High Impedance, High CMR, В±10 V Analog Front End Signal Conditioner for Industrial Process Control and Automation (CN0225)

The circuit, shown in Figure 1, is a complete analog front end for digitizing ±10 V industrial level signals with a 16-bit differential input PulSAR® ADC. The circuit provides a high impedance instrumentation amplifier input with high CMR, level shifting, attenuation, and differential conversion, with only two analog components. Because of the high level of integration, the circuit saves printed circuit board space and offers a cost effective solution for a popular industrial application.

Signal levels of up to ±10 V are typical in process control and industrial automation systems. With smaller signal inputs from sensors such as thermocouples and load cells, large commonmode voltage swings are often encountered. This requires a flexible analog input that handles both large and small differential signals with high common-mode rejection and also has a high impedance input.



Figure 1. High Performance Analog Front for Industrial Process Control (Simplified Schematic: All Connections and Decoupling Not Shown)


Attenuation and level shifting are necessary to process industrial level signals with modern low voltage ADCs. In addition, fully differential input ADCs offer the advantages of good common-mode rejection, reduction in second-order distortion products, and simplified dc trim algorithms. Industrial signals, therefore, need further conditioning to properly interface with differential input ADCs.

The circuit in Figure 1 is a complete and highly integrated analog front end industrial level signal conditioner that uses only two active components to drive an AD7687 differential input 16-bit PulSAR ADC: the AD8295 precision in-amp (with two on-chip auxiliary op amps) and the AD8275 level translator/ADC driver. An ADR431 low noise 2.5V XFET® reference supplies the voltage reference for the ADC.


The AD8295 is a precision instrumentation amplifier with two uncommitted on-chip signal processing amplifiers and two precisely matched 20 kΩ resistors in a small 4 mm × 4 mm package.

The AD8275 is a G = 0.2 difference amplifier that can be used to attenuate ±10 V industrial signals, and the attenuated signal can be easily interfaced to a single supply low voltage ADC. The AD8275 performs the attenuation and level shifting function in the circuit, maintaining good CMR without any need for external components.

The AD7687 is a 16-bit, successive approximation ADC that operates from a single power supply between 2.3 V and 5.5 V. It has a differential input for good CMR and also offers the ease of use associated with SAR ADCs.

Возможности

  • Analog front end for +/- 10V inputs
  • High common mode rejection
  • 16 bit resolution
  • Board space reduction

Файлы

High Impedance, High CMR, В±10 V Analog Front End Signal Conditioner for Industrial Process Control and Automation  CN0225

Используемые компоненты

Производитель: Analog Devices Inc.
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AD7687BRM
AD7687BRM
Analog Devices Inc.
Арт.: 183508 ИНФО RD
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IC, 16-BIT ADC; Resolution, Bits:16bit; Sampling Rate:250kSPS; Channels, No. of:1; Input Type:Differential; Interface Type:Serial, SPI; Voltage, Supply Min:2.3V; Voltage, Supply Max:5.5V; Termination Type:SMD; Case Style:MSOP; Pins, No.…
AD7687BRM
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AD7687BRMZ
AD7687BRMZ
Analog Devices Inc.
Арт.: 284772 ИНФО PDF RD
Доступно: 5696 шт. от: 888 руб.
LS: 100Ksps/400Ksps 16 bit SAR ADC
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AD8295BCPZ-WP
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Analog Devices Inc.
Арт.: 441268 PDF RD
Доступно: 527 шт.
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INSTRUMENTATION, AMP, 1.2MHZ, 16LFCSP
AD8295BCPZ-WP
527 шт.
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AD8295BCPZ-R7
Analog Devices Inc.
Арт.: 659891 ИНФО RD
Доступно: 1422 шт.
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IC AMP PREC FE +/-18V 16LFCSP
AD8295BCPZ-R7
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AD8295ACPZ-WP
AD8295ACPZ-WP
Analog Devices Inc.
Арт.: 1113393 PDF RD
Доступно: 2842 шт.
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INSTRUMENTATION, AMP, 1.2MHZ, 16LFCSP
AD8295ACPZ-WP
2842 шт.
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AD8295ACPZ-R7
AD8295ACPZ-R7
Analog Devices Inc.
Арт.: 1348827 PDF RD
Доступно: 17062 шт.
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AMPLIFIER, INSTRUMENTATION, 1.2MHZ, 140DB, LFCSP-16
AD8295ACPZ-R7
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AD7687BRMZ-REEL7
Analog Devices Inc.
Арт.: 2094494 RD
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AD7687BRMZ-REEL7
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AD7687BCPZRL7
Analog Devices Inc.
Арт.: 2236094 RD
Доступно: 16045 шт.
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AD7687BCPZRL7
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