MPR084
Rev 6, 5/2010
Freescale Semiconductor
Technical Data
© Freescale Semiconductor, Inc., 2007–2010 . All rights reserved.
This document contains a product under development. Freescale Semiconductor reserves the right to change or
discontinue this product without notice.
Product Preview
Proximity 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 ran ge of
implementations through 3 output mechanisms, and many configurable
options.
Features
• 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 minimu m time between successive interrupts
• Current touched pad position is always available on dema nd 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
Implementations
• Control Panels
• Switch Replacements
• Touch Pads
Typical Applica t ions
• Appliances
• PC Peripherals
• Access Controls
• MP3 Players
• Remote Controls
• Mobile Phones
ORDERING INFORMATION
Device Name Temperature Range Case Number Touch Pads
MPR084Q
-40C to +85C
1679
(16-Lead QFN) 8-pads
MPR084EJ 948F
(16-Lead TSSOP)
MPR084
Capacitive Touch
Sensor Controller
16-LEAD TSSOP
CASE 948F
Top View
Figure 1. Pin Connections
Bottom View
E1
E2
E3
E4
E5
E6
E7
E8
VDD
VSS
SCL
SDA
AD0
SOUNDER
ATTN
IRQ MPR084
3
4
1
2
10
9
12
11
7856
14 1316 15
16-LEAD QFN
CASE 1679
E1
E2
E3
E4
E5
E6
E7
E8
VDD
VSS
SCL
SDA
AD0
SOUNDER
ATTN
IRQ
MPR084
1
4
3
2
5
8
7
6
16
13
14
15
12
9
10
11
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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 p ads. 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 pi ezo sounder drive which provides audible fe edback 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 suite d for other
application interface situ ations 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 compute r pe ripherals.
1.1.1 Devices in the MPR08X series
The MPR08X series of Proximity Capacitive Touch Sensor Controllers allows for a wide range of app lications and
implementations. Each of the products in Table 1 perform a different application specific task and are optimized for this specific
functionality.
1.1.2 Internal Block Diagram
The MPR084 consists of primary functional blocks; Interrupt Controller, I2C Serial Interface, Sounder Control ler, 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.
Figure 2. Functional Block Diagram
Table 1. MPR08X Family Overview
Product Bus Sounder Rotary/Slider Touch Pad Array
MPR083 I2CYes 8-pads —
MPR084 I2CYes — 8 keys
CONFIGURATION AND STATUS REGISTERS
MAGNITUDE COMPARATOR AND RECALIBRATOR
EMI BURST/NOISE REJECT FILTER
CAPACITANCE MEASUREMENT A.F.E.
8 88
PAD
ENABLED
IRQ
SDA
SCL I2C
SERIAL
INTERFACE
INTERRUPT
CONTROLLER
MASKS
SET
RATE
ATTN
AD0
SOUNDER SOUNDER
DRIVER
CONTROLLER
CLEAR
TOUCHED
PAD
IDENTIFY
DECODER
PAD
CURRENT 8
8 TOUCH PADS
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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 whe n 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 differentiati ng between high and low capacitance s. 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-k ey 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.
I2CInter-Integrated Circuit Communication
MPR084
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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.
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.
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 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.
Table 3. Device Pin Assignment
Pin Name Function
1ATTN
Attention Pin. Input, active low, when asserted sets the Config uration Register’s DCE bit high
allowing communication with the part.
2IRQInterrupt Request Pin. Output, active-low, open-drain interrupt request signaling new events.
3 VDD Positive Supply Voltage
4 VSS Ground
5SCL
I2C Serial Clock
6SDA
I2C Serial Data
7 AD0 Address input. Low = slave address 0x5C. High = slave address 0x5D.
8 SOUNDER Sounder driver output. Connect a piezo sounder from this output to ground. Output is push-pull
9 - 16 E1, E2, E3, E4, E5,
E6, E7, E8 Touch Pad Electrode connections.
