power state available, drawing 5µA (typical) of current. In this state, no sensor inputs are active, and communications will wake the device.
Datasheet
Applications
Desktop and Notebook PCsLCD MonitorsConsumer ElectronicsAppliances
Features
Eight (8) Capacitive Touch Sensor Inputs
— Programmable sensitivity — Automatic recalibration — Calibrates for parasitic capacitance — Individual thresholds for each button
Proximity DetectionSignal Guard
— Isolates the proximity antenna from attenuation — Reduces system noise sensitivity effects on inputs
Mu ltiple Button Pattern DetectionPower Button SupportPress and Hold Feature for Volume-like Applications3.3V or 5V SupplyAnalog Filtering for System Noise SourcesRF Detection and Avoidance FiltersDigital EMI Blocker8kV ESD Rating on All Pins (HBM)Low Power Operation
— 5µA quiescent current in Deep Sleep — 50µA quiescent current in Standby (1 sensor input
monitored)
— Samples one or more channels in Standby
SMBus / IAvailable in a 16-pin 3mm x 3mm QFN RoHS compliant
package
2
C Compliant Communication Interface
Block Diagram
2013 Microchip Technology Inc. DS01571A-page 1
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Ordering Information:
ORDERING
NUMBER PACKAGE FEATURES
Datasheet
CAP1298-1-A4-TR 16-pin QFN 3mm x 3mm
(RoHS compliant)
Reel size is 4,000 pieces for 16-Pin QFN
This product meets the halogen maximum concentration values per IEC 61249-2-21
Eight capacitive touch sensor inputs, SMBus interface, SMBus address 0101_000(r/w). Proximity and signal guard.
DS01571A-page 2  2013 Microchip Technology Inc.
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Datasheet
Table of Contents
Chapter 1 Pin Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Chapter 2 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Chapter 3 Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.1 Communications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2 System Management Bus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2.1 SMBus Start Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2.2 SMBus Address and RD / WR
3.2.3 SMBus Data Bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2.4 SMBus ACK and NACK Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2.5 SMBus Stop Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.2.6 SMBus Timeout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.2.7 SMBus and I
3.3 SMBus Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3.1 SMBus Write Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3.2 SMBus Read Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3.3 SMBus Send Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3.4 SMBus Receive Byte. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.4 I
2
C Protocols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.4.1 Block Read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.4.2 Block Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2
C Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Chapter 4 General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.1 Power States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.2 Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.3 Capacitive Touch Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.3.1 Capacitive Touch Sensing Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.3.1.1 Active State Sensing Settings........................................................................................20
4.3.1.2 Standby State Sensing Settings ... .... ... ... ... .... ... ... .......................................... ................21
4.3.1.3 Combo State Sensing Settings......................................................................................21
4.3.2 Sensing Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.4 Sensor Input Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.4.1 Automatic Recalibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.4.2 Negative Delta Count Recalibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.4.3 Delayed Recalibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.5 Proximity Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.5.1 Signal Guard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.6 Power Button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.7 Multiple Touch Pattern Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.8 Noise Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.8.1 Low Frequency Noise Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.8.2 RF Noise Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.8.3 Noise Status and Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.9 Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.9.1 ALERT# Pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.9.2 Capacitive Sensor Input Interrupt Behavior. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.9.3 Interrupts for the Power Button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.9.4 Interrupts for Multiple Touch Pattern Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.9.5 Interrupts for Sensor Input Calibration Failures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.9.6 Interrupts for Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2013 Microchip Technology Inc. DS01571A-page 3
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Datasheet
Chapter 5 Register Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
5.1 Main Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.2 Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
5.2.1 General Status - 02h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
5.2.2 Sensor Input Status - 03h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.3 Noise Flag Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.4 Sensor Input Delta Count Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.5 Sensitivity Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.6 Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.6.1 Configuration - 20h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.6.2 Configuration 2 - 44h. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.7 Sensor Input Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.8 Sensor Input Configuration Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.9 Sensor Input Configuration 2 Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
5.10 Averaging and Sampling Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
5.11 Calibration Activate and Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
5.12 Interrupt Enable Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
5.13 Repeat Rate Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
5.14 Signal Guard Enable Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
5.15 Multiple Touch Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
5.16 Multiple Touch Pattern Configuration Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
5.17 Multiple Touch Pattern Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
5.18 Base Count Out of Limit Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
5.19 Recalibration Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
5.20 Sensor Input Threshold Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
5.21 Sensor Input Noise Threshold Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
5.22 Standby Channel Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
5.23 Standby Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
5.24 Standby Sensitivity Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
5.25 Standby Threshold Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
5.26 Sensor Input Base Count Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
5.27 Power Button Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
5.28 Power Button Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
5.29 Sensor Input Calibration Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
