Remote Thermal Monitor and Fan Controller with PECI 3.0 Interface and SMBus Compatible Master

The NCT7491 is a two wire serially programmable hardware monitor. It can monitor 2 remote temperature zones and its own ambient temperature. A PECI 3.0 single wire interface allows the NCT7491 to monitor CPU temperatures. The NCT7491 also implements an SMBus compatible master, allowing it to read automatically from thermal sensors on the SMBus. The NCT7491 can automatically control the speed of 3 fans using PWM control, and monitor the speed of 4 fans. There are 4 analog inputs, used for measuring 12 V, 5 V, 2.5 V and Vccp channels. The NCT7491 supply voltage and PECI VTT voltage are also monitored. Each of the measured temperature, voltage and fan speed values are compared with programmable limits and if any channel is outside the programmed limit an interrupt is generated via the ALERT output pin. A THERM output is also available for fail safe thermal control. Up to 3 GPIO pins are available for digital control or signalling. Communication with the NCT7491 is accomplished via the SMBus/I2C interface which is compatible with industry standard protocols. The SMBus address is set by 2 address selection pins. The NCT7491 is available in a 24 lead QFN or QSOP package and operates over a supply range of 3.0 V to 3.6 V.