Freescale Semiconductor
Technical Data
MPR084
Rev 6, 5/2010
Product Preview
Proximity Capacitive Touch
Sensor Controller
MPR084 OVERVIEW
The MPR084 is an Inter-Integrated Circuit Communication (I
2
C) driven
Capacitive Touch Sensor Controller, optimized to manage an 8-touch pad
capacitive array. The device can accommodate a wide range of
implementations through 3 output mechanisms, and many configurable
options.
Features
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1.8 V to 3.6 V operation
41 µA average supply current with 1 s response time
2 µA low Standby Current
Variable low power mode response time (32 ms – 4 s)
Rejects unwanted multi-key detections from EMI events such as PA
bursts or user handling
Ongoing pad analysis and detection is not reset by EMI events
Data is buffered in a FIFO for shortest access time
IRQ output advises when FIFO has data
System can set interrupt behavior as immediate after event, or
program a minimum time between successive interrupts
Current touched pad position is always available on demand for
polling-based systems
Sounder output can be enabled to generate key-click sound when pad
is touched
Two hardware selectable I
2
C addresses allowing two devices on a
single I
2
C bus
Configurable real-time auto calibration
5 mm x 5 mm x 1 mm 16 lead QFN package
-40°C to +85°C operating temperature range
Control Panels
Switch Replacements
Touch Pads
Appliances
PC Peripherals
Access Controls
MP3 Players
Remote Controls
Mobile Phones
ORDERING INFORMATION
Device Name
MPR084Q
MPR084EJ
-40C to +85C
Temperature Range
Case Number
1679
(16-Lead QFN)
948F
(16-Lead TSSOP)
Touch Pads
MPR084
Capacitive Touch
Sensor Controller
Bottom View
16-LEAD QFN
CASE 1679
16-LEAD TSSOP
CASE 948F
Top View
E1
E2
E3
14
E4
13
12 E5
11 E6
10 E7
9
5
SCL
6
SDA
7
AD0
8
SOUNDER
E8
16
ATTN
IRQ
VDD
VSS
1
2
3
4
15
MPR084
Implementations
Typical Applications
ATTN
IRQ
VDD
VSS
SCL
SDA
AD0
SOUNDER
1
2
3
4
5
6
7
8
16
15
14
E1
E2
E3
E4
E5
E6
E7
E8
MPR084
13
12
11
10
9
8-pads
Figure 1. Pin Connections
This document contains a product under development. Freescale Semiconductor reserves the right to change or
discontinue this product without notice.
© Freescale Semiconductor, Inc., 2007–2010. All rights reserved.
1
1.1
Device Overview
Introduction
Freescale Semiconductor’s MPR084 proximity capacitive touch sensor controller is one of a family of products designed to detect
the state of capacitive touch pads. The MPR084 offers designers a cost-efficient alternative to mechanical keys for control panel
applications.
The MPR084 uses an I
2
C interface to communicate with the host which configures the operation and an interrupt to advise the
host of status changes. The MPR084 includes a piezo sounder drive which provides audible feedback to simulate mechanical
key clicks. The MPR08X family has several implementations to use in your design including control panels and switch
replacements. The MPR084 controls individual touch pads. Other members of the MPR08X family are well suited for other
application interface situations such as individual touch pads or rotary/touch pad combinations.
Freescale offers a broad portfolio of proximity sensors for products ranging from appliance control panels to portable electronics.
Target markets include consumer, appliance, industrial, medical and computer peripherals.
1.1.1
Devices in the MPR08X series
The MPR08X series of Proximity Capacitive Touch Sensor Controllers allows for a wide range of applications and
implementations. Each of the products in
Table 1
perform a different application specific task and are optimized for this specific
functionality.
