Digital IC measures temperature with 0.1°C accuracy

20th November 2014

Barney Scott

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Datasheet

Linear introduces the LTC2983 high performance digital temperature measurement IC which directly digitises RTDs, thermocouples, thermistors and external diodes with 0.1°C accuracy and 0.001°C resolution. A high performance AFE 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 LTC2983 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 and then outputs the results in °C or °F.

The simple, yet feature-rich, LTC2983 interfaces with a wide variety of temperature sensors, including type B, E, J, K, N, S, R, T thermocouples, two-, three-, or four-wire RTDs, 2.25-30kΩ thermistors and temperature sensing diodes. The LTC2983 works with ground referenced sensors without the need for amplifiers, negative supplies, or level shift circuitry.

Up to twenty 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 allows easy customising of the LTC2983.

Signals are simultaneously digitised with three, high accuracy, 24-bit sigma-delta ADCs using an internal 10ppm/°C reference. Automatic thermocouple cold junction compensation can be done using any type of external sensor. Included on the chip are linearisation algorithms for all common sensor types. Custom sensors can be linearised with custom coefficients programmed into the chip.

Dual programmable excitation current sources feature current reversal and current ranging to improve accuracy and reduce noise. To ensure resistive measurements are accurate, current reversal eliminates thermocouple effects in the resistive sensor. Sensor specific fault detection alerts the user of short circuits, open circuits, over temperature, under temperature, and ADC overranging.

The LTC2983 is offered in commercial and industrial versions, supporting operating temperature ranges from 0 to +70 and -40 to +85°C respectively. The LTC2983 is available in a RoHS compliant, 7x7mm LQFP-48. Pricing starts at $20.66 each in 1,000 unit quantities.