Rainbow Electronics LM75 - Manual

LM75
Digital Temperature Sensor and Thermal Watchdog with
Two-Wire Interface
General Description
The LM75 is a temperature sensor, Delta-Sigma
analog-to-digital converter, and digital over-temperature de-
tector with I
2 C ® interface. The host can query the LM75 at
any time to read temperature. The open-drain Overtempera-
ture Shutdown (O.S.) output becomes active when the tem-
perature exceeds a programmable limit. This pin can operate
in either “Comparator” or “Interrupt” mode.
The host can program both the temperature alarm threshold
(T
OS
) and the temperature at which the alarm condition goes
away (T
HYST
). In addition, the host can read back the con-
tents of the LM75’s T
OS
and T
HYST
registers. Three pins (A0,
A1, A2) are available for address selection. The sensor
powers up in Comparator mode with default thresholds of
80˚C T
OS
and 75˚C T
HYST
.
The LM75’s 3.0V to 5.5V supply voltage range, low supply
current and I
2 C interface make it ideal for a wide range of
applications. These include thermal management and pro-
tection applications in personal computers, electronic test
equipment, and office electronics.
Features
n SOP-8 and Mini SOP-8 (MSOP) packages save space
n I 2 C Bus interface
n Separate open-drain output pin operates as interrupt or
comparator/thermostat output
n Register readback capability
n Power up defaults permit stand-alone operation as
thermostat
n Shutdown mode to minimize power consumption
n Up to 8 LM75s can be connected to a single bus
Key Specifications
j Supply Voltage 3.0V to 5.5V
j Supply Current operating 250 µA (typ)
1 mA (max)
shutdown 4 µA (typ)
j Temperature Accuracy −25˚C to 100˚C ± 2˚C(max)
−55˚C to 125˚C ± 3˚C(max)
Applications
n System Thermal Management
n Personal Computers
n Office Electronics
n Electronic Test Equipment
Simplified Block Diagram
01265801
I2C ® is a registered trademark of Philips Corporation.
October 2002
LM75
Digital
T
emperature
Sensor
and
Thermal
W
atchdog
with
T
wo-W
ire
Interface
© 2002 National Semiconductor Corporation DS012658 www.national.com