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PDF TMP17FS Data sheet ( Hoja de datos )

Número de pieza TMP17FS
Descripción Low Cost/ Current Output Temperature Transducer
Fabricantes Analog Devices 
Logotipo Analog Devices Logotipo



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a
FEATURES
Operating Temperature Range: ؊40؇C to ؉105؇C
Single Supply Operation: ؉4 V to ؉30 V
Excellent Repeatability and Stability
High Level Output: 1 A/K
Monolithic IC: Temperature In/Current Out
Minimal Self-Heating Errors
APPLICATIONS
Appliance Temperature Sensor
Automotive Temperature Measurement and Control
HVAC System Monitoring
Industrial Temperature Control
Thermocouple Cold Junction Compensation
GENERAL DESCRIPTION
The TMP17 is a monolithic integrated circuit temperature
transducer that provides an output current proportional 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 TMP17 to
achieve absolute accuracy levels and nonlinearity errors
previously unattainable at a comparable price.
The TMP17 can be employed in applications between Ϫ40°C
to ϩ105°C where conventional temperature sensors (i.e.,
thermistor, RTD, thermocouple, diode) are currently being
used. Expensive linearization circuitry, precision voltage
references, bridge components, resistance measuring circuitry
and cold junction compensation are not required with the
TMP17.
378
343
1µA/K
273
248
45 25 0
70
TEMPERATURE – C
105 125
Figure 1. Transfer Characteristic
Low Cost, Current Output
Temperature Transducer
TMP17*
FUNCTIONAL DIAGRAM
NC NC
V NC
V NC
NC NC
PACKAGE DIAGRAM
SO-8
NC 1
8 NC
V2
7 NC
TOP VIEW
V 3 (Not to Scale) 6 NC
NC 4
5 NC
NC = NO CONNECT
The TMP17 is available in a low cost SO-8 surface-mount
package.
PRODUCT HIGHLIGHTS
1. A wide operating temperature range (Ϫ40°C to ϩ105°C)
and highly linear output make the TMP17 an ideal substi-
tute for older, more limited sensor technologies (i.e., therm-
istors, RTDs, diodes, thermocouples).
2. The TMP17 is electrically rugged; supply irregularities and
variations or reverse voltages up to 20 V will not damage
the device.
3. Because the TMP17 is a temperature dependent current
source, it is immune to voltage noise pickup and IR drops in
the signal leads when used remotely.
4. The high output impedance of the TMP17 provides greater
than 0.5°C/V rejection of supply voltage drift and ripple.
5. Laser wafer trimming and temperature testing insures that
TMP17 units are easily interchangeable.
6. Initial system accuracy will not degrade significantly over
time. The TMP17 has proven long term performance and
repeatability advantages inherent in integrated circuit design
and construction.
*Protected by U.S. Patent No. 4,123,698
REV. 0
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.
© Analog Devices, Inc., 1996
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703

1 page




TMP17FS pdf
If greater accuracy is desired, initial calibration and scale factor
errors can be removed by using the TMP17 in the circuit of
Figure 11.
+5V
REF43
8.66k
R1
1k
97.6k
R2
5k
OP196
7.87k
TMP17
VOUT = 100mV/oC
V–
Figure 11. 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 by adjusting R2 trims out scale
factor error. The only error remaining over the temperature
range being trimmed for its nonlinearity. A typical plot of two
trim accuracy is given in Figure 12.
SUPPLY VOLTAGE AND THERMAL ENVIRONMENT
EFFECTS
The power supply rejection characteristics of the TMP17
minimize 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 TMP17 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
2.0
40 25
0 25
TEMPERATURE – C
75
105
TMP17
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
ϩ25°C with a 5 V supply the magnitude of the error is 0.2°C or
less. A small glued-on heat sink will reduce the temperature
error in high temperature, large supply voltage situations.
Table I. Thermal Characteristics
Medium
Still Air
Moving Air @ 500 FPM
Fluorinert Liquid
θJA (؇C/watt)
158
60
35
τ (sec)*
52
10
2
NOTES
*τ is an average of one time constant (63.2% of final value). In cases where the
thermal response is not a simple exponential function, the actual thermal
response may be better than indicated.
Response of the TMP17 output to abrupt changes in ambient
temperature can be modeled by a single time constant τ
exponential function. Figures 3 and 4 show typical response
time plots for media of interest.
The time constant, τ, is dependent on θJA and the thermal
capacities of the chip and the package. Table I lists the effective
τ (time to reach 63.2% of the final value) for several different
media. Copper printed circuit board connections will sink or
conduct heat directly through the TMP17’s soldered leads.
When faster response is required a thermally conductive grease
or glue between the TMP17 and the surface temperature being
measured should be used.
MOUNTING CONSIDERATIONS
If the TMP17 is thermally attached and properly protected, it
can be used in any temperature measuring situation where the
maximum range of temperatures encountered is between Ϫ40°C
and ϩ105°C. Thermally conductive epoxy or glue is recom-
mended under typical mounting conditions. In wet environ-
ments condensation at cold temperatures can cause leakage
current related errors and should be avoided by sealing the
device in nonconductive epoxy paint or conformal coating.
APPLICATIONS
Connecting several TMP17 devices in parallel adds the currents
through them and produces a reading proportional to the
average temperature. Series TMP17s will indicate the lowest
temperature because the coldest device limits the series current
flowing through the sensors. Both of these circuits are depicted
in Figure 13.
Figure 12. Typical Two Trim Accuracy
The thermal environment in which the TMP17 is used deter-
mines two performance traits: the effect of self-heating on
accuracy 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
variables; the power consumption level of the circuit and the
thermal resistance between the chip and the ambient environ-
REV. 0
–5–

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