[AK4185] AK4185 Low Power Touch Screen Controller with SPI™ Interface GENERAL DESCRIPTION The AK4185 is a 4-wire/ 5-wire resistive touch screen controller that incorporates 12bit SAR A/D converter. The AK4185 operates down to 1.6V supply voltage in order to connect a low voltage microprocessor. The AK4185 can detect the pressed screen location by performing two A/D conversions and it can also measure touch pressure. The AK4185 is the best fit for cellular phone, DSC, DVC, smart phone, or other portable devices. FEATURES 4-wire or 5-wire Touch Screen Interface SPITM Serial Interface 12bit SAR A/D Converter with S/H circuit Sampling Frequency: 300Ksps Pen Pressure Measurement (4-wire) Continuous Read Function (External Clock Mode) Integrated Internal Osc (Sequence Mode) Low Voltage Operation: VDD = 1.6V ~ 3.6V PENIRQN Buffer Output Low Power Consumption: 240μA at 1.8V Auto Power Down Package: 12pin CSP (1.96mm x 1.46mm, pitch 0.5mm) Software Compatible with AK4182A VDD CSN XP/BR YP/TR XN/TL 4/5wire Touch Screen Drivers Interface SPI Serial I/F & Control Logic VREF+ AIN+ SAR MUX ADC AIN- YN/BL DIN SCLK DOUT VREF- IN/ WIPER PENIRQN TEMP Internal Osc VSS Figure 1. Block Diagram SPITM is a registered trademark of Motorola, Inc. MS0954-E-00 2008/05 -1- [AK4185] ■ Ordering Guide AK4185ECB −40 ∼ +85°C 12pin CSP (1.96mm x 1.46mm, 0.5mm pitch) AKD4185 AK4185 Evaluation Board Black Type ■ Pin Layout 3 Top View 2 1 A B C D 3 XP/BR YP/TR XN/TL YN/BL 2 VDD CSN DIN VSS 1 IN/WIPER PENIRQN DOUT SCLK A B C D TOP View MS0954-E-00 2008/05 -2- [AK4185] PIN/FUNCTION No. C2 Pin Name DIN B2 CSN D1 A2 A3 B1 SCLK VDD XP BR YP TR XN TL YN BL VSS IN WIPER PENIRQN C1 DOUT B3 C3 D3 D2 A1 I/O I I I I/O I/O I/O I/O I/O I/O I/O I/O I I O O Function Serial Data Input Data is clocked on the rising edge of SCLK. Must keep “L” while not issuing command. Chip Select Input Enables writing data to registers when CSN = “L”. Serial Clock Input Power Supply and External Reference Input: 1.6V ~ 3.6V Touch Panel X+ Input (4-wire, PANEL bit = “0”) Touch Panel Bottom Right Input (5-wire, PANEL bit = “1”) Touch Panel Y+ Input (4-wire, PANEL bit = “0”) Touch Panel Top Right Input (5-wire, PANEL bit = “1”) Touch Panel X- Input (4-wire, PANEL bit = “0”) Touch Panel Top Left Input (5-wire, PANEL bit = “1”) Touch Panel Y- Input (4-wire, PANEL bit = “0”) Touch Panel Bottom Right Input (5-wire, PANEL bit = “1”) Ground Auxiliary Analog Input (4-wire, PANEL bit = “0”) Top Touch Panel Input (5-wire, PANEL bit = “1”) Pen Interrupt Output (CMOS output) The PENIRQN pin is “L” when touch-screen press is detected and CSN = “H”. This pin is always “H” irrespective of touch-screen press when pen interrupt is not enabled. Serial A/D Data Output Data is clocked at SCLK falling edge. This pin is Hi-Z when CSN keeps “H”. Note 1. All digital input pins (DIN, CSN, SCLK) must not be left floating. MS0954-E-00 2008/05 -3- [AK4185] ■ Handling of Unused Pin The unused I/O pin must be processed appropriately as below. Classification Analog Pin Name IN/WIPER Setting This pin must be open. ABSOLUTE MAXIMUM RATINGS (VSS = 0V (Note 2)) Parameter Symbol min Power Supply VDD -0.3 Input Current, Any Pins except for supply IIN Touch Panel Drive Current IOUTDRV Input Voltage (Note 3) VIN −0.3 Ambient Temperature (power applied) Ta -40 Storage Temperature Tstg -65 max 4.6 ±10 50 VDD+0.3 or 4.6 85 150 Units V mA mA V °C °C Note 2. All voltages with respect to ground. Note 3. XP/BR, XN/TL, YP/TR, YN/TL, IN/WIPER, CSN, DIN and SCLK pins. The maximum value is smaller value between (VDD+0.3)V and 4.6V. WARNING: Operation at or beyond these limits may result in permanent damage to the device. Normal operation is not guaranteed at these extremes. RECOMMEND OPERATING CONDITIONS (VSS = 0V (Note 2)) Parameter Power Supply Symbol VDD min 1.6 typ 1.8 max 3.6 Units V Note 2. All voltages with respect to ground. WARNING: AKEMD assumes no responsibility for the usage beyond the conditions in this datasheet. MS0954-E-00 2008/05 -4- [AK4185] ANALOG CHARACTERISTICS (Ta = -40°C to 85°C, VDD = 1.8V, fSCLK = fs x 16=5.0MHz, 12bit mode) Parameter min A/D Converter Resolution No Missing Codes 11 Integral Nonlinearity (INL) Error Differential Nonlinearity (DNL) Error -2 Offset Error Gain Error Touch Panel Drivers Switch On-Resistance XP, YP XN, YN PENIRQ Pull Up Resistor RIRQ Auxiliary IN Input Input Voltage Range 0 Temperature Measurement Temperature Range -40 Resolution (Note 4) Accuracy (Note 5) Power Supply Current Normal Mode (Internal Oscillator mode) (Note 6) VDD=18V VDD=3.6V Normal Mode (Bus clock mode) PD0 = “0” (Note 7) VDD=1.8V VDD=3.6V Full Power Down (when writing control command with PD0 = “0”) - typ max Units 12 12 ±1 - ±2 +3 ±6 ±4 Bits Bits LSB LSB LSB LSB 5 5 50 - Ω Ω kΩ VDD V 1.2 ±3 85 - °C °C °C 240 340 0 550 800 3 μA μA μA μA μA Note 4. “Ideal” value derived from a theory when VDD = 1.8V. This value according to the supplied VDD voltage is 0.6466 x VDD. Note 5. The typical value has +6°C(typ) offset. Note 6. The signal of 1kHz, 1.6Vpp (-1dB) is input to the IN/WIPER pin, when COUNT