ATA8520
Single-Chip SIGFOX RF Transmitter
DATASHEET
Features
●
Fully integrated, single-chip RF transmitter (SIGFOX
™
compliant)
●
System-on-chip solution including SIGFOX related protocol handling for modem
operation
●
AVR
®
microcontroller core with embedded firmware, SIGFOX, protocol stack and
ID/PAC
●
Supports uplink operation, i.e. transmit data telegram to SIGFOX base stations
●
Operating frequency range: 868.0MHz to 868.6MHz
●
Low current consumption: 32.7mA during telegram transmit with +14.5dBm TX
output power
●
Typical OFF mode current: 5nA (maximum 600nA at V
S
= +3.6V and T = +85°C)
●
Data rate: 100bit/s with DBPSK modulation
●
SPI interface for TX data access and transmitter configuration
●
Event signal indicates the status of the IC to an external microcontroller
●
Power-up (typical 10ms OFF mode -> IDLE mode)
●
Supply voltage ranges 1.9V to 3.6V and 2.4V to 5.5V (SIGFOX compliant supply
range 3V±5% and 3.3V to 5.5V)
●
Temperature range –40°C to +85°C
●
ESD protection at all pins (±4kV HBM, ±200V MM, ±750V FCDM)
●
Small 5
5mm QFN32 package/pitch 0.5mm
Applications
SIGFOX compatible modem for long-range, low-power and low-cost applications using the
SIGFOX network
●
Home and building automation
●
Alarm and security systems
●
Smart environment and industrial
●
Smart parking
●
Tracking
●
Metering
9372H-INDCO-11/15
1.
1.1
General Description
Introduction
The Atmel
®
ATA8520 is a highly integrated, low-power RF transmitter with an integrated AVR
®
microcontroller for
applications using the wide area SIGFOX
™
network
The Atmel ATA8520 is partitioned into three sections: an RF front end, a digital baseband and the low-power 8-bit AVR
microcontroller. The product is designed for the ISM frequency band in the range of 868.0MHz to 868.6MHz. The external
part count is kept to a minimum due to the very high level of integration in this device. By combining outstanding RF
performance with highly sophisticated baseband signal processing, robust wireless communication can be easily achieved.
The transmit path uses a closed loop fractional-N modulator.
The SPI interface enables external control and device configuration.
1.2
System Overview
Figure 1-1. Circuit Overview
AVCC
VS
DVCC
Supply and Reset
RF Frontend
TX
DSP
RF_OUT
PLL
Peripherals
CPU
SIGFOX
Protocol Stack
DATA BUS
XTO
Port B
Port C
XTAL
PB[7..0]
(SPI)
PC[5..0]
Figure 1-1
shows an overview of the main functional blocks of the Atmel ATA8520. External control of the Atmel ATA8520 is
performed through the SPI pins SCK, MOSI, MISO, and NSS. The functionality of the device is defined by the internal
firmware and processed by the AVR. SPI commands are used to control the device and to start the data telegram
transmission. The end of the telegram transmission is signaled to an external microcontroller on pin 28 (PB6/EVENT).
It is important to note that all PWRON and NPWRON pins (PC1..5, PB4, PB7) are active in OFF mode. This means that
even if the Atmel ATA8520 is in OFF mode and the DVCC voltage is switched off, the power management circuitry within the
Atmel ATA8520 biases these pins with VS.
The AVR microcontroller ports can be used as button inputs, LED drivers, EVENT pin, general purpose digital inputs, or
wake-up inputs, etc. Functionality of these ports is already implemented in the firmware.
2
ATA8520 [DATASHEET]
9372H–INDCO–11/15
ID and PAC
Firmware
1.3
Pinning
Figure 1-2. Pin Diagram
AGND
PB7
PB6
PB5
PB4
26
32
31
30
29
28
27
25
24
NC
NC
NC
NC
NC
NC
RF_OUT
VS_PA
PB3
NC
NC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
exposed die pad
PB2
PB1
PB0
DGND
DVCC
PC5
PC4
PC3
23
22
Atmel
ATA8520
21
20
19
18
17
AVCC
NC
VS
PC0
PC1
XTAL1
Note:
Table 1-1.
Pin No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
The exposed die pad is connected to the internal die.
Pin Description
Pin Name
NC
NC
NC
NC
NC
NC
RF_OUT
VS_PA
NC
XTAL1
XTAL2
AVCC
VS
PC0
PC1
PC2
PC3
Analog
Analog
–
Analog
Analog
Analog
Analog
Digital
Digital
Digital
Digital
Type
Description
Connected to GND
Connected to GND
Connected to GND
Connected to GND
Leave open
Connected to GND
Power amplifier output
Power amplifier supply. 3V supply: connect to VS.
