Электронный компонент: TMP36

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REV. C

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 that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.

a

TMP35/TMP36/TMP37

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700

www.analog.com

Fax: 781/326-8703

� Analog Devices, Inc., 2002

Low Voltage Temperature Sensors

FUNCTIONAL BLOCK DIAGRAM

+Vs (2.7V to 5.5V)

V

OUT

SHUTDOWN

TMP35/
TMP36/

TMP37

PACKAGE TYPES AVAILABLE

RT-5 (SOT-23)

1

2

3

5

4

TOP VIEW

(Not to Scale)

NC = NO CONNECT

V

OUT

SHUTDOWN

GND

NC

+V

S

RN-8 (SOIC)

1

2

3

4

8

7

6

5

TOP VIEW

(Not to Scale)

NC = NO CONNECT

V

OUT

SHUTDOWN

NC

NC

+V

S

NC

NC

GND

TO-92

1

3

2

BOTTOM VIEW

(Not to Scale)

PIN 1, +Vs; PIN 2, V

OUT

; PIN 3, GND

FEATURES
Low Voltage Operation (2.7 V to 5.5 V)
Calibrated Directly in C
10 mV/ C Scale Factor (20 mV/ C on TMP37)

2 C Accuracy over Temperature (Typ)
0.5 C Linearity (Typ)

Stable with Large Capacitive Loads
Specified �40 C to +125 C, Operation to +150 C
Less than 50 A Quiescent Current
Shutdown Current 0.5 A Max
Low Self-Heating

APPLICATIONS
Environmental Control Systems
Thermal Protection
Industrial Process Control
Fire Alarms
Power System Monitors
CPU Thermal Management

PRODUCT DESCRIPTION

The TMP35, TMP36, and TMP37 are low voltage, precision
centigrade temperature sensors. They provide a voltage output
that is linearly proportional to the Celsius (Centigrade) tem-
perature. The TMP35/TMP36/TMP37 do not require any
external calibration to provide typical accuracies of

�1�C at

+25

�C and �2�C over the �40�C to +125�C temperature range.

The low output impedance of the TMP35/TMP36/TMP37 and
its linear output and precise calibration simplify interfacing to
temperature control circuitry and A/D converters. All three
devices are intended for single-supply operation from 2.7 V to
5.5 V maximum. Supply current runs well below 50

�A, providing

very low self-heating--less than 0.1

�C in still air. In addition, a

shutdown function is provided to cut supply current to less
than 0.5

�A.

The TMP35 is functionally compatible with the LM35/LM45 and
provides a 250 mV output at 25

�C. The TMP35 reads temperatures

from 10

�C to 125�C. The TMP36 is specified from �40�C to

+125

�C, provides a 750 mV output at 25�C, and operates to

+125

�C from a single 2.7 V supply. The TMP36 is functionally

compatible with the LM50. Both the TMP35 and TMP36 have
an output scale factor of 10 mV/

�C. The TMP37 is intended for

applications over the range 5

�C to 100�C and provides an output

scale factor of 20 mV/

�C. The TMP37 provides a 500 mV output

at 25

�C. Operation extends to 150�C with reduced accuracy for all

devices when operating from a 5 V supply.

The TMP35/TMP36/TMP37 are all available in low cost 3-lead
TO-92, SOIC-8, and 5-lead SOT-23 surface-mount packages.

REV. C

�2�

TMP35/TMP36/TMP37�SPECIFICATIONS

1

(V

S

= 2.7 V to 5.5 V, �40 C

T

A

+125 C, unless

otherwise noted.)

Parameter

Symbol

Conditions

Min

Typ

Max

Unit

ACCURACY

TMP35/TMP36/TMP37F

T

A

= 25

�C

�1

�2

�C

TMP35/TMP36/TMP37G

T

A

= 25

�C

�1

�3

�C

TMP35/TMP36/TMP37F

Over Rated Temperature

�2

�3

�C

TMP35/TMP36/TMP37G

Over Rated Temperature

�2

�4

�C

Scale Factor, TMP35

10

�C T

A

125�C

10

9.8/10.2

mV/

�C

Scale Factor, TMP36

�40

�C T

A

+125�C

10

9.8/10.2

mV/

�C

Scale Factor, TMP37

5

�C T

A

85�C

20

19.6/20.4

mV/

�C

5

�C T

A

100�C

20

19.6/20.4

mV/

�C

3.0 V

+V

S

5.5 V

Load Regulation

0

�A I

L

50 �A

�40

�C T

A

+105�C

6

20

m

�C/�A

�105

�C T

A

+125�C

25

60

m

�C/�A

Power Supply Rejection Ratio

PSRR

T

A

= 25

�C

30

100

m

�C/V

3.0 V

+V

S

5.5 V

50

m

�C/V

Linearity

0.5

�C

Long-Term Stability

T

A

= 150

�C for 1 kHrs

0.4

�C

SHUTDOWN

Logic High Input Voltage

V

IH

V

S

= 2.7 V

1.8

V

Logic Low Input Voltage

V

IL

V

S

= 5.5 V

400

mV

OUTPUT

TMP35 Output Voltage

T

A

= 25

�C

250

mV

TMP36 Output Voltage

T

A

= 25

�C

750

mV

TMP37 Output Voltage

T

A

= 25

�C

500

mV

Output Voltage Range

100

2000

mV

Output Load Current

I

L

0

50

�A

Short-Circuit Current

I

SC

Note 2

250

�A

Capacitive Load Driving

C

L

No Oscillations

2

1000

10000

pF

Device Turn-On Time

Output within

�1�C

0.5

1

ms

100 k

100 pF Load

2

POWER SUPPLY

Supply Range

+V

S

2.7

5.5

V

Supply Current

I

SY (ON)

Unloaded

50

�A

Supply Current (Shutdown)

I

SY (OFF)

Unloaded

0.01

0.5

�A

NOTES

1

Does not consider errors caused by self-heating.

