THMC50 (sensor)

Added by ALMICO on 20 sep 2001

The THMC50 is a local/remote temperature monitor with two voltage supervisor circuits and an 8-bit, 0-V to 2.5-V DAC designed for temperature monitoring and fan control via a two-wire SMBus serial interface. The THMC50 is intended for use in personal computer applications according to the Advanced Configuration and Power Interface (ACPI) thermal model. The device is also suitable for use in network routers and hubs, office equipment, telephone switching networks, industrial control applications, and any other application requiring temperature monitoring, fan speed control, and two 3.3-V supply voltage supervisors. Temperature data is reported in a 2s complement, 8-bit binary format. The local temperature sensor can be used to monitor the ambient temperature, while a remote thermal diode, such as the one present on the Intel Pentium II, III, and the Sun UltraSPARC microprocessors, can be used to monitor the actual CPU die temperature. For applications not using a microprocessor with an integrated thermal diode, an inexpensive diode-connected 2N3904 NPN transistor can also be used to sense the remote temperature. The THMC50 provides maskable interrupts for under/over temperature condition with default or user adjustable limit values. If the temperature limit values are exceeded, the THMC50 asserts INT low. If the default thermal limits are exceeded, the THERM terminal is asserted low, and the FAN_SPD analog output automatically goes to full-scale voltage to set the fan at maximum speed. THERM can also be used as an input to instantly command full fan speed. The 8-bit, 0–2.5 V DAC output of the THMC50, along with an external amplifier circuit, provides the means to control the speed of a cooling fan. Fault tolerant fan-speed control is achieved through default and user-programmable values for high temperature limits that command the fan to full speed once the temperature limits are exceeded.