Analog Devices TMP12 b Datasheet

a

HYSTERESIS

CURRENT

CURRENT

MIRROR

TMP12

I

HYS

WINDOW

COMPARATOR

HYSTERESIS
VOLTA G E

1k

100

VOLTA G E

REFERENCE

AND

SENSOR

V

REF

SET

HIGH

SET

LOW

GND

V+

OVER

UNDER

HEATER

Airflow and Temperature Sensor

FEATURES
Temperature Sensor Includes 100  Heater
Heater Provides Power IC Emulation
Accuracy 3 Typ from –40C to +100C
Operation to 150C
5 mV/C Internal Scale Factor
Resistor Programmable Temperature Setpoints
20 mA Open-Collector Setpoint Outputs
Programmable Thermal Hysteresis
Internal 2.5 V Reference
Single 5 V Operation
400 A Quiescent Current (Heater Off)
Minimal External Components

APPLICATIONS
System Airflow Sensor
Equipment Overtemperature Sensor
Overtemperature Protection
Power Supply Thermal Sensor
Low Cost Fan Controller

GENERAL DESCRIPTION

The TMP12 is a silicon-based airflow and temperature sensor
designed to be placed in the same airstream as heat generating
components that require cooling. Fan cooling may be required
continuously or during peak power demands. For example, if
the cooling systems of a power supply fails, system reliability
and/or safety may be impaired. By monitoring temperature
while emulating a power IC, the TMP12 can provide a warning
of cooling system failure.

The TMP12 generates an internal voltage that is linearly propor­tional to Celsius (Centigrade) temperature, nominally 5 mV/°C.
The linearized output is compared with voltages from an exter­nal resistive divider connected to the TMP12’s 2.5 V precision
reference. The divider sets up one or two reference voltages, as
required by the user, providing one or two temperature setpoints.
Comparator outputs are open-collector transistors able to sink
over 20 mA. There is an on-board hysteresis generator provided
to speed up the temperature-setpoint output transitions; this
also reduces erratic output transitions in noisy environments.
Hysteresis is programmed by the external resistor chain and
is determined by the total current drawn from the 2.5 V reference.
The TMP12 airflow sensor also incorporates a precision, low
temperature coefficient 100 Ω heater resistor that may be con-
nected directly to an external 5 V supply. When the heater is
activated, it raises the die temperature approximately 20°C

*Protected by U.S. Patent No. 5,195,827.

TMP12

*

FUNCTIONAL BLOCK DIAGRAM

PIN CONNECTION

8-Lead SOIC

V

REF

SET HIGH

SET LOW

GND

1

2

TMP12

TOP VIEW

3

(Not to Scale)

4

8

7

6

5

V+

OVER

UNDER

HEATER

above ambient (in still air). The purpose of the heater in the
TMP12 is to emulate a power IC, such as a regulator or Pentium

®

CPU, which has a high internal dissipation.

When subjected to a fast airflow, the package and die tempera­tures of the power device and the TMP12 (if located in the
same airstream) will be reduced by an amount proportional to
the rate of airflow. The internal temperature rise of the TMP12
may be reduced by placing a resistor in series with the heater, or
by reducing the heater voltage.

The TMP12 is intended for single 5 V supply operation, but will
operate on a 12 V supply. The heater is designed to operate from
5 V only. Specified temperature range is from –40°C to +125°C,
and operation extends to 150°C at 5 V with reduced accuracy.

The TMP12 is available in 8-lead SOIC packages.

REV. B

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. Trademarks and
registered trademarks are the property of their respective owners.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] © 2003 Analog Devices, Inc. All rights reserved.

TMP12–SPECIFICATIONS

(VS = 5 V, –40C ≤ TA s ≤ 125C, unless otherwise noted.)