2

Guaranteed but not tested.

Specifications subject to change without notice.

TEMPERATURE � C

�50

LOAD REG � m

C/

A

0

50

100

150

50

30

20

10

0

40

Figure 1. Load Reg vs. Temperature (m

�C/�A)

REV. C

TMP35/TMP36/TMP37

�3�

ABSOLUTE MAXIMUM RATINGS

1, 2, 3

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7 V

Shutdown Pin . . . . . . . . . . . . . . GND

SHUTDOWN

+V

S

Output Pin . . . . . . . . . . . . . . . . . . . . . . GND V

OUT

+V

S

Operating Temperature Range . . . . . . . . . .

�55�C to +150�C

Dice Junction Temperature . . . . . . . . . . . . . . . . . . . . . . 175

�C

Storage Temperature Range . . . . . . . . . . . .

�65�C to +160�C

Lead Temperature (Soldering, 60 sec) . . . . . . . . . . . . . 300

�C

NOTES

1

Stresses above those listed under Absolute Maximum Ratings may cause perma-

nent damage to the device. This is a stress rating only; functional operation at or
above this specification is not implied. Exposure to maximum rating conditions for
extended periods may affect device reliability.

2

Digital inputs are protected; however, permanent damage may occur on unpro-
tected units from high energy electrostatic fields. Keep units in conductive foam
or packaging at all times until ready to use. Use proper antistatic handling
procedures.

3

Remove power before inserting or removing units from their sockets.

Package Type

JA

JC

Unit

TO-92 (T9 Suffix)

162

120

�C/W

SOIC-8 (S Suffix)

158

43

�C/W

SOT-23 (RT Suffix)

300

180

�C/W

JA

is specified for device in socket (worst-case conditions).

ORDERING GUIDE

Accuracy

Linear

at 25 C

Operating

Package

Model

( C max)

Temperature Range

Options

1

TMP35FT9

�2.0

10

�C to 125�C

TO-92

TMP35GT9

�3.0

10

�C to 125�C

TO-92

TMP35FS

�2.0

10

�C to 125�C

RN-8

TMP35GS

�3.0

10

�C to 125�C

RN-8

TMP35GRT

2

�3.0

10

�C to 125�C

RT-5

TMP36FT9

�2.0

�40

�C to +125�C

TO-92

TMP36GT9

�3.0

�40

�C to +125�C

TO-92

TMP36FS

�2.0

�40

�C to +125�C

RN-8

TMP36GS

�3.0

�40

�C to +125�C

RN-8

TMP36GRT

2

�3.0

�40

�C to +125�C

RT-5

TMP37FT9

�2.0

5

�C to 100�C

TO-92

TMP37GT9

�3.0

5

�C to 100�C

TO-92

TMP37FS

�2.0

5

�C to 100�C

RN-8

TMP37GS

�3.0

5

�C to 100�C

RN-8

TMP37GRT

2

�3.0

5

�C to 100�C

RT-5

NOTES

1

SOIC = Small Outline Integrated Circuit; RT = Plastic Surface Mount;

TO = Plastic.

2

Consult factory for availability.

FUNCTIONAL DESCRIPTION

An equivalent circuit for the TMP3x family of micropower,
centigrade temperature sensors is shown in Figure 2. At the
heart of the temperature sensor is a band gap core, which is
comprised of transistors Q1 and Q2, biased by Q3 to approxi-
mately 8

�A. The band gap core operates both Q1 and Q2 at the

same collector current level; however, since the emitter area of
Q1 is 10 times that of Q2, Q1's V

BE

and Q2's V

BE

are not equal

by the following relationship:

V

BE

=V

T

� ln

A

E ,Q1

A

E ,Q2

SHDN

+V

OUT

+V

S

3X

25 A

2X

Q2
1X

R1

R2

R3

7.5 A

Q3

2X

GND

Q4

Q1

10X

6X

Figure 2. Temperature Sensor Simplified

Equivalent Circuit

Resistors R1 and R2 are used to scale this result to produce the
output voltage transfer characteristic of each temperature sensor
and, simultaneously, R2 and R3 are used to scale Q1's V

BE

as

an offset term in V

OUT

. Table I summarizes the differences

between the three temperature sensors' output characteristics.

Table I. TMP3x Output Characteristics

Offset

Output Voltage

Output Voltage

Sensor

Voltage (V)

Scaling (mV/ C)

@ 25 C (mV)

TMP35

0

10

250

TMP36

0.5

10

750

TMP37

0

20

500

The output voltage of the temperature sensor is available at the
emitter of Q4, which buffers the band gap core and provides
load current drive. Q4's current gain, working with the available
base current drive from the previous stage, sets the short-circuit
current limit of these devices to 250

�A.

CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although
the TMP35/TMP36/TMP37 features proprietary ESD protection circuitry, permanent damage
may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD
precautions are recommended to avoid performance degradation or loss of functionality.

WARNING!