bit = “0”, INTERVAL = 0µs and command cycle is 50µs. DOUT CL = 0pF, the current of touch panel drivers is excluded. Note 7. The signal of 1kHz, 1.6Vpp (-1dB) is input to the IN/WIPER pin, when Single Mode for external clock (CONTINUE bit = “0”) and 15 SCLK clock cycles. DOUT CL = 0pF, the current of touch panel drivers is excluded. DC CHARACTERISTTICS (Logic I/O) (Ta=-40°C to 85°C, VDD =1.6V to 3.6V) Parameter Symbol min Digital Input (CSN, SCLK, DIN) “H” level input voltage VIH 0.8xVDD “L” level input voltage VIL Input Leakage Current. IILK -10 Digital Output (DOUT, PENIRQN) VOH VDD-0.4 “H” level output voltage (@ Iout = -250μA) VOL “L” level output voltage (@ Iout = 250μA) Tri-state Leakage Current IOLK All pins except for XP, YP, XN, YN pins -10 XP, YP, XN, YN pins -10 MS0954-E-00 typ max Units - 0.2xVDD 10 V V μA - 0.4 V V - 10 10 μA μA 2008/05 -5- [AK4185] SWITCHING CHARACTERISTICS (Ta=-40°C to 85°C, VDD=1.6V to 3.6V, CL=50pF) Parameter Symbol min Internal OSCILLATOR Clock Frequency fOSC 2.5 Touch Panel (A/D Converter) Throughput Rate fs SCLK frequency fSCLK 30 duty duty 40 Sampling Time (Rin = 600Ω) (Note 8) tTRK 0.6 Conversion Time tCONV CSN edge to First SCLK “↑” tCSS 50 CSN edge to DOUT Tri-State Disabled 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 40 Data Output Delay after SCLK “↓” tDOD CSN “↑” to SCLK Ignored tCSI 50 CSN “↑” to DOUT Hi-Z state tCCZ CSN Hold Time tCSW 150 typ max Units 3.6 5.1 MHz 300 - kHz 50 - 5000 60 12 50 70 90 - KHz % μs 1/fSCLK ns ns ns ns ns ns ns ns ns ns Note 8. The actual tracking periods are 3tSCLK. (tSCLK = 1/fSCLK) tCSW CSN 50%VDD tCKL tCSS tCSI tDOD tCKH SCLK 50%VDD tDH tDS PD0 50%VDD DIN tCCZ tDCD DOUT D11 D10 D0 VOH VOL Figure 2. Timing Diagram MS0954-E-00 2008/05 -6- [AK4185] OPERATION OVERVIEW ■ Function Overview The AK4185 consists of the following blocks: ● 1.6V Successive Approximation Resister (SAR) A/D converter ● 4-wire or 5-wire resistive touch screen controller interface ● Single or Continuous A/D conversion ● SAR A/D Converter conversion clock select function - External Clock (SCLK) - Internal Clock ● SPITM I/F ■ A/D Converter for Touch Screen The AK4185 incorporates a 12bit successive approximation resistor (SAR) A/D converter for position measurement, temperature, and auxiliary input. The architecture is based on capacitive redistribution algorithm, and an internal capacitor array functions as the sample/hold (S/H) circuit. The SAR A/D converter output is a straight binary format as shown below: Input Voltage Output Code FFFH (ΔVREF-1.5LSB)~ ΔVREF FFEH (ΔVREF-2.5LSB) ~ (ΔVREF-1.5LSB) ----------------0.5LSB ~ 1.5LSB 001H 0 ~ 0.5LSB 000H ΔVREF: (VREF+) – (VREF-) Table 1. Output Code The AK4185 can select SCLK of the digital interface and internal clock within oscillator for A/D conversion clock. The full scale (ΔVREF) of the A/D converter depends on the input mode. Position and pen pressure is actually measured by differential mode, then IN and temperature is actually measured by single-ended mode. The AK4185 is controlled by the 8bit serial command on the DIN pin. A/D conversion result is 12bit data output on the DOUT pin. ■ Analog Inputs Analog input is selected via the A2, A1, and A0 bits in the converter register. If the analog inputs are selected to the X, Y, or Z-axis, at differential mode, the full scale (ΔVREF) is the voltage difference between the non-inverting terminal and the inverting terminal of the measured axis (e.g. X-axis measurement: (XP) - (XN)). Analog non-inverting input to A/D converter is the non-inverting terminal of the non-measured axis while the inverting input is the inverting terminal of the measured axis. At single-ended mode, the full scale of A/D converter (ΔVREF) is the external reference voltage (VDD). The analog input of A/D converter (ΔAIN) is the voltage difference between the selected channel (IN, TEMP) and the VSS. In case of external clock mode, tracking time is the period from the falling edge of 5th SCLK to that of 8th SCLK after the detection of START bit during CSN = “L”. If the source impedance of analog input is larger than 600Ω, longer tracking time is required. Then A/D conversion should be started. MS0954-E-00 2008/05 -7- [AK4185] ■ Position Detection of Touch Screen 1. The Position Detection for 4-wire Touch Screen The position on the touch screen is detected by taking the voltage of one axis when the voltage is supplied between the two terminals of another axis. At least two A/D conversions are needed to get the two-dimensions (X/Y-axis) position. VDD VDD X-Plate XP-Driver SW ON XP VREF+ AIN+ VREF XP Y-Plate VREF+ YP ADC X-Plate YP-Driver SW ON AIN+ YP ADC AIN- Y-Plate VREF- AIN- XN XN XN-Driver SW ON YN YN Touch Screen YN-Driver SW ON a) X-Position Measurement Differential Mode b) Y-Position Measurement Differential Mode The X-plate and Y-plate are connected on the dotted line when the panel is touched. X+ X-Plate (Top side) X- Y-Plate (Bottom side) Y- Y+ c) 4-wire Touch Screen Construction Figure 3. Axis Measurements for 4-wire Touch Screen MS0954-E-00 2008/05 -8- [AK4185] 