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TMP36GRT View Datasheet(PDF) - Analog Devices

Part Name
Description
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TMP36GRT
ADI
Analog Devices ADI
TMP36GRT Datasheet PDF : 16 Pages
First Prev 11 12 13 14 15 16
3.3V < VS < 5.5V
TMP35/TMP36/TMP37
0.1F
VS
TMP35
VOUT
R3
10M
5%
R4
4.99k
R5*
1.21M
P1
50k
GND
TYPE K
THERMO-
COUPLE
CHROMEL
ALUMEL
COLD
JUNCTION
0؇C Յ T Յ 250؇C
ISOTHERMAL
BLOCK
R1*
24.9k
CU
0.1F
7
2
6
OP193
3
4
CU
NOTE: ALL RESISTORS 1%
UNLESS OTHERWISE NOTED
R2*
102
VOUT
0V – 2.5V
R6
100k
5%
Figure 8. A Single-Supply, Type K Thermocouple Signal Conditioning Circuit with Cold-Junction Compensation
Illustrated in Figure 9 is a way to convert the output voltage of a
TMP3x sensor into a current to be transmitted down a long
twisted-pair shielded cable to a ground referenced receiver. The
temperature sensors do not possess the capability of high output
current operation; thus, a garden variety PNP transistor is used
to boost the output current drive of the circuit. As shown in the
table, the values of R2 and R3 were chosen to produce an arbi-
trary full-scale output current of 2 mA. Lower values for the
full-scale current are not recommended. The minimum-scale
output current produced by the circuit could be contaminated
by nearby ambient magnetic fields operating in the vicinity of
the circuit/cable pair. Because of the use of an external transis-
tor, the minimum recommended operating voltage for this
circuit is 5 V. Note, to minimize the effects of EMI (or RFI),
both the circuit’s and the temperature sensor’s supply pins are
bypassed with good quality, ceramic capacitors.
R1
4.7k
0.1F
0.01F
VS
TMP3x
2N2907
VOUT
5V
VOUT
R3
GND
R2
SENSOR R2 R3
TMP35 634 634
TMP36 887 887
TMP37 1k 1k
TWISTED PAIR
BELDEN TYPE 9502
OR EQUIVALENT
Figure 9. A Remote, 2-Wire Boosted Output Current Tem-
perature Sensor
A Temperature to 4–20 mA Loop Transmitter
In many process control applications, 2-wire transmitters are
used to convey analog signals through noisy ambient environ-
ments. These current transmitters use a “zero-scale” signal
current of 4 mA that can be used to power the transmitter’s
signal conditioning circuitry. The “full-scale” output signal in
these transmitters is 20 mA.
A circuit that transmits temperature information in this fashion
is illustrated in Figure 10. Using a TMP3x as the temperature
sensor, the output current is linearly proportional to the tem-
perature of the medium. The entire circuit operates from the
3 V output of the REF193. The REF193 requires no external
trimming for two reasons: (1) the REF193’s tight initial output
voltage tolerance and (2) the low supply current of TMP3x, the
OP193 and the REF193. The entire circuit consumes less than
3 mA from a total budget of 4 mA. The OP193 regulates the
output current to satisfy the current summation at the noninverting
node of the OP193. A generalized expression for the KCL
equation at the OP193’s Pin 3 is given by:
IOUT
=
1
 R 7
×

TMP
3x
R1
×
R3
+VREF ×
R2
R3

For each of the three temperature sensors, the table below illus-
trates the values for each of the components, P1, P2, and R1–R4:
Table II. Circuit Element Values for Loop Transmitter
Sensor R1() P1() R2() P2() R3() R4()
TMP35 97.6 k 5 k
TMP36 97.6 k 5 k
TMP37 97.6 k 5 k
1.58 M 100 k 140 k 56.2 k
931 k 50 k 97.6 k 47 k
10.5 k 500 84.5 k 8.45 k
REV. C
–11–
 

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