Core specifications
The AD693AQ is a monolithic signal conditioning circuit that accepts low-level inputs from a variety of sensors and controls a standard 4-20mA two-wire current loop.Compared with traditional transmitter solutions built with discrete components, it integrates the instrumentation amplifier front end, V/I converter, precision voltage reference, auxiliary amplifier and laser trimming resistor network into a single chip, and the peripheral circuits are compressed to the extreme.
In terms of power supply, it supports loop power supply mode: the entire circuit (including the sensor) only needs two wires for power supply and signal transmission. When the device works in loop power supply mode, the on-chip voltage reference and auxiliary amplifier can provide up to 3.5mA excitation current to the sensor.The typical loop power supply voltage range is 12V to 36V, and the industrial-grade wide voltage input allows it to work stably under various harsh power supply conditions.In terms of power consumption, the typical quiescent current of the chip is 0.5mA (500µA), which is very suitable for low-power designs with two-wire loop power supply.
Accuracy is the most noteworthy highlight of this chip.Its front-end instrumentation amplifier can directly process millivolt-level differential voltage signals from sensors such as thermocouples, RTDs (resistance temperature detectors) or strain bridges. The built-in laser trimmed resistor network achieves excellent initial accuracy and extremely low temperature drift.Under normal temperature conditions of +25°C, the total unadjusted error is less than 0.5% of the full scale, and does not exceed 0.75% in the full industrial temperature range of -40°C to 85°C. The residual nonlinearity is less than 0.05%, which means that engineers can directly obtain high-precision measurement results without the need for cumbersome external calibration.
AD693AQ internally integrates a precision 6.2V bandgap reference voltage source with a temperature drift of 50ppm/℃, which can provide a stable and reliable excitation source for external sensors.The nominal transconductance of its V/I conversion stage is 0.2666A/V. An input signal of 75mV can drive a full-scale loop current of 20mA. The ultra-low offset voltage and 90dB common mode rejection ratio (CMRR) ensure the purity of signals in industrial environments with strong electromagnetic interference.The built-in current limiter automatically turns off the driver when the loop current approaches 25mA, effectively protecting the back-end circuit.In terms of packaging, it adopts a 20-pin ceramic DIP package with a solid and reliable physical structure. The operating temperature range is an industrial-grade wide temperature range of -40°C to 85°C. It can operate stably regardless of the outdoor low temperature in northern winter or the high temperature environment of closed cabinets in factories in southern summer.
The input and output ranges are flexibly configurable: the pre-calibrated 30mV and 60mV input ranges can be set via pin jumpers; other ranges from 1mV to 100mV can also be achieved by adding external resistors.In terms of output, three standard ranges of 4-20mA unipolar, 0-20mA unipolar and 12±8mA bipolar can be obtained through pin binding without the need for additional external components.
Model naming analysis
The model name of AD693AQ carries complete specification information:ADRepresents the Analog Devices brand;693Represents the product series number;ARepresents industrial grade accuracy level;QRepresents 20-pin CerDIP ceramic dual in-line package.In the same series, the suffixADFor side soldered ceramic DIP packages, suffixAEAvailable in a 20-pin leadless ceramic chip carrier (LCCC) package.The ceramic package with the AQ suffix has better environmental stability in industrial scenarios such as long-term high humidity and vibration, and the chip has fully passed RoHS compliance certification.
Core advantages
The core value of AD693AQ in the field of industrial field signal acquisition is concentrated in the two characteristics of two-wire loop power supply and high integration.The two-wire 4-20mA standard has been used in the field of industrial control for decades. Its natural anti-interference ability for long-distance transmission far exceeds that of voltage signals, and it can directly power sensors through the loop, solving the problem of power supply wiring for field equipment from the physical layer.The AD693AQ integrates the instrumentation amplifier, V/I converter, precision reference source and auxiliary amplifier into one chip, and only requires a very small number of peripheral components to form a complete two-wire or three-wire transmitter solution.For low-level signal transmission from RTDs, bridges, and pressure sensors, the AD693 provides a cost-effective signal conditioning solution and is recommended as an alternative to discrete circuit designs in a variety of applications such as process control, factory automation, and system monitoring.
Typical application scenarios
The areas where AD693AQ takes root are highly overlapped with industrial process control and equipment automation.