2. The Position Detection for 5-wire Touch Screen A 5-wire touch panel consists of one transparent resistive layer and a top metal contact area separated by insulating spacers. The top layer acts only as a voltage measuring probe, the position detection uses the bottom resistive layer that had metal contacts at the 4 corners. When the top layer is pressed by a pen or stylus, the top layer contacts with the bottom layer. Then the X and Y coordinates is detected. The 5-wire touch screen works properly even with damages or scratches on the top layer, therefore the 5-wire touch panel has higher durability than the 4-wire touch panel. Connect the metal contact of the top layer to the WIPER pin, which connected inside of the AK4185, to AIN+ to measure the Y-axis of current position. The top right and top left contacts at the 4 corners are connected to VDD and the bottom right and bottom left contacts connected to VSS. Then the AK4185 initiates A/D conversion of AIN+ input voltage, and Y-axis position is determined. Terminal X-axis Y-axis SW TL VSS VDD Switch VDD/VSS TR VDD VDD VDD ON/OFF BL VSS VSS VSS ON/OFF BR VDD VSS Switch VDD/VSS Table 2. Driver SW configuration VDD VDD VDD TR SW ON VDD TL SW ON BR SW ON VREF+ BR TR TR SW ON WIPER AIN+ VREF+ ADC AIN+ WIPER ADC TL AIN- VREF TL TR AIN- VREF- BL TL SW ON BR BL SW ON BL BL SW ON BR SW ON a) X-Position Measurement Differential Mode b) Y-Position Measurement Differential Mode The Top layer and Bottom layer are connected on the dotted line when the panel is touched. Detection side (Top layer) ADC WIPER TL BL TR Drive side (Bottom Layer) BR 5-wire Touch Screen Construction Figure 4. Axis Measurements for 5-wire Touch Screen MS0954-E-00 2008/05 -9- [AK4185] ■ Pen Pressure Measurement (Only 4-wire Touch Screen) The touch screen pen pressure can be derived from the measurement of the contact resistor between two plates. The contact resistance depends on the size of the depressed area and the pressure. The area of the spot is proportional to the contact resistance. This resistance (Rtouch) can be calculated using two different methods. The first method is that when the total resistance of the X-plate sheet is already known. The resistance, Rtouch, is calculated from the results of three conversions, X-position, Z1-position, and Z2-position, and then using following formula: R TOUCH = R X -plate ⋅ X Position 4096 ⎛ Z2 ⎞ ⎜⎜ − 1⎟⎟ ⎝ Z1 ⎠ The second method is that when both the resistances of the X-plate and Y-plate are known. The resistance, Rtouch, is calculated from the results of three conversions, X-position, Y-position, and Z1-position, and then using the following formula: R X-plate ⋅ X Position ⎛ 4096 ⎞ ⎛ Y ⎞ ⎜⎜ − 1⎟⎟ − R Y -plate ⋅ ⎜1 - Position ⎟ 4096 ⎝ 4096 ⎠ ⎝ Z1 ⎠ R TOUCH = VDD VDD ON ON YP YP XP VREF+ AIN+ VREF- AIN- touch ADC XP VREF+ AIN+ VREF- AIN- touch ADC XN XN ON ON YN a) YN b) Z1-Position Measurement Differential Mode Z2-Position Measurement Differential Mode Figure 5. Pen Pressure Measurements MS0954-E-00 2008/05 - 10 - [AK4185] ■ Temperature Measurement Equation <1> describes the forward characteristics of the diode. i D = I0 ( ) ⋅e VD VT (VT = kT ) q <1> I0: reverse saturation current q: 1.602189×10-19 (electron charge) k: 1.38054×10-23 (Boltzmann’s constant) VD: voltage across diode T: absolute temperature K The diode characteristic is approximately shown as a diode junction voltage. That is theoretically to the temperature; the ambient temperature can be predicated by knowing this voltage. Temp. Sensor I 80 1 TEMP0 TEMP1 Figure 6. Temperature Measurement As the AK4185 has two different fixed current circuits and a diode (temperature sensor), the temperature can be measured by using two different methods. The first method needs two conversions, but can derive the temperature directly without knowing the voltage at a specific temperature. From equation <1> ⎧ ( V (1)− V (80 ) ) ⎫ ⎛ I ⎞ ⎪ ⎪ ⎨ ⎬ VT ⎛ i D1 ⎞ ⎜ 1 ⎟ ⎪⎩ ⎪⎭ ⎜⎜ ⎟⎟ = ⎜ ⎟ = 80 = e I ⎝ i D0 ⎠ ⎜⎜ ⎟⎟ ⎝ 80 ⎠ q T[ °C ] = ΔVbe ⋅ − 273 k ⋅ In(80) ΔVbe = V(1) − V(80) T[° C ] = 2.648 × 10 3 × ΔVbe − 273 The second method needs only one conversion as the following equation, but requires knowing the junction voltage at the specific temperature. ⎛ k ⎞ VD T = ⎜⎜ ⎟⎟ ⋅ ⎝ q ⎠ In⎛⎜ i D ⎞⎟ ⎝ I0 ⎠ <2> MS0954-E-00 2008/05 - 11 - [AK4185] ■ Digital I/F The AK4185 operates with the microprocessor via SPITM bus. The microprocessor starts to transmit data synchronized with serial clock. The AK4185 operates off of supply voltage down to 1.6V in order to connect a low voltage microprocessor. VDD=1.6V – 3.6V CSN SCLK AK4185 Micro- DIN Processor DOUT PENIRQN 4/5-wire touch panel Figure 7. Digital I/F Standard Sequence: 8bit Control Command However Setup Command (write) writes Setup Function (4bit) after 8bit Control Command. 