A4938 Datasheet, PDF (1/10 Pages) Allegro MicroSystems – 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.

A4938
3-Phase Brushless DC Motor Pre-Driver
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
Package: 28-contact QFN (ET package)
Approximate Scale 1:1
Description
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
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Typical Application
0.1 μF
0.1 μF
CLD HBIAS CP1 CP2 VCP VBB
V_IN
System
Control
Logic
OVP
GHA
SA
A4938
GLA
GHB
FG
SB
GLB
BRAKEZ
ENABLE
DIR
GHC
SC
GLC
SENSE
GND HA+ HA– HB+ HB– HC+ HC–
0.1 μF 2 kΩ
V_IN
M
0.1 μF
A4938-DS