"Tiny Cooling Fan" two speed without warning and the speed sensor of the control circuit, the MAX1669 constitute PWM control mode, is composed MAX1669 linear regulator control. MAX1669 both a temperature sensor and a fan controller, two-part work independently and cooperate with the micro controller, its interface mode is SMB. "Tiny Cooling Fan" temperature sensor installed in the distal end of the diode to complete, this diode can also be contained within some devices, such as the company's VIRTEX XILINX devices, it will be more precisely control the temperature of key components and eliminates the need for external diodes. When the MAX1669 detects the temperature increases by software to control and improve the "Tiny Cooling Fan" speed. Fan speed control and temperature measurement independent of, so this is an open-loop control system, there is no stability problems. But not directly know the actual temperature is controlled member can not direct knowledge of whether the fan fails or if the cooling efficiency.