APPLICATION NOTE AT03303: Coin Cell operated Wireless ePaper Display ATmega2564RFR2 Introduction ® Coin cell operated ePaper Display is an Atmel ATmega2564RFR2 based reference design specifically designed for applications like medical display devices, electronic security badges, smart tags, electronic shelf labels, display product pricing, barcode/QR codes, etc. Pervasive Display’s ePaper provides paper-like readability, high resolution, high contrast, and 180 degree viewing angle. This application note covers hardware design, validation results, radiation patterns, electrical characteristics, pre-compliance testing, and example reference application. Features • Low cost design • Optimized for lower power consumption • ePaper display • Chip antenna based design • Temperature sensing • Pre-compliance tested Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 1 Hardware Design 1.1 Atmel ATmega2564RFR2 [1] ® The Atmega2564RFR2 combines the industry's leading Atmel AVR 8-bit Microcontroller and a best-in-class ® ® 2.4GHz RF transceiver in industry's best single-chip targeting IEEE 802.15.4 and ZigBee applications. It offers the industry's highest RF performance for single chip devices, with a link budget of 103.5dBm while consuming 50% less current than the existing offerings. The device features hardware assisted: 2 • Multiple PAN address filtering (MAF) • Wake-on radio • Improved link efficiency and reliability using RX override • 32-bit MAC symbol counter • Internal temperature sensor • Automatic transmission modes • 128-bit AES crypto engine • True random number generator • Advanced hardware assisted reduced power consumption modes AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 1.2 Pervasive ePaper Display ePaper Display (EPD) panel display on the market. Figure 1-1. [2] is the most power efficient, easy to read, industrial purposed reflective ePaper EPD Current Profile By combining the high resolution of a TFT backplane and the dependability/maturity of E Ink technology, this display offers its user the freedom to display any image with excellent definition and contrast. The small and thin form factor makes it easy to design it into a variety of applications. 1.3 • Ultra-low-power (Battery Drive/Energy Harvest) • Easy to Read (Sunlight readable) • High Resolution (Display small details) • Thin & Light (Easy to Integrate) • Green (Paper Replacement) • Wide Viewing Angle (180 degrees – like paper) RF Design Atmel ATmega2564RFR2 SoC provides 100Ω differential (balanced) impedance through RFP and RFN pins; hence a Balun is used to convert this 100Ω differential to 50Ω single-ended (unbalanced) impedance. Johanson Balun/Filter (P/N - 2450BM15A0015) and is tuned for ATmega2564RFR2 device. Figure 1-2. [3] is chosen for this reference design as it has integrated filter RF Design AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 3 1.4 Chip Antenna Design The single-ended (unbalanced) output from Balun/Filter needs to be connected with antenna through a transmission line of impedance 50Ω. Johanson Chip antenna (P/N - 2450AT42B100) [4] was chosen as it is a recommended choice for small boards with limited ground plane and corner mounting. PCB trace in combination with tuning capacitors C34, C36, and C37 are used for impedance matching. Figure 1-3. 1.5 Chip Antenna Design Clock Circuit Design Reference board contains two external crystals as described below. Application note AVR2067: Crystal [5] Characterization for AVR RF covers different recommended crystal options. 