A4915MLPTR-T

The A4915MLPTR-T is a comprehensive three-phase MOSFET gate driver from Allegro MicroSystems, specifically designed for brushless DC (BLDC) motor control applications using block (trapezoidal) commutation. This highly integrated device simplifies BLDC motor drive designs by incorporating commutation logic, synchronous rectification, PWM control, and comprehensive protection features into a single package, significantly reducing external component count and overall design complexity. Operating from a load supply voltage range of 5V to 50V and a logic supply of 3.3V to 5.5V, the A4915 can drive six external N-channel power MOSFETs in a three-phase bridge configuration. An internal charge pump regulator ensures full gate drive voltage at supply voltages as low as 7V, with limited gate drive capability extending down to 5V, making it well-suited for battery-powered applications. The device features three Hall sensor inputs (HA, HB, HC) for direct connection to Hall-effect position sensors in the motor, with built-in commutation logic that automatically determines which MOSFETs to activate based on the rotor position. This eliminates the need for a microcontroller to perform commutation sequencing, reducing system cost and firmware complexity. Speed control is achieved through a dedicated analog SPEED input pin that controls the internal PWM duty cycle from 0% to 100%, or alternatively through external PWM applied to the ENABLE pin. The PWM operates at 30 kHz typical using a center-aligned architecture that improves power dissipation distribution and helps reduce electromagnetic interference (EMI). Internally controlled synchronous rectification improves efficiency by turning on the appropriate MOSFET during the current decay period instead of relying on the body diode. Adjustable dead time, set via an external resistor, prevents shoot-through (cross-conduction) between high-side and low-side MOSFETs. Comprehensive protection features include undervoltage lockout (UVLO), crossover current protection, and latched thermal shutdown with a dedicated fault output pin. The BRAKEn input provides a brake function that activates all three low-side drivers simultaneously, effectively shorting the motor windings for dynamic braking. The low-power sleep mode draws minimal supply current when the ENABLE pin is held low for an extended period, making the A4915 ideal for battery-operated equipment. Packaged in a 28-pin TSSOP with an exposed thermal pad for enhanced thermal performance, the A4915MLPTR-T is supplied in tape-and-reel packaging with 4000 pieces per reel and features 100% matte-tin lead plating for RoHS compliance.

The A4915 operates as a complete three-phase BLDC motor controller and gate driver. It receives position feedback from three Hall-effect sensors (HA, HB, HC) mounted in the motor, which indicate the current rotor position. Based on these Hall inputs and the direction (DIR) control signal, the internal commutation logic determines which pair of MOSFETs (one high-side and one low-side on different phases) should be activated to produce torque in the desired direction. This is known as block or trapezoidal commutation, where only two phases are energized at any time. The gate drive for the high-side MOSFETs is provided through bootstrap capacitors connected between each phase output and the corresponding high-side gate drive pin. When the low-side MOSFET of a phase is on, the bootstrap capacitor charges to the VREG voltage through the bootstrap diode. When the high-side MOSFET is subsequently turned on, the bootstrap capacitor provides the voltage source needed to drive the gate above the source voltage (which is at the phase voltage). The low-side gate drives are powered directly from an internal charge pump regulator that generates a regulated voltage above VBB to ensure proper N-channel MOSFET gate drive even at low supply voltages. PWM speed control can be implemented in two modes: internal PWM mode where the SPEED analog input controls the duty cycle of an internally generated 30 kHz carrier, or external PWM mode where the ENABLE pin is pulsed with an external PWM signal. The center-aligned PWM scheme switches both high-side and low-side drivers symmetrically around the center of the PWM period, resulting in lower EMI compared to edge-aligned alternatives. During the PWM off-time, synchronous rectification is implemented by turning on the complementary low-side or high-side MOSFET (depending on current direction), allowing current to recirculate through the low-resistance MOSFET channel rather than the higher-loss body diode, improving overall efficiency. Dead time is inserted between the turn-off of one MOSFET and the turn-on of the complementary MOSFET to prevent shoot-through currents. Protection features include UVLO that disables the outputs if the supply voltage drops below acceptable levels, cross-conduction prevention logic, and thermal shutdown that latches off the device in case of overheating, with the fault condition indicated by the fault output pin. When ENABLE is held low for longer than the sleep timer threshold, the device enters a low-current sleep mode to minimize power consumption in standby.

• Cordless power tools: drills, saws, impact drivers, and garden tools
• Industrial BLDC motor control and variable speed drives
• Robotics: robotic arm joints, wheel drives, actuator control
• E-bikes, electric scooters, and light electric vehicles
• 2-wheeler chassis and safety systems (brake, steering motors)
• Home appliances: refrigerators, air conditioners, washing machines
• Battery-powered pumps and fans for portable equipment
• Automotive auxiliary motor drives (HVAC blowers, pumps)
• Consumer electronics: drones, camera gimbals, robotic vacuums
• Medical equipment and laboratory instrument motor drives