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PDF AD592 Data sheet ( Hoja de datos )
| Número de pieza | AD592 | |
| Descripción | Low Cost / Precision IC Temperature Transducer | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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FEATURES
High Precalibrated Accuracy: 0.5؇C max @ +25؇C
Excellent Linearity: 0.15؇C max (0؇C to +70؇C)
Wide Operating Temperature Range: –25؇C to +105؇C
Single Supply Operation: +4 V to +30 V
Excellent Repeatability and Stability
High Level Output: 1 A/K
Two Terminal Monolithic IC: Temperature In/
Current Out
Minimal Self-Heating Errors
Low Cost, Precision IC
Temperature Transducer
AD592
CONNECTION DIAGRAM
PIN 3 PIN 2 PIN 1
(–)
(NC)
(+)
* PIN 2 CAN BE EITHER ATTACHED OR UNCONNECTED
BOTTOM VIEW
PRODUCT DESCRIPTION
The AD592 is a two terminal monolithic integrated circuit tem-
perature transducer that provides an output current propor-
tional to absolute temperature. For a wide range of supply
voltages the transducer acts as a high impedance temperature
dependent current source of 1 µA/K. Improved design and laser
wafer trimming of the IC’s thin film resistors allows the AD592
to achieve absolute accuracy levels and nonlinearity errors previ-
ously unattainable at a comparable price.
The AD592 can be employed in applications between –25°C
and +105°C where conventional temperature sensors (i.e., ther-
mistor, RTD, thermocouple, diode) are currently being used.
The inherent low cost of a monolithic integrated circuit in a
plastic package, combined with a low total parts count in any
given application, make the AD592 the most cost effective tem-
perature transducer currently available. Expensive linearization
circuitry, precision voltage references, bridge components, resis-
tance measuring circuitry and cold junction compensation are
not required with the AD592.
Typical application areas include: appliance temperature sens-
ing, automotive temperature measurement and control, HVAC
(heating/ventilating/air conditioning) system monitoring, indus-
trial temperature control, thermocouple cold junction compen-
sation, board-level electronics temperature diagnostics,
temperature readout options in instrumentation, and tempera-
ture correction circuitry for precision electronics. Particularly
useful in remote sensing applications, the AD592 is immune to
voltage drops and voltage noise over long lines due to its high
impedance current output. AD592s can easily be multiplexed;
the signal current can be switched by a CMOS multiplexer or
the supply voltage can be enabled with a tri-state logic gate.
The AD592 is available in three performance grades: the
AD592AN, AD592BN and AD592CN. All devices are pack-
aged in a plastic TO-92 case rated from –45°C to +125°C. Per-
formance is specified from –25°C to +105°C. AD592 chips are
also available, contact the factory for details.
PRODUCT HIGHLIGHTS
1. With a single supply (4 V to 30 V) the AD592 offers
0.5°C temperature measurement accuracy.
2. A wide operating temperature range (–25°C to +105°C)
and highly linear output make the AD592 an ideal sub-
stitute for older, more limited sensor technologies (i.e.,
thermistors, RTDs, diodes, thermocouples).
3. The AD592 is electrically rugged; supply irregularities
and variations or reverse voltages up to 20 V will not
damage the device.
4. Because the AD592 is a temperature dependent current
source, it is immune to voltage noise pickup and IR
drops in the signal leads when used remotely.
5. The high output impedance of the AD592 provides
greater than 0.5°C/V rejection of supply voltage drift and
ripple.
6. Laser wafer trimming and temperature testing insures
that AD592 units are easily interchangeable.
7. Initial system accuracy will not degrade significantly over
time. The AD592 has proven long term performance
and repeatability advantages inherent in integrated cir-
cuit design and construction.
378
343
1µA/oK
273
248
–45 –25 0
+70 +105 +125
TEMPERATURE – oC
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: 781/329-4700
Fax: 781/461-3113
1 page  
AD592
+V
AD592
R
100Ω
950Ω
VOUT = 1mV/K
Figure 4. Basic Voltage Output (Single Temperature Trim)
To trim the circuit the temperature must be measured by a ref-
erence sensor and the value of R should be adjusted so the out-
put (VOUT) corresponds to 1 mV/K. Note that the trim
procedure should be implemented as close as possible to the
temperature highest accuracy is desired for. In most applications
if a single temperature trim is desired it can be implemented
where the AD592 current-to-output voltage conversion takes
place (e.g., output resistor, offset to an op amp). Figure 5 illus-
trates the effect on total error when using this technique.
SUPPLY VOLTAGE AND THERMAL ENVIRONMENT
EFFECTS
The power supply rejection characteristics of the AD592 mini-
mizes errors due to voltage irregularity, ripple and noise. If a
supply is used other than 5 V (used in factory trimming), the
power supply error can be removed with a single temperature
trim. The PTAT nature of the AD592 will remain unchanged.
The general insensitivity of the output allows the use of lower
cost unregulated supplies and means that a series resistance of
several hundred ohms (e.g., CMOS multiplexer, meter coil
resistance) will not degrade the overall performance.
+2.0
+1.0
0
–1.0
+1.0
+0.5
0
–0.5
–1.0
ACCURACY
WITHOUT TRIM
AFTER SINGLE
TEMPERATURE
CALIBRATION
–25 +25
+105
TEMPERATURE – oC
Figure 5. Effect of Scale Factor Trim on Accuracy
If greater accuracy is desired, initial calibration and scale factor
errors can be removed by using the AD592 in the circuit of
Figure 6.
+5V
AD1403
8.66kΩ
R1
1kΩ
97.6kΩ
R2
5kΩ
AD741
7.87kΩ
AD592
VOUT = 100mV/oC
V–
Figure 6. Two Temperature Trim Circuit
With the transducer at 0°C adjustment of R1 for a 0 V output
nulls the initial calibration error and shifts the output from K to
°C. Tweaking the gain of the circuit at an elevated temperature
by adjusting R2 trims out scale factor error. The only error
remaining over the temperature range being trimmed for is
nonlinearity. A typical plot of two trim accuracy is given in
Figure 7.
–2.0
–25 0 +25
+75
TEMPERATURE – oC
+105
Figure 7. Typical Two Trim Accuracy
The thermal environment in which the AD592 is used deter-
mines two performance traits: the effect of self-heating on accu-
racy and the response time of the sensor to rapid changes in
temperature. In the first case, a rise in the IC junction tempera-
ture above the ambient temperature is a function of two vari-
ables; the power consumption level of the circuit and the
thermal resistance between the chip and the ambient environ-
ment (θJA). Self-heating error in °C can be derived by multiply-
ing the power dissipation by θJA. Because errors of this type can
vary widely for surroundings with different heat sinking capaci-
ties it is necessary to specify θJA under several conditions. Table
I shows how the magnitude of self-heating error varies relative
to the environment. In typical free air applications at +25°C
with a 5 V supply the magnitude of the error is 0.2°C or less. A
common clip-on heat sink will reduce the error by 25% or more
in critical high temperature, large supply voltage situations.
Table I. Thermal Characteristics
Medium
Still Air
Without Heat Sink
With Heat Sink
Moving Air
Without Heat Sink
With Heat Sink
Fluorinert Liquid
Aluminum Block**
θJA (°C/watt)
175
130
60
40
35
30
τ (sec)*
60
55
12
10
5
2.4
NOTES
*τ is an average of five time constants (99.3% of final value). In cases where the
thermal response is not a simple exponential function, the actual thermal re-
sponse may be better than indicated.
**With thermal grease.
REV. B
–5–
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| PDF Descargar | [ Datasheet AD592.PDF ] | |
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