LM40

LM40 Hardware Monitor with Dual Thermal Diodes and SensorPath™ Bus May 2004 LM40 Hardware Monitor with Dual Thermal Diodes and SensorPath™ Bus General Description The LM40 is a hardware monitor that measures 3 temperature zones, 5 voltages and has a single-wire interface compatible with National Semiconductor’s SensorPath bus. SensorPath data is pulse width encoded, thereby allowing the LM40 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 LM40 can realize a hardware monitor function that includes limit checking for measured values, autonomous fan speed control and many other functions. The LM40 measures the temperature of its own die as well as two external devices such as a processor thermal diode or a diode connected transistor. The LM40 can resolve temperatures up to 255˚C and down to -256˚C. The operating temperature range of the LM40 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 LM40s to be placed on one SensorPath bus. — Internal scaling resistors for all inputs — Monitors +1.2V, +2.5 V, +3.3 V, +5 V and +12 V n Temperature Sensing — 2 remote diode temperature sensor zones — Internal local temperature zone — 0.5 ˚C resolution — Measures temperatures up to 140 ˚C n 14-lead TSSOP package Key Specifications n ...