Microchip Technology Inc.’s MCP9805 digital temperature sensor converts temperatures between -40°C and +125°C to a digital word. This sensor is designed to meet the JEDEC standard JC42.4 for Mobile Platform Memory Module Thermal Sensor. This device provides an accuracy of ±1°C （max.） from a temperature range of +75°C to +95°C （active range） and ±2°C （max.） from +40°C to +125°C （monitor range） as defined in the JEDEC standard. The MCP9805 comes with user-programmable registers that provide flexibility for DIMM temperature-sensing applications. The registers allow user-selectable settings such as Shutdown or Low-Power modes and the specification of temperature event and critical output boundaries. When the temperature changes beyond the specified boundary limits， the MCP9805 outputs an Event signal. The user has the option of setting the Event output signal polarity as either an active-low or active-high comparator output for thermostat operation， or as a temperature event interrupt output for microprocessor-based systems. The Event output can also be configured as a critical temperature output. This sensor has a 2-wire industry-standard SMBus and Standard mode I2C compatible （100 kHz bus clock） serial interface protocol， allowing up to eight sensors to be controlled in a single serial bus. These features make the MCP9805 ideal for sophisticated multi-zone temperature-monitoring applications.