5.30 Calibration Sensitivity Configuration Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
5.31 Product ID Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
5.32 Manufacturer ID Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
5.33 Revision Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Chapter 6 Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
6.1 CAP1298 Package Drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
6.2 Package Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Appendix ADevice Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
A.1 Delta from CAP1128 / CAP1188 to CAP1298 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Revision History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
DS01571A-page 4  2013 Microchip Technology Inc.
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Datasheet
List of Figures
Figure 1.1 CAP1298-1 Pin Diagram (16-Pin QFN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 3.1 SMBus Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 4.1 System Diagram for CAP1298 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure 4.2 POR and PORR With Slow Rising V
Figure 4.3 Signal Guard. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Figure 4.4 Sensor Interrupt Behavior - Repeat Rate Enabled. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Figure 4.5 Sensor Interrupt Behavior - No Repeat Rate Enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Figure 6.1 CAP1298 Package Drawing - 16-Pin QFN 3mm x 3mm . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Figure 6.2 CAP1298 Package Dimensions - 16-Pin QFN 3mm x 3mm . . . . . . . . . . . . . . . . . . . . . . . 63
Figure 6.3 CAP1298 PCB Land Pattern and Stencil - 16-Pin QFN 3mm x 3mm . . . . . . . . . . . . . . . . 64
Figure 6.4 CAP1298-1 Package Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
and BOR with Falling V
DD
DD . . . . . . . . . . . . . . . . . . . . . . . 20
2013 Microchip Technology Inc. DS01571A-page 5
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Datasheet
List of Tables
Table 1.1 Pin Description for CAP1298 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Table 1.2 Pin Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Table 2.1 Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Table 2.2 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Table 3.1 Protocol Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 3.2 Write Byte Protocol. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 3.3 Read Byte Protocol. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 3.4 Send Byte Protocol. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 3.5 Receive Byte Protocol. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 3.6 Block Read Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Table 3.7 Block Write Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Table 4.1 Ideal Base Counts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Table 5.1 Register Set in Hexadecimal Order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Table 5.2 Main Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Table 5.3 Power State Bit Overrides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Table 5.4 GAIN and C_GAIN Bit Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Table 5.5 Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Table 5.6 Noise Flag Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Table 5.7 Sensor Input Delta Count Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Table 5.8 Sensitivity Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Table 5.9 DELTA_SENSE Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Table 5.10 BASE_SHIFT Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Table 5.11 Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Table 5.12 Sensor Input Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Table 5.13 Sensor Input Configuration Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Table 5.14 MAX_DUR Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Table 5.15 RPT_RATE Bit Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Table 5.16 Sensor Input Configuration 2 Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Table 5.17 M_PRESS Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Table 5.18 Averaging and Sampling Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Table 5.19 AVG Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Table 5.20 SAMP_TIME Bit Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Table 5.21 CYCLE_TIME Bit Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Table 5.22 Calibration Activate and Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Table 5.23 Interrupt Enable Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Table 5.24 Repeat Rate Enable Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Table 5.25 Signal Guard Enable Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Table 5.26 Multiple Touch Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Table 5.27 B_MULT_T Bit Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Table 5.28 Multiple Touch Pattern Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Table 5.29 MTP_TH Bit Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Table 5.30 Multiple Touch Pattern Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Table 5.31 Base Count Out of Limit Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Table 5.32 Recalibration Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Table 5.33 NEG_DELTA_CNT Bit Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Table 5.34 CAL_CFG Bit Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Table 5.35 Sensor Input Threshold Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Table 5.36 Sensor Input Noise Threshold Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Table 5.37 CSx_BN_TH Bit Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Table 5.38 Standby Channel Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Table 5.39 Standby Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Table 5.40 STBY_AVG Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
DS01571A-page 6  2013 Microchip Technology Inc.
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Datasheet
Table 5.41 STBY_SAMP_TIME Bit Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Table 5.42 STBY_CY_TIME Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Table 5.43 Standby Sensitivity Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Table 5.44 STBY_SENSE Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Table 5.45 Standby Threshold Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Table 5.46 Sensor Input Base Count Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Table 5.47 Power Button Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Table 5.48 PWR_BTN Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Table 5.49 Power Button Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Table 5.50 Power Button Time Bits Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Table 5.51 Sensor Input Calibration Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Table 5.52 Calibration Sensitivity Configuration Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Table 5.53 CALSENX Bit Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Table 5.54 Product ID Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Table 5.55 Vendor ID Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Table 5.56 Revision Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Table A.1 Register Delta. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Table 6.1 Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
2013 Microchip Technology Inc. DS01571A-page 7
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
1 2 3 4
12 11 10
9
16
15
14
13
5
6
7
8
VDD
SMCLK
SMDATA
CS7
GND
CS5 / SG CS6
CS1
CS2
CS4
CS8
CS3
GND
N/C
N/C
Exposed pad
ALERT#

