Equipped with an independent fan controller with a low current logic output requiring external power components to interface to a dc brushless fan, the MAX1669 fan controller features a precise digital thermometer that reports the temperature of a remote sensor. The remote sensor is a diode-connected transistor. The fan controller has two operating modes: a low frequency PWM mode intended for driving the fan motor; and a high-impedance DAC output that generates a variable linear dc control voltage. In the PWM mode, the fan frequency can be synchronized to an external clock. Other key features of the controller chip include general-purpose I/Os for fan presence detection and a thermometer output intended as a fan override signal in case the host system loses the ability to communicate. The device asserts an SMBus alert interrupt if the measured temperature equals or exceeds the alarm threshold value.