ESD SENSITIVE DEVICE

REV. C

TMP35/TMP36/TMP37

�4�

TEMPERATURE � C

1.4

0

1.2

1.0

0.8

0.6

0.4

0.2

1.6

1.8

2.0

50

25

0

25

50

75

100

125

OUTPUT VOLTAGE � V

a

b

c

a. TMP35
b. TMP36
c. TMP37

V

S

= 3V

TPC 1. Output Voltage vs. Temperature

a. MAXIMUM LIMIT (G GRADE)
b. TYPICAL ACCURACY ERROR
c. MINIMUM LIMIT (G GRADE)

TEMPERATURE � C

2

5

1

0

1

2

3

4

3

4

5

0

20

40

60

80

100

120

140

a

b

c

ACCURACY ERROR �

C

TPC 2. Accuracy Error vs. Temperature

TEMPERATURE � C

0.4

0.3

0

50

125

25

0

25

50

75

100

0.2

0.1

POWER SUPPLY REJECTION �

C/V

V+ = 3V to 5.5V, NO LOAD

TPC 3. Power Supply Rejection vs. Temperature

FREQUENCY � Hz

100

0.01

20

100k

100

1k

10k

31.6

10

3.16

1

0.32

0.1

0.032

POWER SUPPLY REJECTION �

C/V

TPC 4. Power Supply Rejection vs. Frequency

TEMPERATURE � C

4

3

0

2

1

5

50

125

25

0

25

50

75

100

MINIMUM SUPPLY VOLTAGE � V

b

a

MINIMUM SUPPLY VOLTAGE REQUIRED TO MEET
DATA SHEET SPECIFICATION

NO LOAD

a. TMP35/TMP36
b. TMP37

TPC 5. Minimum Supply Voltage vs. Temperature

SUPPLY CURRENT �

A

TEMPERATURE � C

50

40

10

30

20

60

50

125

25

0

25

50

75

100

NO LOAD

b

a

a. V+ = 5V
b. V+ = 3V

TPC 6. Supply Current vs. Temperature

� Typical Performance Characteristics

REV. C

TMP35/TMP36/TMP37

�5�

SUPPLY VOLTAGE � V

40

30

0

20

10

50

0

7

1

2

3

4

5

6

SUPPLY CURRENT �

A

T

A

= 25�C, NO LOAD

8

TPC 7. Supply Current vs. Supply Voltage

TEMPERATURE � C

40

30

0

20

10

50

50

125

25

0

25

50

75

100

a. V+ = 5V

b. V+ = 3V

NO LOAD

a

b

SUPPLY CURRENT � nA

TPC 8. Supply Current vs. Temperature (Shutdown = 0 V)

TEMPERATURE � C

400

300

0

200

100

50

125

25

0

25

50

75

100

= V+ AND SHUTDOWN PINS
LOW TO HIGH (0V TO 3V)
V

OUT

SETTLES WITHIN �1�C

= V+ AND SHUTDOWN PINS
HIGH TO LOW (3V TO 0V)

RESPONSE TIME �

s

TPC 9. V

OUT

Response Time for V+ Power-Up/Power-

Down vs. Temperature

TEMPERATURE � C

400

300

0

200

100

50

125

25

0

25

50

75

100

= SHUTDOWN PIN
HIGH TO LOW (3V TO 0V)

= SHUTDOWN PIN
LOW TO HIGH (0V TO 3V)
V

OUT

SETTLES WITHIN �1�C

RESPONSE TIME �

s

TPC 10. V

OUT

Response Time for Shutdown Pin vs.

Temperature

TIME � �s

0

1.0

0.8

0.6

0.4

0.2

50

250

0

100

50

150

200

300

350

400

450

OUTPUT VOLTAGE � V

0

1.0

0.8

0.6

0.4

0.2

V+ = 3V

SHUTDOWN =
SIGNAL

T

A

= 25 C

V+ AND SHUTDOWN =

T

A

= 25 C

SIGNAL

TPC 11. V

OUT

Response Time to Shutdown and V+

Pins vs. Time

TIME � sec

70

0

60

50

40

30

20

10

80

90

100

110

0

100

200

300

400

500

600

a

b

c

V

IN

= 3V, 5V

PERCENT OF CHANGE � %

a. TMP35 SOIC SOLDERED TO 0.5" x 0.3" Cu PCB
b. TMP36 SOIC SOLDERED TO 0.6" x 0.4" Cu PCB
c. TMP35 TO-92 IN SOCKET SOLDERED TO
1" x 0.4" Cu PCB

TPC 12. Thermal Response Time in Still Air

REV. C

TMP35/TMP36/TMP37

�6�

AIR VELOCITY � FPM

0

60

40

20

80

140

100

120

0

100

200

300

400

500

600

TIME CONSTANT � sec

a

b

c

a. TMP35 SOIC SOLDERED TO 0.5" x 0.3" Cu PCB
b. TMP36 SOIC SOLDERED TO 0.6" x 0.4" Cu PC
c. TMP35 TO-92 IN SOCKET SOLDERED TO
1" x 0.4" Cu PCB

V

IN

= 3V, 5V

700

TPC 13. Thermal Response Time Constant in Forced Air

TIME � sec

70

0

60

50

40

30

20

10

80

90

100

110

0

10

20

30

40

50

60

a

b

c

CHANGE � %

V

IN

= 3V, 5V

a. TMP35 SOIC SOLDERED TO 0.5" x 0.3" Cu PCB
b. TMP36 SOIC SOLDERED TO 0.6" x 0.4" Cu PCB
c. TMP35 TO-92 IN SOCKET SOLDERED TO
1" x 0.4" Cu PCB