Pressure/temperature transmitter is its core application direction.At industrial sites, the weak electrical signals output by pressure sensors and platinum resistance temperature sensors are directly converted into 4-20mA current loop signals through AD693AQ, and transmitted to remote PLC, DCS control systems or digital display instruments. Such applications have been widely deployed in DCS distributed control systems in chemical, petroleum, electric power and other industries.
Flow meters and liquid level meters also use this chip extensively.The front-end conditioning circuits of electromagnetic flowmeters and vortex flowmeters often work with the AD693AQ to map instantaneous flow data into a 4-20mA current loop output in real time, making it easy to connect to existing industrial automation networks.In the historical solutions of industrial instrument brands such as Rosemount, the AD693 series has appeared many times as the core component of the field transmitter.
In terms of factory automation and system monitoring, the analog input module of the PLC needs to collect on-site sensor data back to the controller. AD693AQ is suitable for data collection through discrete transmitter boards and main control systems.The reference solution applied by Shiqiang shows that AD693AQ has been widely used in systems for real-time monitoring of temperature, pressure or flow in factory automation.
In distributed data acquisition systems and SCADA systems, AD693AQ is responsible for V/I conversion of low-frequency sensor data and gathering analog quantities to the central control room in a wired manner to meet the rigid demand for reliable long-distance data transmission in industrial control environments.
Related models and alternative references
ADI has built a complete sensor transmitter product matrix around the AD693 series, providing engineers with flexible selection space in different packaging forms and platform levels.
Same series, same function, different package replacement: If you need to design under stricter physical size restrictions or simply surface mount the chip on the PCB, you can chooseAD693AE(20-pin LCCC leadless ceramic chip carrier) package version with consistent functional and temperature specifications.If you have higher requirements on cost control and procurement channels, you can choose the same 20-pin CerDIP package.AD693AD, the performance and functions are exactly the same as those of AD693AQ, only the internal classification of the original packaging is different, the supply is stable, and it can be directly replaced by pin-to-pin.The AD693AQ package is a through-hole CerDIP, which is suitable for continuation designs of early industrial product DIP packages or scenarios with special requirements for welding strength and experimental debugging.
Related functional products in the series: If you need to handle a wider range of sensor inputs, you can refer to models such as the AD694 (single channel, 4-20mA transmitter), which has a wider input range, but the pin functions are not directly compatible with the AD693AQ.When AD693AQ is used as a typical core material for reference designs, it is often seen in official application documents that it is functionally benchmarked with industrial transmitter chips such as AD694 and XTR101/XTR115.
Cross-brand compatible alternative reference: In terms of application functions, AD693AQ partially overlaps with integrated precision current transmitters such as XTR101, XTR106 and XTR115 from Burr-Brown (later acquired by TI), as well as ADI's subsequent SPI programmable current/voltage output drivers such as AD5748, AD5750 and AD5751.These competing products can also convert voltage input to 4-20mA standard current output, but they differ in packaging form, temperature range, front-end instrumentation amplifier integration and power supply method (some are local power supply). When replacing, it is necessary to focus on checking the input impedance and loop voltage compatibility, and complete sufficient on-site verification before mass production.
write at the end
As a classic industrial-grade 4-20mA sensor transmitter, the ADI AD693AQ integrates a complete instrumentation amplifier, V/I converter, precision reference source, and auxiliary amplifier in a 20-pin ceramic DIP package. With a two-wire loop power supply, a wide temperature range of -40°C to 85°C, and a total unadjusted error of less than 0.5% of full scale, it has established a reliable technical benchmark for sensor signal conditioning in industrial sites.Whether it is a pressure transmitter, temperature transmitter or factory automation data collection, this chip provides a high-precision and low-cost conditioning solution that has been verified in large-scale applications.
As a chip agent distributor that has been deeply involved in the electronic components industry since 2011, Shenzhen Hongmai Electronics Co., Ltd. has long-term stock of ADI AD693AQ and AD693 full series of loop-powered 4-20mA transmitters in original stock. It also supplies different package versions such as AD693AD and AD693AE and various peripheral components such as precision operational amplifiers, voltage references, and MCUs. It supports factory batch direct shipment, small batch samples, and technical selection assistance.If you need to inquire about prices or need to know the selection suggestions of different packages of the same series, please feel free to contact us (tel: 0755-23815611, QQ 2355878270).Shenzhen Hongmai Electronics Co., Ltd.
