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Table Of Contents

Document Number: MPR121

Rev. 4, 02/2013

Freescale Semiconductor

Data Sheet: Technical Data

An Energy Efficient Solution by Freescale

Proximity Capacitive Touch

Sensor Controller

The MPR121 is the second generation sensor controller following the

initial release of the MPR03x series of devices. The MPR121 features an

increased internal intelligence plus Freescale’s second generation

capacitance detection engine. Some major enhancements include an

increased electrode count, a hardware configurable I

C address, an

expanded filtering system with debounce, and completely independent

electrodes with built-in autoconfiguration. The device also features a 13

simulated electrode which represents the simultaneous charging of all the

electrodes connected together. When used with a touch panel or touch

screen array, the 13

simulated electrode allows a greater near proximity

detection distance and an increased sensing area.

Features

• 1.71V to 3.6V operation

• 29 μA typical run current at 16 ms sampling interval

•3 μA in scan stop mode current

• 12 electrodes/capacitance sensing inputs in which 8 are

multifunctional for LED driving and GPIO

• Integrated independent autocalibration for each electrode input

• Autoconfiguration of charge current and charge time for each

electrode input

• Separate touch and release trip thresholds for each electrode,

providing hysteresis and electrode independence

•I

C interface, with IRQ Interrupt output to advise electrode status

changes

• 3 mm x 3 mm x 0.65 mm 20 lead QFN package

• -40°C to +85°C operating temperature range

Implementations

• General Purpose Capacitance Detection

• Switch Replacements

• Touch Pads, Touch Wheel, Touch Slide Bar, Touch Screen Panel

• Capacitance Near Proximity Detection

Typical Applications

• PC Peripherals

• MP3 Players

• Remote Controls

• Mobile Phones

• Lighting Controls

ORDERING INFORMATION

Device Name Temperature Range Case Number Touch Pads

C Address

Shipping

MPR121QR2 -40°C to +85°C 2059 (20-Pin QFN) 12-pads 0x5A - 0x5D Tape & Reel

MPR121

Top View

Pin Connections

Bottom View

20-PIN QFN

CASE 2059-01

678910

1617181920

ELE4

ELE3

ELE6

ELE7

ELE5

REXT

ELE0

ELE1

ADDR

REG

SCL

IRQ

SDA

ELE2

ELE11

ELE10

ELE9

ELE8

Summary of content (27 pages)

