BLDC fan speed controller with I²C bus control
The MAX6650EUB+ is a brushless DC (BLDC) fan speed controller from Analog Devices, designed to regulate the speed of a 4-wire fan via an I²C interface. It integrates a pre-driver low-side output stage that drives external N-channel MOSFETs, so the actual power handling is set by the external FETs and the thermal design of the board, not by the controller itself.
I²C interface and output drive
Speed control is set through the I²C bus — the controller reads the target RPM from the bus and adjusts the drive PWM to the external low-side FETs. The pre-driver output configuration means the controller handles the gate drive logic while the external MOSFETs switch the fan current, keeping the heat out of the controller package. The 10-uMAX/uSOP package (3.00 mm × 3.00 mm body, 0.118-inch pitch) is a compact surface-mount footprint that fits on the control side of a power supply PCB without consuming board area that belongs to the power stage.