PAD Exposed pad Exposed pad on package underside (QFN only). Connect to VSS.
E1
E2
E3
E4
E5
E6
E7
E8
VDD
VSS
SCL
SDA
AD0
SOUNDER
ATTN
IRQ
3
4
1
2
10
9
12
11
7856
14 1316 15
E1
E2
E3
E4
E5
E6
E7
E8
VDD
VSS
SCL
SDA
AD0
SOUNDER
ATTN
IRQ
1
4
3
2
5
8
7
6
16
13
14
15
12
9
10
11
QFN TSSOP
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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 I2C interface to communicate with the MPR084. All of the connections for the MPR084 are shown by the schematic
in Figure 4.
Figure 4. Recommended System Connections Sc he mat ic
Note that in this configuration the AD0 add ress 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 specific s of communicating with the Touch
Sensor Controller are detailed in the follow ing 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 4.7k, 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 ST AR T 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.
Figure 5. Wire Serial Interface Timing Details
E1
E2
E3
E4
E5
E6
E7
E8
VDD
VSS
SCL
SDA
AD0
SOUNDER
ATTN
IRQ
1
4
3
2
5
8
7
6
16
13
14
15
12
9
10
11
780kΩ
1
4
3
2
5
8
7
6
E1
E2
E3
E4
E5
E6
E7
E8
9GND
GND
MPR084
SCL
SDA
SOUNDER
ATTN
IRQ
8-TOUCH
PAD
ELECTRODE
ARRAY
780kΩ780kΩ780kΩ780kΩ780kΩ780kΩ780kΩ
GND
1μF
4.7kΩ
VDD
VDD
VDD
SCL
SDA
tLOW
tHIGH
tF
tR
tHD STA
tHD DAT
tHD STA
tSU DAT tSU STA
tBUF
tSU STO
START
CONDIT IO N
STOP
CONDIT IO N
REPEATED START
CONDIT IO N
START
CONDIT IO N
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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.
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.
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 g enerates 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.
Figure 8. Acknowledg e
DATA LINE STABLE
DATA VALID CHANGE OF
DATA ALLOWED
SDA
SCL
START
CONDITION
SDA
SCL
STOP
CONDITION
PS
START
CONDITION
SDA
BY TRANSMITTER
S
12 89
CLOCK PULSE FOR
ACKNOWLEDGEMENT
SDA
BY RECEIVER
SCL
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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.
Figure 9. Slave Address Transaction
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 ar e da ta bytes.
Figure 1 0. 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).
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 reg i ste r s be ca u se th e 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.
Slave address: 0x5C
SAAAP
0
SL AVE AD DRES S COM MAND BY T E DATA BYT E
acknowledge from MPR084
R/W 1byte
auto-i ncrement memory
word address
D15 D14 D13 D12 D11 D10 D9 D8 D1 D0D3 D2D5 D4D7 D6
How command byte and data byte
map into MPR084's registers
acknowledge from
MPR084
acknowledge from
MPR084
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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).
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, ho wever, 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.
Figure 13. Low Voltage (1.8 V - 2.0 V) Power-up Sequence
SAAAP1
SLAVE ADDRESS COMMAND BYTE DATA BYT E
acknowledge from MPR084
R/W nbytes
auto-i ncrement memory
word address
D15 D14 D13 D12 D11 D10 D9 D8 D1 D0D3 D2D5 D4D7 D6
How command byte and data byte
map into MPR084's registers
acknowledge from
MPR084
acknowledge from
MPR084
Established Commswith
Sensor Controller?