TPC 14. Thermal Response Time in Stirred Oil Bath

10

0%

100

90

1ms

10mV

TIME/DIVISION

VOLT/DIVISION

TPC 15. Temperature Sensor Wideband Output
Noise Voltage. Gain = 100, BW = 157 kHz

a

b

FREQUENCY � Hz

2400

1000

0

10

10k

100

1k

2200

2000

1600

1800

1400

1200

800

600

400

200

a. TMP35/36

b. TMP37

VOLTAGE NOISE DENSITY � nV/

Hz

TPC 16. Voltage Noise Spectral Density vs. Frequency

REV. C

TMP35/TMP36/TMP37

�7�

APPLICATIONS SECTION
Shutdown Operation

All TMP3x devices include a shutdown capability that reduces the
power supply drain to less than 0.5

�A maximum. This feature,

available only in the SOIC-8 and the SOT-23 packages, is TTL/
CMOS level compatible, provided that the temperature sensor
supply voltage is equal in magnitude to the logic supply voltage.
Internal to the TMP3x at the

SHUTDOWN pin, a pull-up current

source to V

IN

is connected. This permits the

SHUTDOWN pin to

be driven from an open-collector/drain driver. A logic LOW, or
zero-volt condition on the

SHUTDOWN pin, is required to turn

the output stage OFF. During shutdown, the output of the
temperature sensors becomes a high impedance state where the
potential of the output pin would then be determined by external
circuitry. If the shutdown feature is not used, it is recommended
that the

SHUTDOWN pin be connected to V

IN

(Pin 8 on the

SOIC-8, Pin 2 on the SOT-23).

The shutdown response time of these temperature sensors is
illustrated in TPCs 9, 10, and 11.

Mounting Considerations

If the TMP3x temperature sensors are thermally attached and
protected, they can be used in any temperature measurement
application where the maximum temperature range of the
medium is between �40

�C to +125�C. Properly cemented or

glued to the surface of the medium, these sensors will be within
0.01

�C of the surface temperature. Caution should be exercised,

especially with TO-92 packages, because the leads and any
wiring to the device can act as heat pipes, introducing errors if
the surrounding air-surface interface is not isothermal. Avoiding
this condition is easily achieved by dabbing the leads of the
temperature sensor and the hookup wires with a bead of
thermally conductive epoxy. This will ensure that the TMP3x
die temperature is not affected by the surrounding air temperature.

Because plastic IC packaging technology is used, excessive
mechanical stress should be avoided when fastening the device
with a clamp or a screw-on heat tab. Thermally conductive epoxy
or glue, which must be electrically nonconductive, is recommended
under typical mounting conditions.

These temperature sensors, as well as any associated circuitry,
should be kept insulated and dry to avoid leakage and corrosion.
In wet or corrosive environments, any electrically isolated metal
or ceramic well can be used to shield the temperature sensors.
Condensation at very cold temperatures can cause errors and
should be avoided by sealing the device, using electrically non-
conductive epoxy paints or dip or any one of many printed circuit
board coatings and varnishes.

Thermal Environment Effects

The thermal environment in which the TMP3x sensors are used
determines two important characteristics: self-heating effects
and thermal response time. Illustrated in Figure 3 is a thermal
model of the TMP3x temperature sensors that is useful in
understanding these characteristics.

T

J

JC

T

C

CA

C

CH

C

C

P

D

T

A

Figure 3. Thermal Circuit Model

In the TO-92 package, the thermal resistance junction-to-case,

JC

, is 120

�C/W. The thermal resistance case-to-ambient,

CA

, is

the difference between

JA

and

JC

, and is determined by the

characteristics of the thermal connection. The temperature
sensor's power dissipation, represented by P

D

, is the product of

the total voltage across the device and its total supply current
(including any current delivered to the load). The rise in die
temperature above the medium's ambient temperature is given by:

T

P

T

D

C

CA

A

J

J

=

�

+

(

)

+

Thus, the die temperature rise of a TMP35 "RT" package
mounted into a socket in still air at 25

�C and driven from a 5 V

supply is less than 0.04

�C.

The transient response of the TMP3x sensors to a step change
in the temperature is determined by the thermal resistances and
the thermal capacities of the die, C

CH

, and the case, C

C

. The

thermal capacity of the case, C

C

, varies with the measurement

medium since it includes anything in direct contact with the
package. In all practical cases, the thermal capacity of the case is
the limiting factor in the thermal response time of the sensor
and can be represented by a single-pole RC time constant
response. TPCs 12 and 14 illustrate the thermal response time
of the TMP3x sensors under various conditions. The thermal
time constant of a temperature sensor is defined as the time
required for the sensor to reach 63.2% of the final value for a
step change in the temperature. For example, the thermal time
constant of a TMP35 "S" package sensor mounted onto a 0.5"
by 0.3" PCB is less than 50 sec in air, whereas in a stirred oil
bath, the time constant is less than 3 seconds.

Basic Temperature Sensor Connections

Figure 4 illustrates the basic circuit configuration for the
TMP3x family of temperature sensors. The table shown in the
figure illustrates the pin assignments of the temperature sensors
for the three package types. For the SOT-23, Pin 3 is labeled as
"NC" as are Pins 2, 3, 6, and 7 on the SOIC-8 package. It is
recommended that no electrical connections be made to
these pins. If the shutdown feature is not needed on the
SOT-23 or the SOIC-8 package, the

SHUTDOWN pin

should be connected to V

S

.

