FREESCALE MPR084

MPR084
Rev 2, 04/2008
Freescale Semiconductor
Technical Data
Product Preview
Proximity Capacitive Touch
Sensor Controller
MPR084
Capacitive Touch
Sensor Controller
MPR084 OVERVIEW
The MPR084 is an Inter-Integrated Circuit Communication (I2C) 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.
Bottom View
Features
Implementations
•
•
•
ATTN
1
10 E7
VSS
4
9
VSS
MPR084Q
MPR084EJ
-40°C to +85°C
1679
(16-Lead QFN)
948F
(16-Lead TSSOP)
SDA
Touch Pads
AD0
SOUNDER
8-pads
This document contains a product under development. Freescale Semiconductor reserves the right to change or
discontinue this product without notice.
© Freescale Semiconductor, Inc., 2007, 2008. All rights reserved.
Preliminary
E4
3
VDD
Case Number
E3
2
IRQ
Temperature Range
11 E6
IRQ
SCL
Device Name
13
VDD
ATTN
ORDERING INFORMATION
14
12 E5
Control Panels
Switch Replacements
Touch Pads
Appliances
PC Peripherals
Access Controls
MP3 Players
Remote Controls
Mobile Phones
15
MPR084
Typical Applications
•
•
•
•
•
•
16
5
6
7
8
SOUNDER
•
•
•
E2
•
Top View
AD0
•
16-LEAD TSSOP
CASE 948F
E1
•
16-LEAD QFN
CASE 1679
SCL
•
•
•
•
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 I2C addresses allowing two devices on a
single I2C 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
SDA
•
•
•
•
•
1
16
2
15
3
14
4
MPR084
13
5
12
6
11
7
10
8
9
E8
E1
E2
E3
E4
E5
E6
E7
E8
Figure 1. Pin Connections
1
Device Overview
1.1
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 I2C 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
Bus
Sounder
Rotary/Slider
Touch Pad Array
MPR083
I2C
Yes
8-pads
—
MPR084
I2C
Yes
—
8 keys
1.1.2
Internal Block Diagram
SET
RATE
CLEAR
SDA
SCL
ATTN
I2C
SERIAL
INTERFACE
AD0
SOUNDER
SOUNDER
DRIVER
CONTROLLER
PAD
ENABLED
CURRENT
PAD
TOUCHED
PAD
IDENTIFY
DECODER
8
8
8
CAPACITANCE MEASUREMENT A.F.E.
INTERRUPT
CONTROLLER
EMI BURST/NOISE REJECT FILTER
IRQ
CONFIGURATION AND STATUS REGISTERS
MASKS
MAGNITUDE COMPARATOR AND RECALIBRATOR
The MPR084 consists of primary functional blocks; Interrupt Controller, I2C 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.
8
8 TOUCH PADS
Figure 2. Functional Block Diagram
MPR084
Preliminary
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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
Definition
Touch Sensor
A Touch Sensor is the combination of a Touch Sensor Controller and a connected conductive area
referred to as an electrode.
Touch Sensor Controller
A Touch Sensor Controller is the intelligent part of a Touch Sensor which measures capacitance and
differentiates between touched and untouched pads.
Key
A Key or Switch is a mechanical device that makes an electrical connection only when pressed.
Touch Pad
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.
Solid Pad
A Solid or Full Pad is a type of touch pad where exactly one electrode is used
Split Pad
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
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
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.
I2C
Inter-Integrated Circuit Communication
MPR084
Sensors
Freescale Semiconductor
Preliminary
3
2
External Signal Description
2.1
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
Name
Function
1
ATTN
Attention Pin. Input, active low, when asserted sets the Configuration Register’s DCE bit high
allowing communication with the part.
2
IRQ
Interrupt Request Pin. Output, active-low, open-drain interrupt request signaling new events.
3
VDD
Positive Supply Voltage
4
VSS
Ground
5
SCL
I2C Serial Clock
6
SDA
I2C Serial Data
7
AD0
Address input. Low = slave address 0x5C. High = slave address 0x5D.
8
SOUNDER
9 - 16
E1, E2, E3, E4, E5,
E6, E7, E8
PAD
Exposed pad
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.
E1
E2
E3
E4
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.
16
15
14
13
ATTN
1
16
E1
IRQ
2
15
E2
1
12 E5
VDD
3
14
E3
IRQ
2
11 E6
VSS
4
13
E4
VDD
3
10 E7
SCL
5
12
E5
VSS
4
9
SDA
6
11
E6
AD0
7
10
E7
SOUNDER
8
9
E8
7
E8
8
SOUNDER
6
AD0
SCL
5
SDA
ATTN
QFN
TSSOP
Figure 3. Package Pinouts
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 780kΩ.
Some electrode arrays will require higher or lower values depending on the application.
In addition to the 8 resistors a bypass capacitor of 10µF should always be used between the VDD and VSS lines.and a 4.7 Ωk
pull-up resistor should be included on the IRQ.
MPR084
Preliminary
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Freescale Semiconductor
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 I2C interface to communicate with the MPR084. All of the connections for the MPR084 are shown by the schematic
in Figure 4.
VDD
VDD
780kΩ 780kΩ
4.7kΩ
VDD
1μF
ATTN
1 ATTN
2
IRQ
IRQ
GND
SOUNDER 8
E2
3
E3
13
4
12
5
E5
11
6
E6
10
7
E7
9
8
E5
SDA
7
E1
2
E4
5 SCL
6
SDA
1
15
E2
14
E3
VSS
SCL
ELECTRODE
780kΩ 780kΩ 780kΩ ARRAY
16
E1
3 VDD
4
780kΩ 780kΩ 780kΩ
E6
AD0
E7
SOUNDER
E8
9
MPR084
GND
E4
E8
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 I2C Serial Interface. The I2C 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 I2C 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 4.7kΩ, is required on SDA.
The MPR084 SCL line operates only as an input. A pull-up resistor, typically 4.7kΩ, 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
SCL
tHD DAT
tSU STA
tBUF
tHD STA
tSU STO
tHIGH
tHD STA
ST ART
CONDIT ION
tR
tF
REPEAT ED ST ART
CONDIT ION
ST OP
CONDIT ION
ST ART
CONDIT ION
Figure 5. Wire Serial Interface Timing Details
MPR084
Sensors
Freescale Semiconductor
Preliminary
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2.3.2
Start and Stop Conditions
Both SCL and SDA remain high when the interface is not busy. A master signals the beginning of a transmission with a START
(S) condition by transitioning SDA from high to low while SCL is high. When the master has finished communicating with the
slave, it issues a STOP (P) condition by transitioning SDA from low to high while SCL is high. The bus is then free for another
transmission.
SDA
DATA LINE STABLE
DATA VALID
SCL
CHANGE OF
DATA ALLOWED
Figure 6. Start and Stop Conditions
2.3.3
Bit Transfer
One data bit is transferred during each clock pulse (Figure 7). The data on SDA must remain stable while SCL is high.