Table 1. MPR08X Family Overview
Product
MPR083
MPR084
Bus
I
2
C
I
2
C
Sounder
Yes
Yes
Rotary/Slider
8-pads
—
Touch Pad Array
—
8 keys
1.1.2
Internal Block Diagram
The MPR084 consists of primary functional blocks; Interrupt Controller, I
2
C Serial Interface, Sounder Controller, Configuration
and Status registers, Touch Pad Decoder, Magnitude Comparator and Recalibrator, EMI Burst/Noise Rejection Filter,
Capacitance Measurement Analog Front End. Each of these blocks will be described in detail in their respective sections.
CLEAR
SDA
SCL
ATTN
AD0
I2C
SERIAL
INTERFACE
PAD
ENABLED
CURRENT
PAD
TOUCHED
PAD
IDENTIFY
DECODER
EMI BURST/NOISE REJECT FILTER
RATE
CAPACITANCE MEASUREMENT A.F.E.
SET
CONFIGURATION AND STATUS REGISTERS
IRQ
INTERRUPT
CONTROLLER
MAGNITUDE COMPARATOR AND RECALIBRATOR
MASKS
8
8
8
8
8 TOUCH PADS
SOUNDER
SOUNDER
DRIVER
CONTROLLER
Figure 2. Functional Block Diagram
MPR084
2
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Freescale Semiconductor
1.1.3
Terminology
The following terms are used to describe front panel interface and capacitive touch sensor technology throughout this document.
Table 2. Terminology
Term
Touch Sensor
Touch Sensor Controller
Key
Touch Pad
Definition
A Touch Sensor is the combination of a Touch Sensor Controller and a connected conductive area
referred to as an electrode.
A Touch Sensor Controller is the intelligent part of a Touch Sensor which measures capacitance and
differentiates between touched and untouched pads.
A Key or Switch is a mechanical device that makes an electrical connection only when pressed.
A Touch Pad is a type of capacitive sensor that is used for direct replacement of a Key. A capacitive
touch sensor determines touch state by differentiating between high and low capacitances. When
there is a change in the state this can be interpreted in the same way as a mechanical Key.
A Solid or Full Pad is a type of touch pad where exactly one electrode is used
A Split Pad is a type of touch pad where more than one electrode is used. Split Pads are used to
increase the total number of possible touch pads without increasing the electrical connections to the
Touch Sensor Controller.
N-Key Lockout refers to the logic that determines how many keys can be simultaneously touched in
a system. For example, 1-key lockout would only allow a single key to be touched before ignoring
all future touches.
N-Key Rollover refers to the logic that determines how many keys can be pressed in succession
without releasing previous keys. For example, a system with 1-key lockout and 2-key rollover would
allow 2-keys to be pressed in succession but would only report the second key once the first key
was released.
Inter-Integrated Circuit Communication
Solid Pad
Split Pad
N-key Lockout
N-key rollover
I
2
C
MPR084
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3
2
2.1
External Signal Description
Device Pin Assignment
Table 3
shows the pin assignment for the MPR084. For a more detailed description of the functionality of each pin, refer to the
appropriate chapter.
Table 3. Device Pin Assignment
Pin
1
2
3
4
5
6
7
8
9 - 16
PAD
Name
ATTN
IRQ
VDD
VSS
SCL
SDA
AD0
SOUNDER
E1, E2, E3, E4, E5,
E6, E7, E8
Exposed pad
Function
Attention Pin. Input, active low, when asserted sets the Configuration Register’s DCE bit high
allowing communication with the part.
Interrupt Request Pin. Output, active-low, open-drain interrupt request signaling new events.
Positive Supply Voltage
Ground
I
2
C Serial Clock
I
2
C Serial Data
Address input. Low = slave address 0x5C. High = slave address 0x5D.
Sounder driver output. Connect a piezo sounder from this output to ground. Output is push-pull
Touch Pad Electrode connections.
Exposed pad on package underside (QFN only). Connect to VSS.
The two packages available for the MPR084 are a 5x5mm 16 pin QFN and a 4x5mm 16 pin TSSOP. Both of the packages and
their respective pinouts are shown in
Figure 3.
