TMP12 Fast Delivery |IC PHOENIX CO.,LIMITED

TMP12 ,Airflow and Temperature SensorSpecifications subject to change without notice.1k20pFFigure 1. Test Load–2– REV. ATMP12ABSOLUTE ..
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TMP12
Airflow and Temperature Sensor
REV.A
Airflow and Temperature Sensor
FUNCTIONAL BLOCK DIAGRAM
PIN CONNECTIONS
8-Lead SOIC
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 Over-Temperature Sensor
Over-Temperature Protection
Power Supply Thermal Sensor
Low-Cost Fan Controller
*. Patent No. 5,195,827.
Pentium is a registered trademark of Intel Corporation.
GENERAL DESCRIPTION
The TMP 12 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, e.g., for a power
supply; and if the cooling systems fails, system reliability and/or
safety may be impaired. By monitoring temperature while emu-
lating a power IC, the TMP12 can provide a warning of cooling
system failure.
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 in the DIP package
approximately 20°C 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
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,
operation extends to 150°C at 5 V with reduced accuracy.
The TMP12 is available in 8-pin SO packages.
TMP12–SPECIFICATIONS
VREF OUTPUT
OPEN-COLLECTOR OUTPUTS
POWER SUPPLY
NOTES
1Guaranteed but not tested.
2TMP12 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.
Figure 1. Test Load
(VS = 5 V, –40�C ≤ TA s ≤ 125�C unless otherwise noted.)
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000V 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.
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
NOTES�JA is specified for device in socket (worst case conditions).�JC is specified for device mounted on PCB.
CAUTIONStresses 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.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.Remove power before inserting or removing units from their
sockets.
ORDERING GUIDE
NOTESXIND = –40°C to +125°CNot for new design, obsolete April 2002.
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 which provides both a constant 2.5 V output
and a voltage which 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:
which generates a temperature rise of about 32°C in still air for
the SO packaged device. With an airflow of 450 feet per minute
(FPM), the temperature rise is about 22°C. By selecting a tem-
perature 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.
TMP12
–Typical Performance Characteristics
TPC 1.SOIC Junction Temperature
Rise vs. Heater Dissipation
TPC 4.Thermal Response Time in
Stirred Oil Bath
TPC 7.Start-Up Voltage vs.
Temperature

TPC 2.Junction Temperature Rise in
Still Air
TPC 5.Heater Resistance vs.
Temperature

TPC 8.Supply Current vs.
Temperature

TPC 3.Package Thermal Time
Constant in Forced Air
TPC 6.Reference Voltage vs.
Temperature

TPC 9.Accuracy Error vs.
Temperature
TPC 10.Supply Current vs. Supply
Voltage
TPC 11.VPTAT Power Supply
Rejection vs. Temperature
TPC 12.Open-Collector Output Sink
Current vs. Temperature
APPLICATIONS INFORMATION
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.
Figure 2.Typical Application
TPC 13.Open-Collector Voltage vs.
Temperature
Figure 3.Choosing Temperature Setpoints
Temperature Hysteresis
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
TMP12
Figure 4 shows the TMP12’s hysteresis profile. The hysteresis is
programmed, by the user, by setting a specific load current on
the reference voltage output VREF. This output current, IREF, is
also called the hysteresis current. IREF is mirrored internally by
the TMP12, as shown in the Functional Block Diagram, and
fed to a buffer with an analog switch.
Figure 4.Hysteresis Profile
After a temperature setpoint has been exceeded and a compara-
tor tripped, the hysteresis buffer output is enabled. The result is
a current of the appropriate polarity, which generates a hyster-
esis offset voltage across an internal 1 kΩ resistor at the
comparator input. The comparator output remains on until the
voltage at the comparator input, now equal to the temperature
sensor voltage VPTAT summed with the hysteresis effect, has
returned to the programmed setpoint voltage. The comparator
then returns LOW, deactivating the open-collector output and
disabling the hysteresis current buffer output. The scale factor
for the programmed hysteresis current is:
Thus, since VREF = 2.5 V, a reference load resistance of 357 kQ
or greater (output current of 7 µA or less) will produce a tempera-
ture setpoint hysteresis of zero degrees. For more details, see the
temperature programming discussion below. Larger values of
load resistance will only decrease the output current below but
will have no effect on the operation of the device. The amount
of hysteresis is determined by selecting an appropriate value of
load resistance for VREF, as shown below.
Programming the TMP12
The basic thermal monitoring application only requires a simple
three-resistor ladder voltage divider to set the high and low
setpoints and the hysteresis. These resistors are programmed in
the following sequence:Select the desired hysteresis temperature.Calculate the hysteresis current, IVREF.Select the desired setpoint temperatures.Calculate the individual resistor divider ladder values needed
to develop the desired comparator setpoint voltages at the
Set High and Set Low inputs.
The hysteresis current is readily calculated, as shown above. For
example, to produce two degrees of hysteresis, IVREF should be
set to 17 µA. Next, the setpoint voltages VSETHIGH and VSETLOW
are determined using the VPTAT scale factor of
which is 1.49 V for 25°C. Finally, the divider resistors are calcu-
lated, based on the setpoint voltages.
The setpoint voltages are calculated from the equation:
This equation is used to calculate both the VSETHIGH and the
VSETLOW values. A simple 3-resistor network, as shown in Figure 5,
determines the setpoints and hysteresis value. The equations
used to calculate the resistors are:
Figure 5.Setpoint Programming
For example, setting the high setpoint for 80°C, the low setpoint
for 55°C, and hysteresis for 3°C produces the following values:
The total of R1 + R2 + R3 is equal to the load resistance needed to
draw the desired hysteresis current from the reference, or IVREF.
The nomograph of Figure 6 provides an easy method of determin-
ing the correct VPTAT voltage for any temperature. Simply locate
the desired temperature on the appropriate scale (K, °C, or °F)

Partno	Mfg	Dc	Qty	Available	Descript
TMP12	PMI	N/a	5	avai	Airflow and Temperature Sensor