Analog front-end IC linearizes sensors
A 10-channel temperature-measurement IC, the LTC2986 from Linear Technology directly digitizes any combination of thermocouples, RTDs, thermistors, and external diodes with 0.1°C accuracy and 0.001°C resolution. The analog front-end device combines three 24-bit delta-sigma ADCs with all the necessary excitation and control circuits for each sensor. On-chip EEPROM stores user configuration data and custom sensor coefficients, eliminating IC or sensor programming by a host processor.The LTC2986 measures absolute microvolt-level signals from thermocouples and ratiometric resistance from RTDs and thermistors. It performs linearization and outputs the results in °C or °F. With 10 analog inputs, the LTC2986 accommodates up to 9 thermocouples, 4 RTDs, 4 thermistors, and/or 10 diodes, with support for Type B, E, J, K, N, S, R, and T thermocouples; 2-wire, 3-wire, and 4-wire RTDs; and 2.25-kΩ to 30-kΩ thermistors.
Dual programmable excitation current sources feature current reversal and current ranging to improve accuracy and reduce noise. To ensure resistive measurement accuracy, current reversal eliminates thermocouple effects in the resistive sensor. Sensor-specific fault detection circuitry warns of short circuits, open circuits, overtemperature, undertemperature, and ADC overranging.
Housed in a 7×7-mm LQFP-48 package, the LTC2986 is offered in variants that operate over commercial, industrial, and automotive temperature ranges. Prices start at $16.56 each in lots of 1000 units.
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