AllegroMicro公司的 A4938是三相无刷直流（BLDC）马达预驱动器，能驱动6路N沟功率MOSFET三相桥电路。器件集成了三个霍尔元件" title="霍尔元件">霍尔元件输入，用于换向控制的时序，固定关机时间PWM电流控制" title="电流控制">电流控制和锁定转子检测。A4938提供5V电源，给三个霍尔元件供电，内部电路保护" title="电路保护">电路保护包括带滞后的热关断，欠压锁住和死区保护。本文介绍了A4938主要特性" title="主要特性">主要特性和优势，功能方框图和典型应用电路。
3-Phase Brushless DC Motor Pre-Driver
The A4938 is a complete 3-phase brushless DC (BLDC) motor pre-driver, supplying 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 detection.
Output current is scaled by the capability of the external MOSFETs. Locked rotor detection delay is set by an external capacitor on the CLD terminal. The ENABLE, DIR, and BRAKEZ inputs can be used to control motor speed, position, and torque. Motor speed can be determined using the FG1 output.
The external MOSFETS can be PWMed using an external signal on the PWM input, or using the internal PWM current regulator. In either case, the A4938 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 A4938 provides a regulated 5.0 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 –40℃ to 85℃
The A4938 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.
A4938主要特性和优势：
▪ 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
图1。A4938功能方框图
图2。A4938应用电路图
详情请见：
http://www.allegromicro.com/en/Products/Part_Numbers/4938/4938.pdf
