Two-Terminal IC
Temperature Transducer
AD590
Rev. C
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FEATURES
Linear current output: 1 µA/K
Wide temperature range: −55°C to +150°C
Probe compatible ceramic sensor package
2-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
00533-C-001
–
+
TO-52 SOIC-8
NC = NO CONNECT
TOP VIEW
(Not to Scale)
NC
1
V+
2
V–
3
NC
4
NC
NC
NC
NC
8
7
6
5
FLATPAC
+–
Figure 1. Pin Designations
GENERAL DESCRIPTION
The AD590 is a 2-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 298.2 K
(25°C).
The AD590 should be used in any temperature-sensing
application 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
components, 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 at 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.
PRODUCT HIGHLIGHTS
1. The AD590 is a calibrated, 2-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
conjunction with extensive final testing ensures that
AD590 units are easily interchangeable.
3. Superior interface rejection occurs, because the output is a
current rather than a voltage. In addition, power
requirements 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 withstands a forward
voltage of up to 44 V and a reverse voltage of 20 V.
Therefore, supply irregularities or pin reversal does not
damage the device.
