TMP37GT9Z Analog Devices Inc, TMP37GT9Z Datasheet - Page 14

• Manufacturer Part Number: TMP37GT9Z
• Description: 3V TEMPERATURE SENSOR
• Manufacturer: Analog Devices Inc

Specifications of TMP37GT9Z

• Sensing Temperature: 5°C ~ 100°C
• Output Type: Voltage
• Voltage - Supply: 2.7 V ~ 5.5 V
• Accuracy: ±1°C
• Package / Case: TO-226-3, TO-92-3 (TO-226AA)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

TMP35/TMP36/TMP37
THERMOCOUPLE SIGNAL CONDITIONING WITH
COLD-JUNCTION COMPENSATION
The circuit in Figure 31 conditions the output of a Type K
thermocouple, while providing cold-junction compensation for
temperatures between 0°C and 250°C. The circuit operates from
a single 3.3 V to 5.5 V supply and is designed to produce an
output voltage transfer characteristic of 10 mV/°C.
A Type K thermocouple exhibits a Seebeck coefficient of
approximately 41 μV/°C; therefore, at the cold junction, the
TMP35, with a temperature coefficient of 10 mV/°C, is used
with R1 and R2 to introduce an opposing cold-junction temp-
erature coefficient of −41 μV/°C. This prevents the isothermal,
cold-junction connection between the PCB tracks of the circuit
TYPE K
THERMO-
COUPLE
0°C ≤ T
A
CHROMEL
ALUMEL
Figure 31. Single-Supply, Type K Thermocouple Signal Conditioning Circuit with Cold-Junction Compensation
0.1µF
≤ 250°C
+
–
ISOTHERMAL
JUNCTION
TMP35
COLD
BLOCK
GND
+V
S
V
OUT
CU
CU
Rev. F | Page 14 of 20
102Ω
R1
24.9kΩ
R2
1
1
3.3V < +V
NOTE:
1
ALL RESISTORS 1% UNLESS OTHERWISE NOTED.
and the wires of the thermocouple from introducing an error in
the measured temperature. This compensation works extremely
well for circuit ambient temperatures in the range of 20°C to 50°C.
Over a 250°C measurement temperature range, the thermocouple
produces an output voltage change of 10.151 mV. Because the
required output full-scale voltage of the circuit is 2.5 V, the gain
of the circuit is set to 246.3. Choosing R4 equal to 4.99 kΩ sets
R5 equal to 1.22 MΩ. Because the closest 1% value for R5 is
1.21 MΩ, a 50 kΩ potentiometer is used with R5 for fine trim of
the full-scale output voltage. Although the OP193 is a superior
single-supply, micropower operational amplifier, its output stage
is not rail-to-rail; therefore, the 0°C output voltage level is 0.1 V.
If this circuit is digitized by a single-supply ADC, the ADC
common should be adjusted to 0.1 V accordingly.
S
R3
10MΩ
5%
< 5.5V
4.99kΩ
R4
2
3
–
+
OP193
7
4
0.1µF
1.21MΩ
6
R5
1
R6
100kΩ
5%
50kΩ
P1
V
0V TO 2.5V
OUT