Atmel AT03303: Coin Cell operated Wireless ePaper Display

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]
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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]
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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]
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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]
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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.
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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]
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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]
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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]
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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]
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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]
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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
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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
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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]
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Revision History
Doc Rev.
Date
42358A
09/2014
Comments
Initial document release.
AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE]
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AT03303: Coin Cell operated Wireless ePaper Display [APPLICATION NOTE]
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