1. A/D Data Read (1) External Clock Mode (Single Read) D7 DIN S D0 Command Byte D11 DOUT D0 A/D Data (Left justified) 0 Figure 8. Single Read (External Clock Mode) (2) External Clock Mode (Continuous Read) DDLY bit = “0” D7 DIN D0 Command Byte S D11 0 00 0 DOUT D0 D11 00 00 A/D Data (1) D11 D0 00 00 A/D Data (2) D0 A/D Data (n) * In 8bit output mode, the A/D data is LSB justified. Figure 9. Continuous Read (External Clock Mode: DDLY bit = “0”) DDLY bit = “1” D7 DIN D0 Command Byte S D11 0 DOUT D0 A/D Data (1) D11 0 00 0 D11 D0 A/D Data (2) 0 00 0 D0 0 00 A/D Data (n) * * In 8bit output mode, the A/D data is MSB justified. Figure 10. Continuous Read (External Clock Mode: DDLY bit = “1”) (3) Internal Clock Mode (Sequential Mode: X-Y-Z1-Z2) DDLY bit = “0” D7 DIN S D0 Command Byte “0 1 0 1 1 1 1” DOUT 0 00 0 D11 D0 A/D Data (X) D11 00 00 D11 D0 A/D Data (Y) 0 00 0 D0 A/D Data (Z1) D11 00 00 D0 A/D Data (Z2) Figure 11. Sequential Read (Internal Clock Mode: DDLY bit = “0”) MS0954-E-00 2008/05 - 12 - [AK4185] DDLY bit = “1” D7 DIN S D0 Command Byte “0 1 0 1 1 1 1” D11 DOUT 0 D11 D0 A/D Data (X) 0000 D11 D0 0000 A/D Data (Y) D0 A/D Data (Z1) 0000 D11 D0 A/D Data (Z2) 000 Figure 12. Sequential Read (Internal Clock Mode: DDLY bit = “1”) 2. Setup Command * DIN must keep low state for minimum 7SCLK times (9th-15th SCLK) after command is sent on the DIN. (1) Setup Command Write R/W =“0” D3 omm and S C Byte DIN D7 D0 Data D0 4bit Setup Function Figure 13. Setup Command Write (2) Setup Command Read R/W =“1” DIN omm and S C Byte D7 DOUT D0 D3 D0 Data Figure 14. Setup Command Read MS0954-E-00 2008/05 - 13 - [AK4185] ■ Control Command This command can select the touch panel and ADC conversion clock. This 8bit control command includes channel selection, resolution, and power-down mode, and outputs in synchronization of the falling edge of SCLK after CSN = “L”. The AK4185 latches the serial command at the rising edge of SCLK. Refer to the control command of the AK4185 as shown in Table 4. D7 S D6 A2 D5 A1 D4 A0 D3 MODE D2 x1 D1 x2 D0 PD0 Table 3. Command Byte definition (x1, x2: Don’t care) BIT D7 Name S D6-D4 A2-A0 D3 MODE D2 D1 D0 x1 x2 PD0 Function Start Bit. This bit must be “H” because the AK4185 initiates the command recognition. Channel Selection bit. Analog inputs to the A/D converter, the activated driver switches, and the reference voltage are selected. Resolution of A/D converter. 0: 12bit output 1: 8bt output Don’t care Don’t care Power-down Mode. (reference to “ Power-down Control”) Table 4. Control Command definition (1) 4-wire touch panel configuration Channel Selection A2 A1 0 0 0 0 0 1 0 1 1 1 1 1 0 0 1 1 A0 0 1 0 1 0 1 0 1 Status of Driver Switch X-Driver Y-Driver OFF OFF OFF ON XN-ON XN-ON ON OFF OFF YP-ON YP-ON OFF OFF OFF ADC input (ΔAIN) AIN+ AINTEMP0 VSS XP YN XP YN YP IN TEMP1 XN XN XN VSS VSS Reference Voltage (ΔVREF) VREF+ VREFVREF VSS YP YN YP YP XP VREF VREF XN XN XN VSS VSS Note TEMP0 Y-axis Setup Command (Table 7) Z1 (Pressure) Z2 (Pressure) X-axis AIN TEMP1 Ref. Mode SER DFR DFR DFR DFR SER SER Table 5. Control Command List (4-wire) MS0954-E-00 2008/05 - 14 - [AK4185] (2) 5-wire touch panel configuration TR: VDD ON/OFF, BL: VSS ON/OFF Channel Status of ADC input Driver Switch Selection (ΔAIN) A2 A1 A0 TR-Driver BL-Driver AIN+ AIN0 0 0 OFF OFF TEMP0 VSS 0 0 1 ON ON WIPER BL 0 1 0 0 1 1 1 1 1 0 0 1 1 1 0 1 0 1 Reference Voltage (ΔVREF) VREF+ VREFVREF VSS TR BL - ON ON WIPER BL TR BL OFF OFF TEMP1 VSS VREF VSS Note Ref. Mode TEMP0 Y-axis Setup Command (Table 7) Reserved Reserved X-axis Reserved TEMP1 SER DFR DFR SER Table 6. Control Command List (5-wire) (The combination other than above is invalid.) (3) Setup Command configuration BIT D7 Name S D6-D4 D3-D1 A2-A0 Addr D0 R/W Description Start Bit. This bit must be “H” because the AK4185 initiates the command recognition. Setup command. must write “010” Addr Selection (Table 8) “000”: Function 1 (Table 9) “001”: Function 2 (Table 10) “010”: Function 3 (Table 11) “011”: Function 4 (Table 12) “111”: Command of internal clock mode READ/ WRITE 0: Write (When Addr bits = “111”, Sequential Mode is started.) 1: Read (When Addr bits = “111”, A/D data is read out.) Table 7. Setup Command description Setup Command Function Addr NAME D3 D2 00H Function 1 PANEL CONTINUE 01H Function 2 SEQM[2:0] 02H Function 3 INTERVAL[2:0] 03H Function 4 SLEEP[1:0] 04H Reserved 0 0 05H Reserved 0 0 06H Reserved 0 0 07H Command x x Note 9. Do not write “1” data to the bits named “0”. D1 COUNT D0 DDLY 0 0 SEQST[1:0] 0 0 0 0 0 0 x x Table 8. Setup Command List (x: Don’t care.) MS0954-E-00 2008/05 - 15 - [AK4185] Function 1 [R/W]: External Clock Mode and Internal Clock Mode BIT Name Description D3 PANEL Panel type selection. 0: 4-wire (default) 1: 5-wire D2 CONTINUE Read Mode selection. (only External Clock Mode) 0: Single (default) 1: Continuous D1 COUNT ADC Conversion count. 0: 6 times AD conversion (default) 1: 10 times AD conversion D0 DDLY A/D output data format 0: LSB justified. (default) 1: MSB justified. Table 9. Setup Function 1 description Function 2 [R/W]: only Internal Clock Mode BIT Name Description D3-D1 SEQM Sequence Mode 000: X → Y → Z1 → Z2 Scan (only 4-wire Touch Screen) (default) 001: X → Y Scan 010: X Scan 011: Y Scan 100: Z1 → Z2 Scan (only 4-wire Touch Screen) 101: TEMP0 → TEMP1 110: A-IN (only 4-wire Touch Screen) 111: Reserved D0 Reserved Table 10. Setup Function 2 description Function 3 [R/W]: only Internal Clock Mode BIT Name Description D3-D1 INTERVAL Sampling interval times. 