Chapter 1 Pin Description

Datasheet

Figure 1.1 CAP1298-1 Pin Diagram (16-Pin QFN)

Table 1.1 Pin Description for CAP1298

PIN
NUMBER PIN NAME PIN FUNCTION PIN TYPE
1ALERT#
2SMDATA
3SMCLK
4 VDD Positive Power supply Power n/a
5 N/C Not internally connected n/a
6 N/C Not internally connected n/a
7 GND Ground Power n/a 8 GND Ground Power n/a
ALERT# - Active low alert / interrupt output for SMBus
SMDATA - Bi-directional, open-drain SMBus or I
- requires pull-up resistor
SMCLK - SMBus or I
alert
2
C clock input - requires pull-up
resistor
2
C data
OD
DIOD n/a
DI n/a
UNUSED
CONNECTION
Connect to
Ground
Connect to
Ground
Connect to
Ground
9 CS8 Capacitive Touch Sensor Input 8 AIO
10 CS7 Capacitive Touch Sensor Input 7 AIO
DS01571A-page 8  2013 Microchip Technology Inc.
Connect to
Connect to
Ground
Ground
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Datasheet
Table 1.1 Pin Description for CAP1298 (continued)
PIN
NUMBER PIN NAME PIN FUNCTION PIN TYPE
11 CS6 Capacitive Touch Sensor Input 6 AIO
CS5 - Capacitive Touch Sensor Input 5 AIO
12 CS5 / SG
UNUSED
CONNECTION
Connect to
Ground
Connect to
Ground
SG - Signal Guard Output AIO Leave Open
13 CS4 Capacitive Touch Sensor Input 4 AIO
14 CS3 Capacitive Touch Sensor Input 3 AIO
15 CS2 Capacitive Touch Sensor Input 2 AIO
16 CS1 Capacitive Touch Sensor Input 1 AIO
Connect to
Ground
Connect to
Ground
Connect to
Ground
Connect to
Ground
Bottom pad Exposed pad Not internally connected, but recommend grounding - -
APPLICATION NOTE: All digital pins are 5V tolerant pins.
The pin types are described in Table1.2.

Table 1.2 Pin Types

PIN TYPE DESCRIPTION
Power This pin is used to supply power or ground to th e 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
OD
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.
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.
2013 Microchip Technology Inc. DS01571A-page 9
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard

Chapter 2 Electrical Specifications

Table 2.1 Absolute Maximum Ratings

Voltage on VDD pin -0.3 to 6.5 V Voltage on CS pins to GND -0.3 to 4.0 V
Datasheet
Voltage on 5V tolerant pins (V Voltage on 5V tolerant pins (|V Input current to any pin except VDD +
) -0.3 to 5.5 V
5VT_PIN
- VDD|) (see Note 2.2)0 to 3.6 V
5VT_PIN
10 mA Output short circuit current Continuous N/A Package Power Dissipation up to TA = 85°C for 16-pin QFN
0.5 W
(see Note 2.3) Junction to Ambient (θ
) (see Note 2.4)70 °C/W
JA
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
V
and VDD must never exceed 3.6V.
5VT_PIN
Note 2.3 The Package Power Dissipation specification assumes a recommended thermal via design
consisting of a 2x2 matrix of 0.3mm (12mil) vias at 1.0mm pitch conn ected to the ground plane with a 1.6 x 1.6mm thermal landing.
Note 2.4 Junction to Ambient (θ
) is dependent on the design of the thermal vias. Without thermal
JA
vias and a thermal landing, the θJA will be higher.
DS01571A-page 10  2013 Microchip Technology Inc.
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Datasheet