2.7V < Vs < 5.5V

V

OUT

TMP3x

0.1 F

Vs

GND

PACKAGE

V

S

GND

V

OUT

SHDN

SOIC-8

8

4

1

5

SOT-23-5

2

5

1

4

TO-92

1

3

2

NA

PIN ASSIGNMENTS

SHDN

Figure 4. Basic Temperature Sensor Circuit Configuration

REV. C

TMP35/TMP36/TMP37

�8�

Note the 0.1

�F bypass capacitor on the input. This capacitor

should be a ceramic type, have very short leads (surface mount
would be preferable), and be located as close a physical proxim-
ity to the temperature sensor supply pin as practical. Since these
temperature sensors operate on very little supply current and
could be exposed to very hostile electrical environments, it is
important to minimize the effects of RFI (radio frequency
interference) on these devices. The effect of RFI on these
temperature sensors in specific and analog ICs in general is
manifested as abnormal dc shifts in the output voltage due to
the rectification of the high frequency ambient noise by the IC.
In those cases where the devices are operated in the presence of
high frequency radiated or conducted noise, a large value tanta-
lum capacitor ( 2.2

�F) placed across the 0.1 �F ceramic may

offer additional noise immunity.

Fahrenheit Thermometers

Although the TMP3x temperature sensors are centigrade tem-
perature sensors, a few components can be used to convert the
output voltage and transfer characteristics to directly read Fahr-
enheit temperatures. Shown in Figure 5a is an example of a
simple Fahrenheit thermometer using either the TMP35 or the
TMP37. This circuit can be used to sense temperatures from
41

�F to 257�F, with an output transfer characteristic of 1 mV/�F

using the TMP35 and from 41

�F to 212�F using the TMP37

with an output characteristic of 2 mV/

�F. This particular

approach does not lend itself well to the TMP36 because of its
inherent 0.5 V output offset. The circuit is constructed with an
AD589, a 1.23 V voltage reference, and four resistors whose values
for each sensor are shown in the figure table. The scaling of the
output resistance levels was to ensure minimum output loading
on the temperature sensors. A generalized expression for the
circuit's transfer equation is given by:

V

OUT

=

R1

R1

+ R2

TMP 35

(

)

+

R3

R3

+ R4

AD589

(

)

where: TMP35 = Output voltage of the TMP35, or the TMP37,

at the measurement temperature, T

M

, and

AD589 = Output voltage of the reference = 1.23 V.

Note that the output voltage of this circuit is not referenced to
the circuit's common. If this output voltage were to be applied
directly to the input of an ADC, the ADC's common should be
adjusted accordingly.

SENSOR

TCV

OUT

R1 (k )

TMP35

1mV/ F 45.3

10

10

374

TMP37

2mV/ F

45.3

10

10

182

R2 (k ) R3 (k ) R4 (k )

PIN ASSIGNMENTS

TMP35/37

GND

R1

R2

R3

R4

AD589

1.23V

0.1 F

V

OUT

V

S

V

OUT

V

S

Figure 5a. TMP35/TMP37 Fahrenheit Thermometers

The same circuit principles can be applied to the TMP36, but
because of the TMP36's inherent offset, the circuit uses two less
resistors as shown in Figure 5b. In this circuit, the output
voltage transfer characteristic is 1 mV/

�F but is referenced to

the circuit's common; however, there is a 58 mV (58

�F) offset

in the output voltage. For example, the output voltage of the
circuit would read 18 mV were the TMP36 placed in �40

�F

ambient environment and 315 mV at 257

�F.

TMP36

GND

0.1 F

V

OUT

@ 1mV/ F � 58 F

V

OUT

@ �40 F = 18mV

V

OUT

@ +257 F = 315mV

V

OUT

V

S

R1
45.3k

R2
10k

V

S

Figure 5b. TMP36 Fahrenheit Thermometer Version 1

At the expense of additional circuitry, the offset produced by the
circuit in Figure 5b can be avoided by using the circuit in Figure 5c. In
this circuit, the output of the TMP36 is conditioned by a single-
supply, micropower op amp, the OP193. Although the entire
circuit operates from a single 3 V supply, the output voltage of the
circuit reads the temperature directly, with a transfer character-
istic of 1 mV/

�F, without offset. This is accomplished through

the use of an ADM660, a supply voltage inverter. The 3 V
supply is inverted and applied to the P193's V� terminal. Thus,
for a temperature range between �40

�F and +257�F, the

output of the circuit reads �40 mV to +257 mV. A general
expression for the circuit's transfer equation is given by:

V

OUT

=

R6

R5

+ R6

1+

R4

R3

TMP 36

(

)

-

R4

R3

V

S

2

Average and Differential Temperature Measurement

In many commercial and industrial environments, temperature
sensors are often used to measure the average temperature in a
building, or the difference in temperature between two locations
on a factory floor or in an industrial process. The circuits in
Figures 6a and 6b demonstrate an inexpensive approach
to average and differential temperature measurement.
In Figure 6a, an OP193 is used to sum the outputs of three
temperature sensors to produce an output voltage scaled by
10 mV/

�C that represents the average temperature at three loca-

tions. The circuit can be extended to as many temperature
sensors as required as long as the circuit's transfer equation
is maintained. In this application, it is recommended that one
temperature sensor type be used throughout the circuit; other-
wise, the output voltage of the circuit will not produce an
accurate reading of the various ambient conditions.

