Product Preview MPR084 Proximity Capacitive Touch Sensor .

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MPR084Rev 6, 5/2010Freescale SemiconductorTechnical DataProduct PreviewProximity Capacitive TouchSensor ControllerMPR084Capacitive TouchSensor ControllerMPR084 OVERVIEWThe MPR084 is an Inter-Integrated Circuit Communication (I2C) drivenCapacitive Touch Sensor Controller, optimized to manage an 8-touch padcapacitive array. The device can accommodate a wide range ofimplementations through 3 output mechanisms, and many configurableoptions.Bottom ViewFeaturesImplementations ATTN110 E7VSS49VSSMPR084QMPR084EJ-40 C to 85 C1679(16-Lead QFN)948F(16-Lead TSSOP)SDATouch PadsAD0SOUNDER8-padsThis document contains a product under development. Freescale Semiconductor reserves the right to change ordiscontinue this product without notice. Freescale Semiconductor, Inc., 2007–2010. All rights reserved.E43VDDCase NumberE32IRQTemperature Range11 E6IRQSCLDevice Name13VDDATTNORDERING INFORMATION1412 E5Control PanelsSwitch ReplacementsTouch PadsAppliancesPC PeripheralsAccess ControlsMP3 PlayersRemote ControlsMobile Phones15MPR084Typical Applications 165678SOUNDER E2 Top ViewAD0 16-LEAD TSSOPCASE 948FE1 16-LEAD QFNCASE 1679SCL 1.8 V to 3.6 V operation41 µA average supply current with 1 s response time2 µA low Standby CurrentVariable low power mode response time (32 ms – 4 s)Rejects unwanted multi-key detections from EMI events such as PAbursts or user handlingOngoing pad analysis and detection is not reset by EMI eventsData is buffered in a FIFO for shortest access timeIRQ output advises when FIFO has dataSystem can set interrupt behavior as immediate after event, orprogram a minimum time between successive interruptsCurrent touched pad position is always available on demand forpolling-based systemsSounder output can be enabled to generate key-click sound when padis touchedTwo hardware selectable I2C addresses allowing two devices on asingle I2C busConfigurable real-time auto calibration5 mm x 5 mm x 1 mm 16 lead QFN package-40 C to 85 C operating temperature rangeSDA ure 1. Pin Connections

1Device Overview1.1IntroductionFreescale Semiconductor’s MPR084 proximity capacitive touch sensor controller is one of a family of products designed to detectthe state of capacitive touch pads. The MPR084 offers designers a cost-efficient alternative to mechanical keys for control panelapplications.The MPR084 uses an I2C interface to communicate with the host which configures the operation and an interrupt to advise thehost of status changes. The MPR084 includes a piezo sounder drive which provides audible feedback to simulate mechanicalkey clicks. The MPR08X family has several implementations to use in your design including control panels and switchreplacements. The MPR084 controls individual touch pads. Other members of the MPR08X family are well suited for otherapplication 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.1.1.1Devices in the MPR08X seriesThe MPR08X series of Proximity Capacitive Touch Sensor Controllers allows for a wide range of applications andimplementations. Each of the products in Table 1 perform a different application specific task and are optimized for this specificfunctionality.Table 1. MPR08X Family OverviewProductBusSounderRotary/SliderTouch Pad ArrayMPR083I2CYes8-pads—MPR084I2CYes—8 keys1.1.2Internal Block TOUCHEDPADIDENTIFYDECODER888CAPACITANCE MEASUREMENT A.F.E.INTERRUPTCONTROLLEREMI BURST/NOISE REJECT FILTERIRQCONFIGURATION AND STATUS REGISTERSMASKSMAGNITUDE COMPARATOR AND RECALIBRATORThe MPR084 consists of primary functional blocks; Interrupt Controller, I2C Serial Interface, Sounder Controller, Configurationand 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.88 TOUCH PADSFigure 2. Functional Block DiagramMPR0842SensorsFreescale Semiconductor