000: 0μs (default) 001: 5μs 010: 10μs 011: 20μs 100: 50μs 101: 100μs 110: 200μs 111: 500μs D0 Reserved Table 11. Setup Function 3 description Function 4 [R/W]: External Clock Mode and Internal Clock Mode BIT Name Description D3-D2 SLEEP Sleep Command (Sleep mode is valid after CSN = “H”.) 00: Normal Mode (default) 01: Sleep Mode 1 (PENIRQN disabled and output “H”. Touch Panel is open.) 10: Sleep Mode 2 (PENIRQN disabled and open. Touch Panel is open.) 11: Reserved D1-D0 SEQST Status Bits [Read only] 00: Not Busy 01: Sampling Wait 10: Sequence Busy 11: Data Available Table 12. Setup Function 4 description MS0954-E-00 2008/05 - 16 - [AK4185] ■ Power on Sequence To fix the internal register, send the control command when first power up. It initiates all registers such as PD0 bit and sequence register. The sequence is that 1) Power On with CSN= “H” or “L” then CSN = “H”. 2) Send control command after CSN = “L”. 3) CSN = “H” again. Once sending command to fix the internal register after first power up, the state of the AK4185 is held on the same condition as last command issued. ■ Power-down Control Power-down and pen interrupt function are controlled by PD0 bit. In order to achieve minimum current, it is recommended to set PD0 bit = “0” for automatic power down of the A/D converter after A/D conversion. It is possible to reduce the variation in data by setting PD0 = “1” during measurements. A/D converter keeps power up after every measurement complete. PD0 0 1 Function Auto Power-down Mode A/D converter is automatically powered up at the start of the conversion, and powered down automatically at the end of the conversion. The AK4185 is always powered down at this mode if CSN = “H”. All touch screen driver switches except YN or BL switch are turned off and relative pins are open state. Only YN or BL driver switch is turned ON and forced to VSS in this case. PEN interrupt function is enabled except when in the sampling time and conversion time. ADC ON Mode A/D converter is always powered up while CSN = “L”. If X-axis or Y-axis is selected as analog input, touch screen driver switches are always turned ON and the current flows through the touch plate if CSN = “L”. This is effective if more settling time is required to suppress the electrical bouncing of touch plate. If CSN = “H”, A/D converter is always powered down and touch screen driver switches are always off. (Only YN or BL driver switch is turned ON and forced to VSS.) And while CSN = “H”, PEN interrupt function is enabled. When CSN state sets from “H” to “L”, the input channel and driver switches is set to the last setting. Table 13. Power-down Control ■ Sleep Mode The AK4185 supports sleep mode that puts touch panel to open state and disables pen interrupt function, effective for reducing power consumption caused by unnecessary pen touch. The AK4185 changes to sleep mode when the micro-controller writes to SLEEP1-0 bits of AK4185’s register. After writing the sleep command, this sleep mode starts when the CSN pin is “H”. The AK4185 returns to normal operation out of sleep mode when the CSN pin is “L” and receives the normal control command. 00 CSN = “L” PENIRQN Touch Panel Normal Operation Normal Operation 01 Normal Operation Normal Operation 10 Normal Operation Normal Operation 11 - - SLEEP[1:0] CSN = “H” PENIRQN Touch Panel Normal Operation Normal Operation Disable Open (PENIRQN=H) Disable Open (PENIRQN=Hi-z) - Table 14. Sleep Mode MS0954-E-00 2008/05 - 17 - [AK4185] CONTROL SEQUENCE ■ Touch Screen Controller Control Sequence (External Clock Mode) (1) Single Mode (CONTINUE bit = “0”) The timing of sampling and A/D conversion is shown in Figure 15 and Figure 16. The AK4185 is controlled via 4-wire serial interface (CSN, SCLK, DIN, and DOUT pins). The DOUT pin changes to “L” from Hi-Z state at the falling edge of CSN. The AK4185 latches the 8bit control word serially via the DIN pin at the rising edge of SCLK. The DIN pin must keep low state for minimum 7SCLK times (9th-15th SCLK) after command is sent on the DIN pin. As the AK4185 starts the command decoding at the first “H” bit after CSN = “↓”, MSB (S bit) of the command must be “H”. Tracking time is the period from the falling edge of 5th SCLK to the falling edge of 8th SCLK. The SAR A/D conversion is synchronized with SCLK. The AK4185 outputs 12bit or 8bit A/D data with MSB first via the DOUT pin from the falling edge of 9th SCLK. The AK4185 can output one A/D data per 15 SCLK clock cycles for the fastest way as shown in the dotted line. Please see “Switching Characteristics” for the detail. CSN 1 2 3 4 5 A0 MO 6 8 7 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 SCLK S DIN A2 A1 X1 X2 PD0 Hi-Z 11 10 9 8 7 6 S A2 A1 5 4 3 A0 2 MO X1 1 0 X2 PD0 11 10 DOUT Touch Screen Driver SW (Internal Node) (DFR Mode, PD0 =”0”) Figure 15. External Clock Mode Control Sequence (Single12bit Mode) CSN 1 2 3 4 5 A0 MO 6 8 7 