i.e. Read from FIFO
IsDatavalid? (0 x 40)
Idle Delay Loop
Apply 2.0V to VDD Max
To Sensor Controller
Lower VDD to the desired operating voltage
1.8 V to 2.0 V
False
True
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2.4 Register Address Map
The MPR084 is a peripheral that is controlled and monitored thou gh 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 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 10x04 0x05
Sensitivity Threshold Registers 20x05 0x06
Sensitivity Threshold Registers 30x06 0x07
Sensitivity Threshold Registers 40x07 0x08
Sensitivity Threshold Registers 50x08 0x09
Sensitivity Threshold Registers 60x09 0x0A
Sensitivity Threshold Registers 70x0A 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
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3 Touch Detection
3.1 Introduction
When using a capacitive touch sensor system the raw data must be filter ed 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. Touch Pad unto uched
2. Touch Pad touched on on e 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 pa st 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 sign al 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 to uch will continue to be reported.
If the second touch is released befo re 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 Con fi guration 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.
Figure 14. Touch Pad Config uration Regis te r
76543210
RTPSE 0BKA ACE TPRBE TPTBE 0TPE
W
Reset:10000001
= Unimplemented
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3.5 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.
Figure 15. Touch Acquisition Sample Period Register
Table 4. Touch Pad Configuration Regist er Field Descriptions
Field Description
7
TPSE Touch Pad Sounder Enable – The Tou c h Pad Sounder Enable bit controls if da ta
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 electrode s that are deco ding 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 FIF O 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 lo gged
1 Enable – Touches are logged
0
TPE Touch Pad Enable – The Touch Pad Enable bit enables or disables the touch
sensor. When disabled, no touches are detected.
0 Disable – Touches not de tected
1 Enable – Touches detected
76543210
RTASP
W
Reset:00000001
= Unimplemented
Table 5. Touch Acquisition Sample Register Field Description
Field Description
7:0
TASP Touch Acquisition Sample Period – The Touch Acquisition Samp le Period Field
selects or reports the multiplication factor that is used to determine how often
electrodes are scanned. The resulti ng 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
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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.
Figure 16. Maximum Number of Touched Positions Registers
3.7 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.
Figure 17. Electrode Channel Enable Mask Position Register
76543210
R0 0 0 0 0 TPC
W
Reset:00000100
= Unimplemented
Table 6. Maximum Number of Touched Positions Register Field Descriptions
Field Description
2:0
TPC 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
76543210
RE8EN E7EN E6EN E5EN E4EN E3EN E2EN E1EN
W
Reset:11111111
= Unimplemented
Table 7. Electrode Channel Enable Mask Register Field Descriptions
Field Description
7
E8EN Electrode 8 Enable – The Electrode 8 Enable bit enables or disables ele ctrod e
number 8.
0 Electrode 8 Disable
1 Electrode 8 Enable
6
E7EN Electrode 7 Enable – The Electrode 7 Enable bit enables or disables ele ctrod e
number 7.
0 Electrode 7 Disable
1 Electrode 7 Enable
5
E6EN Electrode 6 Enable – The Electrode 6 Enable bit enables or disables ele ctrod e
number 6.
0 Electrode 6 Disable
1 Electrode 6 Enable
4
E5EN Electrode 5 Enable – The Electrode 5 Enable bit enables or disables ele ctrod e
number 5.
0 Electrode 5 Disable
1 Electrode 5 Enable
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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
Table 7. Electrode Channel Enable Mask Register Field Descriptions (Co ntinued)
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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 S top 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 S top1 mode, write to the registers and change the mode to “Run”.
4.2 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 8. Mode Enable Register Bits
Mode RUNE DCE
Run1 1 1
Run2 1 0
Stop1 0 1
Stop2 0 0
Table 9. Power-Up Register Configu rations
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 1Maximum sensitivity 0x04 0x00
Sensitivity Threshold Registers 2Maximum sensitivity 0x05 0x00
Sensitivity Threshold Registers 3Maximum sensitivity 0x06 0x00
Sensitivity Threshold Registers 4Maximum sensitivity 0x07 0x00
Sensitivity Threshold Registers 5Maximum sensitivity 0x08 0x00
Sensitivity Threshold Registers 6Maximum sensitivity 0x09 0x00
Sensitivity Threshold Registers 7Maximum sensitivity 0x0A 0x00
Sensitivity Threshold Registers 8Maximum 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 Informa tion Register Fixed SensorInfo based on re vision 0x14 0xFF
MPR084
Sensors
Freescale Semiconductor 15
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.
Figure 18. Master Tick Period Register
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 S top1 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 instant aneous 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.
76543210
RMTP
W
Reset:00000101
= Unimplemented
Table 10. Master Tick Period Register Field Descriptions
Field Description
7:0
MTP 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
MPR084
Sensors
16 Freescale Semiconductor
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.
Figure 19. Configuration Register
4.8 Attention Pin
The Attention (AT TN) 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 St op1 (depending on the previous state).
When in Run2 or Stop2 modes this is the only way to enable the I2C communica tion.
76543210
RIRQR RST 0DCE IRQEN RUNE
W
Reset:00010100
= Unimplemented
Table 11. Configuration Register Field Descriptions
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 In terrupts.
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 Enab l ed (2 mo de s)
1 Duty Cycle Disab l ed ( 1 mode s)
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)
MPR084
Sensors
Freescale Semiconductor 17
5 Low Power Configuration
5.1 Introduction
The MPR084 features a Low Power mo de 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 en abled.
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 T ime (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.
Equation 1
First, the Idle Interface T imeout (IIT) represents the tot al 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:
Equation 2
Second, the Max Response T ime (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, T ASP and primary clock (8ms) with a factor of 5. Thus
the MRT is represented as follows:
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 scan ning at MRT 2 and a touch is
detected the scan rate will transition back to MRT1.
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 follow ing section .
MRT1MTP 5+
8
----------------------1+


TASP 48ms=
MRT2MTP 5+
8
----------------------1+


TASP SCD 48ms=
ITT MTP 5+
8
----------------------1+


TASP ITP 68ms=
LP DISABLED
ITT PERIOD
run2 SET
TOUCH DETECTED
MRT1MRT2
MPR084
Sensors
18 Freescale Semiconductor
5.3.1 Low Power Configuration Register
The Low Power Configuration register is used to set both the Idle T imeout Period and Sleep Cycle Duration multiplication factors.
The I2C slave address of the Low Power Configuration Reg iste r is 0x11.
Figure 21. Low Power Configuration Register
76543210
RITP SCD
W
Reset:00000000
= Unimplemented
Table 12. Low Power Configuration Register Field Des criptions
Field Description
7:5
ITP Idle Timeout Period – The Idle Timeout Period selects the amount to multi ply 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
Sensors
Freescale Semiconductor 19
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 p ad. The I2C slave address
of the Touch Pad Status Register is 0x02.
Figure 22. Touch Pad Status Register
76543210
R E8S E7S E6S E5S E4S E3S E2S E1S
W
Reset:00000000
= Unimplemented
Table 13. Touch Pad Status Reg is te r Fi el d 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
20 Freescale Semiconductor
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.
Figure 23. FIFO Register
6.4 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).
76543210
R MDF NDF OF TRF BP
W
Reset:01000000
= Unimplemented
Table 14. FIFO Register Field Descriptions
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 buff er.
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
MPR084
Sensors
Freescale Semiconductor 21
6.4.1 Fault Register
The Fault Register is a read only register that shows the fault number under the curre nt sensor c onditions. A ny write to th e Fault
Register will clear the register , when in S top 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.
Figure 24. Fault Register
76543210
R00000MNKEFAULT
W
Reset:00000000
= Unimplemented
Table 15. Fault Register Field Descriptions
Field Description
4
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 th e currently asserted fault condition.
00 Encoding 0 – No fault detected
01 Encoding 1 – Short to VSS detected
10 Encoding 2 – Short to VDD de te cted
MPR084
Sensors
22 Freescale Semiconductor
7Interrupts
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 Inte rrupt buffered data available or fault detected.
7.2.1 Buffered Data Available
The interrupt for Buffered Data Av ailable 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 deasse r ted 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). T wo 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.
Equation 4
If the MPR084 is using Run2, the mi nimum interrupt perio d would be represented by the following equation.
Equation 5
7.4 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 th e pin.
MinInterruptPeriod ms MCP IRQR4=
MinInterruptPeriod ms MTP 5+
8
----------------------1+


8IRQR 4=
MPR084
Sensors
Freescale Semiconductor 23
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 MinInte r ruptPeriod 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.
Figure 25. IRQ Timing Diagram - Case 1
Figure 26. IRQ Timing Diagram - Case 2
Initial Interrupt Event
MinInterruptPeriod
Second Interrupt Event
IRQ
Initial Interrupt Event
MinInterruptPeriod
Second Interrupt Event
IRQ
MPR084
Sensors
24 Freescale Semiconductor
8Calibration
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 fi rst key detecti on 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-calib ration 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-cali bration 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.
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 S tuck 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.
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 S tuck Key T imeout Register is used to determine the electrode scan period of the system. The I2C slave address of the S tuck
Key Timeout Register is 0x12.
Figure 27. Stuck Key Timeout Register
76543210
RSKT
W
Reset:00000000
= Unimplemented
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 – Se ts the SKT multiplication factor to 2
~
11111111 Encoding 255 – Sets the SKT multiplication factor to 256
AutoCalibrationPeriod ms MCP TASP64=
AutoCalibrationPeriod ms MCPTASPSKT 64=
MPR084
Sensors
Freescale Semiconductor 25
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 fa cto rs th at must be taken in to 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.
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 sensit ivity of the MPR084 is adjuste d 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.
Figure 28. Sensitivity Threshold Register Format
76543210
RSL
W
Reset:00000000
= Unimplemented
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 outsid e of this rang e the ST will be set to 00111111.
00000000 Encoding 0 – Sets the sensitivity to level 1
~
00111111 Encoding 63 – Sets the se nsitivity to level 64
Cke0A
d
------------
=
MPR084
Sensors
26 Freescale Semiconductor
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
Figure 29. Sounder Configuration Register
10.2 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.
Figure 30. Sensor Information Register
76543210
R0 0 0 0 0 CP FREQ SEN
W
Reset:00000001
= Unimplemented
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 Sounder Enable – The Sounder Enable bit enables or disables the sounder output.
0 Disable
1 Enable
76543210
R SensorInfo
W
Reset:01000110
= Unimplemented
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"
MPR084
Sensors
Freescale Semiconductor 27
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. S tress 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.
A.3 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 perfor med per the applicable device specificati on at room temperature followed by hot
temperature, unless specified otherwise in the device specification.
Table 20. Absolute Maximum Ratings - Voltage (with respect to VSS)
Rating 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
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
MPR084
Sensors
28 Freescale Semiconductor
A.4 DC Characteristics
This section includes information about powe r supply requirements and I/O pin characteristics.
*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 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 n oted. Typical current values are at VDD = 3 .3 V,
TA = +25°C.)
Parameter Symbol Conditions Min Typ Max Units
Operating Supply Voltage VDD 1.8* 3.6 V
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 VIH 0.7 x VDD V
Input Low Voltage
SDA, SCL VIL 0.35 x VDD V
Input Leakage Current
SDA, SCL IIH, IIL 0.025 1 µA
Input Capacitance
SDA, SCL 7pF
Output Low Voltage
SDA, IRQ VOL IOL = 6mA 0.5V V
Table 23. I2C AC Characteristics
(T ypica l Operating Circui t, V+ = 1.8 V to 3.6 V, T A = TMIN to TMAX, unless otherwis e noted. Typical values are at V+ = 3.3 V, T A = +25°C.)
Parameter Symbol Conditions Min Typ Max Units
Serial Clock Frequency (1)
1. Clock Stretching is required for reliable communications
fSCL 100 kHz
Capacitive Load for Each Bus Line Cb400 pF
MPR084
Sensors
Freescale Semiconductor 29
Appendix B Brief Register Descriptions
FIFO Register: 0x00
Fault Regi st er: 0x0 1
Touch Pad Status Register: 0x02
Touch Pad Configuration Register: 0x03
Sensitivity Threshold Registers: 0x04
76543210
R MDF NDF OF TRF BP
W
Reset:01000000
= Unimplemented
76543210
R00000MNKEFAULT
W
Reset:00000000
= Unimplemented
76543210
R E8S E7S E6S E5S E4S E3S E2S E1S
W
Reset:00000000
= Unimplemented
76543210
RTPE 0BKA ACE TPRBE TPTBE 0TPE
W
Reset:10000001
= Unimplemented
76543210
RSL
W
Reset:00000000
= Unimplemented
MPR084
Sensors
30 Freescale Semiconductor
Master Tick Period Register: 0x05
Touch Acquisition Sample Period Register: 0x06
Sounder Configuration Register: 0x07
Low Power Configuration Register: 0x08
Stuck Key Timeout Register: 0x09
Sensor Information Register: 0x14
76543210
RMTP
W
Reset:00000101
= Unimplemented
76543210
RTASP
W
Reset:00000001
= Unimplemented
76543210
R0 0 0 0 0 CP FREQ SEN
W
Reset:00000001
= Unimplemented
76543210
RITP SCD
W
Reset:00000000
= Unimplemented
76543210
RSKT
W
Reset:00000000
= Unimplemented
76543210
R SensorInfo
W
Reset:01000110
= Unimplemented
MPR084
Sensors
Freescale Semiconductor 31
Configuration Register: 0x0A
Electrode Channel Enable Mask Register: 0x0C
Maximum Number of Touched Positions Register: 0x0D
76543210
RRST 0DCE IRQEN RUNE
W
Reset:00010100
= Unimplemented
76543210
RE8EN E7EN E6EN E5EN E4EN E3EN E2EN E1EN
W
Reset:11111111
= Unimplemented
76543210
R00000 TPC
W
Reset:00000100
= Unimplemented
MPR084
Sensors
32 Freescale Semiconductor
Appendix C Ordering Information
C.1 Ordering Information
This section contains ordering information for MPR084Q and MPR084EJ devices.
C.2 Device Numbering Scheme
All Proximity Sensor Products have a similar numbering scheme. The below diagram explains what each part number in the
family represents.
ORDERING INFORMATION
Device Name Temperature Range Case Number Touch Pads
MPR084Q
-40C to +85C
1679
(16-Lead QFN) 8-pads
MPR084EJ 948F
(16-Lead TSSOP)
M
Status
(M = Fully Qualified, P = Preproduction)
PR
Proximity Sensor Product
EE X P
Number of Electrodes
(08 = 8 electrode device)
Package Designator
Version
(Q = QFN, EJ = TSSOP)
MPR084
Sensors
Freescale Semiconductor 33
PACKAGE DIMENSIONS
PAGE 1 OF 3
MPR084
Sensors
34 Freescale Semiconductor
PACKAGE DIMENSIONS
PAGE 2 OF 3
MPR084
Sensors
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PACKAGE DIMENSIONS
PAGE 3 OF 3
MPR084
Sensors
36 Freescale Semiconductor
PACKAGE DIMENSIONS
PAGE 1 OF 3
MPR084
Sensors
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PACKAGE DIMENSIONS
PAGE 2 OF 3
MPR084
Sensors
38 Freescale Semiconductor
PACKAGE DIMENSIONS
PAGE 3 OF 3
MPR084
Sensors
Freescale Semiconductor 39
MPR084
Rev 6, 5/2010
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