1.5.1 32.768kHz Crystal Due to the low power operation of 32.768kHz crystal, it is used as time keeper when the CPU enters Deep Sleep operation. In the application 32.768kHz crystal clock is used as input to Timer/Counter2 running in asynchronous mode which acts as interrupt for waking up from Power Save mode of ATmega2564RFR2. Figure 1-4. 4 32.768kHz Design AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 1.5.2 16MHz Crystal RF frequency of transceiver is derived from 16MHz crystal clock, so accuracy of this external 16MHz crystal is important for proper RF operation. Maximum deviation of RF carrier frequency as per IEEE 802.15.4 standard is ±40ppm, so the 16MHz crystal and its load capacitance need to be chosen in order to meet this requirement. In order to achieve the best accuracy and stability, large parasitic capacitances should be avoided. Crystal lines should be routed as short as possible. XTAL_TRIM register can be used to tune the crystal frequency such that it exactly matches to 16MHz. Refer Section 2.1 for XTAL_TRIM tuning test results. Figure 1-5. 1.6 16MHz Design Interfacing ePaper Display [2] Pervasive ePaper Displays (EPD) circuit design is given in Figure 1-6 and the basic components required for EPD is included in the reference design. ATmega2564RFR2 and EPD are interfaced via SPI and few GPIO lines for controlling and communicating the display information. Current consumption profile of EPD is shown in Figure 2-4. AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 5 Figure 1-6. 1.7 EPD Design JTAG Connectors JTAG connector is required for programming or debugging the reference design. Atmel Programmers/Debuggers like the JTAGICE3 can be used for this purpose. Figure 1-7. 6 JTAG Connectors AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 1.8 Test Points Reference design contains few test points which provides access to few pins of ATmega2564RFR2. These test points can be used during validation or for connecting with external circuits. Table 1-1. 2 Test Points S. no. Test point Test point reference 1 ADC0 ADC input pin which is connected to PF0/Pin46 2 ADC1 ADC input pin which is connected to PF1/Pin47 3 CLKO Clock output pin which is connected to CLKO/Pin40 4 SCL TWI Clock pin which is connected to SCL/Pin17 5 SDA TWI Data pin which is connected to SDA/Pin18 6 PB4 Pin change interrupt which is connected to PCINT4/Pin30 7 PB5 Pin change interrupt which is connected to PCINT5/Pin31 Electrical Characteristics Electrical characteristics provided in Table 2-1 correspond to the typical measurement values in room temperature, 25°C. Table 2-1. 2.1 Typical Electrical Characteristics S. no. Parameter Typical value Units 1 Supply voltage 3.0 V 2 Data rate 250 kbps 3 TX output power 3.75 dBm 4 Antenna Gain -0.06 dB 5 Antenna efficiency 36 % Crystal Frequency Tuning After choosing the load capacitance of the 16MHz crystal, it is possible to slightly alter the oscillation frequency of a crystal by changing the internal capacitance of XTAL pins. This gives the freedom for the application to tune internal trimming capacitance to compensate the environmental effects. Table 2-2 shows the pullability result (at 25°C) of 16MHz crystal achieved by changing the XTAL_TRIM register of ATmega2564RFR2. AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 7 Table 2-2. 