Allegro introduces a new automotive grade three-phase MOSFET pre-driver IC targeted at automotive and industrial applications. Adoption of three-phase BLDC motors in automotive and industrial applications is growing rapidly in the marketplace. Allegro has addressed this particular need by introducing the A4935 device. This new device is a third generation three-phase driver that includes enhanced performance and operational features over its predecessors. Allegro’s new robust design is ideal for systems that use sinusoidal control of the motor phase currents. This commutation method provides smooth operation reducing audible noise and minimizing torque ripple at the load.

The A4935 is a 3-phase controller for use with N-channel external power MOSFETs and is specifically designed for automotive applications. This new device integrates a regulating charge pump which provides full gate drive capability for battery voltages (Vbb) down to 7 V and reduced gate drive for battery voltages as low as 5.5 V. It also includes performance enhancements of the current sense amplifier, as well as better fault diagnostics and reporting to decode and identify faults. Features such as top-off charge pump and boot strap charge management make this new device much easier to manage in terms of ensuring an adequate boot capacitor charge under varying PWM conditions.

Full control over all six power FETs in the 3-phase bridge is provided, allowing motors to be driven with block commutation or sinusoidal excitation. The power FETs are protected from shoot-through by integrated crossover control and resistoradjustable dead time. Allegro’s A4935KJP-T is supplied in a 48L eLQFP small profile thermally efficient exposed pad package. A unique charge pump regulator provides full (>10 V) gate drive for battery voltages down to 7 V and allows the A4935 to operate with a reduced gate drive, down to 5.5 V. A bootstrap capacitor is used to provide the above-battery supply voltage required for N-channel MOSFETs. An internal charge pump for the high-side drive allows DC (100% duty cycle) operation.

Integrated diagnostics provide indication of undervoltage, overtemperature, and power bridge faults. They can be configured to protect the power FETs under most short circuit conditions. Detailed diagnostics are available as a serial data word. Bridge current can be measured using an integrated current sense amplifier. This is an uncommitted differential amplifier with a below-ground common mode range allowing it to be used in low-side current sense applications. Gain and offset are defined by external resistors. The A4935 is supplied in a 48-pin LQFP with exposed thermal pad, (suffix JP). This is a small footprint (81 mm2) power package. It is lead (Pb) free with 100% matte tin leadframe plating.

Features and Benefits

• High current 3-phase gate drive for N-channel MOSFETs
• Compatible with 3.3 V and 5 V logic
• Cross-conduction protection with adjustable dead time
• Uncommitted current sense amplifier
• Top-off charge pump for 100% PWM
• Charge pump for low supply voltage operation
• 5.5 to 50 V supply voltage range
• Extensive diagnostic outputs
• Low-current sleep mode

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