SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET -----4 KEY PRODUCT FEATURES GENERAL DESCRIPTION The SX8653 is a touch controller for 4 or 5 wire resistive touchscreen. With 4-wire touchscreen, the multitouch feature enables a completely different user interaction. It enables detection of 2 fingers on the touchscreen and several gestures like rotation and pinch/ stretch. It features a wide input supply range from 1.65V to 3.7V and low power modes to preserve current when the screen is unintentionally touched. To compute touch screen X-Y coordinates and touch pressure with precision, a low power 12-bit analog-digital converter is activated with the possibility to enable on-chip data averaging processing algorithms to reduce host activity and suppress system noise. The touch screen controller inputs have been specially designed to provide robust on-chip ESD protection of up to 15kV in both HBM and Contact Discharge, and eliminates the need for external protection devices. The SX8653 is controlled by a high speed SPITM serial interface. The SX8653 is available in a 4.0 mm x 3.0 mm 14-DFN package and a 1.5 mm x 2.0 mm wafer level chip scale package (WLCSP) for space conscience applications. APPLICATIONS DSC, DVR, Cell Phones PDA, Pagers Point-of-Sales Terminals Touch-Screen Monitors ORDERING INFORMATION Part Number Package (Dimension in mm) Marking SX8653ICSTRT1 12 - Ball WLCSP (1.5x2.0) NB2A SX8653IWLTRT1 14 - Lead DFN (4.0x 3.0) NB2A Extremely Low Power Consumption: 23uA@1.8V 8kSPS Support Multi-touch operation (4-wire) Superior On-chip ESD Protection 15kV HBM (X+,X-,Y+,Y-) 2kV CDM 25kV Air Gap Discharge 15kV Contact Discharge 300V MM Pin-compatible with SX8652 Single 1.65V to 3.7V Supply/Reference 4-Wire or 5-Wire Resistive Touch Screen Interface Integrated Preprocessing Block to Reduce Host Loading and Bus Activity Four User Programmable Operation Modes provides Flexibility to address Different Application Needs Manual, Automatic, Pen Detect, Pen Trigger Precision, Low Noise, High Speed 12-bit SAR ADC Operating At 74k SPS Throughput: 5000 (X-Y) coordinates/second (c/s) with 7Sample Averaging Low Power Shut-Down Mode < 1uA Hardware & Software reset SPITM Serial Interface Touch Pressure Measurement (4-Wire) Auxiliary Input (4-Wire) For Alternate ADC Input or Start of Conversion Trigger -40C to +85C operation Pb-Free, Halogen Free, RoHS/WEEE compliant product Windows CE 6.0, Linux Driver Support Available Packages: 14-LD (4.0 mm x 3.0 mm) DFN 12-Ball (1.5 mm x 2.0 mm) WLCSP 1. 3000 Units / reel VD D S X 8653 VD D C ontrol N IR Q A U X /W IP ER N R S T (D FN only) PO R To the touch screen SPI X +/BR Y+/TR Touch Screen Interface SC LK ref+ X -/TL Y-/BL Vref NCS O SC in AD C out ref- D ig ital Filter T o the H ost DOUT D IN GND Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 1 www.semtech.com SX8653 ADVANCED COMMUNICATIONS & SENSING DATASHEET Table of contents Section 1. 2. 3. 4. 5. Page General Description ................................................................................................................................................. 4 1.1. DFN Pinout Diagram and Marking Information (Top View).............................................................................. 4 1.2. WLCSP Pinout Diagram and Marking Information (Top View) ........................................................................ 4 1.3. Pin Description................................................................................................................................................. 5 1.4. Simplified Block Diagram ................................................................................................................................. 5 Electrical Characteristics ......................................................................................................................................... 6 2.1. Absolute Maximum Ratings ............................................................................................................................. 6 2.2. Recommended Operating Conditions.............................................................................................................. 6 2.3. Thermal Characteristics ................................................................................................................................... 6 2.4. Electrical Specifications ................................................................................................................................... 7 2.5. Host Interface Specifications ........................................................................................................................... 9 2.6. Host Interface Timing Waveforms.................................................................................................................... 9 Functional Description ........................................................................................................................................... 10 3.1. General Introduction ..................................................................................................................................... 10 3.2. Device Interface and ESD protection............................................................................................................. 11 3.2.1. Touchscreen interface............................................................................................................................. 11 3.2.2. Host Interface and Control Pins .............................................................................................................. 11 4-wire Touch Screen Detailed Description ............................................................................................................ 12 4.1. Touch Screen Operation................................................................................................................................ 12 4.2. Coordinates Measurement............................................................................................................................. 12 4.3. Pressure Measurement.................................................................................................................................. 13 4.4. Pen Detection ................................................................................................................................................ 13 4.5. Double touch measurement........................................................................................................................... 14 5-wire Touch Screen Detailed Description ............................................................................................................ 15 5.1. Touch Screen Operation................................................................................................................................ 15 5.2. Coordinates Measurement............................................................................................................................. 15 5.3. Pen Detection ................................................................................................................................................ 