SDA
SCL
S
P
START
CONDITION
STOP
CONDITION
Figure 7. Bit Transfer
2.3.4
Acknowledge
The acknowledge bit is a clocked 9th bit (Figure 8) which the recipient uses to handshake receipt of each byte of data. Thus each
byte transferred effectively requires 9 bits. The master generates the 9th clock pulse, and the recipient pulls down SDA during
the acknowledge clock pulse, such that the SDA line is stable low during the high period of the clock pulse. When the master is
transmitting to the MPR084, the MPR084 generates the acknowledge bit because the MPR084 is the recipient. When the
MPR084 is transmitting to the master, the master generates the acknowledge bit because the master is the recipient.
START
CONDITION
SCL
CLOCK PULSE FOR
ACKNOWLEDGEMENT
1
2
8
9
SDA
BY TRANSMITTER
SDA
S
BY RECEIVER
Figure 8. Acknowledge
MPR084
Preliminary
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Freescale Semiconductor
2.3.5
The Slave Address
The MPR084 has a 7-bit long slave address (Figure 9). The bit following the 7-bit slave address (bit eight) is the R/W bit, which
is low for a write command and high for a read command.
SDA
1
MSB
0
0
1
1
0
0
R/W
ACK
SCL
Figure 9. Slave Address
The MPR084 monitors the bus continuously, waiting for a START condition followed by its slave address. When a MPR084
recognizes its slave address, it acknowledges and is then ready for continued communication.
2.3.6
Message Format for Writing the MPR084
A write to the MPR084 comprises the transmission of the MPR084’s keyscan slave address with the R/W bit set to 0, followed
by at least one byte of information. The first byte of information is the command byte. The command byte determines which
register of the MPR084 is to be written by the next byte, if received. If a STOP condition is detected after the command byte is
received, then the MPR084 takes no further action (Figure 10) beyond storing the command byte. Any bytes received after the
command byte are data bytes.
Command byte is stored on receipt ofSTOP condition
D7
D6
D5
D4
D3
D2
D1
D0
acknowledge from MPR084
S
0
SLAVE ADDRESS
A
A
COMMAND BYTE
R/W
P
acknowledge from MPR084
Figure 10. Command Byte Received
Any bytes received after the command byte are data bytes. The first data byte goes into the internal register of the MPR084
selected by the command byte (Figure 11).
acknowledge from
MPR084
How command byte and data byte
map into MPR084's registers
D15 D14 D13 D12 D11 D10 D9
acknowledge from
MPR084
D8
D7
D6
D5
D4
D3
D2
D1
D0
acknowledge from MPR084
S
SLAVE ADDRESS
0
A
COMMAND BYTE
A
DATA BYTE
A
P
1 byte
R/W
auto-increment memory
word address
Figure 11. Command and Single Data Byte Received
If multiple data bytes are transmitted before a STOP condition is detected, these bytes are generally stored in subsequent
MPR084 internal registers because the command byte address generally auto-increments (Section 2.4).
2.3.7
Message Format for Reading the MPR084
The MPR084 is read using the MPR084’s internally stored command byte as address pointer, the same way the stored command
byte is used as address pointer for a write. The pointer generally auto-increments after each data byte is read using the same
rules as for a write (Section 6.4.1). Thus, a read is initiated by first configuring the MPR084’s command byte by performing a write
(Figure 12). The master can now read ‘n’ consecutive bytes from the MPR084, with the first data byte being read from the register
addressed by the initialized command byte.
MPR084
Sensors
Freescale Semiconductor
Preliminary
7
When performing read-after-write verification, remember to re-set the command byte’s address because the stored command
byte address will generally have been auto-incremented after the write (Section 2.4).
How command byte and data byte
map into MPR084's registers
acknowledge from
MPR084
acknowledge from
MPR084
D15 D14 D13 D12 D11 D10 D9 D8
D7 D6 D5 D4 D3 D2 D1 D0
acknowledge from MPR084
S
SLAVE ADDRESS
1
COMMAND BYTE
A
A
DATA BYTE
A
P
n bytes
R/W
auto-increment memory
word address
Figure 12. ‘n’ Data Bytes Received
2.3.8
Operation with Multiple Master
The application should use repeated starts to address the MPR084 to avoid bus confusion between I2C masters.On a I2C bus,
once a master issues a start/repeated start condition, that master owns the bus until a stop condition occurs. If a master that does
not own the bus attempts to take control of that bus, then improper addressing may occur. An address may always be rewritten
to fix this problem. Follow I2C protocol for multiple master configurations.
2.3.9
Device Reset
The RST is an active-low software reset. This is implemented in the Configuration Register by activating the RST bit. When
asserted, the device clears any transaction to or from the MPR084 on the serial interface and configures the internal registers to
the same state as a power-up reset (Table 4). The MPR084 then waits for a START condition on the serial interface.
The sensor controller is capable of operating down to 1.8 V, however, in order for the sensor controller to exit reset and startup
correctly the host system must initially provide 2.0 V to 3.6 V input to VDD and then follow the process in Figure 13. This process
is required in applications that require regulated operation in the 1.8 V to 2.0 V range. In the case that the application uses an
unregulated battery, then the battery must initially provide at least 2.0 V to correctly power-up the sensor controller which limits
battery selection to the 2.0 V to 3.6 V range.
Apply 2.0V to VDD Max
To Sensor Controller
Idle Delay Loop
False
Established Comms with
Sensor Controller?
i.e. Read from FIFO
Is Data valid? (0 x 40)
True
Lower VDD to the desired operating voltage
1.8 V to 2.0 V
Figure 13. Low Voltage (1.8 V - 2.0 V) Power-up Sequence
MPR084
Preliminary
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Freescale Semiconductor
2.4
Register Address Map
The MPR084 is a peripheral that is controlled and monitored though a small array of internal registers which are accessed
through the I2C bus. When communicating with the MPR084 each of the registers in Table 4 are used for specific tasks. The
functionality of each specific register is detailed in the following sections.
Register Address
Burst Mode
Auto-Increment Address
FIFO Register
0x00
0x00
Fault Register
0x01
0x02
Touch Pad Status Register
0x02
0x00
Touch Pad Configuration Register
0x03
0x04
Sensitivity Threshold Registers 1
0x04
0x05
Sensitivity Threshold Registers 2
0x05
0x06
Sensitivity Threshold Registers 3
0x06
0x07
Sensitivity Threshold Registers 4
0x07
0x08
Sensitivity Threshold Registers 5
0x08
0x09
Sensitivity Threshold Registers 6
0x09
0x0A
Sensitivity Threshold Registers 7
0x0A
0x0B
Sensitivity Threshold Registers 8
0x0B
0x0C
Electrode Channel Enable Mask Register
0x0C
0x0D
Maximum Number of Touched Positions Register
0x0D
0x0E
Master Tick Period Register
0x0E
0x0F
Touch Acquisition Sample Period Register
0x0F
0x10
Sounder Configuration Register
0x10
0x11
Low Power Configuration Register
0x11
0x12
Stuck Key Timeout Register
0x12
0x13
Configuration Register
0x13
0x00
Sensor Information Register
0x14
0x14
Register
MPR084
Sensors
Freescale Semiconductor
Preliminary
9
3
Touch Detection
3.1
Introduction
When using a capacitive touch sensor system the raw data must be filtered and interpreted. This process can be done many
different ways but the method used in the MPR084 is explained in this chapter.
