AD592 to LTC1298 interface

J^3

Good Morning everyone,
I am trying to use an AD592 temp sensor with an LTC1298 ADC.· I believe the AD592 outputs micro amps linear to Kelvin temp, and the LTC1298 accepts an input from 0 to 5 VDC.· I was thinking I could use a voltage divider on the output of the AD592 to create an input for my LTC1298, but am new to this and unsure.· If anyone has any experience with these two devices I would greatly appreciate your input.· Thank You.

·

Tracy Allen

A resistor in series with the sensor will convert the current to voltage that can be sensed by the ADC. Just a resistor, not a divider. For example, with a 1.21 kOhm resistance, the output will be 1.21 millivolts per Kelvin, which matches the per bit resolution of the LTC1298 on the 5 volt supply (5/4096=0.0012207). For a better resolution, use a higher resistance. For example, 2.43 kΩ for 1/2 degree or 6.19 kΩ for 0.1 degree. Those are not the only choices, and for best results a simple calibration multiplier will be needed in software. The program can then subtract an offset to get Celsius temperature. The voltage across a 1.21 kΩ resistor at 0 degrees Celsius will be about 330 millivolts. The sensor may have to be powered on the top side from Vin instead of Vdd.

See also www.emesys.com/OL2heat.htm#AD590 or the Stamps in Class course Applied Sensors.

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Tracy Allen
www.emesystems.com

J^3

Thank you, your help is much appreciated.