AllegroMicro公司的 A4938是三相無刷直流（BLDC）馬達預驅動器，能驅動6路N溝功率MOSFET三相橋電路。器件集成了三個霍爾元件" title="霍爾元件">霍爾元件輸入，用于換向控制的時序，固定關機時間PWM電流控制" title="電流控制">電流控制和鎖定轉子檢測。A4938提供5V電源，給三個霍爾元件供電，內部電路保護" title="電路保護">電路保護包括帶滯后的熱關斷，欠壓鎖住和死區保護。本文介紹了A4938主要特性" title="主要特性">主要特性和優勢，功能方框圖和典型應用電路。
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主要特性和優勢：
? 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
圖1。A4938功能方框圖
圖2。A4938應用電路圖
詳情請見：
http://www.allegromicro.com/en/Products/Part_Numbers/4938/4938.pdf