3.2
Understanding the Basics
The touch pad interface has to distinguish touch status through varying user conditions (different finger sizes in bare hands or
gloves) and environmental conditions (electrical and RF noise, sensor contamination with dirt or moisture).
The touch pad circuitry reports touch status as one of the following two conditions:
1.
2.
Touch Pad untouched
Touch Pad touched on one of eight pads.
The touch pad is only touched in one position, ideally near the middle of one of the eight pads. If a touch occurs between pads,
untouched will be reported.
3.3
Conditional Output Scenarios
Since it is unlikely that in a real world case a single independent touch will occur two specific multi-touch response cases are
outlined. Methods for changing the sensitivity of the device will be discussed in another Chapter, but the important part is that the
sensitivity is determined by the strength of an input signal. If more than one input signal is above the selected sensitivity then the
touch sensor controller interprets this in a specific way. This functionality is broken down into two different cases.
3.3.1
Simultaneous Touches
Any time multiple touches are detected at the same time the touch sensor controller recognizes this case and accounts for it. The
number of allowed reported touches is settable using the Maximum Number of Touched Positions Register (Section 3.6). In the
case where this register is set to 1, all touches past the first will be ignored and unreported.
A special case is when exact 2 keys are involved in the interaction. In most cases one of the two electrodes will receive a stronger
signal than the other. If the difference in capacitance is statistically significant between the pad with the stronger signal will be
reported
This functionality is sometimes called 1-Keyed Lockout. by changing the Maximum Number of Touched Positions Register
(Section 3.6). this value can be set. Thus the n-key lockout is determined by this register.
3.3.2
Sequential Touches
Another case is when one touch pad is touched and held and a second touch pad is then touched and held. For this situation the
second touch will be ignored and the first touch will continue to be reported.
If the second touch is released before the first touch then the second touch will be completely ignored. But, if the first touch is
released before the second then the system will report that the first key is released and that the second key is now touched. This
functionality is sometimes called 2-Key Rollover.
3.4
Touch Pad Configuration Register
The Touch Pad Configuration Register configures a variety of the MPR084 features. Each of these features is described in
following sections. The I2C slave address of the Touch Pad Configuration Register is 0x03.
7
R
W
Reset:
TPE
1
6
0
0
5
4
3
2
BKA
ACE
TPRBE
TPTBE
0
0
0
0
1
0
0
0
TPE
1
= Unimplemented
Figure 14. Touch Pad Configuration Register
MPR084
Preliminary
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Freescale Semiconductor
Table 4. Touch Pad Configuration Register Field Descriptions
Field
Description
7
TPSE
Touch Pad Sounder Enable – The Touch Pad Sounder Enable bit controls if data
is sent to the sounder.
0 Disable – Click Feedback Off
1 Enable – Click Feedback On
5
BKA
Best Key Algorithm - The Best Key Algorithm, when enabled the Maximum Number
of Touches register is ignored and the algorithm reports the single best key based
upon the BKA algorithm and all electrodes that are decoding a touch.
0 BKA Disabled
1 BKA Enabled
4
ACE
Auto Calibration Enable – The Auto Calibration Enable bit enables or disables the
auto calibration function.
0 Disable
1 Enable
3
TPRBE
Touch Pad Release Buffer Enable – The Touch Pad Release Buffer Enable bit
determines whether or not data is logged in the FIFO when the touch pad
transitions from a touched to untouched state.
0 Disable – No Release Data Logged
1 Enable – Release Data Logged
2
TPTBE
Touch Pad Touch Buffer Enable – The Touch Pad Touch Buffer Enable bit
determines whether or not data is logged in the FIFO any time a button is pressed.
0 Disable – Touches are not logged
1 Enable – Touches are logged
0
TPE
3.5
Touch Pad Enable – The Touch Pad Enable bit enables or disables the touch
sensor. When disabled, no touches are detected.
0 Disable – Touches not detected
1 Enable – Touches detected
Touch Acquisition Sample Period Register
The Touch Acquisition Sample Period Register is used to determine the electrode scan period of the system. The I2C slave
address of the Touch Acquisition Sample Period Register is 0x0F.
7
6
5
4
R
2
1
0
0
0
0
1
TASP
W
Reset:
3
0
0
0
0
= Unimplemented
Figure 15. Touch Acquisition Sample Period Register
Table 5. Touch Acquisition Sample Register Field Description
Field
7:0
TASP
Description
Touch Acquisition Sample Period – The Touch Acquisition Sample Period Field
selects or reports the multiplication factor that is used to determine how often
electrodes are scanned. The resulting factor must be in the range 1 to 32. If the
value is outside of this range the TASP will be set to 00011111.
00000000 Encoding 0 – Sets the TASP multiplication factor to 1
~
00011111 Encoding 31 – Sets the TASP multiplication factor to 32
MPR084
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Freescale Semiconductor
Preliminary
11
3.6
Maximum Number of Touched Positions Register
The Maximum Number of Touched Positions Register adjusts the number of keys that can be concurrently reported as touched.
The I2C slave address of the Maximum Number of Touched Positions Register is 0x0D.
R
7
6
5
4
3
0
0
0
0
0
0
0
0
0
0
2
1
TPC
W
Reset:
0
1
0
0
= Unimplemented
Figure 16. Maximum Number of Touched Positions Registers
Table 6. Maximum Number of Touched Positions Register Field Descriptions
Field
Description
2:0
TPC
3.7
Touched Positions Count – The Touched Positions Count selects or reports the
number of simultaneously reported touches.
000 Encoding 0 – Sets the number of allowed touches to 0
~
111 Encoding 7 – Sets the number of allowed touches to 7
Electrode Channel Enable Mask Register
The Electrode Channel Mask Register adjusts to the number of keys that are scanned by the MPR084. The I2C slave address
of the Electrode Channel Mask Register is 0x0C.
R
W
Reset:
7
6
5
4
3
2
1
0
E8EN
E7EN
E6EN
E5EN
E4EN
E3EN
E2EN
E1EN
1
1
1
1
1
1
1
1
= Unimplemented
Figure 17. Electrode Channel Enable Mask Position Register
Table 7. Electrode Channel Enable Mask Register Field Descriptions
Field
Description
7
E8EN
Electrode 8 Enable – The Electrode 8 Enable bit enables or disables electrode
number 8.
0 Electrode 8 Disable
1 Electrode 8 Enable
6
E7EN
Electrode 7 Enable – The Electrode 7 Enable bit enables or disables electrode
number 7.
0 Electrode 7 Disable
1 Electrode 7 Enable
5
E6EN
Electrode 6 Enable – The Electrode 6 Enable bit enables or disables electrode
number 6.
0 Electrode 6 Disable
1 Electrode 6 Enable
4
E5EN
Electrode 5 Enable – The Electrode 5 Enable bit enables or disables electrode
number 5.
