Rainbow Electronics LM41 - Manual

LM41
Hardware Monitor with Thermal Diode Inputs and
SensorPath
™ Bus
General Description
The LM41 is a hardware monitor that measures 2 tempera-
ture zones, 5 voltages and has a single-wire interface com-
patible with National Semiconductor’s SensorPath bus. Sen-
sorPath data is pulse width encoded, thereby allowing the
LM41 to be easily connected to many general purpose
micro-controllers. Several National Semiconductor Super I/O
products include a fully integrated SensorPath master, that
when connected to the LM41 can realize a hardware monitor
function that includes limit checking for measured values,
autonomous fan speed control and many other functions.
The LM41 measures the temperature of its own die as well
as one external device such as a processor thermal diode or
a diode connected transistor. The LM41 can resolve tem-
peratures up to 255˚C and down to -256˚C. The operating
temperature range of the LM41 is 0˚C to +125˚C. Using
Σ∆
ADC it measures +1.2V, +2.5V, +3.3V, +5V and +12V analog
input voltages with internal scaling resistors. The address
programming pin allows two LM41’s to be placed on one
SensorPath bus.
Features
n SensorPath Interface
— 2 hardware programmable addresses
n Voltage Monitoring
— 9-bit Σ∆ ADC
— Internal scaling resistors for all inputs
— Monitors +1.2V, +2.5 V, +3.3 V, +5 V and +12 V
n Temperature Sensing
— Remote diode temperature sensor zone
— Internal local temperature zone
— 0.5 ˚C resolution
— Measures temperatures up to 140 ˚C
n 14-lead TSSOP package
Key Specifications
n Voltage Measurement Accuracy ± 2 % (max)
n Temperature Sensor Accuracy ± 3 ˚C (max)
n Temperature Range:
— LM41 junction 0 ˚C to +85 ˚C
— Remote Temp Accuracy 0 ˚C to +100 ˚C
n Power Supply Voltage +3.0 V to +3.6 V
n Average Power Supply Current 0.5 mA (typ)
n Conversion Time (all Channels) 22.1ms to 1456ms
Applications
n Microprocessor based equipment
(Motherboards, Video Cards, Base-stations, Routers,
ATMs, Point of Sale, …)
n Power Supplies
Typical Application
20070301
SensorPath ™ is a trademark of National Semiconductor Corporation
May 2004
LM41
Hardware
Monitor
with
Thermal
Diode
Inputs
and
SensorPath
™
Bus
© 2004 National Semiconductor Corporation DS200703 www.national.com