CN-0164 Datasheet, PDF (1/5 Pages) Analog Devices – Low Power, Long Range, ISM Wireless Measuring Node

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Circuit Note
CN-0164
Devices Connected/Referenced
ADF7020 ISM Band, FSK/ASK Transceiver
ADuC7060
Low Power, ARM7TDMI, Precision Analog
Microcontroller
ADP121
150 mA, Low Quiescent Current, CMOS
Linear Regulator
Low Power, Long Range, ISM Wireless Measuring Node
CIRCUIT FUNCTION AND BENEFITS
Ideally, a wireless measurement node is low power, has good
range, and is easily interfaced to different sensors. Through the
combination of three Analog Devices, Inc., parts, an intelligent
measurement node with an average current consumption of
<70 µA, a range of almost 1 km (in free space), and a data rate
of one transmission/minute can be achieved, while also main-
taining a 16-bit ADC performance (see Figure 1). This makes
the circuit suitable for battery power and such applications as
automation and remote sensing.
The system consists of a low power temperature measurement
node that wakes once a minute, measures temperature, transmits
this measurement at 10 kbps to the base node, and then returns
to sleep. The base node continuously listens for a package from
the measurement node and sends this information to the PC via
the UART for display in HyperTerminal.
ADP121
3V
V_CC = 2.5V
55µA IN DEEP SLEEP MODE
ID = 1µA WHEN CE = 0V
100Ω
PT RTD
100Ω
0.1%
ADuC7060
PROGRAMMABLE
CURRENT SOURCE
PGA
ADC
P0.0
P0.2
P0.4
P1.2
P1.3
OUTGOING DATA
P0.6
INCOMING DATA
P0.5
P2.0
P2.1
V_CC
4.7kΩ
BAT54C
CE
SCLK
SDATA
SLE
SREAD
ADF7020
SERIAL CONFIGURATION
BUS
DATA I/O
INT/LOCK
DATA CLK
SERIAL DATA BUS
Figure 1. Low Power, Long Range, ISM Wireless Measurement Node (Simplified Schematic: All Connections and Decoupling Not Shown)
Rev. A
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