LM82 Remote Diode and Local Digital Temperature Sensor with Two-Wire Interface
January 2000
LM82
Remote Diode and Local Digital Temperature Sensor
with Two-Wire Interface
General Description
The LM82 is a digital temperature sensor with a 2 wire serial
interface that senses the voltage and thus the temperature of
a remote diode using a Delta-Sigma analog-to-digital con-
verter with a digital over-temperature detector. The LM82 ac-
curately senses its own temperature as well as the tempera-
ture of external devices, such as Pentium II
®
Processors or
diode connected 2N3904s. The temperature of any ASIC
can be detected using the LM82 as long as a dedicated di-
ode (semiconductor junction) is available on the die. Using
the SMBus interface a host can access the LM82’s registers
at any time. Activation of a T_CRIT_A output occurs when
any temperature is greater than a programmable comparator
limit, T_CRIT. Activation of an INT output occurs when any
temperature is greater than its corresponding programmable
comparator HIGH limit.
The host can program as well as read back the state of the
T_CRIT register and the 2 T_HIGH registers. Three state
logic inputs allow two pins (ADD0, ADD1) to select up to 9
SMBus address locations for the LM82. The sensor powers
up with default thresholds of 127˚C for T_CRIT and all
T_HIGHs. The LM82 is pin for pin and register compatible
with the LM84, Maxim MAX1617 and Analog Devices
ADM1021.
n
On-board local temperature sensing
n
SMBus and I
2
C compatible interface, supports
SMBus 1.1 TIMEOUT
n
Two interrupt outputs: INT and T_CRIT_A
n
Register readback capability
n
7 bit plus sign temperature data format, 1 ˚C resolution
n
2 address select pins allow connection of 9 LM82s on a
single bus
Key Specifications
j
Supply Voltage
j
Supply Current
3.0V to 3.6V
0.8mA (max)
0˚C to +85˚C
j
Local Temp Accuracy (includes quantization error)
±
3.0˚C (max)
j
Remote Diode Temp Accuracy (includes quantization
error)
+25˚C to +100˚C
0˚C to +125˚C
±
3˚C (max)
±
4˚C (max)
Applications
n
n
n
n
n
System Thermal Management
Computers
Electronic Test Equipment
Office Electronics
HVAC
Features
n
Accurately senses die temperature of remote ICs, or
diode junctions
Simplified Block Diagram
DS101297-1
SMBus
™
is a trademark of the Intel Corporation.
Pentium II
®
is a registered trademark of the Intel Corporation.
I2C
®
is a registered trademark of the Philips Corporation.
© 2000 National Semiconductor Corporation
DS101297
www.national.com
NSC [ NATIONAL SEMICONDUCTOR ]