Table 2.2 Electrical Specifications

VDD = 3V to 5.5V, TA = 0°C to 85°C, all Typical values at TA = 25°C unless otherwise noted.
CHARACTERISTIC SYMBOL MIN TYP MAX UNIT CONDITIONS
DC POWER
Supply Voltage V
Supply Current
Maximum Base
Capacitance
Minimum Detectable
Capacitive Shift
DD
I
STBY_DEF
I
STBY_LP
I
DSLEEP_3V
I
DSLEEP_5V
I
DD
C
BASE
ΔC
TOUCH
3.0 5.5 V Standby state active
120 170 µA
1 sensor input monitored
Default conditions (8 avg, 70ms
cycle time)
Standby state active
50 µA
1 sensor input monitored
1 avg, 140ms cycle time
Deep Sleep state active
5TBDµA
No communications
T
< 40°C
A
3.135 < V
< 3.465V
DD
Deep Sleep state active
TBD TBD µA
500 750 µA
No communications
T
< 40°C
A
V
= 5V
DD
Capacitive Sensing Active
signal guard disabled
CAPACITIVE TOUCH SENSOR INPUTS
50 pF Pad un touched
20 fF Pad touched - defaul t conditions
Recommended Cap
Shift
ΔC
TOUCH
0.1 2 pF Pad touched - Not tested
Untouched Current Counts
Power Supply
Rejection
PSR ±3 ±10
counts
/ V
Base Capacitance 5pF - 50pF
Negative Delta Counts disabled
Maximum sensitivity
All other parameters default
POWER-ON AND BROWN-OUT RESET (SEE Section 4.2, "Reset")
Power-On Reset
Voltage
Power-On Reset Release Voltage
Brown-Out Reset V
V
V
PORR
POR
BOR
1 1.3 V Pin States Defined
2.85 V
Rising V
Ensured by design
2.8 V Falling V
DD
DD
VDD Rise Rate
(ensures internal
POR signal)
2013 Microchip Technology Inc. DS01571A-page 11
SV
DD
0.05 V/ms 0 to 3V in 60ms
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Table 2.2 Electrical Specifications (continued)
V
= 3V to 5.5V, TA = 0°C to 85°C, all Typical values at TA = 25°C unless otherwise noted.
DD
CHARACTERISTIC SYMBOL MIN TYP MAX UNIT CONDITIONS
Datasheet
Power-Up Timer
Period
Brown-Out Reset
Voltage Delay
t
t
BORDC
Time to
Communications
Ready
Time to First
Conversion Ready
t
COMM_DLY
t
CONV_DLY
Output Low Voltage V
Output High Voltage V
Input High Voltage V
Input Low Voltage V
Leakage Current I
PWRT
OL
OH
IH
IL
LEAK
10 ms
1µsV
DD
= V
BOR
- 1
TIMING
15 ms
170 200 ms
I/O PINS
VDD -
0.4
0.4 V I
VI
SOURCE_IO
SINK_IO
= 8mA
= 8mA
2.0 V
0.8 V powered or unpowered
T
< 85°C
±5 µA
pull-up voltage <
A
3.6V if
unpowered
SG PIN
Capacitive Drive
Capability
C
BASE_SG
20 20 0 pF capacitance to ground
SMBUS TIMING
Input Capacitance C
Clock Frequency f
Spike Suppression t
Bus Free Time Stop
to Start
Start Setup Time t
Sta rt Ho ld Ti me t
Stop Setup Time t
Data Hold Time t Data Hold Time t
Data Setup Time t
DS01571A-page 12  2013 Microchip Technology Inc.
IN
SMB
SP
t
BUF
SU:STA
HD:STA
SU:STO
HD:DAT
HD:DAT
SU:DAT
10 400 kHz
1.3 µs
0.6 µs
0.6 µs
0.6 µs 0 µs W hen transmitting to the master
0.3 µs When receiving from the master
0.6 µs
5pF
50 ns
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Datasheet
Table 2.2 Electrical Specifications (continued)
VDD = 3V to 5.5V, TA = 0°C to 85°C, all Typical values at TA = 25°C unless otherwise noted.
CHARACTERISTIC SYMBOL MIN TYP MAX UNIT CONDITIONS
Clock Low Period t
Clock High Period t
Clock / Data Fall
Time
Clock / Data Rise
Time
Capacitive Load C
LOW
HIGH
t
FALL
t
RISE
LOAD
1.3 µs
0.6 µs
300 ns Min = 20+0.1C
300 ns Min = 20+0.1C
400 pF per bus line
LOAD
LOAD
ns
ns
2013 Microchip Technology Inc. DS01571A-page 13
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
SMDATA
SMCLK
T
BUF
P
S
S - Start Condition
P - Stop Condition
PS
T
HIGH
T
LOW
T
HD:STA
T
SU:STO
T
HD:STA
T
HD:DAT
T
SU:DAT
T
SU:STA
T
FALL
T
RISE

