Universal temperature sensor IC with EEPROM for modular and custom sensor systems

     Linear Technology Corporation introduced the LTC2984, a high-performance digital temperature measurement IC that directly digitizes resistance temperature detectors (RTDS), thermocouples, thermistors, and external diodes. It has an accuracy of 0.1°C and a resolution of 0.001°C. The LTC2984 builds on Linear Technology's LTC2983 with the addition of an EEPROM (electrically erasable programmable read-only memory) for storing user configuration data and custom sensor coefficients.

     The addition of an EEPROM eliminates the need for any IC or sensor programming with a host processor and facilitates the use of a self-contained temperature detection circuit board or module. The LTC2984 has pin and software compatibility with the LTC2983. The LTC2984's non-volatile memory simplifies design and increases the reliability of modular and custom sensor systems. The LTC2984 is available in commercial and industrial temperature grade versions, supporting operating temperature ranges from 0°C to 70°C and from -40 °C to 85°C, respectively. The LTC2984 comes in a RoHS-compliant 7mm x 7mm LQFP 48-lead package.

     The LTC2984 has all the features of the LTC2983 with the addition of an EEPROM. A high-performance analog front end combines a low-noise and low-offset buffered ADC with all the necessary excitation and control circuits for each sensor. The measurements are carried out under the control of a digital engine that integrates all the algorithms and linearized functional circuitry required for each sensor. The LTC2984 provides a multiplex, high-precision interface that can be connected to virtually any sensor. The device accurately measures absolute microvolt signals from thermocouples and proportional resistance measurements from RTDS and thermistors, digitizing the measurement results and output them in °C or °F. Up to 20 analog inputs are available and digital measurements can be output in Celsius or Fahrenheit. The SPI interface works with almost any digital system, and a comprehensive software support system with drop-down menus enables easy customization of the LTC2984.

     The simple, feature-rich LTC2984 connects a wide range of temperature sensors, including class B, E, J, K, N, S, R and T thermocouples, two -, three - or four-wire RTDS, 2.25 kω to 30 kω thermistors, and temperature detection diodes. The LTC2984 can be used with ground-based sensors without the need for amplifiers, negative power supplies, or level shift circuits. Using an internal 15ppm/°C reference, the signal can be digitized simultaneously by three high-accuracy 24-bit ΔΣ ADCs.

     Automatic thermocouple cold junction compensation can be implemented with any type of external sensor. Built-in on the chip is a linearization algorithm for all common types of sensors. Custom sensors can be linearized with customization factors set and stored in the chip. Dual programmable excitation current source with current reversal and current range to improve accuracy and reduce noise. In order to ensure the accuracy of the resistance measurement, the current reversal eliminates the thermocouple effect of the resistive sensor. The sensor-specific fault detection circuit alerts the user to short circuit, open circuit, overtemperature, undertemperature ADC out of the rated range.