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TMP17FS Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer TMP17FS
Beschreibung Low Cost/ Current Output Temperature Transducer
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 8 Seiten
TMP17FS Datasheet, Funktion
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






TMP17FS Datasheet, Funktion
TMP17
+5V
TMP17
333.3
(0.1%)
VTAVG (1mV/K)
+15V
TMP17
TMP17
TMP17
10k
(0.1%)
VTAVG (10mV/K)
Figure 13. Average and Minimum Temperature
Connections
The circuit of Figure 14 demonstrates a method in which a
voltage output can be derived in a differential temperature
measurement.
+V
TMP17
R1
TMP17 50k
5M
10k
10k
OP196
VOUT = (T1 – T2) x
(10mV/oC)
–V
Figure 14. Differential Measurements
R1 can be used to trim out the inherent offset between the two
devices. By increasing the gain resistor (10 k) temperature
measurements can be made with higher resolution. If the
magnitude of Vϩ and VϪ is not the same, the difference in
power consumption between the two devices can cause a
differential self-heating error.
Cold junction compensation (CJC) used in thermocouple signal
conditioning can be implemented using a TMP17 in the circuit
configuration of Figure 15. Expensive simulated ice baths or
hard to trim, inaccurate bridge circuits are no longer required.
MEASURING
JUNCTION
+7.5V
REF43
2.5V
10k
Cu 1k
TMP17
REFERENCE
Cu JUNCTION
100k
THERMOCOUPLE
TYPE
J
K
T
E
S
R
APPROX.
R VALUE
52
41
41
61
6
6
OP193
VOUT
RG2
(1k)
RG1
R
Figure 15. Thermocouple Cold Junction Compensation
The circuit shown can be optimized for any ambient tempera-
ture range or thermocouple type by simply selecting the correct
value for the scaling resistor – R. The TMP17 output (1 µA/K)
times R should approximate the line best fit to the thermocouple
curve (slope in V/°C) over the most likely ambient temperature
range. Additionally, the output sensitivity can be chosen by
selecting the resistors RG1 and RG2 for the desired noninverting
gain. The offset adjustment shown simply references the
TMP17 to °C. Note that the TC’s of the reference and the
resistors are the primary contributors to error. Temperature
rejection of 40 to 1 can be easily achieved using the above
technique.
Although the TMP17 offers a noise immune current output, it
is not compatible with process control/industrial automation
current loop standards. Figure 16 is an example of a tempera-
ture to 4–20 mA transmitter for use with 40 V, 1 ksystems.
In this circuit the 1 µA/K output of the TMP17 is amplified to
1 mA/°C and offset so that 4 mA is equivalent to 17°C and
20 mA is equivalent to 33°C. Rt is trimmed for proper reading
at an intermediate reference temperature. With a suitable choice
of resistors, any temperature range within the operating limits of
the TMP17 may be chosen.
REF01E
TMP17
35.7k
10mV/ C RT
5k
17 C 4mA
33 C 20µA
1mA/ C
+20V
OP97
C 10k12.7k
5k500
10
VT
–20V
Figure 16. Temperature to 4–20 mA Current Transmitter
Reading temperature with a TMP17 in a microprocessor based
system can be implemented with the circuit shown in Figure 17.
+5V
REF43
2.5V
ROFFSET
R RCAL
ROFFSET/RGAIN
RGAIN
OP196
ROFFSET
C 9.1k
F 9.8k
RGAIN
100k
180k
VOUT = 100mV/( C OR F)
TMP17
V–
Figure 17. Temperature to Digital Output
By using a differential input A/D converter and choosing the
current to voltage conversion resistor correctly, any range of
temperatures (up to the 145°C span the TMP17 is rated for)
centered at any point can be measured using a minimal number
of components. In this configuration the system will resolve up
to 1°C.
–6– REV. 0

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