Chapter 3 Communications

3.1 Communications

The CAP1298 communicates using the SMBus or I2C protocol.

3.2 System Management Bus

The CAP1298 communicates with a host controller, such as an MCHP 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 CAP1298 will not stretch the clock signal.
Datasheet

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.
The CAP1298 responds to SMBus address 0101_000(r/w).

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 cl ient device
DS01571A-page 14  2013 Microchip Technology Inc.
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.
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Datasheet

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 CAP1298 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 CAP1298 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, "Configuration Registers").

3.2.7 SMBus and I2C Compatibility

The major differences between SMBus and I2C devices are highlighted here. For more information, refer to the SMBus 2.0 specification.
1. CAP1298 supports I
2. Minimum frequency for SMBus communications is 10kHz.
2
C fast mode at 400kHz. This covers the SMBus max time of 100kHz.
3. The SMBus client protocol will reset if the clock is held low longer than 30ms (timeout condition). This can be enabled in the CAP1298 by setting the TIMEOUT bit in the Configuration register. I2C does not have a timeout.
4. The SMBus client protocol will reset if both the clock and the data line are high for longer than 200us (idle condition). This can be enabled in the CAP1298 by setting the TIMEOUT bit in the Configuration register. I
2
5. I
C devices do not support the Alert Response Address functionality (which is op tional for SMBus).
2
C devices support block read and write differently. I2C protocol allows for unlimited number of
6. I 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 CAP1298 supports I
2
C does not have an idle condition.

3.3 SMBus Protocols

The CAP1298 is SMBus 2.0 compatible and supports Write Byte, Read Byte, Send Byte, and Receive Byte as valid protocols as shown below.
All of the below protocols use the convention in Table 3.1.
DATA SENT
TO DEVICE
Data sent Data sent

Table 3.1 Protocol Format

DATA SENT TO
THE HOST
2
C formatting only .
2013 Microchip Technology Inc. DS01571A-page 15

3.3.1 SMBus Write Byte

The Write Byte is used to write one byte of data to a specific register as shown in Table 3.2.
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Datasheet
Table 3.2 Write Byte Protocol
START
SLAVE
ADDRESS WR
ACK
REGISTER
ADDRESS ACK
REGISTER
DATA ACK STOP
1 ->0 0101_000 0 0 XXh 0 XXh 0 0 -> 1

3.3.2 SMBus Read Byte

The Read Byte protocol is used to read one byte of data from the registers as show n in Table 3.3.
Table 3.3 Read Byte Protocol
START SLAVE
ADDRESS
WR ACK REGISTER
ADDRESS
ACK START CLIENT
ADDRESS
RD ACK REGISTER
DATA
NACK STOP
1->0 0101_000 0 0 XXh 0 1 ->0 0101_000 1 0 XXh 1 0 -> 1

3.3.3 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 3.4.
APPLICATION NOTE: The Send Byte protocol is not functional in Deep Sleep (i.e., DSLEEP bit is set).
Table 3.4 Send Byte Protocol
START
SLAVE
ADDRESS WR ACK
REGISTER
ADDRESS ACK STOP
1 -> 0 0101_000 0 0 XXh 0 0 -> 1

3.3.4 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 3.5.
APPLICATION NOTE: The Receive Byte protocol is not functional in Deep Sleep (i.e., DSLEEP bit is set).
Table 3.5 Receive Byte Protocol
SLAVE
START
1 -> 0 0101_000 1 0 XXh 1 0 -> 1
DS01571A-page 16  2013 Microchip Technology Inc.
ADDRESS RD
ACK REGISTER DATA NACK STOP
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Datasheet

3.4 I2C Protocols

The CAP1298 supports I2C Block Read and Block Write. The protocols listed below use the convention in Table 3.1.

