CN-0300 Datasheet, PDF (1/7 Pages) Analog Devices – Complete Closed-Loop Precision Analog Microcontroller Thermocouple

Circuit Note
CN-0300
Circuits from the Lab™ reference circuits are engineered and
tested for quick and easysystem integration to help solve today’s
analog, mixed-signal, and RF design challenges. For more
information and/or support, visit www.analog.com/CN0300.
Devices Connected/Referenced
ADuCM360
Cortex-M3 Based Microcontroller with
Dual 24-Bit Σ-Δ ADCs
ADP1720-3.3 Low Dropout Linear Regulator
Complete Closed-Loop Precision Analog Microcontroller Thermocouple
Measurement System with 4 mA to 20 mA Output
EVALUATION AND DESIGN SUPPORT
a 12-bit digital-to-analog converter(DAC), anda 1.2 V internal
Circuit Evaluation Board
CN-0300 Evaluation Board (EVAL-CN0300-EB1Z) includes
Analog Devices J-Link OB emulator (USB-SWD/UART-
reference, aswell asan ARM Cortex-M3 core, 126 kB flash, 8 kB
SRAM, and various digital peripheralssuch as UART, timers,
SPIs, and I²C interfaces.
EMUZ)
In the circuit, the ADuCM360 is connected to a Type T
Design and Integration Files
thermocouple and a 100 Ω platinum resistance temperature
Schematics, Layout Files, Bill of Materials, source code for
detector(RTD). The RTD is usedforcold junction compensation.
ADuCM360
The low power Cortex-M3 core convertsthe ADC readings to a
CIRCUIT FUNCTION AND BENEFITS
This circuit uses the ADuCM360 precision analogmicrocontroller
in an accurate thermocouple temperature monitoringapplication
and controls the 4 mAto 20 mAoutput current accordingly.The
ADuCM360 integrates dual 24-bitsigma-delta(Σ-Δ) analog-to-
digital converters(ADCs), dual programmable current sources,
real temperature value. The Type T temperature range supported is
−200°C to +350°C, and this temperature range is converted to
an output current range of 4 mA to 20 mA.
The circuit provides a complete solution for thermocouple
measurementswith a minimum requirement for external
components,andit is loop poweredfor loop voltages upto 28 V.
VLOOP
10µF
ADP1720-3.3
IN
OUT
GND
INTERFACE
BOARD
CONNECTOR
RESET
GND
SWDIO
SOUT
SWCLK
RESET
SWDIO
SWCLK
3.3V
1.6Ω
10µF
FERRITE BEAD
600Ω AT 100MHz
MURATA
BLM31AJ601SN1L
10µF
0.1µF
0.1µF
100Ω
PtRTD
10Ω
0.01µF
AVDD
IEXC
ADC0
IOVDD
DAC
CURRENT
METER
VLOOP+
NPN
BC548
RLOOP
47Ω
VLOOP–
SIN
NC
IOVDD
IOVDD
10Ω
0.01µF
ADC1
VREF+
AIN9
ADuCM360
AIN8
100kΩ
100kΩ
R_REF
5.6kΩ
0.1%
VREF–
RESET
RESET
10kΩ
10nF
AIN2
P2.2/BM
SD
THERMOCOUPLE
JUNCTION
10kΩ
10nF
AIN3
DVDD_REG
0.47µF
AIN7/VBIAS
AGND
Figure 1. ADuCM360 as a Temperature Monitor Controller with a Thermocouple Interface (Simplified Schematic, All Connections Not Shown)
Rev. A
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