Rainbow Electronics LM84 - Manual

LM84
Diode Input Digital Temperature Sensor with Two-Wire
Interface
General Description
The LM84 is a remote diode temperature sensor,
Delta-Sigma analog-to-digital converter, and digital
over-temperature detector with an SMBus ™ interface. The
LM84 senses its own temperature as well as the tempera-
ture of a target IC with a diode junction, such as a Pentium
®
II processor or a diode connected 2N3904. A diode junction
(semiconductor junction) is required on the target IC’s die. A
host can query the LM84 at any time to read the temperature
of this diode as well as the temperature state of the LM84
itself. A T_CRIT_A interrupt output becomes active when the
temperature is greater than a programmable comparator
limit, T_CRIT.
The host can program as well as read back the state of the
T_CRIT register. Three state logic inputs allow two pins
(ADD0, ADD1) to select up to 9 SMBus address locations for
the LM84. The sensor powers up with default thresholds of
127˚C for T_CRIT.
Features
n Directly senses die temperature of remote ICs
n Senses temperature of remote diodes
n SMBus compatible interface, supports SMBus Timeout
n Register readback capability
n 7 bit plus sign temperature data format
n 2 address select lines enable 9 LM84s to be connected
to a single bus
Key Specifications
j Supply Voltage 3.0V - 3.6V
j Supply Current 1 mA (max)
j Local Temperature Accuracy ± 1.0˚C (typ)
j Remote Diode Temperature Accuracy
+60˚C to +100˚C ± 3˚C (max)
0˚C to +125˚C ± 5˚C (max)
Applications
n System Thermal Management
n Personal Computers
n Electronic Test Equipment
n Office Electronics
n HVAC
Simplified Block Diagram
SMBus ™ is a trademark of the Intel Corporation.
Pentium ® II processor is a registered trademark of the Intel Corporation.
I2C ® is a registered trademark of the Philips Corporation.
DS100961-1
# Indicates Active Low (”NOT“)
July 2000
LM84
Diode
Input
Digital
T
emperature
Sensor
with
T
wo-W
ire
Interface
© 2001 National Semiconductor Corporation DS100961 www.national.com