a
FEATURES
Linear Current Output: 1 A/K
Wide Range: –55 C to +150 C
Probe Compatible Ceramic Sensor Package
Two Terminal Device: Voltage In/Current Out
Laser Trimmed to 0.5 C Calibration Accuracy (AD590M)
Excellent Linearity: 0.3 C Over Full Range (AD590M)
Wide Power Supply Range: +4 V to +30 V
Sensor Isolation from Case
Low Cost
Two-Terminal IC
Temperature Transducer
AD590
PIN DESIGNATIONS
PRODUCT DESCRIPTION
PRODUCT HIGHLIGHTS
The AD590 is a two-terminal integrated circuit temperature
transducer that produces an output current proportional to
absolute temperature. For supply voltages between +4 V and
+30 V the device acts as a high impedance, constant current
regulator passing 1
µA/K.
Laser trimming of the chip’s thin-film
resistors is used to calibrate the device to 298.2
µA
output at
298.2K (+25°C).
The AD590 should be used in any temperature sensing applica-
tion below +150°C in which conventional electrical temperature
sensors are currently employed. The inherent low cost of a
monolithic integrated circuit combined with the elimination of
support circuitry makes the AD590 an attractive alternative for
many temperature measurement situations. Linearization
circuitry, precision voltage amplifiers, resistance measuring
circuitry and cold junction compensation are not needed in
applying the AD590.
In addition to temperature measurement, applications include
temperature compensation or correction of discrete compo-
nents, biasing proportional to absolute temperature, flow
rate measurement, level detection of fluids and anemometry.
The AD590 is available in chip form making, it suitable for
hybrid circuits and fast temperature measurements in protected
environments.
The AD590 is particularly useful in remote sensing applications.
The device is insensitive to voltage drops over long lines due to
its high impedance current output. Any well insulated twisted
pair is sufficient for operation hundreds of feet from the
receiving circuitry. The output characteristics also make the
AD590 easy to multiplex: the current can be switched by a
CMOS multiplexer or the supply voltage can be switched by a
logic gate output.
1. The AD590 is a calibrated two terminal temperature sensor
requiring only a dc voltage supply (+4 V to +30 V). Costly
transmitters, filters, lead wire compensation and linearization
circuits are all unnecessary in applying the device.
2. State-of-the-art laser trimming at the wafer level in conjunc-
tion with extensive final testing ensures that AD590 units are
easily interchangeable.
3. Superior interface rejection results from the output being a
current rather than a voltage. In addition, power require-
ments are low (1.5 mWs @ 5 V @ +25°C.) These features
make the AD590 easy to apply as a remote sensor.
4. The high output impedance (>10 MΩ) provides excellent
rejection of supply voltage drift and ripple. For instance,
changing the power supply from 5 V to 10 V results in only
a 1
µA
maximum current change, or 1°C equivalent error.
5. The AD590 is electrically durable: it will withstand a forward
voltage up to 44 V and a reverse voltage of 20 V. Hence, sup-
ply irregularities or pin reversal will not damage the device.
REV. B
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
World Wide Web Site: http://www.analog.com
Fax: 617/326-8703
© Analog Devices, Inc., 1997
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