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 DESIGNATIONSPRODUCT DESCRIPTION
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 298.2µA output at 298.2K (+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. Linearizationcircuitry, 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 chipform 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 outputcharacteristics 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 conjunction 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 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 will withstand a forward voltage up to 44 V and a reverse voltage of 20 V. Hence, supply irregularities or pin reversal will not damage the device.
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
AD590–SPECIFICATIONS (@ +25 C and V = +5 V unless otherwise noted)
Model Min ABSOLUTE MAXIMUM RATINGS Forward Voltage ( E+ or E–) Reverse Voltage (E+ to E–) Breakdown Voltage (Case E+ or E–) Rated Performance Temperature Range1 Storage Temperature Range1...
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