15 6. Data Processing .................................................................................................................................................... 16 7. Power-Up, Reset ................................................................................................................................................... 16 8. Modes of Operation ............................................................................................................................................... 16 9. 8.1. MANual Mode ................................................................................................................................................ 17 8.2. AUTOmatic mode .......................................................................................................................................... 17 8.3. PENDET Mode .............................................................................................................................................. 18 8.4. PENTRIG Mode ............................................................................................................................................. 18 Host Interface ........................................................................................................................................................ 20 9.1. SPI Read/Write Registers .............................................................................................................................. 20 9.2. SPI Reading Channel Data............................................................................................................................ 20 9.3. SPI implementation and multiple Read/Write ................................................................................................ 21 9.4. Invalid Qualified Data..................................................................................................................................... 22 Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 2 www.semtech.com SX8653 ADVANCED COMMUNICATIONS & SENSING DATASHEET Table of contents Section 10. Page 9.5. Register Map................................................................................................................................................. 23 9.6. SX8653 register ............................................................................................................................................ 24 Application Information ......................................................................................................................................... 25 10.1. Acquisition Setup ........................................................................................................................................... 25 10.2. Channel Selection.......................................................................................................................................... 25 10.3. Noise Reduction............................................................................................................................................. 25 10.3.1. POWDLY................................................................................................................................................. 25 10.3.2. SETDLY .................................................................................................................................................. 26 10.4. AUX Input - 4-wire touchscreen only ............................................................................................................. 26 10.5. Interrupt Generation....................................................................................................................................... 26 10.6. Coordinate Throughput Rate ......................................................................................................................... 26 10.6.1. SPI Communication Time ....................................................................................................................... 26 10.6.2. Conversion Time ..................................................................................................................................... 27 10.7. ESD event...................................................................................................................................................... 27 11. Multi-Touch Gestures with 4-wire touchscreen...................................................................................................... 28 11.1. Zoom Gesture ................................................................................................................................................ 28 11.2. Rotate Gesture............................................................................................................................................... 28 12. Packaging Information ........................................................................................................................................... 29 12.1. DFN Package................................................................................................................................................. 29 12.2. WLCSP Package ........................................................................................................................................... 30 Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 3 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 1. General Description 1.1. DFN Pinout Diagram and Marking Information (Top View) 1 14 (NC) VDD 2 13 NRST X+/BR 3 12 NCS Y+/TR 4 11 NIRQ X-/TL 5 10 DOUT Y-/BL 6 9 DIN GND 7 8 SCLK 15 PIN 1 IDENTIFIER NB2A YYWW XXXXX AUX/ WIPER Figure 1. SX8653 DFN Top View, Pad on Bottom Side YYWW: date code XXXXX: Lot Number 1.2. WLCSP Pinout Diagram and Marking Information (Top View) X+/BR Y+/TR X-/TL Y-/BL NB2A YYWW XXXXXX 3 VDD NCS DIN GND AUX/WIPER # NIRQ DOUT SCLK A B C D 2 1 BALL A1 IDENTIFIER Figure 2. SX8653 WLCSP Top View, Solder Bumps on Bottom Side YYWW: date code XXXXX: Lot Number Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 4 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 1.3. Pin Description Pin Number # Name Type Description DFN WLCSP 1 A1 AUX/WIPER Digital Input / Analog Input Conversion Synchronization (4-wire) or Analog Auxiliary Input (4-wire) / Wiper Input (5-wire) 2 A2 VDD Power Input Input power supply, connect to a 0.1uF capacitor to GND 3 A3 X+/BR Analog IO X+ Right electrode (4-wire) / Bottom Right (5-wire) channel 4 B3 Y+/TR Analog IO Y+ Top electrode (4-wire) /Top Right (5-wire) channel 5 C3 X-/TL Analog IO X- Left electrode (4-wire) /Top Left (5-wire) channel 6 D3 Y-/BL Analog IO Y- Bottom electrode (4-wire) /Bottom Left (5-wire) channel 7 D2 GND Ground Ground 8 D1 SCLK Digital Input SPI Serial Clock Input 9 C2 DIN Digital Output SPI Serial Data Input 10 C1 DOUT Digital Output SPI Serial Data Output 11 B1 NIRQ Digital Output, open drain Interrupt Request Output, Active low, Need external pull-up 12 B2 NCS Digital Input SPI Chip Select Input, Active low 13 - NRST Digital Input DFN package only, Reset Input, Active low, Internal pull-up resistor 14 - (NC) 15 - GND Not Connected Power input Backside Ground Table 1. Pin description 1.4. Simplified Block Diagram The SX8653 simplified