TMP12 View Datasheet(PDF) - Analog Devices

Part Name

Description

Manufacturer

TMP12

Airflow and Temperature Sensor

Analog Devices 

a

Airflow and Temperature Sensor

FEATURES

Temperature Sensor Includes 100 Ω Heater

Heater Provides Power IC Emulation

Accuracy ؎3°C 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 µA 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

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, 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 pro-

portional 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 refer-

ence 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 hys-

teresis 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 incorpo-

rates a precision, low temperature coefficient 100 Ω heater

resistor that may be connected directly to an external 5 V sup-

ply. When the heater is activated it raises the die temperature in

TMP12*

FUNCTIONAL BLOCK DIAGRAM

VREF

SET

HIGH

SET

LOW

GND

HYSTERESIS

CURRENT

CURRENT

MIRROR

IHYS

WINDOW

COMPARATOR

VOLTAGE

1kΩ

REFERENCE

AND

SENSOR

-

+

+

-

HYSTERESIS

VOLTAGE

100Ω

V+

OVER

UNDER

HEATER

PINOUTS

DIP And SO

VREF 1

8 V+

SET HIGH 2

SET LOW 3

TOP VIEW

(Not to Scale)

7 OVER

6 UNDER

GND 4

5 HEATER

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 plastic DIP and SO packages.

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

REV. 0

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

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

© Analog Devices, Inc., 1995

One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.

Tel: 617/329-4700

Fax: 617/326-8703

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