Microchip EMC2301 RPM-Based PWM Fan Controller Microchip EMC2301 RPM-Based PWM Fan Controller is an SMBus-compliant fan controller with a PWM fan driver. The fan driver is controlled by a programmable frequency PWM driver and Fan Speed Control algorithm that operates in either a closed-loop fashion or as a directly PWM-controlled device. Each closed loop Fan Speed Control algorithm is able to detect aging fans and alert the system. The algorithm can also detect stalled or locked fans and trigger an interrupt. Microchip EMC2301 also offers a clock output so that multiple devices may be chained and slaved to the same clock source for optimal performance in large distributed systems.