3.4.1 Block Read

The Block Read is used to read multiple data bytes from a group of contiguous registers as sh own in
Table 3.6.
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 0101_000 0 0 XXh 0 1 ->0 0101_000 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

3.4.2 Block Write

The Block Write is used to write multiple data bytes to a group of contiguous registers as shown in
Table 3.7.
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 3.7 Block Write Protocol
REGISTER
ADDRESS ACK
START
SLAVE
ADDRESS WR
ACK
1 ->0 0101_000 0 0 XXh 0 XXh 0
REGISTER
DATA
ACK
REGISTER
DATA ACK . . .
REGISTER
DATA ACK STOP
REGISTER
DATA ACK
XXh 0 XXh 0 . . . XXh 0 0 -> 1
2013 Microchip Technology Inc. DS01571A-page 17
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard

Chapter 4 General Description

The CAP1298 is a multiple channel capacitive touch sensor. It contains eight (8) individual capacitive touch sensor inputs with programmable sensitivity for use in touch sensor applications. Each sensor input is calibrated to compensate for system parasitic capacitance and automatically recalibrated to compensate for gradual environmental changes.
In addition, the CAP1298 can be configured to detect proximity on one or more channels with an optional signal guard to reduce noise sensitivity.
The CAP1298 includes Multiple Pattern Touch recognition that allows the user to select a specific set of buttons to be touched simultaneously. If this pattern is detected, a status bit is set and an interrupt is generated.
The CAP1298 has Active and Standby states, each with its own sensor input configuration controls. The Combo state allows a combination of sensor input controls to be used which enab les one or more sensor inputs to operate as buttons while another sensor input is operating as a proximity detector. Power consumption in the Standby and Combo states is dependent on the number of sensor inputs enabled as well as averaging, sampling time, and cycle time. Deep Sleep is the lowest power state available, drawing 5µA (typical) of current. In this state, no sensor inputs are active, and communications will wake the device.
The device communicates with a host controller using SMBus / I device for updated information at any time or it may configure the device to flag an in terrupt whenever a touch is detected on any sensor pad.
Datasheet
2
C. The host controller may poll the
A typical system diagram is shown in Figure 4.1.
DS01571A-page 18  2013 Microchip Technology Inc.
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
CAP1298
CS7
SMDATA
SMCLK
Embedded
Controller
ALERT#
CS8
CS3
CS2
CS1
CS4
CS6
Touch Button
Touch Button
Touch Button
Touch Button
Touch Button
Touch Button
SG*
Proximity
Sensor
VDDGND
3.0V to 5.5V
* CS5 / SG is a multi-function pin. If not using the signal guard show n here, CS5 can be another touch button.
10kOhm resistors
3.0V to 5.5V
1.0uF0.1uF
Datasheet

Figure 4.1 System Diagram for CAP1298

4.1 Power States

The CAP1298 has 4 power states depending on the status of the STBY, COMBO, and DSLEEP bits (see Section 5.1, "Main Control Register"). When the device transitions between power states, previously detected touches (for channels that are being de-activated) a re cleared a nd the sensor i nput status bits are reset.
1. Active - The normal mode of operation. The device is monitoring capacitive sensor inputs enabled in the Active state (see Section 5.7, "Sensor Input Enable Register").
2. Standby - When the STBY bit is set, the device is monitoring the capacitive sensor in puts enabled in the Standby state (see Section 5.22, "Standby Channel Register"). Interrupts can still be generated based on the enabled channels. The device will still respond to communications normally and can be returned to the Active state of operation by clearing the STBY bit. Power consumption in this state is dependent on the number of sensor inputs enabled as well as averaging, sampling time, and cycle time.
3. Combo - When the COMBO bit is set, the device is monitoring capacitive sensor inputs enabled in the Active state as well as inputs enabled in the Standby state (hence the name “Combo”). Interrupts can still be generated based on the enabled channels. The device wi ll still respond to
2013 Microchip Technology Inc. DS01571A-page 19
communications normally and can be returned to the Active state of operation by clearing the
COMBO bit. Power consumption in this state is dependent on the number of sensor inputs enabled
V
DD
V
BOR
T
PWRT
GND
Undefined
SYSRST
V
POR
V
PORR
T
BORDCTPWRT
as well as averaging, sampling time, and cycle time.
4. Deep Sleep - When the DSLEEP bit is set, the device is in its lowest power state. It is not monitoring any capacitive sensor inputs. While in Deep Sleep, the CAP1298 can be awakened by SMBus communications targeting the device. This will not cause the DSLEEP to be cleared so the device will return to Deep Sleep once all communications have stopped. The device can be returned to the Active state of operation by clearing the DSLEEP bit.