Parameter Symbol Conditions Min Typ Max Unit

ACCURACY

Accuracy (High, Low Setpoints) TA = 25°C ± 2 ± 3 °C

T

= –40°C to +100°C ±3 ±5 °C

A

Internal Scale Factor T

= –40°C to +100°C 4.9 5 5.1 mV/°C

A

Power Supply Rejection Ratio PSRR 4.5 V ≤ VS ≤ 5.5 V 0.1 0.5 °C/V
Linearity T
Repeatability T

= –40°C to +125°C 0.5 °C

A

= –40°C to +125°C 0.3 °C

A

Long Term Stability TA = 125°C for 1 k Hrs 0.3 °C

SETPOINT INPUTS

Offset Voltage V

OS

Output Voltage Drift TCV
Input Bias Current I

B

OS

0.25 mV
3 µV/°C
25 100 nA

VREF OUTPUT

Output Voltage VREF TA = 25°C, No Load 2.49 2.50 2.51 V

VREF T
Output Drift TC
Output Current, Zero Hysteresis I

VREF

Hysteresis Current Scale Factor SF

VREF

HYS

= –40°C to +100°C, No Load 2.5 ± 0.015 V

A

–10 ppm/°C
7 µA
5 µA/°C

OPEN-COLLECTOR OUTPUTS

Output Low Voltage V

Output Leakage Current I
Fall Time t

OL

V

OL

OH

HL

I

= 1.6 mA 0.25 0.4 V

SINK

I

= 20 mA 0.6 V

SINK

VS = 12 V 1 100 µA
See Test Load 40 ns

HEATER

Resistance R

H

Temperature Coefficient T
Maximum Continuous Current1I

H

TA = 125°C97100 103 Ω

= –40°C to +125°C 100 ppm/°C

A

60 mA

POWER SUPPLY

Supply Range V
Supply Current I

NOTES

1

Guaranteed but not tested.

2

TMP12 is specified for operation from a 5 V supply. However, operation is allowed up to a 12 V supply, but not tested at 12 V. Maximum heater supply is 6 V.

Specifications subject to change without notice.

S

SY

I

SY

Unloaded at 5 V 400 600 µA
Unloaded at 12 V

2

4.5 5.5 V

450 µA

1k

20pF

Figure 1. Test Load

–2–

REV. B

TMP12

ABSOLUTE MAXIMUM RATINGS*

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +11 V

Heater Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 V

Setpoint Input Voltage . . . . . . . . . . . –0.3 V to [(V+) + 0.3 V]

Reference Output Current . . . . . . . . . . . . . . . . . . . . . . . 2 mA

Open-Collector Output Current . . . . . . . . . . . . . . . . . 50 mA

Open-Collector Output Voltage . . . . . . . . . . . . . . . . . . . . 15 V

Operating Temperature Range . . . . . . . . . . –55°C to +150°C

Storage Temperature Range . . . . . . . . . . . . –65°C to +160°C

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

Package Type ␪

8-Lead SOIC (S) 158

NOTES

1

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

2

JC is specified for device mounted on PCB.

*CAUTION

JA

1

␪

43

JC

2

Unit

°C/W

1. Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only and functional operation at or above this specifi­cation is not implied. Exposure to the above maximum rating
conditions for extended periods may affect device reliability.

2. Digital inputs and outputs are protected; however, permanent
damage may occur on unprotected 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.

ORDERING GUIDE

Temperature Package Package

Model/Grade Range Description Option

TMP12FS –40°C to +85°C SOIC R-8
TMP12FS-REEL –40°C to +125°C SOIC R-8

FUNCTIONAL DESCRIPTION

The TMP12 incorporates a heating element, temperature sensor,
and two user-selectable setpoint comparators on a single substrate.
By generating a known amount of heat, and using the setpoint
comparators to monitor the resulting temperature rise, the TMP12
can indirectly monitor the performance of a system’s cooling fan.

The TMP12 temperature sensor section consists of a band gap
voltage reference that provides both a constant 2.5 V output and
a voltage that is proportional to absolute temperature (VPTAT).
The VPTAT has a precise temperature coefficient of 5 mV/K
and is 1.49 V (nominal) at 25°C. The comparators compare
VPTAT with the externally set temperature trip points and
generate an open-collector output signal when one of their
respective thresholds has been exceeded.

The heat source for the TMP12 is an on-chip 100 Ω low tempco
thin-film resistor. When connected to a 5 V source, this resistor
dissipates

V

P

== =

D

R

100

W

025Ω.

2

2

V

5

which generates a temperature rise of about 32°C in still air
for the SOIC packaged device. With an airflow of 450 feet
per minute (FPM), the temperature rise is about 22°C. By
selecting a temperature setpoint between these two values,
the TMP12 can provide a logic-level indication of problems
in the cooling system.