REV. C

TMP35/TMP36/TMP37

�9�

The circuit in Figure 6b illustrates how a pair of TMP3x sensors
can be used with an OP193 configured as a difference amplifier
to read the difference in temperature between two locations. In
these applications, it is always possible that one temperature
sensor would be reading a temperature below that of the other
sensor. To accommodate this condition, the output of the OP193
is offset to a voltage at one-half the supply via R5 and R6. Thus,
the output voltage of the circuit is measured relative to this point,

OP193

0.1 F

2

3

4

1

7

V

TEMP( AVG)

@ 10mV/ C FOR TMP35/36
@ 20mV/ C FOR TMP35/36

2.7V < +V

S

< 5.5V

FOR R1 = R2 = R3 = R;

V

TEMP( AVG)

= 1 (TMP3x

1

+ TMP3x

2

+ TMP3x

3

)

3

R1

300k

R2

300k

R3

300k

TMP3x

TMP3x

TMP3x

R4

7.5k

R1

3

R4 = R6

R6
7.5k

R5
100k

R5 =

Figure 6a. Configuring Multiple Sensors for Average
Temperature Measurements

ELEMENT

R2

R4

R5

R6

TMP36

V

OUT

R1

50k

V

S

ADM660

TMP36

OP193

R2

50k

R3

R4

+3V

C1

10 F

R5

0.1 F

10 F

�3V

10 F/0.1 F

GND

NC

10 F

NC

R6

1

2

3

4

5

6

7

2

3

4

6

8

8

V

OUT

@ 1mV/ F

�40 F T

A

+257 F

258.6k

10k

47.7k

10k

Figure 5c. TMP36 Fahrenheit Thermometer Version 2

as shown in the figure. Using the TMP36, the output voltage of
the circuit is scaled by 10 mV/

�C. To minimize error in the differ-

ence between the two measured temperatures, a common, readily
available thin-film resistor network is used for R1�R4.

TMP36

@ T1

0.1 F

0.1 F

2

3

4

6

7

OP193

1 F

V

OUT

R3*

R4*

R2*

R1*

2.7V < V

S

< 5.5V

TMP36

@ T2

R5

100k

R6

100k

V

OUT

= T2 � T1 @ 10mV/ C

V

S

2

*R1�R4, CADDOCK T914�100k�100, OR EQUIVALENT

0.1 F

R7
100k

R8
25k

R9
25k

0 T

A

125 C

CENTERED AT

CENTERED AT

Figure 6b. Configuring Multiple Sensors for Differential
Temperature Measurements

REV. C

TMP35/TMP36/TMP37

�10�

Microprocessor Interrupt Generator

These inexpensive temperature sensors can be used with a
voltage reference and an analog comparator to configure an
interrupt generator useful in microprocessor applications. With
the popularity of fast 486 and Pentium

�

laptop computers, the

need to indicate a microprocessor overtemperature condition
has grown tremendously. The circuit illustrated in Figure 7
demonstrates one way to generate an interrupt using a TMP35,
a CMP402 analog comparator, and a REF191, a 2 V precision
voltage reference.

The circuit has been designed to produce a logic HIGH interrupt
signal if the microprocessor temperature exceeds 80

�C. This

80

�C trip point was arbitrarily chosen (final value set by the

microprocessor thermal reference design) and is set using an
R3�R4 voltage divider of the REF191's output voltage. Since
the output of the TMP35 is scaled by 10 mV/

�C, the voltage at

the CMP402's inverting terminal is set to 0.8 V.

Since temperature is a slowly moving quantity, the possibility
for comparator chatter exists. To avoid this condition, hysteresis
is used around the comparator. In this application, a hysteresis
of 5

�C about the trip point was arbitrarily chosen; the ultimate

value for hysteresis should be determined by the end application.
The output logic voltage swing of the comparator with R1 and
R2 determine the amount of comparator hysteresis. Using a 3.3 V
supply, the output logic voltage swing of the CMP402 is 2.6 V;
thus, for a hysteresis of 5

�C (50 mV @ 10 mV/�C), R1 is set to

20 k

and R2 is set to 1 M. An expression for this circuit's

hysteresis is given by:

V

HYS

=

R1

R2

V

LOGIC SWING, CMP 402

(

)

Because of the likelihood that this circuit would be used in
close proximity to high speed digital circuits, R1 is split into
equal values and a 1000 pF is used to form a low-pass filter
on the output of the TMP35. Furthermore, to prevent high
frequency noise from contaminating the comparator trip point,
a 0.1

�F capacitor is used across R4.

Thermocouple Signal Conditioning with Cold-Junction
Compensation

The circuit in Figure 8 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 single 3.3 V to 5.5 V supplies and has been designed to
produce an output voltage transfer characteristic of 10 mV/

�C.

A Type K thermocouple exhibits a Seebeck coefficient of
approximately 41

�V/�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
temperature coefficient of �41

�V/�C. This prevents the

isothermal, cold-junction connection between the circuit's PCB
tracks and the thermocouple's wires 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.
Since the required circuit's output full-scale voltage is 2.5 V, the
gain of the circuit is set to 246.3. Choosing R4 equal to 4.99 k

sets R5 equal to 1.22 M

. Since the closest 1% value for R5 is

1.21 M

, a 50 k 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; as such, the 0

�C output voltage level is 0.1 V.

If this circuit were to be digitized by a single-supply ADC, the
ADC's common should be adjusted to 0.1 V accordingly.

Using TMP3x Sensors in Remote Locations

In many industrial environments, sensors are required to oper-
ate in the presence of high ambient noise. These noise sources
take on many forms; for example, SCR transients, relays, radio
transmitters, arc welders, ac motors, and so on. They may also
be used at considerable distances from the signal conditioning
circuitry. These high noise environments are very typically in the
form of electric fields, so the voltage output of the tempera-
ture sensor can be susceptible to contamination from these
noise sources.

