The inherent low cost of a monolithic integrated circuit combined with the elimination of support circuitry makes the AD 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 AD 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 AD is available in die form, making it suitable for hybrid circuits and fast temperature measurements in protected environments. The AD is particularly useful in remote sensing applications. The device is insensitive to voltage drops over long lines due to its high impedance current output.
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The inherent low cost of a monolithic integrated circuit combined with the elimination of support circuitry makes the AD 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 AD 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 AD is available in die form, making it suitable for hybrid circuits and fast temperature measurements in protected environments. The AD 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 AD easy to multiplex: the current can be switched by a CMOS multiplexer, or the supply voltage can be switched by a logic gate output.
Figure 2. The AD 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. State-of-the-art laser trimming at the wafer level in conjunction with extensive final testing ensures that AD units are easily interchangeable.
Superior interface rejection occurs because the output is a current rather than a voltage. In addition, power requirements are low 1. These features make the AD easy to apply as a remote sensor. The AD 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.
However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P. Box , Norwood, MA , U. Tel: All rights reserved. Technical Support www. F to Rev. G Changes to Endnote 2, Table E to Rev. Temperature: Calibration Error Trimmed Out Temperature: No User Trims D to Rev.
E Changes to Product Description Section C to Rev. D Updated Format Universal Changes to Figure 4 Equation B to Rev. Universal Change to Figure Results fromthose tests are used to calculate outgoing quality levels. All minimum and maximum specifications are guaranteed, although only those shown in boldfaceare tested on all production units.
Results from those tests are used to calculate outgoing quality levels. All minimum and maximum specifications are guaranteed, although only those shown in boldface are tested on all production units. Temperature Scale Conversion Equations Rev. However, the absolute errors specified apply to only the rated performance temperature range. AD Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied.
Exposure to absolute maximum rating conditions for extended periods may affect device reliability. It is available in a variety of accuracy grades and packages. When using the AD in die form, the chip substrate must be kept electrically isolated floating for correct circuit operation. M V— ? For a more detailed description, see M.
Solid State Circuits, Vol. SC, p. Understanding the Specifications—AD The total current of the device is then forced to be a multiple of this PTAT current. Figure 7 is the schematic diagram of the AD R5 and R6 convert the voltage to current. Q10, whose collector current tracks the collector currents in Q9 and Q11, supplies all the bias and substrate leakage current for the rest of the circuit, forcing the total current to be PTAT.
R4 11k? Q9 Q10 Q11 8 R6 ? R5 1 ? V—I Plot Rev. It is important to understand the meaning of the various specifications and the effects of the supply voltage and thermal environment on accuracy. Zero on the Kelvin scale is absolute zero; there is no lower temperature. That is, the output current is equal to a scale factor times the temperature of the sensor in degrees Kelvin.
The device is then packaged and tested for accuracy over temperature. Since this is a scale factory error, its contribution to the total error of the device is PTAT. Figure 9 shows how an exaggerated calibration error would vary from the ideal over temperature.
A Calibration Error vs. Temperature The calibration error is a primary contributor to the maximum total error in all AD grades. However, because it is a scale factor error, it is particularly easy to trim. Figure 10 shows the most elementary way of accomplishing this.
Note that when this error is trimmed out at one temperature, its effect is zero over the entire AD temperature range. In most applications, there is a current-tovoltage conversion resistor or, as with a current input ADC, a reference that can be trimmed for scale factor adjustment. This error consists of a slope error and some curvature, mostly at the temperature extremes.
Figure 11 shows a typical ADK temperature curve before and after calibration error trimming. For example, the ADL maximum total error varies from 2. For simplicity, only the large figure is shown on the specification page. The nonlinearity of the AD over the?
Figure 12 shows the nonlinearity of the typical ADK from Figure Nonlinearity Figure 13 shows a circuit in which the nonlinearity is the major contributor to error over temperature. Other pairs of temperatures can be used with this procedure as long as they are measured accurately by a reference sensor.
Also, note that V? R2 The insensitivity of the output to input voltage allows the use of unregulated supplies. It also means that hundreds of ohms of resistance such as a CMOS multiplexer can be tolerated in series with the device.
In other words, this change is equivalent to a calibration error and can be removed by the scale factor trim see Figure The AD specifications are guaranteed for use in a low thermal resistance environment with 5 V across the sensor.
The thermal environment in which the AD is used determines two important characteristics: the effect of self- heating and the response of the sensor with time. Figure 15 is a model of the AD that demonstrates these characteristics. Thermal Circuit Model Rev. Power source P represents the power dissipated on the chip. The heat sink used was a common clip-on.
However, for the same conditions in still air, the temperature rise is 0. For a given supply voltage, the temperature rise varies with the current and is PTAT.
Therefore, if an application circuit is trimmed with the sensor in the same thermal environment in which it is used, the scale factor trim compensates for this effect over the entire temperature range. Table 4. AD The time response of the AD to a step change in temperature is determined by the thermal resistances and the thermal capacities of the chip, CCH, and the case, CC.
Серия интегральных датчиков температуры AD590
The model number is a specific version of a generic that can be purchased or sampled. Status Status indicates the current lifecycle of the product. This can be one of 4 stages: Pre-Release: The model has not been released to general production, but samples may be available. Production: The model is currently being produced, and generally available for purchase and sampling. Last Time Buy: The model has been scheduled for obsolescence, but may still be purchased for a limited time.
Solid State Temperature Sensor