June 1999
LM80
Serial Interface ACPI-Compatible Microprocessor System
Hardware Monitor
n WATCHDOG comparison of all monitored values
n Separate input to show status in Interrupt Status
Register of additional external temperature sensors such
General Description
The LM80 provides 7 positive voltage inputs, temperature
measurement, fan speed measurement, and hardware
as the LM56 or LM75
2
™
monitoring on an I C
interface. The LM80 performs
n I2C Serial Bus interface compatibility
™
WATCHDOG comparisons of all measured values and an
open-drain interrupt output becomes active when any values
exceed programmed limits. A Chassis Intrusion input is pro-
vided to monitor and reset an external circuit designed to
latch a chassis intrusion event.
n Shutdown mode to minimize power consumption
n Programmable RST_OUT/OS pin: RST_OUT provides a
Reset output; OS provides an Interrupt Output activated
by an Overtemperature Shutdown event
The LM80 is especially suited to interface to both linear and
digital temperature sensors. The 10 mV LSB and 2.56 volt
input range is ideal for accepting inputs from a linear sensor
such as the LM50. The BTI is used as an input from either
digital or thermostat sensors such as LM75 and LM56.
Key Specifications
n Voltage monitoring Error
±
1% (max)
n Temperature Error
±
−25˚C to +125˚C
3˚C (max)
The LM80’s 2.8V to 5.75V supply voltage range, low supply
current, and I2C interface make it ideal for a wide range of
applications. These include hardware monitoring and protec-
tion applications in personal computers, electronic test
equipment, and office electronics.
n Supply Voltage Range
n Supply Current
2.8V to
5.75V
Operating:
Shutdown:
0.2 mA typ
15 µA typ
8 Bits
n ADC Resolution
Features
n Temperature sensing
n Temperature Resolution
0.5˚C
n 7 positive voltage inputs
n 2 programmable fan speed monitoring inputs
n 10 mV LSB and 2.56V input range accepts outputs from
linear temperature sensors such as the LM50
n Chassis Intrusion Detector input
Applications
n System Thermal and Hardware Monitoring for Servers
and PCs
n Office Electronics
n Electronic Test Equipment and Instrumentation
Typical Application
DS100040-1
# Indicates Active Low (“Not”)
TRI-STATE® is a registered trademark of National Semiconductor Corporation.
™
WATCHDOG is a trademark of National Semiconductor Corporation.
2
I
C® is a registered trademark of the Philips Corporation.
© 1999 National Semiconductor Corporation
DS100040
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