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 SCLK S DIN A2 A1 Hi-Z X1 X2 0 7 6 5 4 3 2 S A2 1 0 A1 A0 MO X1 X2 PD0 7 6 DOUT Touch Screen Driver SW (Internal Node) (DFR Mode, PD0 =”0”) Figure 16. External Clock Mode Control Sequence (Single 8bit Mode) MS0954-E-00 2008/05 - 18 - [AK4185] (2) Continuous Mode (CONTINUE bit = “1”) The timing of sampling and A/D conversion is shown in Figure 17 and Figure 18. The DOUT pin changes to “L” from Hi-Z state at the falling edge of CSN. The AK4185 latches the 8bit control word serially via the DIN pin at the rising edge of SCLK. Tracking time is the period from the falling edge of the 5th SCLK to the falling edge of the 8th SCLK. The SAR A/D conversion is synchronized with SCLK from the falling edge of the 9th SCLK. If DDLY bit = “0”, the AK4185 outputs 12bit A/D data with MSB first from the falling edge of the 12th SCLK. In this mode, the AK4185 continuously outputs A/D data according to the number of times by COUNT bit (6 or 10 times A/D conversion) from the falling edge of the 8th SCLK per 16SCLK cycles. (12bit MSB first, LSB justified) CSN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 9 8 7 6 5 20 21 22 23 2 1 24 25 26 27 28 29 37 38 39 40 41 42 SCLK S DIN A2 A1 A0 MO X1 X2 PD0 Hi-Z 11 10 4 3 0 11 3 2 1 0 11 10 9 8 7 6 5 4 3 2 1 0 DOUT Data 1 Data 2 Data n Touch Screen Driver SW (Internal Node) (DFR Mode, PD0 =”0”) 16SCLK 16SCLK Figure 17. External Clock Mode Control Sequence (Continuous Mode: DDLY bit = “0”) If DDLY bit = “1”, the AK4185 outputs MSB first 12bit A/D data from the falling edge of the 9th SCLK. In this mode, the AK4185 continuously outputs A/D data according to the number of times by COUNT bit (6 or 10 times A/D conversion) from the falling edge of the 9th SCLK per 16SCLK cycles. (12bit MSB first, MSB justified) The A/D data output timing is the same as Single Mode. CSN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 9 8 7 6 5 17 18 19 20 2 1 21 22 23 24 25 26 27 28 29 37 8 0 38 39 40 41 42 SCLK S DIN A2 Hi-Z A1 A0 MO X1 X2 PD0 11 10 4 3 0 11 10 9 11 10 9 8 7 6 5 4 3 2 1 0 DOUT Data 1 Data 2 Data n Touch Screen Driver SW (Internal Node) (DFR Mode, PD0 =”0”) 16SCLK 16SCLK Figure 18. External Clock Mode Control Sequence (Continuous Mode: DDLY bit = “1”) If PD0 bit sets to “1” in continuous mode, A/D converter is powered up between A/D conversions. It helps A/D data variation to decrease. In continuous mode, when the AK4185 is executing the operation, the AK4185 ignores all control commands. The AK4185 can receive the next control command from the rising edge of the 96th SCLK (COUNT bit = “0”) or the 160th SCLK (COUNT bit = “1”). When the next control command is sent at the rising edge of the 97th SCLK (COUNT bit = “0”) or the 161st SCLK (COUNT bit = “1”), the AK4185 can output one A/D data per 16 SCLK clock cycles as well as the continuous mode. MS0954-E-00 2008/05 - 19 - [AK4185] ■ Touch Screen Controller Control Sequence (Internal Clock Mode) When the micro-processor sends the sequence start command (10101110b), the AK4185 starts the internal clock mode. The AK4185 sets the PENIRQN pin to “L” and automatically powers up the internal oscillator. Then the AK4185 executes the sequence that selected by SEQM2-0 bits one by one. When the sequence is finished, the AK4185 sets the PENIRQN pin to “H” and notifies that sequence is ended. After 2.8μs (typ.) is passed from the rising edge of the PENIRQN pin, the internal oscillator is powered down and PEN interrupt function is enabled. The micro-controller can confirm that the A/D conversion data is available by checking the PENIRQN pin or reading the status register (SEQST1-0 bits). The micro-processor sends the read command (10101111b) to read the A/D conversion data. Then the AK4185 outputs the A/D data in order of the register selected by SEQM1-0 bits. When the micro-processor reads data as many as more than the actual data number, the AK4185 outputs a zero data. The A/D data is cleared after reading all the A/D data. Must read the A/D conversion data after confirming the PENIRQN pin turns to “H” or a register status SEQST1-0 = “11”(Data Available). Do not read the A/D conversion data when the data is not available. Pen Touch Sequence Start Set PENIRQN Low Start Clock Driver Set Wait Timer ADC No Count End? Yes Sequence End? No Yes Set PENIRQN High Stop Clock & PenTouch Enable Done Figure 19. Internal Clock Mode Control Flowchart MS0954-E-00 2008/05 - 20 - [AK4185] PENIRQN SCN SCLK S Sequential Mode W DIN S=1 DOUT = “010111” W=0 Hi-Z OSCLK Internal Sequence (SEQM2-0 bits=“001”, X - Y Scan) PEN Touch Wait Tracking, Conversion (X-axis 1st) Tracking, Conversion (X-axis 2nd) Tracking, Conversion (X-axis nth) 20 OSCLK 20 OSCLK 20 OSCLK Tracking, Conversion (Y-axis 1st) Tracking, Conversion (Y-axis nth) 20 OSCLK 20 OSCLK Wait PENIRQN Enable DAV Figure 20. Internal Clock Mode Control Sequence (X-Y Scan: SEQM bits = “001”) (Sequence Mode Start → Internal Sequence Processing → Data Available) PENIRQN SCN SCLK S Sequential Mode R DIN DOUT (DDLY bit=0) DOUT (DDLY bit=1) S=1 Hi-Z Hi-Z DAV = “010111” R=1 0000 