TMP12_15 Datasheet, PDF (1/12 Pages) Analog Devices – Airflow and Temperature Sensor

a
Airflow and Temperature Sensor
TMP12
FEATURES
FUNCTIONAL BLOCK DIAGRAM
Temperature Sensor Includes 100 ⍀ Heater
Heater Provides Power IC Emulation
Accuracy ؎3 Typ from –40؇C to +100؇C
V_REF
HYSTERESIS
CURRENT
TMP12
Operation to 150؇C
CURRENT
V+
5 mV/؇C Internal Scale Factor
Resistor Programmable Temperature Setpoints
SET
HIGH
MIRROR
I_HYS
OVER
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
E _APPLICATIONS
System Airflow Sensor
Equipment Overtemperature Sensor
T _{Overtemperature Protection}
Power Supply Thermal Sensor
Low Cost Fan Controller
E _{GENERAL DESCRIPTION}
The TMP12 is a silicon-based airflow and temperature sensor
designed to be placed in the same airstream as heat generating
L _{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
O ^{while emulating 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.
S _{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.
B 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.
O ^{Hysteresis is programmed by the external resistor chain and}
SET
LOW
WINDOW
COMPARATOR
UNDER
GND
VOLTAGE
REFERENCE
AND
SENSOR
1k⍀ ^HYSTERESIS
VOLTAGE
100⍀
HEATER
PIN CONNECTION
8-Lead SOIC
V_REF 1
8 V+
SET HIGH 2 TMP12 7 OVER
TOP VIEW
SET LOW 3 (Not to Scale) 6 UNDER
GND 4
5 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 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.
The TMP12 is intended for single 5 V supply operation, but will
is determined by the total current drawn from the 2.5 V reference. _{operate on a 12 V supply. The heater is designed to operate from}
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
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.