CN0267 Datasheet, PDF (1/8 Pages) Analog Devices – Devices Connected

Circuits from the Lab™ reference circuits are engineered and
tested for quick and easy system integration to help solve today’s
analog, mixed-signal, and RF design challenges. For more
information and/or support, visit www.analog.com/CN0267.
Circuit Note
CN-0267
Devices Connected/Referenced
ADuCM360
Low Power, Precision Analog
Microcontroller
AD5421
16-Bit, Loop Powered, 4 mA to 20 mA
DAC
AD5700
Low Power HART Modem
Complete 4 mA to 20 mA Loop Powered Field Instrument with HART Interface
EVALUATION AND DESIGN SUPPORT
features such as remote calibration, fault interrogation, and
Circuit Evaluation Board
CN0267 Circuit Evaluation Board (DEMO-AD5700D2Z)
transmission of process variables, which are necessary in
applications such as temperature and pressure control.
Design and Integration Files
This circuit has been compliance tested, verified, and registered by
Schematics, Layout Files, Bill of Materials, Code Example
the HART Communication Foundation (HCF). This successful
CIRCUIT FUNCTION AND BENEFITS
registration provides circuit designers with a high level of
The circuit shown in Figure 1 is a complete smart industrial,
confidence using one or all of the components in the circuit.
loop powered field instrument with 4 mA to 20 mA analog output
The circuit uses the ADuCM360, an ultralow power, precision
and a highway addressable remote transducer (HART®) interface.
analog microcontroller, the AD5421, a 16-bit, 4 mA to 20 mA,
HART is a digital 2-way communication in which a 1 mA peak-
loop powered digital-to-analog converter (DAC), and the AD5700,
to-peak frequency-shift-keyed (FSK) signal is modulated on top
the industry’s lowest power and smallest footprint HART-
of the standard 4 mA to 20 mA analog current signal. This allows
compliant IC modem.
PRIMARY
SENSOR
1kΩ
1kΩ
SECONDARY
SENSOR
1kΩ
1kΩ
PT100 1kΩ
1kΩ
RREF
5.62kΩ
10ppm
1.6Ω
L*
10µF
AVDD
VREF+
0.01µF _AIN0
ADuCM360
10µF
10Ω
10µF
10µF
REG_OUT
DVDD
IOVDD
0.1µF
10µF
DV_DD
ADC
10µF
REFOUT1
REFOUT2
VREF
AD5421
VOLTAGE
REGULATOR
TEMPERATURE
SENSOR
REG_IN
V_LOOP
20MΩ
1MΩ
0.1µF _AIN1
ADC0
0.01µF
VREF–
GND_SW
1kΩ AIN4
0.1µF
0.01µF _AIN3
AVDD
I_EXC
CORTEX
M3
+
SRAM
FLASH
+
DMA
UART
SPI
I²C
CLOCK
RESET
WATCHDOG
CS0
SCLK0
MOSI0
MISO0
AVDD_
REG
DVDD_
REG
0.1µF _AIN2
0.01µF
0.1µF
AIN7
AGND
ADC1
VREF
SOUT
SIN
P0.5
P0.4
EXPOSED
PAD
SPI INTERFACE
0.47µF _DVDD
DAC
SYNC
SCLK WATCHDOG
SDIN
TIMER
SDO
LDAC
470Ω
0.47µF
1µF
AD5700
3.8664MHz
UART INTERFACE
V_CC ^HART_OUT
XTAL1
XTAL2
REF
TXD
RXD
CD
ADC_IP
RTS _{REG_CAP}
DGND AGND
C_IN
0.068µF
1µF
1µF
COM
50Ω
LOOP–
4.7V
LOW LEAKAGE
0.22µF
1.2MΩ
300pF
150kΩ
1.2MΩ 150pF
L* ^LOOP+
4700pF
TVS
40V
LOW
LEAKAGE
L* ^LOOP–
AGND
DGND
NOTES
1. L* = FERRITE BEAD, 0.3Ω @ DC, 1kΩ @ 100MHz.
2. THE ADuCM360 EXPOSED PAD IS CONNECTED TO DGND.
Figure 1. 4 mA to 20 mA, Loop Powered Field Instrument with HART Interface (Simplified Schematic: All Connections and Decoupling Not Shown)
Rev. B
Circuits from the Lab™ circuits from Analog Devices have been designed and built by Analog Devices
engineers. Standard engineering practices have been employed in the design and construction of
each circuit, and their function and performance have been tested and verified in a lab environment at
room temperature. However, you are solely responsible for testing the circuit and determining its
suitability and applicability for your use and application. Accordingly, in no event shall Analog Devices
be liable for direct, indirect, special, incidental, consequential or punitive damages due to any cause
whatsoever connected to the use of any Circuits from the Lab circuits. (Continued on last page)
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone]
www.analog.com
Fax: [phone] ©2012–2013 Analog Devices, Inc. All rights reserved.