4.2 Reset

The Power-On Reset (POR) circuit holds the device in reset until VDD has reached an acceptable level, Power-on Reset Release Voltage (V used to extend the start-up period until all device operation conditions have been met. Th e power-up timer starts after V
The Brown-Out Reset (BOR) circuit holds the device in reset when V for longer than the BOR reset delay (t up timer is started again and must finish before reset is released, as shown in Figure 4.2.
reaches V
DD
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Datasheet
), for minimum operation. The power-up timer (PWRT) is
PORR
. POR and PORR with slow rising VDD is shown in Figure 4.2.
PORR
falls to a minimum level, V
). After a BOR, when VDD rises above V
BORDC
DD
PORR
, the power-
BOR
Figure 4.2 POR and PORR With Slow Rising V
and BOR with Falling V
DD
DD

4.3 Capacitive Touch Sensing

The CAP1298 contains eight (8) independent capacitive touch sensor inputs. Each sensor input has dynamic range to detect a change of capacitance due to a touch. Additionally, each sensor input can be configured to be automatically and routinely recalibrated.

4.3.1 Capacitive Touch Sensing Settings

Controls for managing capacitive touch sensor inp uts are determined by the power state.
4.3.1.1 Active State Sensing Settings
The Active state is used for normal operation. Sensor inputs being monitored are determined by the Sensor Input Enable Register (see Section 5.7, "Sensor Input Enable Register"). Sensitivity is controlled by the Sensitivity Control Register (see Section 5.5, "Sensitivity Control Register"). Averaging, sample time, and cycle time are controlled by the Averaging and Sampling Configuration Register (see Section 5.10, "Averaging and Sampling Configuration Register"). Each channel can have a separate touch detection threshold, as defined in the Sensor Input Threshold registers (see Section
5.20, "Sensor Input Threshold Registers").
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8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Datasheet
4.3.1.2 Standby State Sensing Settings
The Standby state is used for standby operation. In general, fewer sensor inputs are enabled, and they are programmed to have more sensitivity. Sensor inputs being monitored are determined by the Standby Channel Register (see Section 5.22, "Standby Channel Register"). Sensitivity is controlled by the Standby Sensitivity Register (see Section 5.24, "Standby Sensitivity Register"). Averaging, sample time, and cycle time are controlled by the Averaging and Sampling Configuration Register (see Section
5.23, "Standby Configuration Register"). There is one touch detection threshold, which applies to all
sensors enabled in Standby, as defined in the Standby Threshold Register (see Section 5.25, "Standby
Threshold Register").
4.3.1.3 Combo State Sensing Settings
The Combo state is used when a combination of proximity detection and norm al button operation is required. When the COMBO bit is set, the sensing cycle includes sensor inputs enabled in the Active state as well as sensor inputs enabled in the Standby state. Sensor inputs enabled in the Active state will use the Active settings described in Section 4.3.1.1, "Active State Sensing Settings". Sensor inputs enabled in the Standby state will use the Standby settings described in Section 4.3.1.2, "Standby State
Sensing Settings". If a sensor input is enabled in both th e Active state and in the Standby state, the
Active state settings will be used in Combo state. The programmed cycle time is determined by STBY_CY_TIME[1:0].
The Combo state also has two gain settings. When the COMBO bit is set, the GAIN[1:0] control only applies to the sensors enabled in the Active state, and the C_GAIN[1:0] control applies to the sensors enabled in the Standby state.

4.3.2 Sensing Cycle

Except when in Deep Sleep, the device automatically initiates a sensing cycle and repeats the cycle every time it finishes. The cycle polls through each enabled sensor input starting with CS1 and extending through CS8. As each capacitive touch sensor i nput is polled, its measurement is compared against a baseline “not touched” measurement. If the delta measurement is large enou gh to exceed the applicable threshold, a touch is detected and an interrupt can be generated (see Section 4.9.2,
"Capacitive Sensor Input Interrupt Behavior").
The sensing cycle time is programmable (see Section 5.10, "Averaging and Sampling Configuration
Register" and Section 5.23, "Standby Configuration Register"). If all enabled inputs can be sampled in
less than the cycle time, the device is placed into a lower power state for the remainder of the sensi ng cycle. If the number of active sensor inputs cannot be sampled within the specified cycle time, the cycle time is extended and the device is not placed in a lower power state.

