Digital Temperature Sensors

The ADT7420 is a high accuracy digital temperature sensor offering breakthrough performance over a wide industrial range, housed in a 4 mm × 4 mm LFCSP package. It contains an internal band gap reference, a temperature sensor, and a 16-bit ADC to monitor and digitize the temperature to 0.0078°C resolution. The ADC resolution, by default, is set to 13 bits (0.0625°C). The ADC resolution is a user programmable mode that can be changed through the serial interface.

The ADT7420 is guaranteed to operate over supply voltages from 2.7 V to 5.5 V. Operating at 3.3 V, the average supply current is typically 210 μA. The ADT7420 has a shutdown mode that powers down the device and offers a shutdown current of typically 2.0 μA at 3.3 V. The ADT7420 is rated for operation over the −40°C to +150°C temperature range.

Pin A0 and Pin A1 are available for address selection, giving the ADT7420 four possible I²C addresses. The CT pin is an open-drain output that becomes active when the temperature exceeds a programmable critical temperature limit. The INT pin is also an open-drain output that becomes active when the temperature exceeds a programmable limit. The INT pin and CT pin can operate in comparator and interrupt event modes.

Product Highlights

1. Ease of use, no calibration or correction required by the user.
2. Low power consumption.
3. Excellent long-term stability and reliability.
4. High accuracy for industrial, instrumentation, and medical applications.
5. Packaged in a 16-lead, 4 mm × 4 mm LFCSP RoHS-compliant package.

Applications

• RTD and thermistor replacement
• Thermocouple cold junction compensation
• Medical equipment
• Industrial control and test
• Food transportation and storage
• Environmental monitoring and HVAC
• Laser diode temperature control

The PMOD compatible evaluation/prototyping board is a small form factor, low cost ambient temperature sensor measurement board. When prototyping, this board is used in conjunction with the ADICUP360 or the ADICUP3029 development platform. Direct electrical and physical connection will enable you to get started quickly with hardware and software, to help develop your solution.

I2C PMOD peripheral connectors can also be found on many 3rd party MCU or FPGA development boards, where the EVAL-ADT7420-PMDZ can be connected directly into those systems, and you can develop your own code using our reference code below.

The EV-COG-AD3029 is a development platform for Analog Devices Ultra Low Power technology across ADI's MCU and RF transceiver portfolio. The board uses CrossCore Embedded Studio, an open source Eclipse based Interactive Development Environment (IDE), which can be downloaded free of charge. The platform contains many hardware and software example projects to make it easier for customers to prototype and create solutions for Internet of Things (IoT) applications.

A Cog development system may consist of these

• A MCU Cog that highlights the differentiating values of ADI ULP portfolio.
• An optional add-on board (Gear) for application specific use case.
• An optional wireless board (RF-Cog) for connectivity

The Cog development system objective is to rapidly create a development/prototyping capability focused on industrial, professional, pro-sumer customers, with a flexible radio, microprocessor, sensor and application development environment.

The EV-COG-AD4050 is a development platform for Analog Devices Ultra Low Power technology across ADI's MCU and RF transceiver portfolio. The board uses CrossCore Embedded Studio, an open source Eclipse based Interactive Development Environment (IDE), which can be downloaded free of charge. The platform contains many hardware and software example projects to make it easier for customers to prototype and create solutions for Internet of Things (IoT) applications.

A Cog development system may consist of these

• A MCU Cog that highlights the differentiating values of ADI ULP portfolio.
• An optional add-on board (Gear) for application specific use case.
• An optional wireless board (RF-Cog) for connectivity.

The Cog development system objective is to rapidly create a development/prototyping capability focused on industrial, professional, pro-sumer customers, with a flexible radio, microprocessor, sensor and application development environment.

The AD-96TOF1-EBZ is a proven hardware platform for depth perception. When paired with processor board from the 96Boards eco system, it can be used for 3D software and algorithm development. While the software and algorithms are being developed, the hardware design can be leveraged for productization. ADI can suggest 3rd party developers to help customize the platform to meet individual application needs.

Depending on customer preferences and development experience, different 96Boards processor boards can be used for overall system evaluation and custom development. There is also a Raspberry Pi interface available on the Mezzanine board for extra customer flexibility.

This solution offers the ability to be very small and low power while measuring depth at up to 6m distances, good outdoor and indoor performance and VGA resolution.

It can be used for applications like:

• Robotics
• Industrial automation
• SLAM (Simultaneous Localization and Mapping)
• Augmented Reality
• Virtual Reality
• Drones
• Automotive sensing

The function of the circuit shown in Figure 1 is to provide a high accuracy multichannel thermocouple measurement solution. Achieving a precision thermocouple measurement requires a signal chain of precision components that amplifies the small thermocouple voltage, reduces noise, corrects nonlinearity, and provides accurate reference junction compensation (commonly referred to as cold junction compensation). This circuit addresses all these challenges for measuring thermocouple temperature with better than ±0.25°C accuracy.

The circuit shown in Figure 1 shows how three K type thermocouples are connected to the AD7793 precision 24-bit sigma-delta (Σ-Δ) analog-to-digital converter (ADC) to measure the thermocouple voltage. Because the thermocouple is a differential device rather than an absolute temperature measurement device, the reference junction temperature must be known to get an accurate absolute temperature reading. This process is known as reference junction compensation, commonly referred to as cold junction compensation. In this circuit, the ADT7320 precision 16-bit digital temperature sensor is used for the cold junction reference measurement and provides the required accuracy.

This type of application is popular where a cost-effective, accurate temperature measurement is required over the wide temperature ranges offered by thermocouples.

Toxic gas detection instruments are widely used to alert people of elevated levels of dangerous gases. Many of these instruments use electrochemical gas sensors that contain multiple metal plates, metal pins, and internal metal-based bond wires. These metal components can make the sensor susceptible to picking up energy from nearby RF communication networks, which may result in the instrument reporting an incorrect gas level or even a false gas alarm. An unnecessary workplace evacuation or factory shutdown due to a false alarm can be very costly to an end user.

The European standard EN 50270: 2015, “Electrochemical compatibility – Electrical apparatus for the detection and measurement of combustible gases, toxic gases or Oxygen” specifies the RF frequency range and power levels that a toxic gas detection instrument must be capable of operating in.

The CN-0425 circuit was extensively tested with a number of sensors in an anechoic chamber to prove compliance with the EN 50270 radiated immunity specifications. Additional tests were performed in close proximity to a high power radio transmitter to prove its robustness to near-field RF interference.

Figure 1 shows an electrochemical gas sensor (M1) connected and how to bias and measure the electrochemical toxic gas sensor. This circuit note also shows and explains the filters used to improve radiated immunity of the whole circuit.