0 Electrode 5 Disable
1 Electrode 5 Enable
MPR084
Preliminary
12
Sensors
Freescale Semiconductor
Table 7. Electrode Channel Enable Mask Register Field Descriptions
3
E4EN
Electrode 4 Enable – The Electrode 4 Enable bit enables or disables electrode
number 4.
0 Electrode 4 Disable
1 Electrode 4 Enable
2
E3EN
Electrode 3 Enable – The Electrode 3 Enable bit enables or disables electrode
number 3.
0 Electrode 3 Disable
1 Electrode 3 Enable
1
E2EN
Electrode 2 Enable – The Electrode 2 Enable bit enables or disables electrode
number 2.
0 Electrode 2 Disable
1 Electrode 2 Enable
0
E1EN
Electrode 1 Enable – The Electrode 1 Enable bit enables or disables electrode
number 1.
0 Electrode 1 Disable
1 Electrode 1 Enable
MPR084
Sensors
Freescale Semiconductor
Preliminary
13
4
Modes of Operation
4.1
Introduction
The operating modes of the MPR084 are described in this section. Implementation and functionality of each mode are described.
The Modes of Operation of the MPR084 combine to form a suite of quick response and low power consumption functionality. This
is achieved through 2 Run modes and 2 Stop Modes. The two modes are enabled by toggling the Configuration Register’s DCE
and RUNE bits as shown in Table 8. Note that while in a run mode, the only register that can be written to is the Configuration
Register. Thus, when changes to registers are needed, enter Stop1 mode, write to the registers and change the mode to “Run”.
Table 8. Mode Enable Register Bits
4.2
Mode
RUNE
DCE
Run1
1
1
Run2
1
0
Stop1
0
1
Stop2
0
0
Initial Power Up
On power-up, the interrupt output IRQ is reset, and IRQ will go high. The registers are reset to the values shown in Table 9.
Table 9. Power-Up Register Configurations
Register Function
Power-Up Condition
Register Address
HEX Value
FIFO Register
FIFO is empty
0x00
0x40
Fault Register
No faults
0x01
0x00
Touch Pad Status Register
Touch Pad is untouched
0x02
0x00
Touch Pad Configuration Register
Touch Pad is enabled, without interrupts,
with sounder enabled and Auto-Cal Disabled
0x03
0x81
Sensitivity Threshold Registers 1
Maximum sensitivity
0x04
0x00
Sensitivity Threshold Registers 2
Maximum sensitivity
0x05
0x00
Sensitivity Threshold Registers 3
Maximum sensitivity
0x06
0x00
Sensitivity Threshold Registers 4
Maximum sensitivity
0x07
0x00
Sensitivity Threshold Registers 5
Maximum sensitivity
0x08
0x00
Sensitivity Threshold Registers 6
Maximum sensitivity
0x09
0x00
Sensitivity Threshold Registers 7
Maximum sensitivity
0x0A
0x00
Sensitivity Threshold Registers 8
Maximum sensitivity
0x0B
0x00
Electrode Channel Enable Mask
Register
All channels enabled
0x0C
0xFF
Maximum Number of Touched
Positions Register
4 maximum concurrent touched position
allowed
0x0D
0x04
Master Tick Period Register
Master tick period is 10ms
0x0E
0x05
Touch Acquisition Sample Period
Register
TASP is 1 master tick period
0x0F
0x01
Sounder Configuration Register
Sounder is globally enabled, 10ms of 1kHz
0x10
0x01
Low Power Configuration Register
Low Power Mode is disabled
0x11
0x00
Stuck Key Timeout Register
Stuck key detector disabled
0x12
0x00
Configuration Register
Stop1 Mode. IRQ is disabled
0x13
0x14
Sensor Information Register
Fixed SensorInfo based on revision
0x14
0xFF
MPR084
Preliminary
14
Sensors
Freescale Semiconductor
4.3
Run1 Mode
When in Run1 mode the sensor controller will run continuously. During Run1 all the modules are synchronized by the Master Tick
Period. This value can be set by using the Master Tick Period Register as outlined in the following section.
While in this mode all functionality of the MPR084 is enabled; touch detection will occur, and I2C communication will be available.
This mode is enabled by setting the Configuration Register’s RUNE and DCE bits high.
4.3.1
Master Tick Period Register
The Master Tick Period Register is used to set the master tick of this system. All parts of the system are synchronized to this
counter. This register is overridden in all modes except for Run1. When not in Run1 mode, the value of this register is ignored
and 8ms is used for the primary clock. The I2C slave address of the Master Tick Period Register is 0x0E.
7
6
5
4
R
2
1
0
0
1
0
1
MTP
W
Reset:
3
0
0
0
0
= Unimplemented
Figure 18. Master Tick Period Register
Table 10. Master Tick Period Register Field Descriptions
Field
Description
7:0
Master Tick Period – The Master Tick Period selects or reports the current value of the
touch sensor controller’s primary clock. The resulting period must be in the range 5ms
to 31ms. If the value is outside of this range the MTP will be set to 00011010.
00000000 Encoding 0 – Sets the primary clock multiplier to 5
~
00011010 Encoding 26 - Sets the primary clock multiplier to 31
MTP
4.4
Run2 Mode
When in Run2 mode the sensor controller will continue to scan the electrodes but a low power state will be enabled between
each cycle. Because of this, any I2C communication that occurs, may or may not respond while the sensor is in this mode
If DCE is enabled the sensor controller transitions between low power and active states. During the active part of the cycle
communication with the sensor controller is possible; however, Freescale always requires users to issue an ATTN signal prior to
initiating communications. Accessing the I2C interface while DCE mode is enabled without sending an ATTN signal first is likely
to produce invalid data.
This mode is enabled by setting the Configuration Register’s RUNE bit high and DCE bit low. The only way to exit this mode is
to toggle the Attention Pin, refer to Section 4.7.
4.5
Stop1 Mode
When in Stop1 mode the sensor controller will not scan the electrodes. While capacitance sensing is disabled I2C
communications will still be accepted and the sensor controller will maintain instantaneous response to all register requests. This
is the only mode in which register values can be set.
This mode is enabled by setting the Configuration Register’s RUNE bit low and DCE bit high.
4.6
Stop2 Mode
When in Stop2 mode the sensor controller will not scan the electrodes or accept I2C communication. The MPR084 is off during
this mode.
This mode is enabled by setting the Configuration Register’s RUNE bit low and DCE bit low. The only way to exit this mode is to
toggle the Attention Pin, refer to Section 4.7.
MPR084
Sensors
Freescale Semiconductor
Preliminary
15
4.7
Configuration Register
The Configuration Register allows a user to reset the part, adjust Interrupt settings, and change the mode. The I2C slave address
of the Configuration Register is 0x13.
7
6
R
4
0
0
3
0
RST
W
Reset:
5
0
1
2
1
0
DCE
IRQEN
RUNE
1
0
0
0
= Unimplemented
Figure 19. Configuration Register
Table 11. Configuration Register Field Descriptions
4.8
Field
Description
7:5
IRQR
Interrupt Rate – The Interrupt Rate Field selects the amount to multiply the MTP by
to determine the minimum delay between sequential Interrupts.
