Microchip Technology

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  • Four-Channel Remote Temperature Sensor

  • Created: Feb 05, 2017

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Temperature monitoring system plays an important role not only in industries but also in residential, commercial, and even in medical areas. Remote monitoring devices are gaining popularity these days because of its ability to track temperature from a distance. These devices use high-speed transmitters and monitor temperature changes remotely. This reference design utilizes the MCP9904 remote temperature sensor, which monitors four temperature channels. It provides ±1ºC accuracy for both external and internal diode temperatures.

This design is comprised primarily of MCP9904 as the temperature sensor, MCP2221 USB Bridge, 2N3904 for remote diode temperature sensing, and few other passive components. Some features of the MCP9904 include Resistance Error Correction (REC), beta compensation, and automatic diode-type detection to provide a robust solution for complex environmental monitoring applications. Resistance Error Correction automatically eliminates the temperature error caused by series resistance allowing greater flexibility in routing thermal diodes. Beta Compensation eliminates temperature errors caused by low, variable beta transistors common in today's fine geometry processors. The automatic beta detection feature monitors the external diode/transistor and determines the optimum sensor settings for accurate temperature measurements regardless of processor technology. The circuit is powered by a 3.3V supply from a 5V USB supply. The MCP9904 communicates with a host controller such as PIC MCU through the SMBus, which is a two-wire serial communication protocol between a computer host and its peripheral devices.

The MCP9904 has two levels of monitoring. The first provides an ALERT signal to the host when the measured temperatures exceed user programmable limits. The second level of monitoring provides an interrupt on the THERM output if the measured temperatures meet or exceed a second programmable limit. This sensor provides a low-cost, highly flexible, and accurate solution for critical temperature monitoring applications such as in general purpose temperature sensing, industrial freezers/refrigerators, base stations, and remote radio unit.



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