Linear introduces the LTC2984, a high performance digital temperature measurement IC that directly digitises RTDs, thermocouples, thermistors and external diodes with 0.1°C conformity and 0.001°C resolution. The LTC2984 builds on Linear’s LTC2983 by adding Electrically Erasable Programmable Read-Only Memory (EEPROM) that stores user configuration data and custom sensor coefficients.
This addition eliminates any IC or sensor programming by a host processor and facilitates the use of self-contained temperature sensing boards or modules. The LTC2984 is pin and software compatible with the LTC2983. The nonvolatile memory in the LTC2984 results in simplified designs and increased reliability for modular and custom sensor systems.
The LTC2984 includes all of the features found on the LTC2983, plus EEPROM. A high performance analogue front end combines low noise and low offset buffered ADCs with all the necessary excitation and control circuits for each sensor. Measurements are performed under the control of a digital engine combining all the algorithms and linearisation required for each.
The LTC2984 provides a multiplexed high precision interface to virtually any sensor. It precisely measures absolute microvolt level signals from thermocouples and ratiometric resistance measurements from RTDs and thermistors, linearises the results and outputs them in °C or °F. Up to 20 analogue inputs are available and digitised measurements can be output in centigrade or Fahrenheit. The SPI interface works with virtually any digital system and a comprehensive software support system with drop-down menus enables easy customisation of the LTC2984.
The simple, feature-rich LTC2984 interfaces with a wide variety of temperature sensors, including type B, E, J, K, N, S, R, T thermocouples, 2-, 3-, or 4-wire RTDs, 2.25 to 30kΩ thermistors and temperature sensing diodes. The LTC2984 works with ground referenced sensors without the need for amplifiers, negative supplies, or level shift circuitry.
Signals are simultaneously digitised with three, high accuracy, 24-bit Δ∑ ADCs, using an internal 15ppm/°C reference. Automatic thermocouple cold junction compensation can be done using any type of external sensor. Included on-chip are linearisation algorithms for all common sensor types. Custom sensors can be linearised with custom coefficients programmed and stored in the chip.
Dual programmable excitation current sources feature current reversal and current ranging to improve accuracy and reduce noise. To ensure accuracy of resistive measurements, current reversal eliminates thermocouple effects in the resistive sensor. Sensor specific fault detection alerts the user of short circuits, open circuits, overtemperature, undertemperature and ADC overranging.
The LTC2984 is offered in commercial and industrial versions, supporting operating temperature ranges from 0 to +70°C and -40 to +85°C, respectively. The LTC2984 is now available in a RoHS-compliant, 7mm2 LQFP 48-lead package.