Intelligent Fan Controller

The commutation of a fan motor as the rotor moves from one pole to the next can be clearly observed as pulses in its current consumption. This property is exploited by the TC652 and TC653 fan controller ICs from Microchip Technology (www.microchip.com). The ‘FanSense’ feature, as the manufacturer calls it, derives an error signal from the commutation pulses. The devices also detect if the fan is jammed or has failed by the absence of these pulses. Resistor Rsense should be chosen so that about 0.5 V is dropped across it at the nominal fan current.