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Document Number: MPR121 Rev. 4, 02/2013 Freescale Semiconductor Data Sheet: Technical Data An Energy Efficient Solution by Freescale Proximity Capacitive Touch Sensor Controller MPR121 The MPR121 is the second generation sensor controller following the initial release of the MPR03x series of devices. The MPR121 features an increased internal intelligence plus Freescale’s second generation capacitance detection engine.
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1 Pin Descriptions Table 1. Pin Descriptions Pin No. Pin Name Description 1 IRQ Open Collector Interrupt Output Pin, active low 2 SCL I2C Clock 3 SDA I2C Data 4 ADDR I2C Address Select Input Pin. Connect the ADDR pin to the VSS, VDD, SDA or SCL line, the resulting I2C addresses are 0x5A, 0x5B, 0x5C and 0x5D respectively 5 VREG Internal Regulator Node – Connect a 0.
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2 Schematic Drawings and Implementation VDD 1.71V to 2.75V 0.1 μF 20 6 5 1 2 3 4 7 VDD ELE11/LED7 VSS ELE10/LED6 VREG ELE9/LED5 IRQ ELE8/LED4 SCL ELE7/LED3 SDA ELE6/LED2 ADDR ELE5/LED1 REXT ELE4/LED0 ELE3 ELE2 75 kΩ 1% ELE1 GND ELE0 GND 19 18 17 16 15 14 13 12 11 10 9 8 MPR121Q TOUCH SENSOR Figure 1. Power Configuration 1: MPR121 runs from a 1.71V to 2.75V supply. VDD 2.0V to 3.6V 0.1 μF 20 6 5 1 2 3 4 7 0.
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3 Device Operation Overview Power Supply The VDD pin is the main power supply input to the MPR121 and is always decoupled with a 0.1 μF ceramic capacitor to the VSS. Excessive noise on the VDD should be avoided. The VDD pin has an operational voltage range specification between 1.71V to 3.6V. The internal voltage regulator, which generates current to internal circuitry, operates with an input range from 2.0V to 3.6V. To work with a power supply below 2.
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Table 2.
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Table 2.
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Table 2.
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4 Electrical Characteristics 4.1 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 3 may affect device reliability or cause permanent damage to the device. For functional operating conditions, refer to the remaining tables in this section.
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4.3 DC Characteristics This section includes information about power supply requirements and I/O pin characteristics. Table 5. DC Characteristics (Typical Operating Circuit, VDD and VREG = 1.8V, TA = 25°C, unless otherwise noted.) Parameter Symbol High Supply Voltage VDD Low Supply Voltage VREG Average Supply Current(1) Conditions Typ Max Units 2.0 3.3 3.6 V 1.8 2.75 1.
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4.5 I2C AC Characteristics Table 7. I2C AC Characteristics (Typical Operating Circuit, VDD and VREG = 1.8V, TA = 25°C, unless otherwise noted.) Parameter Symbol Conditions Min Typ Max Units 400 kHz Serial Clock Frequency fSCL Bus Free Time Between a STOP and a START Condition tBUF 1.3 μs Hold Time, (Repeated) START Condition tHD, STA 0.6 μs Repeated START Condition Setup Time tSU, STA 0.6 μs STOP Condition Setup Time tSU, STO 0.
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5 Register Operation Descriptions 5.1 Register Read/Write Operations and Measurement Run/Stop Mode After power on reset (POR) or soft reset by command, all registers are in reset default initial value (see Table 2). All the registers, except registers 0x5C (default 0x10) and 0x5D (default 0x24), are cleared. Registers 0x2B ~ 0x7F are control and configuration registers which need to be correctly configured before any capacitance measurement and touch detection.
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5.3 Electrode Filtered Data Register (0x04~0x1D) Electrode Filtered Data Low Byte (0x04,0x06,...,0x1C) Bit D7 D6 D5 D4 D3 D2 D1 D0 Read Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Write — — — — — — — — Electrode Filtered Data High Byte (0x05,0x07,...,0x1D) Bit D7 D6 D5 D4 D3 D2 D1 D0 Read — — — — — — Bit 9 Bit 8 Write — — — — — — — — The MPR121 provides filtered electrode output data for all 13 channels.
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Noise Count Limit (NCL): Determines the number of samples consecutively greater than the Max Half Delta value. This is necessary to determine that it is not noise. The range of the effective value is 0~255. Filter Delay Count Limit (FDL): Determines the operation rate of the filter. A larger count limit means the filter delay is operating more slowly. The range of the effective value is 0~255. The setting of the filter is depended on the actual application.
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5.8 Filter and Global CDC CDT Configuration (0x5C, 0x5D) Filter/Global CDC Configuration Register (0x5C) Bit D7 D6 D5 D4 D3 D2 D1 D0 D2 D1 D0 Read FFI CDC Write Filter/Global CDT Configuration Register (0x5D) Bit D7 D6 D5 D4 D3 Read CDT SFI ESI Write Table 8. Bit Descriptions Field Description First Filter Iterations - The first filter iterations field selects the number of samples taken as input to the first level of filtering.
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These two registers set the global AFE settings. This includes global electrode charge/discharge current CDC, global charge/ discharge time CDT, as well as a common filtering setting (FFI, SFI, ESI) for all 13 channels, including the 13th Eleprox channel. The register 0x5C holds the global CDC and the first level filter configuration for all 13 channels.
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5.11 Electrode Configuration Register (ECR, 0x5E) Electrode Configuration Register (0x5E) Bit D7 D6 D5 D4 D3 D2 D1 D0 Read CL ELEPROX_EN ELE_EN Write Table 9.
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baseline value starts from zero, it will require a very long time for the baseline to ramp up. This results in a short period of no response to touch after the MPR121 is first set to Run Mode. Setting the CL = 2b10 will command the MPR121 to load the initial baseline value at the beginning of the Run Mode. This shortens the initial baseline ramp-up time so that user will not notice any delay on touch detection. The MPR121 uses the five high bits of the first measured 10 bit electrode data.
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SCTS: Skip Charge Time Search. 1: Skip CDTx search and update when autoconfiguration or autoreconfiguration, and current global CDT or CDTx are used for respective channels. CDT or CDTx needs to be specified by the designer manually before operation. Setting the SCTS to “1” results in a shorter time to complete autoconfiguration. This is useful for when the designer has obtained the correct CDTx / CDT, and is confident that the current CDT and CDTx settings work in all conditions.
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With above mentioned, one possible example setting is given out below using equation 1~3, with the assumption that setting TL at 90% of USL, and LSL at 65% of USL would cover most of the application case. It may need further adjustment in some cases but will be a very good start. USL = (VDD - 0.7)/VDD x 256 Eqn. 1 TL = USL x 0.9 = (VDD - 0.7)/VDD x 256 x 0.9 Eqn. 2 LSL = USL x 0.65 = (VDD-0.7) / VDD x 256 x 0.65 Eqn. 3 Cin = I x T / V = CDC x CDT / (ADC counts x VDD/1024) Eqn.
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GPIO Registers (0x73~0x7A) Direction Register(0x76) DIR_E11 DIR_E10 DIR_E9 DIR_E8 DIR_E7 DIR_E6 DIR_E5 DIR_E4 Enable Register(0x77) EN_E11 EN_E10 EN_E9 EN_E8 EN_E7 EN_E6 EN_E5 EN_E4 Data Set Register(0x78) SET_E11 SET_E10 SET_E9 SET_E8 SET_E7 SET_E6 SET_E5 SET_E4 Data Clear Register(0x79) CLR_E11 CLR_E10 CLR_E9 CLR_E8 CLR_E7 CLR_E6 CLR_E5 CLR_E4 Data Toggle Register(0x7A) TOG_E11 TOG_E10 TOG_E11 TOG_E8 TOG_E7 TOG_E6 TOG_E5 TOG_E4 These registers control GPIO and
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6 MPR121 Serial Communication 6.1 I2C Serial Communications The MPR121 uses an I2C Serial Interface.The MPR121 operates as a slave that sends and receives data through an I2C twowire interface. The interface uses a Serial Data Line (SDA) and a Serial Clock Line (SCL) to achieve bidirectional communication between master(s) and slave(s). A master (typically a microcontroller) initiates all data transfers to and from the MPR121, and it generates the SCL clock that synchronizes the data transfer.
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6.
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PACKAGE DIMENSIONS PAGE 1 OF 3 MPR121 Sensors Freescale Semiconductor, Inc.
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PAGE 2 OF 3 MPR121 24 Sensors Freescale Semiconductor, Inc.
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PAGE 3 OF 3 MPR121 Sensors Freescale Semiconductor, Inc.
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Table 11.
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