000 Encoding 0 – Sets the IRQR multiplication factor to 1
~
111 Encoding 7 – Sets the IRQR multiplication factor to 8
4
RST
Reset – Asserts a global reset of the sensor controller.
0 Reset Asserted
1 Reset Not Asserted
2
DCE
Duty Cycle Enable – The Duty Cycle Enable bit enables or disables duty cycling on
the MPR084. This bit is active low.
0 Duty Cycle Enabled (2 modes)
1 Duty Cycle Disabled (1 modes)
1
IRQEN
Interrupt Enable – The Interrupt Enable bit enables or disables the IRQ
Functionality.
0 IRQ Disabled
1 IRQ Enabled
0
RUNE
Run Mode Enable – The Run Mode Enable bit enables or disables scanning of the
electrodes for touch detection. This bit is active high.
0 Electrode Scanning Disabled (Stop modes)
1 Electrode Scanning Enabled (Run modes)
Attention Pin
The Attention (ATTN) pin allows a user to externally set the Configuration Register’s DCE bit high. This is latched on a high to
low transition. Since the current mode of the device is enabled through the DCE this will cause duty cycling to be disabled and
change the current mode from Run2 to Run1, or Stop2 to Stop1 (depending on the previous state).
When in Run2 or Stop2 modes this is the only way to enable the I2C communication.
MPR084
Preliminary
16
Sensors
Freescale Semiconductor
5
Low Power Configuration
5.1
Introduction
The MPR084 features a Low Power mode that can reduce the power consumption into the microamps range. This feature can
be used to both adjust the response time of the system, and change the conditions on which Low Power would be enabled.
5.2
Operation
This Low Power configuration is only active when the sensor controller is in Run2 mode. The Low Power mode decreases current
consumption by increasing the response time of the MPR084. This increase is controlled through two factors.
During normal Run2 operation of the sensor controller the Max Response Time (MRT) is calculated by taking the product of the
TASP and the primary clock. From Chapter 4 the primary clock is the (MTP + 5) ms. Since the sensor controller is in Run2, the
primary clock is also multiplied by a factor of 8. The debounce rate of the MPR084 is 4 times the sample rate thus the MRT is
represented by the following equation.
MTP + 5
MRT 1 = ⎛ ---------------------- + 1⎞ × TASP × 4 × 8ms
⎝
⎠
8
Equation 1
First, the Idle Interface Timeout (IIT) represents the total time the touch interface should remain idle before going into Low Power
mode. This value can be calculated by taking the product of the ITP, TASP and primary clock (8ms) with a factor of 64. Thus the
IIT is represented as follows:
MTP + 5
MRT 2 = ⎛ ---------------------- + 1⎞ × TASP × SCD × 4 × 8 ms
⎝
⎠
8
Equation 2
Second, the Max Response Time (MRT) represents the total time the touch interface should remain inactive before scanning the
electrodes. This value can be calculated by taking the product of the SCD, TASP and primary clock (8ms) with a factor of 5. Thus
the MRT is represented as follows:
MTP + 5
ITT = ⎛⎝ ---------------------- + 1⎞⎠ × TASP × ITP × 6 × 8ms
8
Equation 3
When in Run2 mode, the sensor controller will initially scan the electrodes at the rate of MRT1. When scanning at MRT1 and the
touch interface remains idle for the IIT period then the scan period will change to MRT2. When scanning at MRT2 and a touch is
detected the scan rate will transition back to MRT1.
LP DISABLED
run2 SET
MRT1
ITT PERIOD
MRT2
TOUCH DETECTED
Figure 20. Low Power Scan Period Transition Diagram
5.3
Configuration
Low Power Configuration is achieved through setting two values; the Idle Timeout Period and the Sleep Cycle Duration. This
functionality is described in the following section.
MPR084
Sensors
Freescale Semiconductor
Preliminary
17
5.3.1
Low Power Configuration Register
The Low Power Configuration register is used to set both the Idle Timeout Period and Sleep Cycle Duration multiplication factors.
The I2C slave address of the Low Power Configuration Register is 0x11.
7
R
5
4
3
ITP
W
Reset:
6
0
0
2
1
0
0
0
SCD
0
0
0
0
= Unimplemented
Figure 21. Low Power Configuration Register
Table 12. Low Power Configuration Register Field Descriptions
Field
Description
7:5
ITP
Idle Timeout Period – The Idle Timeout Period selects the amount to multiply the
TASP (touch acquisition sample period) by to determine the idle interface timeout
(IIT) period of the sensor controller.
000 Encoding 0 – Disables Low Power Mode
001 Encoding 1 – Sets the ITP multiplication factor to 1
~
111 Encoding 7 – Sets the ITP multiplication factor to 7
4:0
SCD
Sleep Cycle Duration – The Sleep Cycle Duration Field selects the amount to
multiply the TASP (touch acquisition sample period) by to determine the Sleep
period of the sensor controller.
00000 Encoding 0 – Disables Low Power Mode
00001 Encoding 1 – Sets the SCD multiplication factor to 1
~
11111 Encoding 31 – Sets the SCD multiplication factor to 31
MPR084
Preliminary
18
Sensors
Freescale Semiconductor
6
Output Mechanisms
6.1
Introduction
The MPR084 has three primary methods for reporting data in addition to an IRQ output that is described in Chapter 7. The three
output systems are described in this section.
6.2
Instantaneous
The Instantaneous output shows the current status of the user interface. This information is displayed in terms of the current
touched pad position that is touched. Only one touch can be shown at a time.
6.2.1
Touch Pad Status Register
The Touch Pad Status Register is a read only register for determining the current status of the touch pad. The I2C slave address
of the Touch Pad Status Register is 0x02.
R
7
6
5
4
3
2
1
0
E8S
E7S
E6S
E5S
E4S
E3S
E2S
E1S
0
0
0
0
0
0
0
0
W
Reset:
= Unimplemented
Figure 22. Touch Pad Status Register
Table 13. Touch Pad Status Register Field Descriptions
Field
Description
7
E8S
Electrode 8 Status – The Electrode 8 Status bit shows whether or not electrode 8 is touched.
0 Electrode 8 untouched
1 Electrode 8 touched
6
E7S
Electrode 7 Status – The Electrode 7 Status bit shows whether or not electrode 7 is touched.
0 Electrode 7 untouched
1 Electrode 7 touched
5
E6S
Electrode 6 Status – The Electrode 6 Status bit shows whether or not electrode 6 is touched.
0 Electrode 6 untouched
1 Electrode 6 touched
4
E5S
Electrode 5 Status – The Electrode 5 Status bit shows whether or not electrode 5 is touched.
0 Electrode 5 untouched
1 Electrode 5 touched
3
E4S
Electrode 4 Status – The Electrode 4 Status bit shows whether or not electrode 4 is touched.