block diagram is shown in Figure 3. VDD SX8653 VDD Control NIRQ AUX/WIPER NRST (DFN only) POR To the touch screen SPI X+/BR Y+/TR Touch Screen Interface X-/TL Y-/BL Vref NCS OSC SCLK ref+ in ADC out ref- Digital Filter To the Host DOUT DIN GND Figure 3. Simplified block diagram of the SX8653 Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 5 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 2. Electrical Characteristics 2.1. Absolute Maximum Ratings Stresses above the values listed in "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these, or any other conditions beyond the "Recommended Operating Conditions", is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Parameter Symbol Min. Max. Unit Supply Voltage VDDABS -0.5 3.9 V Input voltage (non-supply pins) VIN -0.5 3.9 V Input current (non-supply pins) IIN 10 mA Operating Junction Temperature TJCT 125 C Reflow temperature TRE 260 C Storage temperature TSTOR 150 C ESD HBM (Human Body Model) ESD (Contact Discharge) 15(i) kV 8(ii) kV ESDHBM2 2 kV ESDCD 15 kV ILU 100 mA High ESD pins: X+/BR, X-/TL, Y+/TR, Y-/BL, Aux/Wiper ESDHBM1 All pins except high ESD pins High ESD pins: X+/BR, X-/TL, Y+/TR, Y-/BL, Aux/Wiper Latchup(iii) -50 Table 2. Absolute Maximum Ratings (i) Tested to TLP (10A) (ii) Tested to JEDEC standard JESD22-A114 (iii) Tested to JEDEC standard JESD78 2.2. Recommended Operating Conditions Parameter Supply Voltage Ambient Temperature Range Symbol Min. Max Unit VDD 1.65V 3.7 V TA -40 85 C Min. Max Unit Table 3. Recommended Operating Conditions 2.3. Thermal Characteristics Symbol Parameter Thermal Resistance with DFN package - Junction to Ambient (iii) JA 39 C/W Thermal Resistance with WLCSP package - Junction to Ambient (iii) JA 65 C/W Table 4. Thermal Characteristics (iii) JA is calculated from a package in still air, mounted to 3" x 4.5", 4 layer FR4 PCB with thermal vias under exposed pad (if applicable) per JESD51 standards. Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 6 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 2.4. Electrical Specifications All values are valid within the recommended operating conditions unless otherwise specified. Symbol Parameter Conditions Min. Typ Max Unit Current consumption Mode = MANUAL Ipwd Converter stopped, pen detection off, SPI listening, OSC stopped 0.4 1 uA Mode = PENDET Ipndt Converter stopped, pen detection activated, device generates interrupt upon detection, SPI listening, OSC stopped 0.4 1 uA Mode =PENTRIG Ipntr Converter stopped, pen detection activated, device starts conversion upon pen detection. SPI listening, OSC stopped 0.4 1 uA Mode=AUTO Iauto Converter stopped, pen detection off, SPI listening, OSC on, timer on 1.5 Operation @8kSPS, VDD=1.8V Iopl 23 50 uA Operation @42kSPS, VDD=3.3V Ioph 105 140 uA uA Digital I/O High-level input voltage VIH 0.8VDD VDD+0.2 V Low-level input voltage VIL VSS-0.3 0.2VDD V VHysLow VDD > 2V 0.05 VDD V VHysHigh VDD < 2V 0.1 VDD V Output Logic High VOH IOH>-2mA 0.8VDD Output Logic Low VOL IOL<2mA 0 Input leakage current LI CMOS input High ESD Input - Output capacitance CX+/BR ,CX-/TL ,CY+/TR , CY-/BL, CAUX 50 pF Input - Output capacitance CNRST , CNIRQ ,CNCS ,CDIN , CDOUT, CSCLK 5 pF Hysteresis 0.4 V 1 uA Table 5. Electrical Specifications Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 7 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET Symbol Parameter Conditions Min. Typ Max Unit 1 ms Startup Power-up time tpor Time between rising edge VDD and rising NIRQ ADC Resolution Ares Offset Aoff Gain error Age Differential Non Linearity Integral Non Linearity 12 bits 1 LSB 0.5 LSB Adnl 1 LSB Ainl 1.5 LSB 5 Ohm At full scale Resistors X+, X-, Y+, Y- resistance Rchn Touch Pad Biasing Resistance Pen detect resistance RPNDT_00 RPNDT = 0 100 kOhm RPNDT_01 RPNDT = 1 200 kOhm RPNDT_10 RPNDT = 2 50 kOhm RPNDT_11 RPNDT = 3 25 kOhm 0.1 uF External components Capacitor between VDD, GND recommendations Cvdd Type 0402, tolerance +/-50% Table 5. Electrical Specifications Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 8 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 2.5. Host Interface Specifications Parameter Symbol Condition Min Typ Max Unit 5000 60 kHz % SPI TIMING SPECIFICATIONS (i) SCLK Clock Frequency Duty Cycle fSCLK duty 40 NCS edge to first SCLK "" TCSS 50 NCS edge to DOUT Low TDCD SCLK High Pulse Width TCKH 80 SCLK Low Pulse Width TCKL 80 Data Setup Time TDS 40 Data Valid to SCLK Hold Time TDH 70 Data Output Delay after SCLK "" TDOD NCS "" to SCLK Ignored TCSI NCS "" to DOUT Hi-Z state TCCZ NCS Hold Time TCSW 100 ns 70 50 90 150 (i) All timing specifications refer to voltage levels (50% VDD, VOH, VOL) defined in Table 6 unless otherwise mentioned. Table 6. Host Interface Specifications 2.6. Host Interface Timing Waveforms tCSW CSN 50%VDD tCSS tCKL tDOD tCKH tCSI 50%VDD SCLK tDH tDS DIN 50%VDD tDCD tCCZ DOUT D11 VOH VOL Figure 4. SPI Timing Waveform Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 9 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 3. Functional Description 3.1. General Introduction This section provides an overview of the SX8653 architecture, device pinout and a typical application. The SX8653 is designed for 4-wire and 5-wire resistive touch screen applications. The touch screen or touch panel is the resistive sensor and can be activated by either a finger or stylus. When the top layer is pressed, it makes contact with the bottom sheet and the touch location can be measured. As shown in Figure 5 with a 4-wire panel, the touch screen coordinates and touch pressure are converted into SPI format by the SX8653 for transfer to the host. The auxiliary input can be used to convert with 12-bit resolution any analog input in the supply range. It can also serves as an external synchronisation input to trig the touchscreen acquisition as described in the Application Information section. VDD SX8653 VDD HOST Control 4-wire touchscreen NIRQ INT AUX/WIPER NRST (DFN only) X-/TL Y+/TR SPI Touch Screen Interface CS OSC SCLK ref+ Y-/BL X+/BR DIO NCS in ADC out ref- Vref Digital Filter SCLK DOUT MISO DIN SPI Interface POR MOSI GND Figure 5. SX8653 with a 4-wire touch screen A 5-wire touchscreen application is shown in Figure 6. The 5-wire top sheet acts as a voltage measuring probe. The measurement accuracy is not affected by damage on this sheet and consequently the reliability is improved. Multitouch and touch pressure measurement are not possible with 5-wire touchscreen. 5-wire touchscreen VDD SX8653 VDD HOST Control NIRQ INT AUX/WIPER Y+/TR SPI Touch Screen Interface OSC SCLK ref+ X+/BR Vref Y-/BL NCS in ADC out ref- Digital Filter DOUT DIN DIO CS SCLK MISO SPI Interface NRST (DFN only) POR X-/TL MOSI GND Figure 6. SX8653 with a 5-wire touch screen Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 10 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 3.2. Device Interface and ESD protection The touch screen controller inputs have been specially designed to provide robust on-chip ESD protection of up to 15kV in both HBM and Contact Discharge. 