SerialCoder™ IR UR5HC703-IR20 Extremely Low-Power Keyboard Encoder Interfaces IrDA HID & SYSTEM MANAGEMENT PRODUCTS, KEYCODER™ FAMILY DESCRIPTION FEATURES The SerialCoder™ IR UR5HC703IR20 is an extremely low-power, “offthe-shelf” infrared serial keyboard encoder. Robust, tiny and flexible, the IC is a good match for any application where a low-cost wireless keyboard is attractive and an IrDA host is available. • 8 x 16 Matrix Encoding • IC is independent of the keyboard layout • Extremely low-power operation, transparent to the host • Typical current consumption of less than 1µA at room temperature; 10µA at 85°C • Robust algorithm for ghost-key elimination The IC provides extremely lowpower operation, transparent to the host. Power consumption is reduced to just the circuit’s leakage when all keys are released. The typical current consumption is less than 1µA at room temperature and 10µA at 85°C. • CMOS output-only asynchronous serial interface to the host using standard IrDA • 9600 Baud 8N1 serial data format • Very simple serial protocol — twobyte identification string on power-up; single-byte matrixposition for each key-press or key-release • Low-cost wireless keyboard solution APPLICATIONS • Infrared wireless keyboards • Personal digital assistant (PDA) keyboard • Instrumentation • Remote control • Home entertainment or automation PIN ASSIGNMENTS ROW7 COL12 TXD COL13 COL14 COL0 COL1 COL2 If a key or group of keys stays in the depressed position for ten minutes (with no other keyboard activity), the IC shuts down to save power. PRELIMINARY The SerialCoder™ IR is simple to implement. It requires few external components and utilizes a tiny, lowprofile 32-pin LQFP package that measures 7mm x 7mm. 32 25 24 1 COL3 COL4 COL5 COL6 VDD2 RESET VSS2 VDD ROW6 ROW5 ROW4 ROW3 ROW2 ROW1 ROW0 COL15 UR5HC703-IR20-FG LQFP 17 8 16 OCSIN OSCOUT VSS COL7 COL8 COL9 COL10 COL11 9 SerialCoder is a trademark of Semtech Corporation. All other trademarks belong to their respective companies. Copyright ©1999-2001 Semtech Corporation DOC5-703-IR20-DS-101 1 www.semtech.com ORDERING CODE Package Options 32-pin plastic LQFP Pitch 0.8 mm Ta = -20° C to +85° C UR5HC703-IR20-FG Other Materials UR5HC703-IR20 eval. kit Type Evaluation kit Order number EVK5-703-IR20 SERIALCODER™ IR UR5HC703-IR20 FUNCTIONAL DIAGRAM Key Matrix Interface Data Buffer TxD Communication Interface 2 R0-R7 16 C0-C15 Matrix Scan Logic Reset Logic _RESET Oscillator OSCIN _OSCOUT Power Supply Copyright ©1999-2001 Semtech Corporation DOC5-703-IR20-DS-101 8 4 www.semtech.com PIN DEFINITIONS Mnemonic Power Supply VDD, VDD2 VSS, VSS2 8,5 11,7 PWR PWR Positive supply voltage Negative power Supply: signal ground Reset _RESET 6 I Hardware reset pin: Reset Input for orderly start-up. Low logic level is required whenever VDD is below minimum operating voltage Oscillator pins OSCIN 9 I _OSCOUT 10 O Oscillator input: Connect ceramic resonator with built-in load capacitors or CMOS clock from external oscillator 2 MHz operating frequency Oscillator output: Connect ceramic resonator with built-in load capacitors or keep open if external oscillator is used Host Interface TxD 27 O Serial data output: Idle at high voltage (logical 1), non-inverted data; 4µs pulsed output per IrDA timing specification Scanned matrix pins ROW0-ROW7 18-25 I Row matrix inputs with pulsed pull-up current sources 30-32, 1-4, 12-16, 26, 28, 29, 17 O Column matrix output, open drain COL0-COL15 Pin # Type Name and Function Note: An underscore before a pin mnemonic denotes an active low signal. Copyright ©1999-2001 Semtech Corporation DOC5-703-IR20-DS-101 3 www.semtech.com “GHOST” KEYS KEYBOARD SCANNER In any scanned contact switch matrix, whenever three keys defining a rectangle on the switch matrix are pressed at the same time, a fourth key positioned on the fourth corner of the rectangle is sensed as being pressed. This is known as the “ghost” or “phantom” key problem. The encoder scans a keyboard organized as an 8 row by 16 column matrix for a maximum of 128 keys. Smaller size matrixes can also be accommodated by simply leaving unused pins open. The SerialCoder™ IR provides internal pull-ups for the row input pins. When active, the encoder selects one of the column lines (C0-C15) every 512 µS and then reads the row data lines (R0-R7). A key closure is detected as a zero in the corresponding position of the matrix. Actual key presses A complete scan cycle for the entire keyboard takes approximately 9.2 ms. Each key found pressed is debounced for a period of 20 ms. Once the key is verified, the corresponding key code(s) are loaded into the transmit buffer of the serial communication channel. N-KEY ROLLOVER N-key rollover means the code(s) corresponding to each key press are transmitted to the host system as soon as that key is debounced, independent of the release of other keys. “Ghost” Key Figure 1: “Ghost” or “Phantom” Key Problem Although the problem cannot be totally eliminated without using external hardware, there are methods to neutralize its negative effects for most practical applications. Keys that are intended to be used in combinations should be placed in the same row or column of the matrix, whenever possible. Shift keys (Shift, Alt, Ctrl, Window) should not reside in the same row (or column) as any other keys. The SerialCoder™ IR has built-in mechanisms to detect the presence of “ghost” keys. Copyright ©1999-2001 Semtech Corporation DOC5-703-IR20-DS-101 When a key is released, the corresponding break code is transmitted to the host system. Several keys can be held pressed at the same time. However, if two or more key closures occur within a time interval of less than 5 ms, an error flag is set, and those closures are not processed. This feature protects against the effects of accidental key presses. POWER MANAGEMENT The SerialCoder™ IR achieves uniquely low system power consumption thanks to Self-Power Management™, which powers down the IC between key presses. A key press wakes up the IC immediately without losing any key data. 4 www.semtech.com PROTOCOL Serial transmission rate is 9600 Baud, with 8 data bits, no parity, least significant bits transmitted first, idle/stop level high (logical 1), start bit level low (logical 0), non-inverted data. Each bit with a zero value, including the start bit, is indicated by a four-microsecond low pulse of the TxD line toward the beginning of the time slot for the bit. Infrared signals are based on the Infrared Data Association (IrDA) Serial Infrared Physical Layer Specification. The diagram below shows the electrical wave form of a single transmitted byte, 0x65. (Note that pulse width is not to scale.) 0 Start 1 Data 0 Data 1 Data 0 Data 0 Data 1 Data 1 Data 0 Data 1 Stop Within 5ms after power-up, the IC sends a two-byte identification string of 0xF9, 0xFB. These two bytes are transmitted only once after each power-up or reset of the IC. These two ID values also represent key release action in the locations [row=1, column=15] and [row=3, column=15] on the key matrix. Since the values of these bytes represent release action of the keys, extraneous characters are never generated, even if synchronization between the driver and IC is lost, or power fluctuations/erroneous resets are applied to the chip. If logistics of the host software driver do not permit "shared" use of the identification values 0xF9 and 0xFB, then the user is advised not to incorporate keys in the locations [row=1, column=15] and [row=3, column=15] for the key matrix design. Subsequent single-byte transmissions indicate the row (0-7), column (0-15), and press/release action for each change of the state of every key. If the release of a key leaves all of the keys on the key matrix in the released state, the release report for that key is sent twice. Two release report bytes in a row for the same key are a signal to the host driver that the keyboard is completely idle and all keys are up. Keyboard Report Byte Bit Number b7 b6 b5 b4 b3 b2 b1 b0 Copyright ©1999-2001 Semtech Corporation DOC5-703-IR20-DS-101 5 Comment 0 for key press (make), 1 for key release (break) Column location in the key matrix 4-bit binary value (0-15) Row location in the key matrix (0-7) 3-bit binary value (0-7) www.semtech.com Copyright ©1999-2001 Semtech Corporation DOC5-703-IR20-DS-101 6 32 31 30 29 28 27 26 25 C2 C1 C0 C14 C13 TXD C12 R7 1 C 3 R 6 2 4 R 4 2 2 R 2 2 0 U1 R 3 2 1 R 1 1 9 R 0 1 8 2 C 4 3 C 5 4 C 6 5 V D D 2 7 V S S 2 VSS C7 www.semtech.com VDD OUT 2 GND GND IrED D1 12 R1 MOSFET_P Q1 GROUND 330µF C3 Long-range Driver POWER Note: The infrared-emitting diode (D1 or D2) should be chosen to match the receiver. If the receiver is not known, a standard IrDA-compatible LED should be used, with a wavelength of 850nm to 900nm, e.g. PDI-E802 (Digikey). For IrDA specifications, refer to the Infrared Data Association (IrDA) Serial Infrared Physical Layer Specification. Note: The P-Channel MOSFET (Q1) should ideally have RDS < 0.5 Ohms, e.g. NDS356P (Digikey). A standard MOSFET can be used, e.g. BSS84 (Digikey), but the active range of the infrared is reduced. Note: The circuit segment connecting to ground through C2 is used only for direct IrED drive. 2.00MHz Y1 100 R2 IrED D2 Direct IrED Drive Y1 = PBRC-2.00 BR (AVX), CSTC2.00MG (Murata) U2 = MN1382E (Panasonic), TC54VC2402ECB (Microchip) Partial BOM GND Voltage Detector 2.2V or Higher GND 3 1 C2 1.0µF 10V GND U2 0.1µF 9 10 11 12 13 14 15 16 C1 GND 8 V D D OSCIN OSCOUT GND 6 R E S E T 32-pin LQFP C8 C9 C10 C11 1 7 C 1 5 UR5HC703-IR20-FG R 5 2 3 To Keyboard Matrix SAMPLE SCHEMATIC FOR THE SERIALCODER™ IR UR5HC703-IR20-FG SERIALCODER™ IR UR5HC703-IR20-FG ELECTRICAL CHARACTERISTICS Absolute Maximum Ratings Ratings Symbol (VSS = 0V, Ambient temperature TA is in the range TLOW to THIGH) Supply voltage VDD Input voltage: All input pins VIN Output current: Total peak for all pins ΣIOH (Peak) ΣIOL (Peak) Total average for all pins ΣIOH (Avg) ΣIOL (Avg) Peak for each pin IOH (Peak) IOL (Peak) Average for each pin IOH (Avg) IOL (Avg) Temperature range Operating temperature TLOW to THIGH Storage temperature TSTG ESD rating (human body model) VESD Value Unit -0.3 to +7.0 V -0.3 to VDD +0.3 V -80 80 -40 40 -10 10 -5 5 -20 -40 2.0 mA mA mA mA TO TO 85 125 °C °C KV DC Electrical Characteristics, temperature range=T low to T high unless otherwise noted) Characteristic Symbol Min Typ Max Operating voltage Input voltage High LOW Unit VDD 2.2 5.5 V VIH VIL VIL (_RESET) VIL (OSCIN) 0.8 VDD 0 0 0 VDD 0.3 VDD 0.2 VDD 0.16 VDD V V V V 5.0 4.0 µA µA -4.0 µA µA Input current high lIH lIH (OSCIN) Input current low IIL IIL (OSCIN) -5.0 Output voltage VOH IOH=-1.0mA VOL IOL=1.0mA Power consumption ONE OR MORE KEYS ARE DEPRESSED ALL KEYS ARE RELEASED TA=25°C TA=85°C VDD-1.0 IDD 1.5 IDD IDD 0.1 VDD V 1.0 V mA 1.0 10.0 µA µA Control timing (Vdd=2.2 to 5.5 V, Vss=0 Vdc, Temperature range=T low to T high unless otherwise noted) Characteristic Symbol Value Unit Frequency of operations Ceramic resonator with built-in load fosc 2.0 MHz capacitors Transmit pulse 4 µs Note: Communications Baud rate and active-state power consumption are scaled linearly with operating frequency. Higher operating frequencies are possible within a reduced operating voltage range. Consult Semtech for further information. Copyright ©1999-2001 Semtech Corporation DOC5-703-IR20-DS-101 7 www.semtech.com MECHANICALS FOR THE SERIALCODER™ IR UR5HC703-IR20-FG LQFP PACKAGE HD D 32 e 25 F 24 8 17 E HE 1 y b L1 A2 9 A1 c Symbol L Detail F A b2 ME e MD I2 A A1 A2 b c D E e HD HE L L1 y b2 I2 MD ME 16 Dimension in Millimeters Min Nom Max – – 1.7 0.1 0.2 0 1.4 – – 0.3 0.35 0.45 0.105 0.125 0.175 6.9 7.0 7.1 6.9 7.0 7.1 0.8 – – 8.8 9.0 9.2 8.8 9.0 9.2 0.3 0.5 0.7 1.0 – – 0.1 – – 0ϒ 10ϒ – 0.5 – – – – 1.0 – – 7.4 – – 7.4 Recommended PCB Footprint Copyright ©1999-2001 Semtech Corporation DOC5-703-IR20-DS-101 8 www.semtech.com This Page Left Intentionally Blank Copyright ©1999-2001 Semtech Corporation DOC5-703-IR20-DS-101 9 www.semtech.com For sales information and product literature, contact: HID & System Mgmt Division Semtech Corporation 652 Mitchell Road Newbury Park, CA 91320 [email protected] http://www.semtech.com/ 805 498 2111 Telephone 805 498 3804 Telefax Semtech Western Regional Sales 805-498-2111 Telephone 805-498-3804 Telefax Semtech Central Regional Sales 972-437-0380 Telephone 972-437-0381 Telefax Semtech Eastern Regional Sales 203-964-1766 Telephone 203-964-1755 Telefax Semtech Asia-Pacific Sales Office +886-2-2748-3380 Telephone +886-2-2748-3390 Telefax Semtech Japan Sales Office +81-45-948-5925 Telephone +81-45-948-5930 Telefax Semtech Korea Sales Sales +82-2-527-4377 Telephone +82-2-527-4376 Telefax Northern European Sales Office +44 (0)2380-769008 Telephone +44 (0)2380-768612 Telefax Southern European Sales Office +33 (0)1 69-28-22-00 Telephone +33 (0)1 69-28-12-98 Telefax Central European Sales Office +49 (0)8161 140 123 Telephone +49 (0)8161 140 124 Telefax Copyright ©1999-2001 Semtech Corporation. All rights reserved. SerialCoder and KeyCoder are trademarks of Semtech Corporation. Semtech is a registered trademark of Semtech Corporation. All other trademarks belong to their respective companies. INTELLECTUAL PROPERTY DISCLAIMER This specification is provided "as is" with no warranties whatsoever including any warranty of merchantability, fitness for any particular purpose, or any warranty otherwise arising out of any proposal, specification or sample. A license is hereby granted to reproduce and distribute this specification for internal use only. No other license, expressed or implied to any other intellectual property rights is granted or intended hereby. Authors of this specification disclaim any liability, including liability for infringement of proprietary rights, relating to the implementation of information in this specification. Authors of this specification also do not warrant or represent that such implementation(s) will not infringe such rights. Copyright ©1999-2001 Semtech Corporation DOC5-703-IR20-DS-101 10 www.semtech.com