Features and Benefits
- Drives 6 N-channel MOSFETs
- Synchronous rectification for low power dissipation
- Internal UVLO and thermal shutdown circuitry
- Hall element inputs
- PWM current limiting
- Dead time protection
- FG outputs
- Standby mode
- Lock detect protection
- Overvoltage protection
Description
The A4931 is a complete 3-phase brushless DC motor predriver, supplying up to 38 V output for direct, high-current gate drive of an all N-channel power MOSFET 3-phase bridge. The device has three Hall-element inputs, a sequencer for commutation control, fixed off-time pulse width modulation (PWM) current control, and locked-rotor protection.
Output current is scaled by the capacity of the external MOSFETs. Locked rotor detection delay is set by an external capacitor on the CLD terminal. The ENABLE, DIRECTION, and BRAKE inputs can be used to control motor speed, position, and torque. Output speed can be regulated using the FG1 output (using all three Hall elements transitions) or FG2 (using transitions of Hall element A).
The external MOSFETS can be PWMed using an external signal on the ENABLE input, or using the internal PWM current regulator. In either case, the A4931 synchronous rectification feature reduces power dissipation by turning on the appropriate MOSFETs during current decay.
The Hall elements can be inexpensive types when used with noise filtering to prevent false commutation signals. The A4931 provides a regulated 7.5 V supply to power the three Hall elements.
Internal circuit protection includes thermal shutdown with hysteresis, undervoltage lockout, and dead time protection. Special power-up sequencing is not required. Operating temperature range is –20°C to 105°C.
The A4931 is supplied in a 5 mm × 5 mm, 28-terminal QFN package with exposed thermal pad. This small footprint package is lead (Pb) free with 100% matte tin leadframe plating.
Functional Block Diagram