5V supply: leave open. Use SPI command “Write System
Configuration” (0x11) to enable 5V supply mode
Connected to GND
Crystal oscillator pin 1 (input)
Crystal oscillator pin 2 (output)
RF front-end supply regulator output
Main supply voltage input
Main
Main
Alternate
Main
Alternate
Main
Alternate
: NRESET
: AVR Port C1
: NPWRON1
: AVR Port C2
: NPWRON2
: AVR Port C3
: NPWRON3
XTAL2
PC2
ATA8520 [DATASHEET]
9372H–INDCO–11/15
3
Table 1-1.
Pin No.
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Pin Description (Continued)
Pin Name
PC4
PC5
DVCC
DGND
PB0
PB1
PB2
PB3
PB4
PB5
PB6
PB7
AGND
NC
NC
GND
Type
Digital
Digital
–
–
Digital
Digital
Digital
Digital
Digital
Digital
Digital
Digital
–
–
–
–
Description
Main
Alternate
Main
Alternate
Digital ground
Main
Main
Main
Main
Main
Main
Main
Main
Alternate
Analog ground
Connected to GND
Connected to GND
Ground/backplane on exposed die pad
:--
: SCK
: MOSI (SPI master out Slave in)
: MISO (SPI master in Slave out)
: PWRON
: NSS
: EVENT
: TX active
: NPWRON6
: AVR Port C4
: NPWRON4
: AVR Port C5
: NPWRON5
Digital supply voltage regulator output
4
ATA8520 [DATASHEET]
9372H–INDCO–11/15
1.4
Applications
This section provides application examples for the two supply modes for the Atmel
®
ATA8520 device. In addition the
recommended PCB design and layout is described to achieve the SIGFOX
™
certification.
1.4.1
3V Application Example
Figure 1-3. 3V Application with External Microcontroller
IRQ
NSS
MISO
32
NC
31
NC
30
AGND
29
PB7
28
PB6
27
PB5
26
PB4
25
PB3
1
NC
2
NC
3
NC
4
NC
5
24
PB2
23
PB1
22
MOSI
SCK
Atmel
ATA8520
PB0
21
DGND
20
DVCC
PC5
PC4
19
18
17
C6
RF Filter
L1
C1
C2
6
NC
NC
7
RF_OUT
8
XTAL1
XTAL2
AVCC
Microcontroller
C5
VS_PA
NC
PC3
PC0
PC1
PC2
VS
9
10
11
12
13
14
15
16
Wake/Monitor
Q1
C3
C4
VS = 3V
Supply
VDD
Figure 1-3
shows a typical application circuit with an external host microcontroller operating from a 3V lithium cell. The Atmel
ATA8520 stays in OFFMode until NPWRON1 (PC1) is used to wake it up. In OFFMode the Atmel ATA8520 draws typically
less than 5nA at 25°C.
In OFFMode all Atmel ATA8520 AVR
®
ports PB0..PB7 and PC0..PC5 are switched to input. PC0..PC5 and PB7 have
internal pull-up resistors ensuring that the voltage at these ports is VS. PB0..PB6 are tri-state inputs and require additional
consideration. PB1, PB2, and PB5 have defined voltages since they are connected to the output of the external
microcontroller. PB4 is connected to ground to avoid unwanted power-ups. PB0, PB3 and PB6 do not require external
circuitry since the internal circuit avoids transverse currents in OFFMode. The external microcontroller has to tolerate the
floating inputs. Otherwise additional pull-down resistors are required on these floating lines.
Typically, the Atmel ATA8520 wake-up is done by pulling NPWRON1 (pin 15) to ground.
RF_OUT is matched with C1/L1 for 50 antenna connection. The RF filter is required to suppress unwanted side and
spurious emissions. The design of this filter depends on the final PCB and system layout and is subject to SIGFOX and ETSI
certification procedures.
Together with the fractional-N PLL within the Atmel ATA8520, an external crystal is used to fix the Tx frequency. Accurate
load capacitors for this crystal are integrated to reduce the system part count and cost. Only four supply blocking capacitors
are needed to decouple the different supply voltages AVCC, DVCC, VS, and VS_PA of the Atmel ATA8520. The exposed
die pad is the RF and analog ground of the Atmel ATA8520. It is connected directly to AGND via a fused lead. The Atmel
ATA8520 is controlled using specific SPI commands via the SPI interface.
ATA8520 [DATASHEET]
9372H–INDCO–11/15
5
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