0 Electrode 4 untouched
1 Electrode 4 touched
2
E3S
Electrode 3 Status – The Electrode 3 Status bit shows whether or not electrode 3 is touched.
0 Electrode 3 untouched
1 Electrode 3 touched
1
E2S
Electrode 2 Status – The Electrode 2 Status bit shows whether or not electrode 2 is touched.
0 Electrode 2 untouched
1 Electrode 2 touched
0
E1S
Electrode 1 Status – The Electrode 1 Status bit shows whether or not electrode 1 is touched.
0 Electrode 1 untouched
1 Electrode 1 touched
MPR084
Sensors
Freescale Semiconductor
Preliminary
19
6.3
Buffered
The Buffered output is done through a FIFO. The FIFO will buffer every touch that occurs up to 30 values before the buffer
overflows and data is lost. Any time data is read from the FIFO it is pulled from the buffer and the next item becomes available.
The buffer can be cleared (NDF goes high) by either reading the last entry or attempting to write to the register.
The buffer settings are configured in the Touch Pad Configuration Register as described in Section 3.4.
6.3.1
FIFO Register
The FIFO Register is a read only register for determining the current status of the touch pad. Any time a write is issued to this
register the buffer will be cleared. The I2C slave address of the FIFO Register is 0x00.
R
7
6
5
4
MDF
NDF
OF
TRF
0
1
0
0
3
2
1
0
0
0
BP
W
Reset:
0
0
= Unimplemented
Figure 23. FIFO Register
Table 14. FIFO Register Field Descriptions
6.4
Field
Description
7
MDF
More Data Flag – The More Data Flag shows whether or not data will remain in the
buffer after the current read.
0 No Data Remaining
1 Data Remaining
6
NDF
No Data Flag – The No Data Flag shows whether or not there is currently data in
the buffer.
0 Buffer currently has data
1 Buffer does not currently have data
5
OF
Overflow Flag – The Overflow Flag shows whether or not an overflow has occurred.
If this flag is high then the most current data was lost.
0 No Overflow has occurred
1 Overflow has occurred
4
TRF
Touch Release Flag – The Touch Release Flag shows if the current buffer entry is
a touch or release of a pad.
0 Pad is released
1 Pad is touched
3:0
BP
Buffered Position – The Buffered Position represents the electrode number that is
currently being displayed by the buffer.
0000 Encoding 0 – Buffered touch of electrode 1
~
0111 Encoding 7 – Buffered touch of electrode 8
Error
The MPR084 can generate a fault under two conditions; an electrode is shorted to VDD, or an electrode is shorted to VSS. Once
a fault is asserted the sensor electrodes will no longer be scanned until the fault is cleared. In the event of multiple faults occurring
at the same time, the sensor controller will report the first fault that is detected during scanning. In addition to the VDD or VSS
short, there is also a fault for when too many keys have been touched. The Max Number of Keys Exceeded status bit is an
instantaneous output that is high when more keys are pressed than allowed by the TPC (Section 3.6).
MPR084
Preliminary
20
Sensors
Freescale Semiconductor
6.4.1
Fault Register
The Fault Register is a read only register that shows the fault number under the current sensor conditions. Any write to the Fault
Register will clear the register, when in Stop mode. The Fault register cannot be cleared when the part is in a Run mode. The I2C
slave address of the Fault Register is 0x01.
R
7
6
5
4
3
2
0
0
0
0
0
MNKE
0
0
0
0
0
0
1
0
FAULT
W
Reset:
0
0
= Unimplemented
Figure 24. Fault Register
Table 15. Fault Register Field Descriptions
Field
Description
2
MNKE
Maximum Number of Keys Exceeded - The Maximum Number of Keys Exceeded
status bit indicates whether or not more keys than allowed are currently being
touched.
1 TPC Exceeded
0 TPC Not Exceeded
1:0
FAULT
Fault – The Fault code represents the currently asserted fault condition.
00 Encoding 0 – No fault detected
01 Encoding 1 – Short to VSS detected
10 Encoding 2 – Short to VDD detected
MPR084
Sensors
Freescale Semiconductor
Preliminary
21
7
Interrupts
7.1
Introduction
The MPR084 has one interrupt output that is configured by registers and alerts the application when a touch or fault is detected.
When running in Run2 or Stop2 mode where I2C communication is not available this feature alerts the user to sensor touches.
7.2
Condition for Interrupt
There are two cases that latch the Interrupt buffered data available or fault detected.
7.2.1
Buffered Data Available
The interrupt for Buffered Data Available will only trigger when the NDF (No Data Flag) transitions from high to low. This signifies
that there is new data available in the buffer. The interrupt is deasserted on the first read/write of the FIFO Register and cannot
be reasserted for buffered data until the FIFO is empty (either by reading all the data, or clearing the buffer).
7.2.2
Fault Detected
The interrupt for a Fault Detected condition is triggered any time the Fault condition in the Fault Register transitions from zero to
non-zero. The interrupt is deasserted when the Fault Register is cleared (by writing to the Fault Register).
7.3
Settings
Interrupts are configured through I2C using the Configuration Register (Section 4.7). Two of the settings in this register will affect
the interrupt functionality.
The Interrupt Enable (IRQEN) must be set high for the IRQ to be enabled. When low, all interrupts will be ignored, and the IRQ
pin will never latch.
The Interrupt Rate (IRQR) sets the minimum delay between sequential triggered interrupts. The minimum interrupt period can be
calculated by taking the product of the MCP (master clock period) and IRQR with a factor of 4. Thus, for the minimum setting an
interrupt would be triggered no more often than 4 times the sensor scan rate.
MinInterruptPeriod ( ms ) = MCP × IRQR × 4
Equation 4
If the MPR084 is using Run2, the minimum interrupt period would be represented by the following equation.
MTP + 5
MinInterruptPeriod ( ms ) = ⎛ ---------------------- + 1⎞ × 8 × I RQR × 4
⎝
⎠
8
7.4
Equation 5
IRQ Pin
The IRQ pin is an open-drain, latching interrupt output which requires an external pull-up resistor. The pin will latch down based
on the conditions in Section 6.2. The pin will reset when an I2C transmission reads/writes the appropriate register displaying
information about the source of the interrupt. Thus if the source is buffered data available then a FIFO Buffer read/write will clear
the IRQ pin. If the source is a fault detected then a write of the Fault Register will clear the pin.
MPR084
Preliminary
22
Sensors
Freescale Semiconductor
7.4.1
IRQ Pin Timing
The MinInterruptPeriod is implemented as a hold off of IRQ latching per Figure 25 and Figure 26. In the first case the
MinInterruptPeriod is longer than the interval between sequential interrupt source events, thus it delays the IRQ from latching
until the MinInterruptPeriod has elapsed. In the second case the MinInterruptPeriod is shorter than the interval between
sequential interrupt source events, thus the IRQ latches as it normally would without additional delay.
Initial Interrupt Event
Second Interrupt Event
MinInterruptPeriod
IRQ
Figure 25. IRQ Timing Diagram - Case 1
Initial Interrupt Event
Second Interrupt Event
MinInterruptPeriod
IRQ
Figure 26. IRQ Timing Diagram - Case 2
MPR084
Sensors
Freescale Semiconductor
Preliminary
23
8
Calibration
8.1
Introduction
The MPR084 is self-calibrating. This is done both at initial start-up of the device and during run time.
8.2
Initial Start-up Conditions
Initial calibration of the MPR084 occurs every time the device resets. The first key detection cycle is used as a baseline
capacitance value for all remaining calculations. Thus, a touch is detected by taking the difference between this baseline value
and the current capacitance on the electrode.
8.3
Auto-Calibration
The MPR084 has an auto-calibration feature. This is enabled through the Touch Pad Configuration Register (Section 3.4), by
setting the ACE bit high. Auto calibration is done by two mechanisms. The basic auto-calibration will recalculate the baseline
value after 6 sample periods. Thus the auto calibrate period can be calculate by multiplying the master clock period (in
milliseconds) and the touch acquisition sample period with a factor of 64.
AutoCalibrationPeriod ( ms ) = MCP × TASP × 64
Equation 6
If a touch is currently being detected the auto-calibration will not engage and calibration will be ignored. The device can also be
calibrated when a key is being touched, this is controlled by stuck key detection.
8.4
Stuck Key Detection
The Stuck Key Detection system allows the application to specify the maximum amount of time a touch should be detected before
it is calibrated into the baseline and the touch is ignored. This is controlled by setting the Stuck Key Timeout multiplication factor
(SKT). The timeout period can be calculated by multiplying the SKT, master clock period (in ms) and touch acquisition sample
period with a factor of 64.
AutoCalibrationPeriod ( ms ) = MCP × TASP × SKT × 64
Equation 7
When Stuck Key Detection is off a touched key will remain touched indefinitely and never be calibrated into the baseline value.
8.4.1
Stuck Key Timeout Register
The Stuck Key Timeout Register is used to determine the electrode scan period of the system. The I2C slave address of the Stuck
Key Timeout Register is 0x12.
7
6
5
4
R
2
1
0
0
0
0
0
SKT
W
Reset:
3
0
0
0
0
= Unimplemented
Figure 27. Stuck Key Timeout Register
Table 16. Stuck Key Timeout Register Field Descriptions
Field
Description
7:0
SKT
Stuck Key Timeout – The Stuck Key Timeout field selects or reports the
multiplication factor that is used to determine how often electrodes are calibrated
while a touch is being detected.
00000000 Encoding 0 – Turns off Stuck Key Detection
00000001 Encoding 1 – Sets the SKT multiplication factor to 2
~
11111111 Encoding 255 – Sets the SKT multiplication factor to 256
MPR084
Preliminary
24
Sensors
Freescale Semiconductor
9
Sensitivity
9.1
Introduction
The MPR084 can operate in a variety of environments with a variety of different electrode patterns. Because of this it is necessary
to adjust the relative sensitivity of the sensor controller. Usually this requires fine tuning in any final application.
There are many factors that must be taken into account, but much of the time this value is relative to the capacitance changes
generated by a touch. Since capacitance is directly proportional to the dielectric constant of the material and the area of the pad,
while inversely proportional to the distance between pads these are the primary factors.
ke 0 A
C = -----------d
Equation 8
As the relative capacitance rises the sensitivity setting of the MPR084 should be adjusted accordingly. Thus a very high sensitivity
value represents a large A and a small d.
9.2
Adjusting the Sensitivity
The sensitivity of the MPR084 is adjusted by varying the Sensitivity Threshold Registers.
9.2.1
Sensitivity Threshold Registers
The Sensitivity Threshold registers all sensitivity of the MPR084 to be adjusted for any situation. The I2C slave address of the
Sensitivity Threshold Registers is 0x04 - 0x0B.
7
6
5
4
R
2
1
0
0
0
0
0
SL
W
Reset:
3
0
0
0
0
= Unimplemented
Figure 28. Sensitivity Threshold Register Format
Table 17. Sensitivity Threshold Register Format Descriptions
Field
Description
7:0
ST
Sensitivity Threshold – The Sensitivity Threshold selects or reports the sensitivity
setting of the Sensor Controller. The resulting value must be in the range 1 to 64
units. If the value is outside of this range the ST will be set to 00111111.
00000000 Encoding 0 – Sets the sensitivity to level 1
~
00111111 Encoding 63 – Sets the sensitivity to level 64
MPR084
Sensors
Freescale Semiconductor
Preliminary
25
10
Additional Features
10.1
Key Click Sound Generator
The Key Click Sound Generator allows the MPR084 to generate audible feedback, independent of the I2C communication status.
The sounder is used to drive a piezo buzzer. This output is configured by using the Sounder Register, shown in the following
section.
10.1.1 Sounder Configuration Register
The I2C slave address of the Sounder Configuration Register is 0x07 - 0x10
R
7
6
5
4
3
0
0
0
0
0
0
0
0
0
0
W
Reset:
2
1
0
CP
FREQ
SEN
0
0
1
= Unimplemented
Figure 29. Sounder Configuration Register
Table 18. Sounder Configuration Register Field Descriptions
Field
Description
2
CP
Click Period – The Click Period bit controls the length of the sounder click.
0 Sounder Click Period is 10ms
1 Sounder Click Period is 20ms
1
FREQ
Frequency – The Frequency bit controls the frequency of the driven output.
0 Sounder frequency is 1kHz
1 Sounder frequency is 2kHz
0
SEN
10.2
Sounder Enable – The Sounder Enable bit enables or disables the sounder output.
0 Disable
1 Enable
Sensor Information
The Sensor Information register is a read only register that displays a descriptor which contains static information about the
MPR084 version.
10.2.1 Sensor Information Register
The I2C slave address of the Sensor Information Register is 0x14.
7
6
5
R
4
3
2
1
0
1
1
0
SensorInfo
W
Reset:
0
1
0
0
0
= Unimplemented
Figure 30. Sensor Information Register
Table 19. Sensor Information Register Field Descriptions
Field
Description
7-0
SensorInfo
SensorInfo – The Sensor Information register describes the version information for
the part. Burst reads will display ASCII data in the following format:
VENDOR_LABEL",PN:"PRODUCT_LABEL",QUAL:"BUILD_TYPE_LABEL",VER:"
BUILD_VERSION_MAJOR"_"BUILD_VERSION_MINOR"_"BUILD_NUMBER"\0"
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Appendix A Electrical Characteristics
A.1
Introduction
This section contains electrical and timing specifications.
A.2
Absolute Maximum Ratings
Absolute maximum ratings are stress ratings only, and functional operation at the maxima is not guaranteed. Stress beyond the
limits specified in Table A-1 may affect device reliability or cause permanent damage to the device. For functional operating
conditions, refer to the remaining tables in this section. This device contains circuitry protecting against damage due to high static
voltage or electrical fields; however, it is advised that normal precautions be taken to avoid application of any voltages higher
than maximum-rated voltages to this high-impedance circuit.