R2

1M

3

4

V

OUT

V

S

TMP35

0.1 F

GND

0.1 F

C1

INTERRUPT

<80 C

>80 C

REF191

R1A

10k

R1B

10k

3.3V

2

6

C

L

1000pF

R3

16k

1 F

R4
10k

V

REF

0.1 F

0.1 F

C1 = CMP402

4

1

2

4

3

14

13

5

6

R5
100k

Figure 7. Pentium Overtemperature Interrupt Generator

Pentium is a registered trademark of Intel Corporation.

REV. C

TMP35/TMP36/TMP37

�11�

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:

I

OUT

=

1

R 7

�

TMP 3x

� R3

R1

+

V

REF

� R3

R2

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

1.58 M

100 k

140 k

56.2 k

TMP36

97.6 k

5 k

931 k

50 k

97.6 k

47 k

TMP37

97.6 k

5 k

10.5 k

500

84.5 k

8.45 k

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.

TWISTED PAIR
BELDEN TYPE 9502
OR EQUIVALENT

TMP3x

R2

R1

4.7k

V

OUT

0.1 F

2N2907

0.01 F

GND

V

S

5V

R3

V

OUT

SENSOR

R2

R3

TMP35

634

634

TMP36

887

887

TMP37

1k

1k

Figure 9. A Remote, 2-Wire Boosted Output Current Tem-
perature Sensor

V

OUT

V

S

TMP35

0.1 F

GND

OP193

0.1 F

R1*
24.9k

R4

4.99k

R5*

1.21M

TYPE K
THERMO-
COUPLE

CU

CU

R2*
102

V

OUT

0V � 2.5V

R6
100k
5%

R3
10M
5%

3.3V < V

S

< 5.5V

COLD

JUNCTION

CHROMEL

ALUMEL

ISOTHERMAL

BLOCK

NOTE:

ALL RESISTORS 1%
UNLESS OTHERWISE NOTED

0 C T 250 C

7

6

4

3

2

P1

50k

Figure 8. A Single-Supply, Type K Thermocouple Signal Conditioning Circuit with Cold-Junction Compensation

REV. C

TMP35/TMP36/TMP37

�12�

The 4 mA offset trim is provided by P2, and P1 provides the
circuit's full-scale gain trim at 20 mA. These two trims do not
interact because the noninverting input of the OP193 is held at
a virtual ground. The zero-scale and full-scale output currents of
the circuit are adjusted according to the operating temperature
range of each temperature sensor. The Schottky diode, D1, is
required in this circuit to prevent loop supply power-on tran-
sients from pulling the noninverting input of the OP193 more
than 300 mV below its inverting input. Without this diode, such
transients could cause phase reversal of the operational amplifier
and possible latchup of the transmitter. The loop supply voltage
compliance of the circuit is limited by the maximum applied
input voltage to the REF193 and is from 9 V to 18 V.

A Temperature to Frequency Converter

Another common method of transmitting analog information
from a remote location is to convert a voltage to an equivalent in
the frequency domain. This is readily done with any of the
low cost, monolithic voltage-to-frequency converters (VFCs)
available. These VFCs feature a robust, open-collector output
transistor for easy interfacing to digital circuitry. The digital
signal produced by the VFC is less susceptible to contamination
from external noise sources and line voltage drops because the
only important information is the frequency of the digital signal.
As long as the conversions between temperature and frequency
are done accurately, the temperature data from the sensors can
be reliably transmitted.

The circuit in Figure 11 illustrates a method by which the
outputs of these temperature sensors can be converted to a
frequency using the AD654. The output signal of the AD654 is
a square wave that is proportional to the dc input voltage across
Pins 4 and 3. The transfer equation of the circuit is given by:

f

OUT

=

V

TMP

- V

OFFSET

10

� R

T

� C

T

(

)

TMP3x

V

S

GND

6

4

2

3

7

8

5

1

AD654

V

OUT

10 F/0.1 F

5V

P2

100k

R

OFF1

470

f

OUT

OFFSET

R

OFF2

10

R1

P1

R

T

*

0.1 F

C

T

*

5V

R

PU

5k

f

OUT

NB: ATT

A

(min),

f

OUT

= 0Hz

*

R

T

AND C

T

� SEE TABLE

SENSOR

R

T

(R1 + P1)

C

T

TMP35

TMP36

TMP37

11.8k + 500

16.2k + 500

18.2k + 1k

1.7nF

1.8nF

2.1nF

Figure 11. A Temperature-to-Frequency Converter

An offset trim network (f

OUT

OFFSET

) is included with this

circuit to set f

OUT

at 0 Hz when the temperature sensor's mini-

mum output voltage is reached. Potentiometer P1 is required to
calibrate the absolute accuracy of the AD654. The table in
Figure 11 illustrates the circuit element values for each of the
three sensors. The nominal offset voltage required for 0 Hz
output from the TMP35 is 50 mV; for the TMP36 and
TMP37, the offset voltage required is 100 mV. In all cases
for the circuit values shown, the output frequency transfer
characteristic of the circuit was set at 50 Hz/

�C. At the receiving

end, a frequency-to-voltage converter (FVC) can be used to
convert the frequency back to a dc voltage for further process-
ing. One such FVC is the AD650.

For complete information on the AD650 and AD654, please
consult the individual data sheets for those devices.

