Circuit Note

CN-0164

Circuit Designs Using Analog Devices Products

Apply these product pairings quickly and with confidence.

For more information and/or support call 1-800-AnalogD

(1-800-262-5643) or visit www.analog.com/circuit.

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

Rev. A

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suitabilityandapplicabilityforyouruseandapplication.Accordingly,innoeventshallAnalogDevices

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whatsoeverconnectedtotheuseofanyCircuitsfromtheLabcircuits. (Continuedonlastpage)

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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.

ADuC7060

ADF7020

PGA

ADC

ADP121

3V

100Ω

PT RTD

100Ω

0.1%

55µA IN DEEP SLEEP MODE

ID = 1µA WHEN CE = 0V

P0.6

P0.5

P2.0

P2.1

DATA CLK

INT/LOCK

DATA I/O

OUTGOING DATA

INCOMING DATA

P0.4

P1.2

P1.3

SREAD

SLE

SDATA

P0.2

SCLK

P0.0

CE

SERIAL CONFIGURATION

BUS

SERIAL DATA BUS

BAT54C

4.7kΩ

PROGRAMMABLE

CURRENT SOURCE

Figure 1. Low Power, Long Range, ISM Wireless Measurement Node (Simplified Schematic: All Connections and Decoupling Not Shown)