2.2 16MHz Crystal Frequency Tuning S. no. XTAL_TRIM Internal capacitance [pF] Measured frequency [MHz] Accuracy [ppm] 1 0x0 0 16.000143 8.937420122 2 0x1 0.3 16.000100 6.249960938 3 0x2 0.6 16.000057 3.562487309 4 0x3 0.9 16.000018 1.124998734 5 0x4 1.2 15.999974 -1.62500264 6 0x5 1.5 15.999937 -3.9375155 7 0x6 1.8 15.999899 -6.31253985 8 0x7 2.1 15.999861 -8.68757547 9 0x8 2.4 15.999825 -10.9376196 10 0x9 2.7 15.999791 -13.0626706 11 0xA 3 15.999754 -15.3752364 12 0xB 3.3 15.999722 -17.3753019 13 0xC 3.6 15.999691 -19.312873 14 0xD 3.9 15.999661 -21.1879489 15 0xE 4.2 15.999631 -23.0630319 16 0xF 4.5 15.999602 -24.8756188 Transmit Output Power Transmit power results shown in Table 2-3 corresponds to the typical measurement values taken by enabling PRBS CW mode at room temperature 25°C. Table 2-3. Transmit Output Power Measured RF output power [dBm] 8 S. no. Channel Frequency [GHz] TX_PWR Supply voltage at 1.8V Supply voltage at 3.0V 1 11 2.405 0x00 3.50 3.75 2 15 2.425 0x00 3.48 3.68 3 20 2.450 0x00 3.41 3.61 4 26 2.480 0x00 3.35 3.57 AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 2.3 Current Consumption Current consumption shown in Table 2-4 corresponds to the typical measurement values in room temperature, 25°C. Table 2-4. Current Consumption Measured RF output power [mA] S. no. Condition Supply voltage at 1.8V Supply voltage at 3.0V 1 TRX_OFF 4.4 5.12 2 PLL_ON 4.74 5.26 3 RX_AACK_ON 10.7 11.29 4 TX_BUSY 18.0 19.1 5 SLEEP 0.002 0.002 6 EPD image update (Duration – 3.6 sec) - 2.95 (avg) Current profile during transmission of frame with 10 bytes of data is taken. Corresponding packet structure and current profile is provided in Figure 2-2 and Figure 2-3. In this example frame we are transmitting 1 byte of application payload (i.e. 0x55) and the remaining bytes are MAC header information. Figure 2-2. Transmitted Packet Structure Current profile shows the transmission on frame followed by the wait time corresponding to ACK frame. In the example application we have enabled RPC modes. For more details, refer AT02594: Smart Reduced Power [8] Consumption Techniques . AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 9 Figure 2-3. Current Consumption Profile Frame PLL Calibration 3 CSMA/CA back off period Transmission Waiting for ACK Chip Antenna Matching Chip antenna tuning is required after assembling the RF shield and ePaper display. Final matching circuit requires two inductor values, 6.8nH and 8.2nH (Figure 3-1), for tuning the operating frequency of the chip antenna to the required band of operation (Figure 3-2). Figure 3-1. 10 Chip Antenna Matching Network AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 Figure 3-2. 4 Chip antenna Matching Plots Radiation Pattern of Chip Antenna at 2.44GHz AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 11 5 Pre-certification Testing This chapter covers the pre-certification test results required for FCC [6] and ETSI [7] certification. Figure 5-1. 12 Peak Power at Channel 20 AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 Figure 5-2. 6dB Bandwidth at Channel 20 AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 13 Figure 5-3. 14 Band Edge and Frequency Range at Channel 11 AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 Figure 5-4. Band Edge and Frequency Range at Channel 26 AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 15 Figure 5-5. 