1.1.3TerminologyThe following terms are used to describe front panel interface and capacitive touch sensor technology throughout this document.Table 2. TerminologyTermDefinitionTouch SensorA Touch Sensor is the combination of a Touch Sensor Controller and a connected conductive areareferred to as an electrode.Touch Sensor ControllerA Touch Sensor Controller is the intelligent part of a Touch Sensor which measures capacitance anddifferentiates between touched and untouched pads.KeyA Key or Switch is a mechanical device that makes an electrical connection only when pressed.Touch PadA Touch Pad is a type of capacitive sensor that is used for direct replacement of a Key. A capacitivetouch sensor determines touch state by differentiating between high and low capacitances. Whenthere is a change in the state this can be interpreted in the same way as a mechanical Key.Solid PadA Solid or Full Pad is a type of touch pad where exactly one electrode is usedSplit PadA Split Pad is a type of touch pad where more than one electrode is used. Split Pads are used toincrease the total number of possible touch pads without increasing the electrical connections to theTouch Sensor Controller.N-key LockoutN-Key Lockout refers to the logic that determines how many keys can be simultaneously touched ina system. For example, 1-key lockout would only allow a single key to be touched before ignoringall future touches.N-key rolloverN-Key Rollover refers to the logic that determines how many keys can be pressed in successionwithout releasing previous keys. For example, a system with 1-key lockout and 2-key rollover wouldallow 2-keys to be pressed in succession but would only report the second key once the first keywas released.I2CInter-Integrated Circuit CommunicationMPR084SensorsFreescale Semiconductor3

2External Signal Description2.1Device Pin AssignmentTable 3 shows the pin assignment for the MPR084. For a more detailed description of the functionality of each pin, refer to theappropriate chapter.Table 3. Device Pin AssignmentPinNameFunction1ATTNAttention Pin. Input, active low, when asserted sets the Configuration Register’s DCE bit highallowing communication with the part.2IRQInterrupt Request Pin. Output, active-low, open-drain interrupt request signaling new events.3VDDPositive Supply Voltage4VSSGround5SCLI2C Serial Clock6SDAI2C Serial Data7AD0Address input. Low slave address 0x5C. High slave address 0x5D.8SOUNDER9 - 16E1, E2, E3, E4, E5,E6, E7, E8PADExposed padSounder driver output. Connect a piezo sounder from this output to ground. Output is push-pullTouch Pad Electrode connections.Exposed pad on package underside (QFN only). Connect to VSS.E1E2E3E4The two packages available for the MPR084 are a 5x5mm 16 pin QFN and a 4x5mm 16 pin TSSOP. Both of the packages andtheir respective pinouts are shown in Figure 3.16151413ATTN116E1IRQ215E2112 E5VDD314E3IRQ211 E6VSS413E4VDD310 DER6AD0SCL5SDAATTNQFNTSSOPFigure 3. Package Pinouts2.2Recommended System ConnectionsThe MPR084 Capacitive Touch Sensor Controller requires ten external passive components. When connecting the MPR084 ina 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 kpull-up resistor should be included on the IRQ.MPR0844SensorsFreescale Semiconductor

The remaining 5 connections are SCL, SDA, IRQ, ATTN, and SOUNDER. Depending on the specific application, each of thesecontrol lines can be used by connecting them to a host system. In the most minimal system, the SCL and SDA must be connectedto a master I2C interface to communicate with the MPR084. All of the connections for the MPR084 are shown by the schematicin Figure 4.VDDVDD780kΩ 780kΩ4.7kΩVDD1μFATTN1 ATTN2IRQIRQGNDSOUNDER 8E23E3134125E5116E6107E798E5SDA7E12E45 SCL6SDA115E214E3VSSSCLELECTRODE780kΩ 780kΩ 780kΩ ARRAY16E13 VDD4780kΩ 780kΩ igure 4. Recommended System Connections SchematicNote that in this configuration the AD0 address line is tied high thus the slave address of the MPR084 0x5D. Alternatively theaddress line can be pulled low if the host system needs the MPR084 to be on address 0x5C. This functionality can also be usedto incorporate two MPR084 devices in the same system.2.3Serial InterfaceThe MPR084 uses an I2C Serial Interface. The I2C protocol implementation and the specifics of communicating with the TouchSensor Controller are detailed in the following sections.2.3.1Serial-AddressingThe MPR084 operates as a slave that sends and receives data through an I2C 2-wire interface. The interface uses a serial dataline (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 synchronizesthe 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 multiplemasters 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 plusR/W bit, a register address byte, one or more data bytes, and finally a STOP condition.SDAtSU DATtLOWSCLtHD DATtSU STAtBUFtHD STAtSU STOtHIGHtHD STAST ARTCONDIT IONtRtFREPEAT ED ST ARTCONDIT IONST OPCONDIT IONST ARTCONDIT IONFigure 5. Wire Serial Interface Timing DetailsMPR084SensorsFreescale Semiconductor5