3.2.1. Touchscreen interface The X+/BR, X-/TL, Y+/TR,Y-/BL, AUX/WIPER are the pins dedicated for the touchscreen interface. It provides the voltage sequence in order to obtain the coordinates and pressure measurement. The five pins are connected to BR, TL, TR, BL, WIPER on a 5-wire touchscreen. They are the electrodes on the 4 corners of the bottom layer of the touchscreen plus the electrode on the top layer. On a 4-wire touchscreen, only 4 electrodes are used: X+,X-,Y+,Y-. The AUX pin is not needed and therefore can be used to convert an analog signal (range GND - VDD) into 12-bit digital value. The touchscreen interface pins are the most exposed pins for an ESD event. As shown in Figure 7, theses pins have internal ESD protection to GROUND and VDD. 3.2.2. Host Interface and Control Pins The SX8653 is a slave device configured via the SPI interface. DIN and SCLK have internal ESD protection to GROUND and VDD. NIRQ provides an interrupt to the host processor when a pen is detected or when channel data is available. The NIRQ pin is an active low, open drain output to facilitate interfacing to different supply voltages and thus requires an external pull-up resistor (1-10 kOhm). The host can reset the chip via the SPI interface or with the dedicated pin NRST. The NRST pin is an active low input with an internal pull-up that provides a hardware reset. NRST and NIRQ pins are protected to GROUND. VDD Power M anagem ent GND X + /B R R chn X -/T L R chn Y + /T R R chn Y - /B L AUX/ W ip e r R chn Touch S c re e n D r iv e r s In te rfa c e MUX A D C NRST C o n tr o l D a t a P r o c e s s in g SPI N IR Q DIN SCLK DOUT NCS Figure 7. ESD protection Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 11 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 4. 4-wire Touch Screen Detailed Description 4.1. Touch Screen Operation A 4-wire resistive touch screen consists of two resistive sheets separated by an insulator (Figure 4.2). t Y ec el Y+ Y+ tro Contact point R3 with the top conductive sheet de shee c tiv e u d n co T op Y+ s Rytot Bo Y- m tto X+ R4 co nd X- t uc e iv e sh et X e le es c tro d YTop conductive sheet before the stylus contact YTop conductive sheet after the stylus contact Figure 8. 4-wire Touch Screen When a pressure is applied on the top sheet with a stylus for example, a connection with the lower sheet is made. The contact point split the Rxtot bottom resistance in the vertical axis into two resistances R1 and R2. In the same way, the Rytot resistance in the horizontal axis of the top sheet is divided into two resistances R3 and R4. Rxtot = R1 + R2 Rytot = R3 + R4 The touchscreen controller imposes a voltage level on X or Y electrodes allowing the detection of the contact position. 4.2. Coordinates Measurement During the touch, the top and bottom touchscreen layers are connected. The resistance between the two sheets is RT. A current coming from the reference voltage goes from X+ to X- to perform the X coordinate measurement. Figure 9 shows the measurement schematics. X+ Y+ R1 + R3 + ADC - Xpos RT Vref - Since the ADC had a high input impedance, no current flows through RT and R3. The positive ADC input is biased with a voltage created by the R1, R2 voltage divider. R2 X- R4 Y- The conversion with the 12 bit ADC gives the X location. Figure 9. Abscissa (X) coordinates measurement R2 Xpos = 4095 -------------------R1 + R2 The Y coordinate is measured in a similar fashion with the measurement setup given in Table 7. R4 Ypos = 4095 -------------------R3 + R4 Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 12 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 4.3. Pressure Measurement The 4-wire touchscreen allows pressure measurement. The contact resistance between the two sheets are a function of the pressure applied on the top sheet. Indeed, the a low pressure applied with the finger will create a small contact area. With a greater pressure, the contact area will be bigger and the RT resistance smaller. The RT contact resistance is therefore an indication of the applied pressure. RT is deducted from Z1 and Z2 measurement. The measurement setup given in Table 7 allows to find Z1 and Z2. R4 z1 = 4095 --------------------------------R1 + R4 + R T R4 + Rt z2 = 4095 --------------------------------R1 + R4 + R T Arranging Z1 and Z2 with Rxtot and Rytot allows the computation of RT. An alternative calculation method is using Xpos and Ypos. Ypos R T = Rytot ------------ 4095 Rytot Y pos R T = ------------------------------- 4095 z2 ----- - 1 z1 4095Xpos ----------- 1 - Rxtot 1 - ------------z1 4095 Measurement Vref + Vref- ADC + X X+ X- Y+ Y Y+ Y- X+ Z1 X+ Y- Y+ Z2 X+ Y- X- Table 7. Measurement setup 4.4. Pen Detection The pen detection circuitry is used to detect a user action on the touchscreen. The contact between the two layers generates an interrupt or starts an acquisition sequence. Doing a pen detection prior to conversion avoids feeding the host with dummy data and saves power. If the touchscreen is powered between X+ and Y- through a resistor RPNDT, no current will flow so long as pressure is not applied to the surface (see Figure 10). When a pressure is applied, a current path is created and brings X+ to the level defined by the resistive divider determined by RPNDT and the sum of R1, RT and R4. RPNDT Y+ + Vref - X+ R3 RT R1 R4 R2 Y- Sb Q Rb Q IRQ X- Internal logic Figure 10. 4-wire pen detection circuitry RPNDT should be set to the greatest value of 200 kOhm for optimal detection (see Table 16). Increasing PowDly settings can also improve the detection on panel with high resistance. The pen detection will set the PENIRQ bit of the RegStat register. The PENIRQ bit will be cleared and the NIRQ will be deasserted as soon as the host reads the status register. In PENDET mode, the pen detection will set NIRQ low. Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 13 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 4.5. Double touch measurement The simplified model for double touch on the touchscreen is given in Figure 11. Two fingers on the touchscreen create two contacts between the touchscreen top and bottom layer. The two contacts have the resistance Rt1 and Rt2. X+ The two contact points split Rxtot and Rytot on the horizontal and vertical axis. Then we have R1, R2 and R3 on the top plate and R4, R5 and R6 on the bottom plate. Y+ R1 Rxtot = R1 + R2 + R3 Rytot = R4 + R5 + R6 R4 Rt1 R2 R5 The determination of theses resistances is a complex task. The SX8653 allows to measure Rx and Ry which is a combination of theses resistances. With a S/W running in the host, it is possible to detect the gesture described in the section Multi-Touch Gestures with 4-wire touchscreen. Rt2 R3 R6 X- Y- Figure 11. Touchscreen model for double touch To get the best gesture detection, the resistor RmSelX and RmSelY should be set according to the panel resistance and the Table 8. Y Panel resistance (Ohm) RmSelY X Panel resistance (Ohm) RmSelX 100 to 187 000 100 to 187 000 188 to 312 001 188 to 312 001 313 to 938 010 313 to 938 010 939 to 1875 011 939 to 1875 011 1876 to 4375 100 1876 to 4375 100 4376 to 9375 101 4376 to 9375 101 9376 to 18780 110 9376 to 18780 110 Larger than 18780 111 Larger than 18780 111 Table 8. RmSelX and RmSelY resistance selection Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 14 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 5. 