The MAX1669 fan controller includes a precise digital thermometer that reports the temperature of a remote sensor. The remote sensor is a diode-connected transistor--typically a low-cost, easily mounted 2N3906 PNP type--replacing conventional thermistors or thermocouples. Remote accuracy is 3C for transistors from multiple manufacturers, with no calibration needed. The MAX1669 has an independent fan controller with a lowcurrent logic output requiring external power components to interface to a DC brushless fan. The fan controller has two modes of operation: a low-frequency (20Hz to 160Hz) PWM mode intended for driving the fan motor, or a high-impedance DAC output that generates a variable DC control voltage. In PWM mode, the FAN frequency can be synchronized to an external clock.