To smartly control the speed of cooling fans in notebooks and desktop computers and such systems where fan speed requires control, Diodes Incorporated is offering brushless DC motor drivers with bridge-tied-load (BTL) drive architecture. These new motor driver chips support lesser audible switching noise and electromagnetic interference (EMI). PWM control supporting AM9468/AM9469 adjusts duty cycle of the full-bridge output driver stage based on the input signal and a separate frequency generator provides a tachometer output for external monitoring of motor speed. The low noise is achieved through the BTL architecture, which amplifies the sinusoidal magnetizing flux density signal used to drive the motor’s coils avoiding large changes in current during commutation and helps achieve low noise operation. The speed control PWM duty cycle is superimposed on the BTL drive signal. The quick-start circuit and rotor lock detection of AM9468/AM9469 protect the motor coil from overheating/burning out and also ensures an automatic restart when the lock is removed. Current limit circuit and a Hall bias output are some of the other features available in these devices. The AM9468 is available in a standard, power-capable TSSOP-16 package and the AM9469 is available in a thermally enhanced, exposed-paddle TSSOP-16EP package, which can source or sink output currents up to 700mA. Over-temperature protection is provided with a thermal shutdown circuit to protect the enclosed coil and PCB of cooling fans found in thermally-demanding consumer applications. Both devices are specified for an operating temperature range from -40°C to 105°C.