16 Spurious Emission between 30MHz to 1GHz AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 Figure 5-6. Spurious Emission between 1MHz to 26GHz 6 Appendix 6.1 Layer Stack-up AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 17 6.2 Bill of Material Qty Description MPN Manufacturer Comment 1 B1 2,4GHz Filter Balun, SMD 1.25x2.0mm 1 Antenna Antennas 2.45GHz ANTENNA 2450AT42B100E JOHANSON TECHNOLOGY 2450AT42B100E 5 C1, C2, C3, C4,C27 Ceramic capacitor, SMD0402, X5R, 6.3V,+/- 10% 04026D105KAT2A AVX 1uF 16 C5, C16, C17, C18,C19,C20, C21,C22,C23, C24,C25,C26, C28,C29,C30, C31 Ceramic capacitor, SMD 0402, X5R, 6.3V,+/- 10% 04026D225KAT2A AVX 2.2uF 2 C8,C9 Ceramic capacitor, SMD 0402,50V,C0G (NP0),+/-1 % 04025A100FAT2A AVX 10pF 2 C6, C7 Ceramic capacitor, SMD 0402, NP0, 50V, +/-5% C1005C0G1H220J0 50BA TDK 22pF 5 C10, C11, C13, C14, C32 Ceramic capacitor, SMD 0402, X7R, 16V, +/-10% 0402YC104KAT2A AVX 100nF 1 C15 Tantalum capacitor,CASE B,6.3V,+/-10% 293D476X96R3B2T E3 VISHAY SPRAGUE 47uF 1 D2 Dual schottky diode, If:30mA @Vf: 0.5V; Vrrm:30V,SOT-23 BAT54S DIODES INC. BAT54S 1 J1 CR2450 coin-cell battery clip, SMD 105 KEYSTONE BATTERY HOLDER 1 J2 20021121-00010C4 LF FCI 20021121-00010C4 LF 1 J3 1226-40-02-H12 MULTICOMP 1226-40-02-H12 BLM21AG102SN1D MURATA BLM21AG102SN1D 1 18 Designator L1 2x5 pin header, 1.27mm 40 pin double sided FPC connector with 0.5mm pitch FERRITE, BEAD, 0805, 0.28OHM, 0.5A 2450BM15A0015E JOHANSON TECHNOLOGY 2450BM15A0015E AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 Qty Designator Description MPN Manufacturer Comment 4 Q1, Q3, Q4, Q7 MOSFET, N, 0.2A, 60V, SOT-23 2N7002 STMICROELECTRONICS 2N7002 1 Q2 MOSFET, P, 50V, SOT-23 BSS84LT1G ON SEMICONDUCTOR BSS84LT1G 1 Q5 MOSFET, P, -20V ,SOT-23 DMG2305UX-13 DIODES INC. DMG2305UX-13 1 Q6 MOSFET, P,-50V, SOT-23 BSS84W-7-F DIODES INC. BSS84W-7-F 2 R1, R2 RESISTOR, 0402, 33K, 1%,63 mW CRCW040233K0FK ED VISHAY DRALORIC 33k0 2 R3, R6 RESISTOR, 0402,10K,1%, 63mW CRCW040210K0FK ED VISHAY DRALORIC 10k0 2 R4, R27 RESISTOR, 0402,0R, 63mW, JUMPER CRCW04020000Z0 ED VISHAY DRALORIC 0R0 1 R7 RESISTOR, 0402, 2K, 1%,63mW CRCW04022K00FK ED VISHAY DRALORIC 2k0 3 R8, R9, R10 RESISTOR, 0402,100K,1%, 63mW CRCW0402100KFK ED VISHAY DRALORIC 100k0 1 SH1 EMI Shield Frame 25x30x3mm LT08AD4303F Laird Technologies LT08AD4303F 1 SH2 EMI Shield Cover 25.6x30.6x2mm LT08AD4303C Laird Technologies LT08AD4303C 1 X2 CRYSTAL, 32.768KHZ , 12.5PF, SMD Q13FC13500004 EPSON 32.768KHZ 1 XC2 CRYSTAL, 16MHZ,8PF,SMD NX3225SA-16.000 MHZ-STD-CSR-1 NDK 16MHZ 1 U1 8-bit AVR Microcontroller with Low Power 2.4GHz Transceiver for ZigBee and IEEE 802.15.4 ATMEGA2564RFR2- ZU ATMEL ATMEGA2564RFR2- ZU 1 C36 6.8nH, +/-5%, SMD 0402 L-07C6N8JV6T JOHANSON TECHNOLOGY Antenna tuning 1 C37 8.2nH, +/-5%, SMD 0402 L-07C8N2JV6T JOHANSON TECHNOLOGY Antenna tuning 1 C34 - - - Not Mounted AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 19 7 20 References 1. ATmega2564RFR2 datasheet 2. ePaper Display datasheet 3. Johanson Balun 4. Johanson Chip Antenna 5. AVR2067:Crystal characterization for AVR RF 6. FCC Part 15 Subpart C 7. ETSI EN 300 328 V1.7.1 8. AT02594: Smart Reduced Power Consumption Techniques AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 8 Revision History Doc Rev. Date 42358A 09/2014 Comments Initial document release. AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE] Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 21 Atmel Corporation 1600 Technology Drive, San Jose, CA 95110 USA T: (+1)(408) 441.0311 F: (+1)(408) 436.4200 │ www.atmel.com © 2014 Atmel Corporation. / Rev.:Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014. 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Atmel-42358A-Wireless-Coin-Cell-operated-Wireless-ePaper-Display-ApplicationNote_092014 22 AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE]