4 mA-to-20 mA Loop-Powered Temperature Monitor Using the ADuC7060/ADuC7061 Precision Analog Microcontroller (CN0145)

This circuit provides a simple highly integrated temperature monitor solution that can interface to a 4 mA-to-20 mA host controller. This circuit provides a very low cost solution to temperature monitoring because so much of the circuit functionality is integrated on the ADuC7060/ ADuC7061 precision analog microcontroller, including dual 24-bit Σ-Δ ADCs, the ARM7 processor core, and the DAC/PWM features for controlling the 4 mA-to-20 mA feedback circuit.

The performance of the ADCs and other analog circuits within the ADuC7060/ADuC7061 is superior to competitive microcontrollers that have integrated analog circuits. The circuit presented here represents the most cost-effective, lowest power, lowest board area solution compared to using discrete ADCs and a separate microcontroller. Because of its high level of integration and low power, the ADuC7060/ADuC7061 can operate directly from the loop power in the 4 mA-to-20 mA application. With the ARM7 core running at 640 kHz, the primary ADC active and measuring the external RTD tempera-ture sensor, and the PWM controlling the 4 mA-to-20 mA feedback circuit, the entire circuit typically consumes 3.15 mA. Further details on the power consumption are provided in the Circuit Description section.

Figure 1. ADuC7061 Controlling 4 mA-to-20 mA Loop-Based Temperature Monitor Circuit. (Simplified Schematic: All Connections and Decoupling Not Shown)

During the intervals between temperature measurements, the ADC and the RTD excitation current sources can be turned off to further reduce power.

The 100 Ω Pt RTD is an Enercorp #PCS11503.1. The complete circuit meets a better than ±1°C specification. The temperature range of this RTD is −50°C to +130°C. The RTD is available in a 1206 size SMD package and has a temperature coefficient of 0.385 Ω/°C.

The primary ADC within the ADuC7060/ADuC7061 has a peak-to-peak noise-free code resolution of greater than 18 bits. The PWM based DAC output provides 12 effective bits of resolution. The performance of the overall circuit is discussed in the Circuit Description section.

Due to the small form factor of the ADuC7061, a 5 mm × 5 mm 32-LFCSP package, the entire circuit will fit on an extremely small PCB thus further reducing cost.

The focus here is primarily the 4 mA-to-20 mA interface aspect of the circuit. For details on the RTD sensor interface to the ADC and on linearization techniques of the RTD measurements, see Application Note AN-0970 and Circuit Note CN-0075.

Возможности

  • Temperature monitoring solution
  • Interfaces with 4-20 mA controller
  • 24 bit precision conversion with integrated processor

Файлы

Используемые компоненты

Производитель: Analog Devices Inc.
Наименование
Производитель
Описание Корпус/
Изображение
Цена, руб. Наличие
OP193FSZ
OP193FSZ
Analog Devices Inc.
Арт.: 25050 ИНФО PDF RD
Доступно: 3570 шт. от: 264 руб.
OP AMP, MICROPOWER R/R, SOIC8, 193; Amplifiers, No. of:1; Op Amp Type:Precision; Gain, Bandwidth -3dB:35kHz; Slew Rate:10V/ms; Voltage, Supply Min:1.7V; Voltage, Supply Max:18V; Termination Type:SMD; Case Style:SOIC; Pins, No.…
OP193FSZ 264,00 от 13 шт. 227,00 от 28 шт. 208,00
1747 шт.
(на складе)
1823 шт.
(под заказ)
OP193FP
OP193FP
Analog Devices Inc.
Арт.: 25735 ИНФО RD
Поиск
предложений
Precision, Micropower, Operational Amplifier
OP193FP
-
Поиск
предложений
OP293FP
OP293FP
Analog Devices Inc.
Арт.: 32024 ИНФО RD
Поиск
предложений
Dual, Precision, Micropower, Operational Amplifier
OP293FP
-
Поиск
предложений
ADR280ART-R2
ADR280ART-R2
Analog Devices Inc.
Арт.: 163493 ИНФО RD
Доступно: 2585 шт.
Выбрать
условия
поставки
IC, VOLT REF
ADR280ART-R2
2585 шт.
(под заказ)
Выбрать
условия
поставки
OP293FSZ
OP293FSZ
Analog Devices Inc.
Арт.: 199141 ИНФО PDF RD
Доступно: 5546 шт. от: 341 руб.
OP AMP, DUAL PRECISION UPOWER, 293; Amplifiers, No. of:2; Op Amp Type:Precision; Gain, Bandwidth -3dB:35kHz; Slew Rate:15mV/чs; Voltage, Supply Min:1.7V; Voltage, Supply Max:18V; Termination Type:SMD; Case Style:SOIC; Pins, No.…
OP293FSZ 341,00 от 10 шт. 292,00 от 22 шт. 268,00
1000 шт.
(на складе)
4546 шт.
(под заказ)
OP293ESZ
OP293ESZ
Analog Devices Inc.
Арт.: 213788 ИНФО PDF RD
Доступно: 1517 шт. от: 685 руб.
Operational Amplifier (Op-Amp) IC; No. of Amplifiers:2; Op Amp Type:Precision; Gain Bandwidth -3db:35kHz; Slew Rate:0.015V/чs; Supply Voltage Min:1.7V; Supply Voltage Max:36V; No. of Pins:8
OP293ESZ 685,00 от 5 шт. 588,00 от 11 шт. 539,00
173 шт.
(на складе)
1344 шт.
(под заказ)
ADR280AKSZ-R2
Analog Devices Inc.
Арт.: 264196 ИНФО RD
Доступно: 580 шт.
Выбрать
условия
поставки
IC VREF ULTRALOW PWR 1.2V SC70-3
ADR280AKSZ-R2
580 шт.
(под заказ)
Выбрать
условия
поставки
ADR280ARTZ-R2
ADR280ARTZ-R2
Analog Devices Inc.
Арт.: 304742 ИНФО PDF RD
Доступно: 6902 шт. от: 160 руб.
Voltage Reference IC; Termination Type:SMD; Package/Case:3-SOT-23; No. of Pins:3; Operating Temperature Range:-40°C to +85°C; Output Voltage:1.2V; Temperature Coefficient:5 ppm/°C
ADR280ARTZ-R2 160,00 от 22 шт. 137,00 от 46 шт. 126,00
377 шт.
(на складе)
6525 шт.
(под заказ)
ADR280ARTZ-REEL7
ADR280ARTZ-REEL7
Analog Devices Inc.
Арт.: 331171 PDF RD
Доступно: 51436 шт.
Выбрать
условия
поставки
VOLTAGE REF, SERIES, 1.2V, SOT-23-3
ADR280ARTZ-REEL7
51436 шт.
(под заказ)
Выбрать
условия
поставки
OP293ESZ-REEL
Analog Devices Inc.
Арт.: 356981 ИНФО RD
Поиск
предложений
IC OPAMP GP 35KHZ DUAL 8SOIC
OP293ESZ-REEL
-
Поиск
предложений
OP293FSZ-REEL7
Analog Devices Inc.
Арт.: 362660 ИНФО RD
Доступно: 15929 шт.
Выбрать
условия
поставки
IC OPAMP GP 35KHZ DUAL 8SOIC
OP293FSZ-REEL7
15929 шт.
(под заказ)
Выбрать
условия
поставки
ADR280AKSZ-REEL7
ADR280AKSZ-REEL7
Analog Devices Inc.
Арт.: 439059 PDF RD
Доступно: 44324 шт.
Выбрать
условия
поставки
VOLTAGE REF, SERIES, 1.2V, SC-70-3
ADR280AKSZ-REEL7
44324 шт.
(под заказ)
Выбрать
условия
поставки
OP193FSZ-REEL7
Analog Devices Inc.
Арт.: 790902 ИНФО RD
Доступно: 11732 шт. от: 261 руб.
IC OPAMP GP 35KHZ PREC 8SOIC
OP193FSZ-REEL7 261,00 от 13 шт. 224,00 от 29 шт. 206,00
3 шт.
(на складе)
11729 шт.
(под заказ)
OP193EP
Analog Devices Inc.
Арт.: 1923381 RD
Доступно: 9683 шт.
Выбрать
условия
поставки
OP193EP
9683 шт.
(под заказ)
Выбрать
условия
поставки