V

OUT

4

7

1 F

R5
100k

V

OUT

R

L

250

V

LOOP

9V TO 18V

2

3

D1: HP5082�2810

REF193

TMP3x

R7

100

A1: OP193

*SEE TEXT
FOR VALUES

R3*

R1*

V

S

R2*

P2*
4mA
ADJUST

D1

R4*

R6

100k

P1*

20mA

ADJUST

GND

Q1
2N1711

0.1 F

2

4

6

3V

I

L

Figure 10. A Temperature to 4-to-20 mA Loop Transmitter

REV. C

TMP35/TMP36/TMP37

�13�

Driving Long Cables or Heavy Capacitive Loads

Although the TMP3x family of temperature sensors is capable
of driving capacitive loads up to 10,000 pF without oscillation,
output voltage transient response times can be improved with
the use of a small resistor in series with the output of the temperature
sensor, as shown in Figure 12. As an added benefit, this resistor
forms a low-pass filter with the cable's capacitance, which helps
to reduce bandwidth noise. Since the temperature sensor is
likely to be used in environments where the ambient noise level
can be very high, this resistor helps to prevent rectification by the
devices of the high frequency noise. The combination of this
resistor and the supply bypass capacitor offers the best protection.

TMP3x

0.1 F

GND

+V

S

750

LONG CABLE OR
HEAVY CAPACITIVE
LOADS

V

OUT

Figure 12. Driving Long Cables or Heavy Capacitive Loads

Commentary on Long-Term Stability

The concept of long-term stability has been used for many years
to describe by what amount an IC's parameter would shift dur-
ing its lifetime. This is a concept that has been typically applied
to both voltage references and monolithic temperature sensors.
Unfortunately, integrated circuits cannot be evaluated at room
temperature (25

�C) for 10 years or so to determine this shift. As

a result, manufacturers very typically perform accelerated life-
time testing of integrated circuits by operating ICs at elevated
temperatures (between 125

�C and 150�C) over a shorter period

of time (typically, between 500 and 1000 hours).

As a result of this operation, the lifetime of an integrated circuit
is significantly accelerated due to the increase in rates of reac-
tion within the semiconductor material.

REV. C

TMP35/TMP36/TMP37

�14�

3-Pin Plastic Header-Style Package [TO-92]

(TO-92)

Dimensions shown in inches and (millimeters)

0.115 (2.92)
0.080 (2.03)

0.115 (2.92)
0.080 (2.03)

0.165 (4.19)
0.125 (3.18)

SQ

0.019 (0.482)
0.016 (0.407)

0.105 (2.66)
0.095 (2.42)

0.055 (1.40)
0.045 (1.15)

SEATING

PLANE

0.500

(12.70)

MIN

0.205 (5.21)
0.175 (4.45)

0.210 (5.33)
0.170 (4.32)

1

2

3

BOTTOM VIEW

0.135

(3.43)

MIN

0.050
(1.27)
MAX

CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETERS DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN

COMPLIANT TO JEDEC STANDARDS TO-226AA

8-Lead Standard Small Outline Package [SOIC]

Narrow Body

(RN-8)

Dimensions shown in millimeters and (inches)

0.25 (0.0098)
0.19 (0.0075)

1.27 (0.0500)
0.41 (0.0160)

0.50 (0.0196)
0.25 (0.0099)

45

8
0

1.75 (0.0688)
1.35 (0.0532)

SEATING

PLANE

0.25 (0.0098)
0.10 (0.0040)

8

5

4

1

5.00 (0.1968)
4.80 (0.1890)

4.00 (0.1574)
3.80 (0.1497)

1.27 (0.0500)

BSC

6.20 (0.2440)
5.80 (0.2284)

0.51 (0.0201)
0.33 (0.0130)

COPLANARITY

0.10

CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN

COMPLIANT TO JEDEC STANDARDS MS-012AA

5-Lead Plastic Surface-Mount Package [SOT-23]

(RT-5)

Dimensions shown in millimeters

PIN 1

1.60 BSC

2.80 BSC

1.90

BSC

0.95 BSC

1

3

4

5

2

0.22
0.08

0.60
0.45
0.30

10

0

0.50
0.30

0.15 MAX

SEATING
PLANE

1.45 MAX

1.30
1.15
0.90

COMPLIANT TO JEDEC STANDARDS MO-178AA

2.90 BSC

OUTLINE DIMENSIONS

Revision History

Location

Page

10/02--Data Sheet changed from REV. B to REV. C.

Deleted text from Commentary on Long-Term Stability section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Update OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

�15�

�16�

C00337�0�10/02(C)

PRINTED IN U.S.A.

Document Outline

• FEATURES
• APPLICATIONS
• PRODUCT DESCRIPTION
• FUNCTIONAL BLOCK DIAGRAM
• SPECIFICATIONS
• ABSOLUTE MAXIMUM RATINGS
• FUNCTIONAL DESCRIPTION
• ORDERING GUIDE
• Typical Performance Characteristics
• APPLICATIONS SECTION
  • Shutdown Operation
  • Mounting Considerations
  • Thermal Environment Effects
  • Basic Temperature Sensor Connections
  • Fahrenheit Thermometers
  • Average and Differential Temperature Measurement
  • Microprocessor Interrupt Generator
  • Thermocouple Signal Conditioning with Cold-Junction Compensation
  • Using TMP3x Sensors in Remote Locations
  • A Temperature to 4�20 mA Loop Transmitter
  • A Temperature to Frequency Converter
  • Driving Long Cables or Heavy Capacitive Loads
  • Commentary on Long-Term Stability
• OUTLINE DIMENSIONS
• Revision History