National Semiconductor LM40 Hardware Monitor with Dual Thermal Diodes and SensorPath Bus
Summary
Monitor system reliability with the LM40 hardware monitor, a sophisticated chip designed to measure multiple voltages (+1.2V through +12V) and three temperature zones simultaneously. Utilizing the SensorPath Bus interface, this component provides critical data sensing for complex electronics. The accompanying manual details its full capabilities, including voltage/temperature monitoring specs, integration guidelines, and application techniques. It is essential for designers building high-performance microprocessor-based systems such as motherboards, video cards, routers, and Point of Sale equipment requiring autonomous health management.
Manual Details
| Brand | National |
|---|---|
| Pages | 27 |
| File Size | 340.94 KB |
| Published | June 02, 2026 |
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Frequently Asked Questions
What voltages can the LM40 hardware monitor?
It monitors five key analog voltages: +1.2V, +2.5V, +3.3V, +5V, and +12V.
How should I connect external thermal diodes?
Connect the negative monitoring (cathode) to D1- or D2-, and the positive monitoring (anode) to D1+ or D2+.
What is the required bulk capacitance for proper installation?
A bulk capacitance of approximately 10 µF needs to be present in the near vicinity of the LM40 device.
What are the typical accuracy limits for temperature measurement?
The device has a specified Temperature Sensor Accuracy of ±3°C (max) and Remote Temp Accuracy of ±3°C (max).