a
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
Airflow and Temperature Sensor
TMP12
FUNCTIONAL BLOCK DIAGRAM
HYSTERESIS
CURRENT
CURRENT
MIRROR
SET
HIGH
I
HYS
V
REF
TMP12
V+
OVER
TE
GND
VOLTAGE
REFERENCE
AND
SENSOR
1k
SET
LOW
WINDOW
COMPARATOR
UNDER
HYSTERESIS
VOLTAGE
HEATER
100
SO
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.
LE
PIN CONNECTION
8-Lead SOIC
8
V
REF 1
SET HIGH
2
V+
7
OVER
TMP12
TOP VIEW
SET LOW
3
(Not to Scale)
6
UNDER
GND
4
5
HEATER
The TMP12 generates an internal voltage that is linearly propor-
tional to Celsius (Centigrade) temperature, nominally 5 mV/°C.
The linearized output is compared with voltages from an exter-
nal 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
B
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 tempera-
tures 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.
O
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: 781/329-4700
www.analog.com
Fax: 781/326-8703
© 2003 Analog Devices, Inc. All rights reserved.
TMP12–SPECIFICATIONS
(V = 5 V, –40 C
≤
T s
≤
125 C, unless otherwise noted.)
S
A
Parameter
ACCURACY
Accuracy (High, Low Setpoints)
Internal Scale Factor
Power Supply Rejection Ratio
Linearity
Repeatability
Long Term Stability
SETPOINT INPUTS
Offset Voltage
Output Voltage Drift
Input Bias Current
VREF OUTPUT
Output Voltage
Output Drift
Output Current, Zero Hysteresis
Hysteresis Current Scale Factor
OPEN-COLLECTOR OUTPUTS
Output Low Voltage
Output Leakage Current
Fall Time
HEATER
Resistance
Temperature Coefficient
Maximum Continuous Current
1
POWER SUPPLY
Supply Range
Supply Current
Symbol
Conditions
T
A
= 25°C
T
A
= –40°C to +100°C
T
A
= –40°C to +100°C
4.5 V
≤
V
S
≤
5.5 V
T
A
= –40°C to +125°C
T
A
= –40°C to +125°C
T
A
= 125°C for 1 k Hrs
Min
Typ
±
2
±
3
5
0.1
0.5
0.3
0.3
0.25
3
25
Max
±
3
±
5
5.1
0.5
Unit
°C
°C
mV/°C
°C/V
°C
°C
°C
mV
µV/°C
nA
V
V
ppm/°C
µA
µA/°C
V
V
µA
ns
Ω
ppm/°C
mA
V
µA
µA
4.9
PSRR
V
OS
TCV
OS
I
B
VREF
VREF
TC
VREF
I
VREF
SF
HYS
V
OL
V
OL
I
OH
t
HL
R
H
I
H
V
S
I
SY
I
SY
T
A
= 25°C, No Load
T
A
= –40°C to +100°C, No Load
2.49
100
2.51
LE
97
4.5
1k
20pF
I
SINK
= 1.6 mA
I
SINK
= 20 mA
V
S
= 12 V
See Test Load
T
A
= 125°C
T
A
= –40°C to +125°C
SO
Unloaded at 5 V
Unloaded at 12 V
2
–2–
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.
O
B
Figure 1. Test Load
TE
0.25
0.6
1
40
0.4
100
100
60
400
450
2.50
2.5
±
0.015
–10
7
5
100
103
5.5
600
REV. B
TMP12
ABSOLUTE MAXIMUM RATINGS*
FUNCTIONAL DESCRIPTION
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)
JA
JC
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.
Unit
°C/W
158
1
43
2
*CAUTION
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 packag-
ing 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
Model/Grade
TMP12FS
TMP12FS-REEL
Temperature
Range
–40°C to +85°C SOIC
–40°C to +125°C SOIC
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.
O
B
SO
Package
Package
Description Option
R-8
R-8
LE
–3–
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 specifi-
cation is not implied. Exposure to the above maximum rating
conditions for extended periods may affect device reliability.
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. Oper-
ating from a single 5 V supply, the quiescent current is only
600
µA
(max), without the heater resistor current.
TE
NOTES
1
JA
is specified for device in socket (worst-case conditions).
2
JC
is specified for device mounted on PCB.
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
5
2
V
V
2
P
D
=
=
=
0.25
W
R
100
Ω
WARNING!
