RT8749

® RT8749 Digital Single-Phase Full Wave BLDC Fan Controller General Description The RT8749 is a highly integrated digital control IC for regulating single-phase full wave brushless DC (BLDC) fans at a programmed speed. The controller IC accepts a Pulse-Width Modulated (PWM) signal provided by the host, and decodes the duty-ratio of this PWM signal to 256 counts. The decoded duty-ratio will then be used for mapping to the programmed speed which is stored at the embedded flash memory. This speed profile can be programmed by users for different fan models and applications. By integrating a low RDS(ON) power MOSFET, the RT8749 minimizes component count on the PCB, thus reducing board size and cost of the motor/fan module. A frequency generator output is included to provide commutation signals to the host for the current rotating speed. The control IC also provides several protection features, including the peak-current limit, thermal shutdown protection, under-voltage protection and motor lock protection. An automatic restart circuit is designed to rotate the motor after the lock condition is released. Features  Embedded 256 x 16 Bits Flash Memory  Built-in Low RDS(ON) Power MOSFET  External PWM Speed Control  Wide Range External PWM Input Frequency (100Hz to 100kHz)  Built-in Frequency Generator with Selectable FG or FG/2 Output Signal  Built-in Peak Current Limit  Built-in Motor Lock Protection and Automatic Restart Circuit  Built-in Thermal Shutdown Protection  Low...