5-wire Touch Screen Detailed Description 5.1. Touch Screen Operation As the 4-wire, the 5-wire resistive touch screen consists of two resistive sheets separated by an insulator (Figure 12). The main difference is that the 4 wires are connected on the 4 corners of the bottom conductive sheet. They are referred as Top Left, Top Right, Bottom Left, Bottom Right. Top W ip e The fifth wire is embedded in the top sheet and is used for sensing the electrode voltage and is referred as the wiper. cond u c ti v e e she t TR r a t io a r is L in e a t t e r n p TL n BR BL B o tt o m u c ti cond ee ve sh t Figure 12. 5-wire touchscreen 5.2. Coordinates Measurement When the electrodes TL is connected with BL and TR with BR, they form with the linearization pattern 2 electrodes bars which are very similar to the X electrodes in a 4-wire touchscreen. In the same way, the association of TL with TR and BL with BR create Y electrodes. The four corners are therefore able to produce voltage gradients in the horizontal and vertical axis. The wiper is connected to the high input impedance of the ADC. When a pressure is applied on the top sheet, the contact point split the bottom sheet resistance into R1 and R2 on the X axis and R3 and R4 on the Y axis. The X and Y position converted by the 12-bit ADC gives the following result. R2 Xpos = 4095 -------------------R1 + R2 R4 Ypos = 4095 -------------------R3 + R4 5.3. Pen Detection The BR pin is connected to the positive pin of the reference voltage through RPNDT. The wiper panel is grounded at the AUX/WIPER pin to provide the grounding path for a screen touch event. The BR pin is monitored to detect voltage drop. When a pressure is applied on the top surface, a current path is created between the two layers and the PENIRQ bit of the RegStat register will be set. RPNDT should be set to the greatest value of 200 kOhm for optimal detection (see Table 16). Increasing PowDly settings can also improve the detection on panel with high resistance. In PENDET mode, the pen detection will set NIRQ low. R PNDT BR + Vref - Bottom layer Sb R1 Rb Top layer AUX/ WIPER Q - Q Internal logic Figure 13. 5-wire pen detection circuitry Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 15 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 6. Data Processing The SX8653 offers 4 types of data processing which allows the user to make trade-offs between data throughput, power consumption and noise rejection. The parameter FILT is used to select the filter order Nfilt as seen in Table 9. The sn samples from the ADC can be averaged. The processed cn 12-bit value is then send through the SPI bus. The noise rejection will be improved with a high order to the detriment of the power consumption. The K coefficient in Table 9 is a filter constant. Its value is K=4079/4095. FILT Nfilt Explanation 0 1 No average 1 3 3 ADC samples are averaged 2 5 5 ADC samples are averaged 3 7 7 ADC samples are sorted and the 3 center samples are averaged Processing sn = cn 1 s n = --- K ( c n + c n - 1 + c n - 2 ) 3 1 s n = --- K ( c n + c n - 1 + c n - 2 + c n - 3 + c n - 4 ) 5 c max1 c max2 c a c b c c c min1 c min2 1 s n = --- K ( c a + c b + c c ) 3 Table 9. Filter order 7. Power-Up, Reset During power-up, NIRQ pin is kept low, the POR reset all registers and states of the SX8653. The SX8653 is not accessible and SPI communications are ignored. As soon as NIRQ rises, the SX8653 is in manual mode with only the SPI peripheral enabled to minimize power consumption. The host can reset the SX8653 by setting the NRST pin low or via the SPI bus. Writing the code 0xDE to the register RegSoftReset reset the circuit. When NRST is driven LOW by the host, NIRQ will be driven low by the SX8653. After the reset NIRQ will be released by the SX8653. voltage VDD VDD/2 time voltage t POR NIRQ time Figure 14. Power-up, NIRQ 8. Modes of Operation The SX8653 has four operation modes that are configured using the SPI commands as defined in Table 14 and Table 16. These 4 modes are: manual (command `MANAUTO' and RATE=0), automatic (command `MANAUTO' and RATE>0), pen detect (command `PENDET'), pen trigger mode (command `PENTRG'). Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 16 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET In the PENDET mode the pen detection is activated. The SX8653 will generate an interrupt (NIRQ) upon pen detection and set the PENIRQ bit in the SPI status register. To quit the PENDET mode the host needs to configure the manual mode. In the PENTRG mode the pen detection is activated and a channel conversion will start after the detection of a pen. The SX8653 will generate an interrupt (NIRQ) upon pen detection and set the CONVIRQ bit in the SPI status register. To quit the PENTRIG mode the host needs to configure the manual mode. The PENTRG mode offers the best compromise between power consumption and coordinate throughput. 8.1. MANual Mode In manual mode (RATE=0), the host sequences all the actions by the SPI commands described in Table 10. When a command is received, the SX8653 executes the associated task and waits for the next command. Command Action CONVERT(CHAN) Select and bias a channel Wait for the programmed settling time (POWDLY) Start conversion Select and bias a channel SELECT(CHAN) Table 10. CONVERT and SELECT command The channel can be biased for an arbitrary amount of time by first sending a SELECT command and then a CONVERT command once the settling time requirement is met. The SELECT command can be omitted if the large range of POWDLY settings cover the requirements. In the latter case, the CONVERT command alone is enough to perform an acquisition. With CHAN=SEQ, multiple channels are sampled. This requires programming the POWDLY field in register RegCTRL0. The selected channel will be powered during POWDLY before a conversion is started. The channel bias is automatically removed after the conversion has completed. 8.2. AUTOmatic mode In automatic mode (RATE > 0), SX8653 start the acquisition when a touch is detected. It converts all the channels selected with RegChnMsk and set NIRQ low when it is finished. After the host has read the channels, if CONDIRQ=1 and the touch is detected again, the SX8653 starts a new conversion cycle. To not loose data, the SX8653 does not begin conversion before the host read all the channels. We can define the time ts between the start of the conversion and the end of the channels reading by the host. The rate programmed is achieved if ts<1/RATE otherwise the new rate is 1/ts. When the control CONDIRQ bit (see register RegStat Table 16) is set to `1' then the interrupts will only be generated if the pen detect occurred. This result in a regular interrupt stream, as long as the host performs the read channel commands, and the screen is touched. When the screen is not touched, interrupts does not occur. If the control CONDIRQ bit is cleared to `0', the interrupts will be always generated. In case there is no pen detected on the screen then the coordinate data will be qualified as invalid, see section [9.5]. This result in a regular interrupt stream as long as the host performs the read channel commands, This working is illustrated in Figure 17. Figure 15 shows the SPI working in automatic mode with CONDIRQ=1. After the first sentence send through the SPI to make the initialization, traffic is reduced as only reads are required. Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 17 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET The processing time is the necessary time for the SX8653 to makes the pen detection, the settling time (POWDLY) and the conversion of the selected channels. This time increases with the number of channel selected and the filter used. NIRQ interrupt signal notifies the host when the conversions are done. TOUCH NIRQ CS DIN DOUT The host just need to read the channels data to release the interrupt. Read Channel Data CMD Processing time Data from SX8652 Time is 1/ RATE Figure 15. SPI working in AUTO mode 8.3. PENDET Mode The PENDET mode can be used if the host only needs to know if the screen has been touched or not and take from that information further actions. When pen detect circuitry is triggered the interrupt signal NIRQ will be generated and the status register bit `PENIRQ' will be set. The bit is cleared by reading the status register RegStat. The PENDET working is illustrated in Figure 17. 8.4. PENTRIG Mode The PENTRIG mode offers the best compromise between power consumption and coordinate throughput. In this mode the SX8653 will wait until a pen is detected on the screen and then starts the coordinate conversions. The host will be signaled only when the screen is touched and coordinates are available. The flowchart is describes in Figure 17. The coordinate rate in pen trigger mode is determined by the speed of the host reading the channels and the conversion times of the channels. The host performs the minimum number of SPI commands in this mode. The host has to wait for the NIRQ interrupt to make the acquisition of the data. TOUCH NIRQ CS DIN DOUT Read Channel Data CMD Data from SX8652 Conversion time The SPI working is illustrated in Figure 16. Figure 16. SPI working in PENTRIG mode Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 18 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET yes AUTO MODE PENDET MODE CONDIRQ=1 ? Touch Detected ? PENTRIG MODE no no yes yes Touch Detected ? Touch Detected ? Set interrupt NIRQ=0 Start channel conversion no RegStat read yes Set timer=RATE Start timer Start channel conversion Release Interrupt NIRQ=1 All conversion finished Set interrupt NIRQ=0 All channel data read All conversion finished Release Interrupt NIRQ=1 Set interrupt NIRQ=0 All channel data read Release Interrupt NIRQ=1 Timer expire Figure 17. AUTO, PENDET and PENTRIG Mode Flowchart Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 19 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 9. Host Interface The host interfaced is composed of a SPI bus. It performs the read/ write operations on the registers and channels data. 9.1. SPI Read/Write Registers The WRITE command allows the host to write a single or multiple registers in the SX8653. The host can read single or multiple registers from the SX8653 by the READ command. This is defined in Table 11. W/R command name CR(7:0) 4 3 Function 7 6 5 WRITE(RA) 0 0 0 RA(4:0) Write register (see Table 15 for RA) READ(RA) 0 1 0 RA(4:0) Read register (see Table 15 for RA) Table 11. 2 1 0 W/R commands 9.2. SPI Reading Channel Data Five channels can be sampled by the SX8653: X, Y, Z1, Z2 and AUX. They are defined in Table 13. They can be converted in sequence with the RegChanMsk register. The READCHAN command allows the host to read the data obtained after the channels conversion and processing. W/R command name READCHAN 7 6 5 CR(7:0) 4 3 2 1 0 0 0 1 x x x x Table 12. Channel x Function Read data from channel Read Channels Data CHAN(2:0) 2 1 0 Function X 0 0 0 X channel Y 0 0 1 Y channel Z1 0 1 0 First channel for pressure measurement Z2 0 1 1 Second channel for pressure measurement AUX 1 0 0 Auxiliary channel RX 1 0 1 Double touch RX measurement RY 1 1 0 Double touch RY measurement SEQ 1 1 1 Channel sequentially selected from RegChanMsk register, (see Table 16) Table 13. Channel definition The channel data are 12-bit of unsigned format which corresponds to integers between 0 and 4095. This is send on two bytes, MSB first then LSB. A mask with the value 0x0FFF (4095) must be done to filter the four first unknown bit. When a channel data has been transmitted, the next one is sent in the successive order: X,Y, Z1, Z2 and AUX. If a channel has not been converted, the data is not transmitted. When the channel data buffer gets empty, the data will carry an invalid data as explained in the channel data format. Remark: After a conversion sequence, it is possible to read only one time the same channel. Example: the SX8653 is set to convert X and Y. The value 0xC0 is set in RegChanMsk. The first byte read after the READCHAN command will be X(MSB), then X(LSB), Y(MSB) and at the end Y(LSB). If the host carry on the reading, it will get invalid data. Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 20 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 9.3. SPI Host Commands .The host can issue commands to change the operation mode or perform manual actions as defined in Table 14. command name 7 6 5 CR(7:0) 4 3 SELECT(CHAN) 1 0 0 0 x CONVERT(CHAN) 1 0 0 1 x MANAUTO 1 0 1 1 x Function 2 1 0 CHAN(2:0) Bias channel (see Table 13 for CHAN) CHAN(2:0) x x Bias channel (see Table 13 for CHAN) x Enter manual or automatic mode. PENDET 1 1 0 0 x x x x Enter pen detect mode. PENTRG 1 1 1 0 x x x x Enter pen trigger mode. Table 14. Host Commands 9.4. SPI implementation and multiple Read/Write The SPI implemented on the SX8653 is set to the common setting CPOL=0 and CPHA=0 which means data are sampled on the rising edge of the clock, and shifted on the falling one. The default state of the clock when NCS gets asserted is low. If a host send a command while the system is busy, the command is discarded. The SPI protocol is designed to be able to do multiple read/write during a transaction. During one single operation, as long as NCS stay asserted, the register address is automatically increased to allow sequential read/write (or sequential retrieval of data). Between each different operation though (READ/WRITE/READCHAN), the communication should be restarted. This is described in Figure 18. Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 21 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET Writing Register NCS Single Write Multiple Write SCLK DIN RA[4:0] 0 0 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 DOUT Reading Register NCS Single Read Multiple Read SCLK DIN RA[4:0] 0 1 0 DOUT 7 6 5 4 3 2 1 0 Reading Channel Data NCS 7 6 5 4 3 2 1 0 Single Read Multiple Read SCLK DIN 0 0 1 DOUT 11 10 9 8 7 6 5 4 3 2 1 0 11 10 9 8 7 6 5 4 3 2 1 0 Other command NCS SCLK DIN Unknown bit CMD Single access DOUT Multiple access Figure 18. Data channel format 9.5. Invalid Qualified Data The SX8653 returns 0xFFFF data in case of invalid qualified data. This occurs: When the SX8653 has read all the channel data in the FIFO When a conversion is done without a pen being detected. Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 22 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 9.6. Register Map Register Address RA(4:0) Register Description 0 0000 RegCtrl0 Write, Read 0 0001 RegCtrl1 Write, Read 0 0010 RegCtrl2 Write, Read 0 0011 RegCtrl3 Write, Read 0 0100 RegChanMsk Write, Read 0 0101 RegStat Read 1 1111 RegSoftReset Write Table 15. Register address The details of the registers are described in the next sections. Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 23 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 9.7. SX8653 register Register Bit Default Description Set rate in coordinates per sec (cps) ( 20%) If RATE =0: Manual mode. if RATE >0: Automatic mode 7:4 0000 RATE RegCtrl0 0000: Timer disabled -Manual mode 0001: 10 cps 0010: 20 cps 0011: 40 cps 0100: 60 cps 0101: 80 cps 0110: 100 cps 0111: 200 cps 1000: 300 cps 1001: 400 cps 1010: 500 cps 1011: 1k cps 1100: 2k cps 1101: 3k cps 1110: 4k cps 1111: 5k cps Conversion (or first conversion when filtering is enabled) settling time ( 10%) 3:0 7:6 0000 00 POWDLY AUXAQC 0000: Immediate (0.5 us) 0001: 1.1 us 0010: 2.2 us 0011: 4.4 us 0100: 8.9 us 0101: 17.8 us 0110: 35.5 us 0111: 71.0 us 1000: 0.14 ms 1001: 0.28 ms 1010: 0.57 ms 1011: 1.14 ms 1100: 2.27 ms 1101: 4.55 ms 1110: 9.09 ms 1111: 18.19 ms 00: AUX is used as an analog input (4wire only) 01: On rising AUX edge, wait POWDLY and start acquisition 10: On falling AUX edge, wait POWDLY and start acquisition 11: On rising and falling AUX edges, wait POWDLY and start acquisition The AUX trigger works only in manual mode with 4-wire touchscreen 5 1 CONDIRQ Enable conditional interrupts 0: interrupt always generated at end of conversion cycle. If no pen is detected the data is set to `invalid qualified'. 4 0 SCREEN Select the type of screen: 0: 4-wire 1: 5 -wire 10: 50 kOhm 11: 25 kOhm RegCtrl1 RegCtrl2 1: interrupt generated when pen detect is successful 3:2 00 RPDNT Select the Pen Detect Resistor 00: 100 kOhm 01: 200 kOhm 1:0 00 FILT Digital filter control 00: Disable 01: 3 sample averaging 10: 5 sample averaging 11: 7 sample acquisition, sort, average 3 middle samples 7:4 0 don't care Settling time while filtering ( 10%) 0000: Immediate (0.5 us) 0001: 1.1 us 0010: 2.2 us 0011: 4.4 us 0100: 8.9 us 0101: 17.8 us 0110: 35.5 us 0111: 71.0 us 1000: 0.14 ms 1001: 0.28 ms 1010: 0.57 ms 1011: 1.14 ms 1100: 2.27 ms 1101: 4.55 ms 1110: 9.09 ms 1111: 18.19 ms 3:0 0000 SETDLY Table 16. SX8653 Register Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 24 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET Register Bit Default 7:6 RegCtrl3 RegChanMsk 0 Description don't care 5:3 RmSelY Check Table 8 2:0 RmSelX Check Table 8 7 1 XCONV 0: no sample 1: Sample X channel 6 1 YCONV 0: no sample 1: Sample Y channel 5 0 Z1CONV 0: no sample 1: Sample Z1 channel 4 0 Z2CONV 0: no sample 1: Sample Z2 channel 3 0 AUXCONV 0: no sample 1: Sample AUX channel 0 0 RXCONV 0: no sample 1: Sample RX channel 0 0 RYCONV 0: no sample 1: Sample RY channel 0 0 don't care Host writing to this register is ignored. RegStat RegSoftReset 7 0 CONVIRQ 0: no IRQ pending 1: Conversion sequence finished IRQ is cleared by the channel data read command 6 0 PENIRQ Operational in pen detect mode 0: no IRQ pending 1: Pen detected IRQ pending IRQ is cleared by the RegStat reading 5 1 RSTEVENT A reset event has occurred 4:0 00000 7:0 0x00 don't care Writing 0xDE to this register reset the SX8653 Any other data will not affect the SX8653 Table 16. SX8653 Register 10. Application Information This section describes in more detail application oriented data. 10.1. Acquisition Setup Prior to an acquisition, the SX8653 can be setup by writing the control registers. Registers are written by issuing the register write command. They can be read by issuing the read command. Please refer to the section [9.7]. 10.2. Channel Selection The SX8653 can be setup to start a single channel conversion or to convert several channels in sequence. For a single conversion, the channel to be converted is determined from the CHAN(2:0) field in the command word (defined in Table 13). Several channels defined in RegChanMsk can be acquired sequentially by setting the CHAN(2:0) field to SEQ. The channels will be sampled in the order X, Y, Z1, Z2, AUX. 10.3. Noise Reduction A noisy environment can decrease the performance of the controller. For example, an LCD display located just under the touch screen can adds a lot of noise on the high impedance A/D converter inputs. 10.3.1. POWDLY Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 25 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET In order to perform correct coordinates acquisition properly, some time must be given for the touch screen to reach a proper level. It is a function of the PCB trace resistance connecting the SX8653 to the touchscreen and also the capacitance of the touchscreen. We can define tau as the RC time constant. POWDLY duration should be programmed to 10 tau to reach 12 bit accuracy. Adding a capacitor from the touch screen drivers to ground is a solution to minimize external noise but it increases settling time and consequently the power consumption. 10.3.2. SETDLY A best method to filter noise is described in section [6] (Data processing). When filtering is enabled, the channel will be biased initially during a time of POWDLY for the first conversion. The parameter SETDLY sets the settling time between the subsequent conversions in a filter set. In most applications, SETDLY can be set to 0. In applications with a high tau and where accuracy of 1LSB is required SETDLY should be increased. 10.4. AUX Input - 4-wire touchscreen only The AUX input can be used to sample an analog signal in the range 0-VDD. For system supply by battery, the battery voltage can be monitored for example. The conversion is done in sequence with the touchscreen acquisition therefore the sample rate is defined with RegCtrl0 in AUTO mode. The AUX pin can also triggered conversions. A rising edge, a falling edge or both applied on the AUX pin can trigger the conversion. This is defined by AUXACQ in RegCtrl1. This method can be used to sample touchscreen when there is noise-free periods. 10.5. Interrupt Generation An interrupt (NIRQ=0) will be generated: During the power-up phase or after a reset After a touch on the panel being detected in PENDET mode. PENIRQ (bit [6] of RegStat) will be set at the same time. After completion of a conversion in MANUAL, PENTRIG or AUTO mode. CONVIRQ (bit [7] of RegStat) will be set at the same time. The NIRQ will be released and pulled high(NIRQ=1) by the external pull-up resistor: When the power-up phase is finished When the host read all channels data that were previously converted by the SX8653 in MANUAL, PENTRIG or AUTO mode. CONVIRQ will be cleared at the same time. When the host read the status register in PENDET mode. PENIRQ, will be cleared at the same time. An active NIRQ (low) needs to be cleared before any new conversions will occur. 10.6. Coordinate Throughput Rate The coordinate throughput rate depends on the following factors: The SPI communication time: Tcom The conversion time: Tconv 1 The coordinate rate is the frequency to get the X, Y, Z1 and Z2 coordinate: CoordRate = ------------------------------T com + T conv 10.6.1. SPI Communication Time The minimum time to read the channel data in PENTRIG mode is: T com = ( 8 + 16 x N chan ) x T SPI The highest throughput will be obtained with a SPI frequency of 5MHz when the host read the channel data as quickly as possible after the NIRQ falling edge. Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 26 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 10.6.2. Conversion Time The maximum possible throughput can be estimated with the following equation T conv = 47 T osc + N chan [ POWDLY + SETDLY ( N filt - 1 ) + T osc ( 21N filt + 1 ) ] with: Nfilt = {1,3,5,7} based on the order defined for the filter FILT (see Figure 9). Nchan = {1,2,3,4,5,6,7} based on the number of channels defined in RegChanMsk POWDLY = 0.5us to 18.19ms, settling time as defined in RegCtrl0 SETDLY = 0.5us to 18.19ms, settling time when filtering as defined in RegCtrl2 Tosc is the oscillator period (555ns +/- 15%) Table 17 gives some examples of Coordinate Rate and Sample Rate for various setting in PENTRIG mode. Nch [1..5 ] Nfilt [1 3 5 7] PowDly [uS] SetDly [uS] 2 1 0.5 - 2 3 71 4 3 140 Tconv [uS] Tcomm [uS] CoordRate [kSPS] 51 8 16.7 0.5 190 8 5.0 0.5 740 14 1.3 Table 17. Coordinate throughput examples 10.7. ESD event In case of ESD event, the chip may reset to protect its internal circuitry. The bit RSTEVENT indicates that a reset event has occurs.ESD event may trig the pen detection circuitry. In this case wrong data will be send to the host. To detect this false coordinates on 4-wire touchscreen, Z1 and Z2 can be read. The conditions Z1<LowThreshold and Z2>HighThreshold may indicate an ESD event. The values LowThreshold and HighThreshold are given for indication only on the table below and should be fine tune according to the system. LowThreshold HighThreshold 10 4070 Table 18. Threshold to detect false coordinates Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 27 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 11. Multi-Touch Gestures with 4-wire touchscreen 11.1. Zoom Gesture A simple thumb and forefinger "pinch" movement that enables a user to enlarge objects onscreen (moving fingers away from each other) or make them smaller (move them towards each other). This intuitive zooming function replaces the standard point-andclick functionality of a mouse and provides far greater accuracy to the user. Figure 19. Zoom gesture 11.2. Rotate Gesture Rotate objects onscreen by making simple clockwise (right) or counterclockwise (left) movements with the anchored thumb and forefinger. This multi-touch function enables swift and accurate positioning of objects without needing to point and click repeatedly on a rotate left-right function button in order to achieve the desired effect. Figure 20. Rotate gesture Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 28 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 12. Packaging Information 12.1. DFN Package A B D DIMENSIONS MILLIMETERS MIN NOM MAX DIM PIN1 INDICATOR (LASER MARK) A A1 A2 b D D1 E E1 e L N aaa bbb E A SEATING PLANE aaa C A1 A2 0.80 0.70 0.00 0.02 0.05 - (0.20) 0.18 0.25 0.30 3.90 4.00 4.10 3.05 3.20 3.30 2.90 3.00 3.10 1.55 1.70 1.80 0.50 BSC 0.30 0.40 0.50 14 0.08 0.10 C LxN D1 1 2 E/2 E1 N bxN e bbb C A B D/2 NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS. Figure 21. DFN Package Outline Drawing DIMENSIONS DIM C G H K P X Y Z MILLIMETERS (2.90) 2.20 1.70 3.30 0.50 0.30 0.70 3.60 NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. 3. THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD SHALL BE CONNECTED TO A SYSTEM GROUND PLANE. FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR FUNCTIONAL PERFORMANCE OF THE DEVICE. Figure 22. DFN Package Land Pattern Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 29 www.semtech.com SX8653 Multitouch 15kV ESD protection 4-Wire / 5-Wire Resistive Touchscreen Controller with SPI Interface ADVANCED COMMUNICATIONS & SENSING DATASHEET 12.2. WLCSP Package B 1.50.10 A INDEX AREA A1 CORNER 2.00.10 0.10 C 0.625 Max. 0.250.02 SEATING PLANE C 1.00 0.08 C 0.50 D 0.50 C 1.50 B 0.25 A 1 2 3 12X O0.3150.03 0.05 C A B NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS Figure 23. WLCSP Package Outline Drawing 1.00 0.50 0.50 0.25 1.50 12X O0.25 NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS 2. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. Figure 24. WLCSP Land Pattern of WLCSP Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 30 www.semtech.com SX8653 DATASHEET ADVANCED COMMUNICATIONS & SENSING (c) S e m te c h 2 0 1 0 A ll rig h ts re s e rv e d . R e p ro d u c tio n in w h o le o r in p a rt is p ro h ib ite d w ith o u t th e p rio r w ritte n c o n s e n t o f th e c o p y rig h t o w n e r. T h e in fo rm a tio n p re s e n te d in th is d o c u m e n t d o e s n o t fo rm p a rt o f a n y q u o ta tio n o r c o n tra c t, is b e lie v e d to b e a c c u ra te a n d re lia b le a n d m a y b e c h a n g e d w ith o u t n o tic e . N o lia b ility w ill b e a c c e p te d b y th e p u b lis h e r fo r a n y c o n s e q u e n c e o f its u s e . P u b lic a tio n th e re o f d o e s n o t c o n v e y n o r im p ly a n y lic e n s e u n d e r p a te n t o r o th e r in d u s tria l o r in te lle c tu a l p ro p e rty rig h ts . S e m te c h a s s u m e s n o re s p o n s ib ility o r lia b ility w h a ts o e v e r fo r a n y fa ilu re o r u n e x p e c te d o p e ra tio n re s u ltin g fro m m is u s e , n e g le c t im p ro p e r in s ta lla tio n , re p a ir o r im p ro p e r h a n d lin g o r u n u s u a l p h y s ic a l o r e le c tric a l s tre s s in c lu d in g , b u t n o t lim ite d to , e x p o s u re to p a ra m e te rs b e y o n d th e s p e c ifie d m a x im u m ra tin g s o r o p e ra tio n o u ts id e th e s p e c ifie d ra n g e . S E M T E C H P R O D U C T S A R E N O T D E S IG N E D , IN T E N D E D , A U T H O R IZ E D O R W A R R A N T E D T O B E S U IT A B L E F O R U S E IN L IF E -S U P P O R T A P P L IC A T IO N S , D E V IC E S O R S Y S T E M S O R O T H E R C R IT IC A L A P P L IC A T IO N S . IN C L U S IO N O F S E M T E C H P R O D U C T S IN S U C H A P P L IC A T IO N S IS U N D E R S T O O D T O B E U N D E R T A K E N S O L E L Y A T T H E C U S T O M E R 'S O W N R IS K . S h o u ld a c u s to m e r p u rc h a s e o r u s e S e m te c h p ro d u c ts fo r a n y s u c h u n a u th o riz e d a p p lic a tio n , th e c u s to m e r s h a ll in d e m n ify a n d h o ld S e m te c h a n d its o ffic e rs , e m p lo y e e s , s u b s id ia rie s , a ffilia te s , a n d d is trib u to rs h a rm le s s a g a in s t a ll c la im s , c o s ts d a m a g e s a n d a tto rn e y fe e s w h ic h c o u ld a ris e . A ll re fe re n c e d b ra n d s , p ro d u c t n a m e s , s e rv ic e n a m e s a n d tra d e m a rk s a re th e p ro p e rty o f th e ir re s p e c tiv e o w n e rs . Contact information Semtech Corporation Advanced Communications & Sensing Products E-mail: sales@semtech.comacsupport@semtech.comInternet: http://www.semtech.com USA 200 Flynn Road, Camarillo, CA 93012-8790. Tel: +1 805 498 2111 Fax: +1 805 498 3804 FAR EAST 12F, No. 89 Sec. 5, Nanking E. Road, Taipei, 105, TWN, R.O.C. Tel: +886 2 2748 3380 Fax: +886 2 2748 3390 EUROPE Semtech Ltd., Units 2 & 3, Park Court, Premier Way, Abbey Park Industrial Estate, Romsey, Hampshire, SO51 9DN. Tel: +44 (0)1794 527 600 Fax: +44 (0)1794 527 601 ISO9001 CERTIFIED Revision V1.0/October 2010 (c)2010 Semtech Corp. Page 31 www.semtech.com