2.3.2Start and Stop ConditionsBoth 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 theslave, it issues a STOP (P) condition by transitioning SDA from low to high while SCL is high. The bus is then free for anothertransmission.SDADATA LINE STABLEDATA VALIDSCLCHANGE OFDATA ALLOWEDFigure 6. Start and Stop Conditions2.3.3Bit TransferOne data bit is transferred during each clock pulse (Figure 7). The data on SDA must remain stable while SCL is high.SDASCLSPSTARTCONDITIONSTOPCONDITIONFigure 7. Bit Transfer2.3.4AcknowledgeThe acknowledge bit is a clocked 9th bit (Figure 8) which the recipient uses to handshake receipt of each byte of data. Thus eachbyte transferred effectively requires 9 bits. The master generates the 9th clock pulse, and the recipient pulls down SDA duringthe acknowledge clock pulse, such that the SDA line is stable low during the high period of the clock pulse. When the master istransmitting to the MPR084, the MPR084 generates the acknowledge bit because the MPR084 is the recipient. When theMPR084 is transmitting to the master, the master generates the acknowledge bit because the master is the recipient.STARTCONDITIONSCLCLOCK PULSE FORACKNOWLEDGEMENT1289SDABY TRANSMITTERSDASBY RECEIVERFigure 8. AcknowledgeMPR0846SensorsFreescale Semiconductor

2.3.5The Slave AddressThe 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, whichis low for a write command and high for a read command.Slave address: 0x5CFigure 9. Slave Address TransactionThe MPR084 monitors the bus continuously, waiting for a START condition followed by its slave address. When a MPR084recognizes its slave address, it acknowledges and is then ready for continued communication.2.3.6Message Format for Writing the MPR084A write to the MPR084 comprises the transmission of the MPR084’s keyscan slave address with the R/W bit set to 0, followedby at least one byte of information. The first byte of information is the command byte. The command byte determines whichregister of the MPR084 is to be written by the next byte, if received. If a STOP condition is detected after the command byte isreceived, then the MPR084 takes no further action (Figure 10) beyond storing the command byte. Any bytes received after thecommand byte are data bytes.Command byte is stored on receipt ofSTOP conditionD7D6D5D4D3D2D1D0acknowledge from MPR084S0SLAVE ADDRESSAACOMMAND BYTER/WPacknowledge from MPR084Figure 10. Command Byte ReceivedAny bytes received after the command byte are data bytes. The first data byte goes into the internal register of the MPR084selected by the command byte (Figure 11).acknowledge fromMPR084How command byte and data bytemap into MPR084's registersD15 D14 D13 D12 D11 D10 D9acknowledge fromMPR084D8D7D6D5D4D3D2D1D0acknowledge from MPR084SSLAVE ADDRESS0ACOMMAND BYTEADATA BYTEAP1 byteR/Wauto-increment memoryword addressFigure 11. Command and Single Data Byte ReceivedIf multiple data bytes are transmitted before a STOP condition is detected, these bytes are generally stored in subsequentMPR084 internal registers because the command byte address generally auto-increments (Section 2.4).2.3.7Message Format for Reading the MPR084The MPR084 is read using the MPR084’s internally stored command byte as address pointer, the same way the stored commandbyte is used as address pointer for a write. The pointer generally auto-increments after each data byte is read using the samerules 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 registeraddressed by the initialized command byte.MPR084SensorsFreescale Semiconductor7