ESD SENSITIVE DEVICE
REV. B
TMP12 –Typical Performance Characteristics
35
JUNCTION TEMPERATURE RISE
ABOVE AMBIENT ( C)
JUNCTION TEMPERATURE ( C)
30
25
20
15
V+ = 5V
SOIC-8 SOLDERED TO
0.5
0.3 CU PCB
250 FPM
0 FPM
450 FPM
10
600 FPM
5
AIR FLOW RATES
0
0
50
100
150
200
HEATER RESISTOR POWER
DISSIPATION (mW)
250
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
140
130
SOIC-8, HTR @ 5V
120
110
100
90
80
70
60
50
40
30
20
10
0
0
100
TRANSITION FROM 100 C STIRRED
BATH TO FORCED 25 C AIR
V+ = 5V, NO LEAD, HEATER OFF
SOIC-8 SOLDERED TO 0.5
0.3 CU PCB
SOIC-8, HTR @ 3V
V+ = 5V RHEATER TO EXTERNAL
SUPPLY TURNED ON @
t
= 5 sec
SOIC-8 SOLDERED TO 0.5
0.3
COPPER PCB
TIME CONSTANT (sec)
SOIC AND PCB
0 10 20 30 40 50 60 70 80 90 100 110120 130
TIME (sec)
200 300 400 500
AIR VELOCITY (FPM)
600
700
120
110
TRANSITION FROM STILL 25 C
AIR TO STIRRED 100 C BATH
102.0
101.5
JUNCTION TEMPERATURE ( C)
HEATER RESISTANCE ( )
100
90
80
70
60
50
40
30
20
10
0
0
2
4
6
8 10 12 14
TIME (sec)
V+ = 5V, NO LEAD, HEATER OFF
SOIC-8 SOLDERED TO 0.5
0.3 CU PCB
16 18
20
SOIC AND PCB
101.0
100.5
100.0
99.5
99.0
98.5
SO
98.0
–75
–25
500
475
450
425
400
375
350
325
300
–75
V+ = 5V
NO LEAD
HEATER OFF
SUPPLY CURRENT ( A)
175
LE
25
75
125
TEMPERATURE ( C)
175
6
5
4
ACCURACY ERROR ( C)
REFERENCE VOLTAGE (V)
TE
2.520
TPC 1. SOIC Junction Temperature
Rise vs. Heater Dissipation
TPC 2. Junction Temperature Rise in
Still Air
TPC 3. Package Thermal Time
Constant in Forced Air
V+ = 5V
2.515
V+ = 5V
NO LOAD
HEATER OFF
2.510
2.505
2.500
2.495
2.490
–75
–25
25
75
125
TEMPERATURE ( C)
175
TPC 4. Thermal Response Time in
Stirred Oil Bath
TPC 5. Heater Resistance vs.
Temperature
TPC 6. Reference Voltage vs.
Temperature
5.0
START-UP SUPPLY VOLTAGE (V)
4.5
NO LEAD, HEATER OFF
B
START-UP VOLTAGE DEFINED AS
OUTPUT READING BEING WITHIN
C OF OUTPUT AT 5V
MAXIMUM LIMIT
3
2
1
0
–1
–2
–3
–4
–5
MINIMUM LIMIT
ACCURACY ERROR
4.0
3.5
3.0
–75
O
–25
25
75
125
TEMPERATURE ( C)
–25
25
75
125
TEMPERATURE ( C)
175
–6
–50
–25
0
25
50
75
TEMPERATURE ( C)
100
125
TPC 7. Start-Up Voltage vs.
Temperature
TPC 8. Supply Current vs.
Temperature
TPC 9. Accuracy Error vs.
Temperature
–4–
REV. B
TMP12
POWER SUPPLY REJECTION ( C/V)
450
400
T
A
= 25 C
NO LOAD
HEATER OFF
0.4
V+ = 4.5V TO 5.5V
NO LOAD
HEATER OFF
OPEN COLLECTION SINK CURRENT (mA)
500
0.5
40
38
36
34
32
30
28
26
24
22
20
–75
–25
25
75
125
TEMPERATURE ( C)
175
V
OL
= 1V
V+ = 5V
SUPPLY CURRENT ( A)
350
300
250
200
150
100
50
0
0
1
2
3
4
5
6
SUPPLY VOLTAGE (V)
7
8
0.3
0.2
0.1
0
–75
–25
25
75
125
TEMPERATURE ( C)
175
OPEN COLLECTION SINK CURRENT (mA)
700
600
500
400
300
200
100
LOAD = 10mA
SO
AIR FLOW
PC BOARD
TMP12
TPC 13. Open-Collector Voltage vs.
Temperature
65
A
60
APPLICATIONS INFORMATION
O
A typical application for the TMP12 is shown in Figure 2. The
TMP12 package is placed in the same cooling airflow as a high
power dissipation IC. The TMP12’s internal resistor produces a
temperature rise that is proportional to air flow, as shown in
Figure 3. Any interruption in the air flow will produce an addi-
tional temperature rise. When the TMP12 chip temperature
exceeds a user-defined setpoint limit, the system controller can
take corrective action, such as reducing clock frequency, shutting
down unneeded peripherals, turning on additional fan cooling,
or shutting down the system.
LE
LOAD = 5mA
LOAD = 1mA
0
–75
–25
25
75
125
TEMPERATURE ( C)
175
DIE TEMPERATURE ( C)
D
55
C
50
E
45
A.
B.
C.
D.
E.
0
TMP12 DIE TEMP NO AIR FLOW
HIGH SETPOINT
LOW SETPOINT
TMP12 DIE TEMP MAX AIR FLOW
SYSTEM AMBIENT TEMPERATURE
50
100
150
TMP12 P
D
(mW)
200
250
B
40
35
PGA
SOCKET
POWER IC
B
PGA
PACKAGE
Temperature Hysteresis
Figure 2. Typical Application
The temperature hysteresis at each setpoint is the number of
degrees beyond the original setpoint temperature that must be
sensed by the TMP12 before the setpoint comparator will be
reset and the output disabled. Hysteresis prevents
chatter
and
motorboating
in feedback control systems. For monitoring tem-
perature in computer systems, hysteresis prevents multiple
interrupts to the CPU which can reduce system performance.
REV. B
–5–
TE
TPC 10. Supply Current vs. Supply
Voltage
TPC 11. VPTAT Power Supply
Rejection vs. Temperature
TPC 12. Open-Collector Output Sink
Current vs. Temperature
Figure 3. Choosing Temperature Setpoints
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