0 X-axis 12bit A/D-data X-axis 12bit A/D-data 16 SCLK 0000 000 0 Y-axis 12bit A/D-data Y-axis 12bit A/D-data 000 16 SCLK Figure 21. Internal Clock Mode Control Sequence (X-Y Scan: SEQM bits = “001”) (Data Available → A/D Data Read) The AK4185 can only accept the Register Read and control commands of A2-0, MODE and PD0 bits for the external clock mode, during executing this sequence. The other commands are ignored. The micro-processor can set CSN = “H” during the sequence. However, the AK4185 can accept sequence commands even if the AK4185 is in the sleep mode. When the sleep mode is selected, the AK4185 goes to the sleep mode after the sequence is finished and CSN = “H”. MS0954-E-00 2008/05 - 21 - [AK4185] ■ Pen Interrupt The AK4185 has pen interrupt function to detect the pen touch. Pen interrupt function is enabled at power-down state. The YN pin (4-wire) or BL pin (5-wire) is connected to VSS at the PEN interrupt enabled state. And the XP pin (4-wire) or WIPER pin (5-wire) is pulled up via an internal resistor (RIRQ: typ.50kΩ). PENIRQN is connected the XP pin (4-wire) or WIPER pin (5-wire) inside. If touch plate is pressed by a pen, the current flows via <VDD> - <Ri> - <X+> - <Y-> (4-wire). If 5-wire, via <VDD> - <Ri> - <WIPER> - <BL>. The resistance of the plate is generally 1kΩ or less, PENIRQN is forced to “L” level. If the pen is released, PENIRQN returns “H” level because two plates are disconnected, and the current does not flow via two plates. If the plate is touched with a pen or finger, PENIRQN changes to “L” at CSN = “H” that PENIRQN is normality enable. PENIRQN is disabled during executing internal sequence (please see “■ Touch Screen Controller Control Sequence (Internal Clock Mode)”) and sleep mode is available (please see “■ Sleep Mode”). The operation of PENIRQN is related to PD0 bit. PD0 bit is updated at the rising edge of 8th SCLK (please see “■ Power-down Control” for the detail). Therefore, the last PD0 bit is valid until this timing and during setting the setup command. When CSN is “L”, PENIRQN is disabled during executing internal sequence (please see “■ Touch Screen Controller Control Sequence (Internal Clock Mode)”). i. The period from CSN↓ to the 5th SCLK↓ The behavior of PENIRQN is related to the combination of the last selected analog input channel, and the last PD0 bit. If the last PD0 bit was set to “0”, PENIRQN is “H” while the plate is not pressed and “L” while the plate is pressed regardless of the last analog input. If the last PD0 bit was set to “1”, the last analog input decides the level of PENIRQN. If the last analog input channel is touch screen (X, Y, Z1, Z2 or WIPER), PENIRQN is “L” for all the time in this period regardless of the touched/non-touched state. On the other hand, if the last analog input channel is not touch screen (temperature or auxiliary), PENIRQN is “H” for all the time in this period regardless of the touched/non-touched state. ii. The period from the 5th SCLK↓ to the 20th SCLK↓ on CSN = “L” (8bit Mode: to the 16th SCLK↓) The behavior of PENIRQN is related to the selected analog input and the last PD0 bit. If the current PD0 bit is set to “0” and the touch screen is selected as analog input, PENIRQN is forced to “L” regardless of the touched/non-touched state. If the temperature or auxiliary input is selected as the input channel, PENIRQN is forced to “H” regardless of the touched/non-touched state. If the current PD0 bit is set to “1”, PENIRQN is forced to “H” regardless of the analog input and the touched/non-touched state. iii. The period from the 20th SCLK↓ to CSN↑ (8bit Mode: from the 16th SCLK↓ to CSN↑) The behavior of PENIRQN is related to the combination of the current selected analog input channel, and the current PD0 bit. If the current PD0 bit set “0”, PENIRQN is “H” while the plate is not pressed and “L” while the plate is pressed regardless of the current selected analog input. If the current PD0 bit set “1”, the current analog input decides the operation of PENIRQN. If the current analog input channel is touch screen, PENIRQN is “L” for all the time in this period regardless of the touched/non-touched state. On the other hand, if the current analog input is temperature or auxiliary input, PENIRQN is “H” for all the time in this period regardless of the touched/non-touched state. It is recommended that the micro controller mask the pseudo-interrupts while the control command is issued or A/D data is output. In continuous mode, AK4185 repeats behavior the period from the 5th SCLK↓ to the 21st SCLK↓ after output command. Therefore, it must be noted that PENIRQN is valid only 1SCLK (equivalent the period from the 20th SCLK↓ to the 21st SCLK↓) when PD0 bit is “0”. Generally recommend to execute continuous mode after PD0 bit is set “1”. MS0954-E-00 2008/05 - 22 - [AK4185] PENIRQN VDD VDD RIRQ = VDD EN2 50kΩ XP/WIPER Driver OFF EN1 YN/BL Driver ON Figure 22. PENIRQN Functional Block Diagram (WIPER does not have a driver.) i ii iii CSN 1 2 3 4 5 A0 MO 6 7 8 9 10 11 12 13 14 15 16 9 8 7 6 5 17 18 19 20 21 22 23 24 SCLK DIN S