Table 20. Absolute Maximum Ratings - Voltage (with respect to VSS)
Rating
A.3
Symbol
Value
Unit
Supply Voltage
VDD
-0.3 to +3.8
V
Input Voltage
SCL, SDA, AD0, IRQ, ATTN,
SOUNDER
VIN
VSS - 0.3 to VDD + 0.3
V
Operating Temperature Range
TSG
-40 to +85
°C
Storage Temperature Range
TSG
-55 to +150
°C
ESD and Latch-up Protection Characteristics
Normal handling precautions should be used to avoid exposure to static discharge.
Qualification tests are performed to ensure that these devices can withstand exposure to reasonable levels of static without
suffering any permanent damage. During the device qualification ESD stresses were performed for the Human Body Model
(HBM), the Machine Model (MM) and the Charge Device Model (CDM).
A device is defined as a failure if after exposure to ESD pulses the device no longer meets the device specification. Complete
DC parametric and functional testing is performed per the applicable device specification at room temperature followed by hot
temperature, unless specified otherwise in the device specification.
Table 21. ESD and Latch-up Test Conditions
Rating
Symbol
Value
Unit
Human Body Model (HBM)
VESD
±2000
V
Machine Model (MM)
VESD
±200
V
Charge Device Model (CDM)
VESD
±500
V
Latch-up current at TA = 85°C
ILATCH
±100
mA
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A.4
DC Characteristics
This section includes information about power supply requirements and I/O pin characteristics.
Table 22. DC Characteristics (Temperature Range = –40°C to 85°C Ambient)
(Typical Operating Circuit, VDD = 1.8 V* to 3.6 V, TA = TMIN to TMAX, unless otherwise noted. Typical current values are at VDD = 3.3 V,
TA = +25°C.)
Parameter
Operating Supply Voltage
Symbol
VDD
Conditions
Run1 mode Current
Irun1
VDD = 1.8 V
1.62
mA
Run2 mode Current
Irun2
VDD = 1.8 V
41
µA
Stop1 mode Current
Istop1
VDD = 1.8 V
1.74
mA
Stop2 mode Current
Istop2
VDD = 1.8 V
2
µA
Input High Voltage
SDA, SCL
Input Low Voltage
SDA, SCL
Input Leakage Current
SDA, SCL
Input Capacitance
SDA, SCL
Output Low Voltage
SDA, IRQ
Min
1.8*
Typ
0.7 x VDD
VIH
IIH, IIL
Units
V
V
VIL
VOL
Max
3.6
0.025
IOL = 6mA
0.35 x VDD
V
1
µA
7
pF
0.5V
V
*The MPR084 requires a specific start-up sequence for VDD< 2.0 V. Refer to Section 2.3.9.
A.5
I2C AC Characteristics
This section includes information about I2C AC Characteristics.
Table 23. I2C AC Characteristics
(Typical Operating Circuit, V+ = 1.8 V to 3.6 V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at V+ = 3.3 V, TA = +25°C.)
Parameter
Symbol
fSCL
(1)
Serial Clock Frequency
Capacitive Load for Each Bus Line
Cb
Conditions
Min
Typ
Max
100
Units
kHz
400
pF
1. Clock Stretching is required for reliable communications
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Appendix B Brief Register Descriptions
FIFO Register: 0x00
R
7
6
5
4
3
MDF
NDF
OF
TRF
0
1
0
0
0
2
1
0
0
0
0
1
0
BP
W
Reset:
= Unimplemented
Fault Register: 0x01
R
7
6
5
4
3
2
0
0
0
0
0
MNKE
0
0
0
0
0
0
0
0
FAULT
W
Reset:
= Unimplemented
Touch Pad Status Register: 0x02
R
7
6
5
4
3
2
1
0
E8S
E7S
E6S
E5S
E4S
E3S
E2S
E1S
0
0
0
0
0
0
0
0
5
4
3
2
1
0
BKA
ACE
TPRBE
TPTBE
0
0
0
0
0
1
4
3
2
1
0
0
0
0
0
W
Reset:
= Unimplemented
Touch Pad Configuration Register: 0x03
7
R
W
Reset:
TPE
1
6
0
0
0
TPE
= Unimplemented
Sensitivity Threshold Registers: 0x04
7
6
5
R
SL
W
Reset:
0
0
0
0
= Unimplemented
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Master Tick Period Register: 0x05
7
6
5
4
3
2
1
0
0
0
1
0
1
4
3
2
1
0
0
0
0
0
1
2
1
0
CP
FREQ
SEN
R
MTP
W
Reset:
0
0
0
= Unimplemented
Touch Acquisition Sample Period Register: 0x06
7
6
5
R
TASP
W
Reset:
0
0
0
= Unimplemented
Sounder Configuration Register: 0x07
R
7
6
5
4
3
0
0
0
0
0
0
0
0
0
0
0
0
1
4
3
2
1
0
W
Reset:
= Unimplemented
Low Power Configuration Register: 0x08
7
R
5
ITP
W
Reset:
6
0
0
SCD
0
0
0
0
0
0
4
3
2
1
0
0
0
0
0
0
4
3
2
1
0
1
1
0
= Unimplemented
Stuck Key Timeout Register: 0x09
7
6
5
R
SKT
W
Reset:
0
0
0
= Unimplemented
Sensor Information Register: 0x14
7
6
5
R
SensorInfo
W
Reset:
0
1
0
0
0
= Unimplemented
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Configuration Register: 0x0A
7
6
R
4
0
0
3
0
RST
W
Reset:
5
0
2
1
0
DCE
IRQEN
RUNE
1
0
1
0
0
= Unimplemented
Electrode Channel Enable Mask Register: 0x0C
R
W
Reset:
7
6
5
4
3
2
1
0
E8EN
E7EN
E6EN
E5EN
E4EN
E3EN
E2EN
E1EN
1
1
1
1
1
1
1
1
2
1
0
= Unimplemented
Maximum Number of Touched Positions Register: 0x0D
R
7
6
5
4
3
0
0
0
0
0
0
0
0
0
0
TPC
W
Reset:
1
0
0
= Unimplemented
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Appendix C Ordering Information
C.1
Ordering Information
This section contains ordering information for MPR084Q and MPR084EJ devices.
ORDERING INFORMATION
Device Name
Temperature Range
MPR084Q
MPR084EJ
C.2
-40°C to +85°C
Case Number
1679
(16-Lead QFN)
948F
(16-Lead TSSOP)
Touch Pads
8-pads
Device Numbering Scheme
All Proximity Sensor Products have a similar numbering scheme. The below diagram explains what each part number in the
family represents.
M
PR EE
X
P
Package Designator
(Q = QFN, EJ = TSSOP)
Status
(M = Fully Qualified, P = Preproduction)
Version
Proximity Sensor Product
Number of Electrodes
(08 = 8 electrode device)
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PACKAGE DIMENSIONS
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PACKAGE DIMENSIONS
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PACKAGE DIMENSIONS
PAGE 1 OF 3
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PACKAGE DIMENSIONS
PAGE 3 OF 3
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MPR084
Rev. 2
04/2008