A proprietary, low tempco thin-film resistor process, in conjunction
with production laser trimming, enables the TMP12 to provide a
temperature accuracy of ±3°C (typ) over the rated temperature
range. The open-collector outputs are capable of sinking 20 mA,
allowing the TMP12 to drive small control relays directly. Oper­ating from a single 5 V supply, the quiescent current is only
600 µA (max), without the heater resistor current.

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 TMP12 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.

REV. B

–3–

WARNING!

ESD SENSITIVE DEVICE

TMP12

TEMPERATURE (C)

REFERENCE VOLTAGE (V)

2.520

–75

2.515

2.510

2.505

2.500

2.495

2.490
–25 25 75 125 175

V+ = 5V
NO LOAD
HEATER OFF

–Typical Performance Characteristics

35

V+ = 5V
SOIC-8 SOLDERED TO

30

0.5  0.3 CU PCB

JUNCTION TEMPERATURE RISE

25

20

15

10

ABOVE AMBIENT (C)

5

0

0

50 100 150 200 250

HEATER RESISTOR POWER

250 FPM

0 FPM

450 FPM

600 FPM

AIR FLOW RATES

DISSIPATION (mW)

TPC 1. SOIC Junction Temperature
Rise vs. Heater Dissipation

120

TRANSITION FROM STILL 25C

110

AIR TO STIRRED 100C BATH

100

90

80

70

60

50

40

30

20

JUNCTION TEMPERATURE (C)

V+ = 5V, NO LEAD, HEATER OFF

10

SOIC-8 SOLDERED TO 0.5  0.3 CU PCB

0

246 81012 14 16 18 20

0

SOIC AND PCB

TIME (sec)

TPC 4. Thermal Response Time in
Stirred Oil Bath

70

65

60

55
50

45

40

35

30

25

20

15

JUNCTION TEMPERATURE (C)

10

5

0

0

SOIC-8, HTR @ 5V

SOIC-8, HTR @ 3V

V+ = 5V RHEATER TO EXTERNAL
SUPPLY TURNED ON @
SOIC-8 SOLDERED TO 0.5  0.3
COPPER PCB

10 20 30 40 50 60 70 80 90 100 110120 130

TIME (sec)

t

= 5 sec

TPC 2. Junction Temperature Rise in
Still Air

102.0

101.5

101.0

100.5

100.0

HEATER RESISTANCE ()

99.5

99.0

98.5

98.0
–25 25 75 125 175

–75

TEMPERATURE (C)

V+ = 5V

TPC 5. Heater Resistance vs.
Temperature

140

TRANSITION FROM 100C STIRRED

130

BATH TO FORCED 25C AIR

120

V+ = 5V, NO LEAD, HEATER OFF

110

SOIC-8 SOLDERED TO 0.5  0.3 CU PCB

100

90

80
70
60

50

40

TIME CONSTANT (sec)

30
20
10

0

0

SOIC AND PCB

100 200 300 400 500 600 700

AIR VELOCITY (FPM)

TPC 3. Package Thermal Time
Constant in Forced Air

TPC 6. Reference Voltage vs.
Temperature

5.0
START-UP VOLTAGE DEFINED AS

OUTPUT READING BEING WITHIN
C OF OUTPUT AT 5V

NO LEAD, HEATER OFF

4.5

4.0

3.5

START-UP SUPPLY VOLTAGE (V)

3.0

–25 25 75 125 175

–75

TEMPERATURE (C)

TPC 7. Start-Up Voltage vs.
Temperature

500

V+ = 5V
NO LEAD

475

HEATER OFF

450

425

400

375

350

SUPPLY CURRENT (A)

325

300

–25 25 75 125 175

–75

TEMPERATURE (C)

TPC 8. Supply Current vs.
Temperature

–4–

6

5

4

3

2

1

0

–1

–2

–3

ACCURACY ERROR (C)

–4

–5

–6

–50

MAXIMUM LIMIT

ACCURACY ERROR

MINIMUM LIMIT

–25 0 25 50 75 100 125

TEMPERATURE (C)

TPC 9. Accuracy Error vs.
Temperature

REV. B