When performing read-after-write verification, remember to re-set the command byte’s address because the stored commandbyte address will generally have been auto-incremented after the write (Section 2.4).How command byte and data bytemap into MPR084's registersacknowledge fromMPR084acknowledge fromMPR084D15 D14 D13 D12 D11 D10 D9 D8D7 D6 D5 D4 D3 D2 D1 D0acknowledge from MPR084SSLAVE ADDRESS1COMMAND BYTEAADATA BYTEAPn bytesR/Wauto-increment memoryword addressFigure 12. ‘n’ Data Bytes Received2.3.8Operation with Multiple MasterThe 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 doesnot own the bus attempts to take control of that bus, then improper addressing may occur. An address may always be rewrittento fix this problem. Follow I2C protocol for multiple master configurations.2.3.9Device ResetThe RST is an active-low software reset. This is implemented in the Configuration Register by activating the RST bit. Whenasserted, the device clears any transaction to or from the MPR084 on the serial interface and configures the internal registers tothe 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 startupcorrectly 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 processis required in applications that require regulated operation in the 1.8 V to 2.0 V range. In the case that the application uses anunregulated battery, then the battery must initially provide at least 2.0 V to correctly power-up the sensor controller which limitsbattery selection to the 2.0 V to 3.6 V range.Apply 2.0V to VDD MaxTo Sensor ControllerIdle Delay LoopFalseEstablished Comms withSensor Controller?i.e. Read from FIFOIs Data valid? (0 x 40)TrueLower VDD to the desired operating voltage1.8 V to 2.0 VFigure 13. Low Voltage (1.8 V - 2.0 V) Power-up SequenceMPR0848SensorsFreescale Semiconductor

2.4Register Address MapThe MPR084 is a peripheral that is controlled and monitored though a small array of internal registers which are accessedthrough the I2C bus. When communicating with the MPR084 each of the registers in Table 4 are used for specific tasks. Thefunctionality of each specific register is detailed in the following sections.Register AddressBurst ModeAuto-Increment AddressFIFO Register0x000x00Fault Register0x010x02Touch Pad Status Register0x020x00Touch Pad Configuration Register0x030x04Sensitivity Threshold Registers 10x040x05Sensitivity Threshold Registers 20x050x06Sensitivity Threshold Registers 30x060x07Sensitivity Threshold Registers 40x070x08Sensitivity Threshold Registers 50x080x09Sensitivity Threshold Registers 60x090x0ASensitivity Threshold Registers 70x0A0x0BSensitivity Threshold Registers 80x0B0x0CElectrode Channel Enable Mask Register0x0C0x0DMaximum Number of Touched Positions Register0x0D0x0EMaster Tick Period Register0x0E0x0FTouch Acquisition Sample Period Register0x0F0x10Sounder Configuration Register0x100x11Low Power Configuration Register0x110x12Stuck Key Timeout Register0x120x13Configuration Register0x130x00Sensor Information Register0x140x14RegisterMPR084SensorsFreescale Semiconductor9

3Touch Detection3.1IntroductionWhen using a capacitive touch sensor system the raw data must be filtered and interpreted. This process can be done manydifferent ways but the method used in the MPR084 is explained in this chapter.3.2Understanding the BasicsThe touch pad interface has to distinguish touch status through varying user conditions (different finger sizes in bare hands orgloves) 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 untouchedTouch 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.3.3Conditional Output ScenariosSince it is unlikely that in a real world case a single independent touch will occur two specific multi-touch response cases areoutlined. Methods for changing the sensitivity of the device will be discussed in another Chapter, but the important part is that thesensitivity is determined by the strength of an input signal. If more than one input signal is above the selected sensitivity then thetouch sensor controller interprets this in a specific way. This functionality is broken down into two different cases.3.3.1Simultaneous TouchesAny time multiple touches are detected at the same time the touch sensor controller recognizes this case and accounts for it. Thenumber of allowed reported touches is settable using the Maximum Number of Touched Positions Register (Section 3.6). In thecase 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 strongersignal than the other. If the difference in capacitance is statistically significant between the pad with the stronger signal will bereportedThis 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.3.3.2Sequential TouchesAnother case is when one touch pad is touched

discontinue this product without notice. Product Preview Proximity Capacitive Touch Sensor Controller MPR084 OVERVIEW The MPR084 is an Inter-Integrated Circuit Communication (I 2C) driven Capacitive Touch Sensor Controller , optimized to manage an 8-touch pad capacitive array. The device can accommodate a wide range of

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