E1
E2
E3
E4
16
ATTN
IRQ
VDD
VSS
1
2
3
4
5
SCL
15
14
13
12 E5
11 E6
10 E7
9
E8
ATTN
IRQ
VDD
VSS
SCL
SDA
AD0
SOUNDER
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
E1
E2
E3
E4
E5
E6
E7
E8
6
SDA
7
AD0
8
SOUNDER
QFN
Figure 3. Package Pinouts
TSSOP
2.2
Recommended System Connections
The MPR084 Capacitive Touch Sensor Controller requires ten external passive components. When connecting the MPR084 in
a touch sensor system, the electrode lines must have pull-up resistors. The recommended value for these pull-ups is 780k.
Some electrode arrays will require higher or lower values depending on the application.
In addition to the 8 resistors a bypass capacitor of 1µF should always be used between the VDD and VSS lines.and a 4.7
k
pull-up resistor should be included on the IRQ.
MPR084
4
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The remaining 5 connections are SCL, SDA, IRQ, ATTN, and SOUNDER. Depending on the specific application, each of these
control lines can be used by connecting them to a host system. In the most minimal system, the SCL and SDA must be connected
to a master I
2
C interface to communicate with the MPR084. All of the connections for the MPR084 are shown by the schematic
in
Figure 4.
VDD
VDD
780k
Ω
780k
Ω
4.7k
Ω
780k
Ω
780k
Ω
780k
Ω
780k
Ω
780k
Ω
780k
Ω
ARRAY
ELECTRODE
1
2
3
4
5
6
7
8
9
E1
E2
E3
E4
E5
E6
E7
E8
GND
VDD
ATTN
IRQ
1
ATTN
2
IRQ
E1
E2
E3
E4
E5
E6
E7
E8
16
15
14
13
12
11
10
9
1μF
3
VDD
4
VSS
SCL
SDA
5
SCL
6
7
AD0
SDA
GND
SOUNDER
8
SOUNDER
MPR084
GND
8-TOUCH
PAD
Figure 4. Recommended System Connections Schematic
Note that in this configuration the AD0 address line is tied high thus the slave address of the MPR084 0x5D. Alternatively the
address line can be pulled low if the host system needs the MPR084 to be on address 0x5C. This functionality can also be used
to incorporate two MPR084 devices in the same system.
2.3
Serial Interface
The MPR084 uses an I
2
C Serial Interface. The I
2
C protocol implementation and the specifics of communicating with the Touch
Sensor Controller are detailed in the following sections.
2.3.1
Serial-Addressing
The MPR084 operates as a slave that sends and receives data through an I
2
C 2-wire interface. The interface uses a serial data
line (SDA) and a serial clock line (SCL) to achieve bi-directional communication between master(s) and slave(s). A master
(typically a microcontroller) initiates all data transfers to and from the MPR084, and generates the SCL clock that synchronizes
the data transfer.
The MPR084 SDA line operates as both an input and an open-drain output. A pull-up resistor, typically 4.7k, is required on SDA.
The MPR084 SCL line operates only as an input. A pull-up resistor, typically 4.7k, is required on SCL if there are multiple
masters on the 2-wire interface, or if the master in a single-master system has an open-drain SCL output.
Each transmission consists of a START condition (Figure
5)
sent by a master, followed by the MPR084’s 7-bit slave address plus
R/W bit, a register address byte, one or more data bytes, and finally a STOP condition.
SDA
tSU DAT
tLOW
tHIGH
tR
tF
REPEAT ED ST ART
CONDIT ION
tHD DAT
tSU STA
tHD STA
tSU STO
tBUF
SCL
tHD STA
ST ART
CONDIT ION
ST OP
CONDIT ION
ST ART
CONDIT ION
Figure 5. Wire Serial Interface Timing Details
MPR084
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