4.4 Sensor Input Calibration

Calibration sets the Base Count Registers (Section 5.26, "Sensor Input Base Count Registers") which contain the “not touched” values used for touch detection comparisons. Calibration automatically occurs after a power-on reset (POR), when sample time is changed, when the gain is changed, when the calibration sensitivity is changed, and whenever a sensor input is newly enabled (for example, when transitioning from a power state in which it was disabled to a power state in which it is enab led). During calibration, the analog sensing circuits are tuned to the capacitance of the untouched pad. Then, samples are taken from each sensor input so that a base count can be established. After calibration, the untouched delta counts are zero.
APPLICATION NOTE: During the calibration routine, the sensor inputs will not detect a press for up to 200ms and
the Sensor Base Count Register values will be invalid. In addition, any press on the corresponding sensor pads will invalidate the calibration.
The host controller can force a calibration for selected sensor inputs at any time using the Calibrati on Activate and Status Register (Section 5.11, "Calibration Activate and Status Register"). When a bit is
2013 Microchip Technology Inc. DS01571A-page 21
8-Channel Capacitive Touch Sensor with Proximity Detection & Signal Guard
Datasheet
set, the corresponding capacitive touch sensor input will be calibrated (both analog and digital). The bit is automatically cleared once the calibration routine has successfully finished.
If analog calibration fails for a sensor input, the corresponding bit is not cleared in the Calibration Activate and Status Register, and the ACAL_FAIL bit is set in the General Status Register (Section 5.2,
"Status Registers"). An interrupt can be generated. Analog calibration will fail if a noise bit is set or if
the calibration value is at the maximum or minimum value. If digital calibrati on fails to generate base counts for a sensor input in the operating range, which is +
Table 4.1), indicating the base capacitance is out of range, the corresponding BC_OUTx bit is set in
the Base Count Out of Limit Register (Section 5.18, "Base Count Out of Limit Register"), and the BC_OUT bit is set in the General Status Register (Section 5.2, "Status Registers"). An interrupt can be generated. By default, when a base count is out of limit, analog calibration is repeated for the sensor input; alternatively, the sensor input can be sampled using the out of limit base count (Section
5.6, "Configuration Registers"). Calibration sensitivity can be ad justed for each sensor input based on
capacitive touch pad capacitance.

Table 4.1 Ideal Base Counts

IDEAL BASE COUNT SAMPLE TIME
3,200 320us
12.5% from the ideal base count (see
6,400 640us 12,800 1.28ms 25,600 2.56ms
During normal operation there are various options for reca librating the capacitive touch sensor inputs. Recalibration is a digital adjustment of the base counts so that the untouched delta count is zero. After a recalibration, if a sensor input’s base count has shifted + calibration will be performed on the sensor input.
12.5% from the ideal base count, a full

4.4.1 Automatic Recalibration

Each sensor input is regularly recalibrated at a programmable rate (see CAL_CFG[2:0] in Section 5.19,
"Recalibration Configuration Register"). By default, the recalibration routine stores the average 64
previous measurements and periodically updates the base “not touched” setting for the capacitive touch sensor input.
APPLICATION NOTE: Automatic recalibration only works when the delta count is below the active sensor input
threshold. It is disabled when a touch is detected.

4.4.2 Negative Delta Count Recalibration

It is possible that the device loses sensitivity to a touch. This may happen as a result of a noisy environment, recalibration when the pad is touched but delta counts do not exceed the threshold, or other environmental changes. When this occurs, the base untouched sensor input may generate negative delta count values. The NEG_DELTA_CNT[1:0] bits (see Section 5.19, "Recalibration
Configuration Register") can be set to force a recalibration after a specified number of consecutive
negative delta readings. After a delayed recalibration (see Section 4.4.3, "Delayed Recalibration") the negative delta count recalibration can correct after the touch is released.
APPLICATION NOTE: During this recalibration, the device will not respond to touches.
DS01571A-page 22  2013 Microchip Technology Inc.
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