A2 A1 X1 X2 PD0 11 10 4 3 2 1 0 DOUT CONV Internal Figure 23. PENIRQN Functional Timing Chart MS0954-E-00 2008/05 - 23 - [AK4185] SYSTEM DESIGN Figure 24, Figure 25 shows the system connection diagram for the AK4185. The evaluation board [AKD4185] demonstrates the optimum layout, power supply arrangements and measurement results. <4-wire Touch Screen Input> 4-wire Analog Ground Touch Screen Digital Ground 0.01µ * 0.01µ * 0.01µ * 0.01µ * XP YP XN YN Top View Analog Supply 1.6∼3.6V 10µ + 0.1µ VDD IN CSN DIN VSS PENIRQN DOUT SCLK Auxiliary Analog Input µP Figure 24. Typical Connection Diagram Notes: - VSS of the AK4185 should be distributed separately from the ground of external controllers. - All digital input pins (CSN, SCLK, DIN pins) must not be left floating. - The DOUT pin is floating except when communicating with the micro-controller. Therefore, a pull-up or pull-down resistor around 100kΩ must be connected to the DOUT pin of the AK4185. MS0954-E-00 2008/05 - 24 - [AK4185] <5-wire Touch Screen Input> 5-wire Analog Ground Touch Screen Digital Ground 0.01µ * 0.01µ * 0.01µ * 0.01µ * BR TR TL BL Top View Analog Supply 1.6∼3.6V 10µ + VDD CSN DIN VSS WIPER PENIRQN DOUT SCLK 0.1µ 0.01µ * µP Figure 25. Typical Connection Diagram Notes: - VSS of the AK4185 should be distributed separately from the ground of external controllers. - All digital input pins (CSN, SCLK, DIN pins) must not be left floating. - The DOUT pin is floating except when communicating with the micro-controller. Therefore, a pull-up or pull-down resistor around 100kΩ must be connected to the DOUT pin of the AK4185. 1. Grounding and Power Supply Decoupling The AK4185 requires careful attention to power supply and grounding arrangements. VDD is usually supplied from the system’s analog supply. VSS of the AK4185 must be connected to the analog ground plane. System analog ground and digital ground should be connected together near to where the supplies are brought onto the printed circuit board. Decoupling capacitors should be as near to the AK4185 as possible, with the small value ceramic capacitor being the nearest. 2. Analog Inputs When an EMI source is close to the touch panel analog signal line, EMI noise affects analog characteristics performance. Connect noise canceling capacitors as close as possible to each pin (XP, XN, YP, YN pins) of the AK4185 to avoid this noise. (Figure 24, Figure 25) MS0954-E-00 2008/05 - 25 - [AK4185] PACKAGE 12pin CSP: 1.96mm x 1.46mm Top View Bottom View 1.96 ± 0.05 A 0.5 3 4 18 5 X XX X 2 1 A B C B 3 1.46 ± 0.05 2 1 D D C B A φ 0.3 ± 0.05 φ 0.05 M S AB 0.25 ± 0.05 0.65 S 0.08 S ■ Material & Lead finish Package molding compound: Epoxy resin Solder ball material: SnAgCu MS0954-E-00 2008/05 - 26 - [AK4185] MARKING 4185 XXXX A1 XXXX: Date code identifier (4 digit) Pin #A1 indication REVISION HISTORY Date (YY/MM/DD) 08/05/09 Revision 00 Reason First Edition Page Contents IMPORTANT NOTICE z These products and their specifications are subject to change without notice. When you consider any use or application of these products, please make inquiries the sales office of Asahi Kasei EMD Corporation (AKEMD) or authorized distributors as to current status of the products. z AKEMD assumes no liability for infringement of any patent, intellectual property, or other rights in the application or use of any information contained herein. z Any export of these products, or devices or systems containing them, may require an export license or other official approval under the law and regulations of the country of export pertaining to customs and tariffs, currency exchange, or strategic materials. z AKEMD products are neither intended nor authorized for use as critical componentsNote1) in any safety, life support, or other hazard related device or systemNote2), and AKEMD assumes no responsibility for such use, except for the use approved with the express written consent by Representative Director of AKEMD. As used here: Note1) A critical component is one whose failure to function or perform may reasonably be expected to result, whether directly or indirectly, in the loss of the safety or effectiveness of the device or system containing it, and which must therefore meet very high standards of performance and reliability. Note2) A hazard related device or system is one designed or intended for life support or maintenance of safety or for applications in medicine, aerospace, nuclear energy, or other fields, in which its failure to function or perform may reasonably be expected to result in loss of life or in significant injury or damage to person or property. z It is the responsibility of the buyer or distributor of AKEMD products, who distributes, disposes of, or otherwise places the product with a third party, to notify such third party in advance of the above content and conditions, and the buyer or distributor agrees to assume any and all responsibility and liability for and hold AKEMD harmless from any and all claims arising from the use of said product in the absence of such notification. MS0954-E-00 2008/05 - 27 -