A4938EETTR-T Allegro Microsystems Inc, A4938EETTR-T Datasheet

IC DC MOTOR PREDRIVER 3PH 28-QFN

A4938EETTR-T

Manufacturer Part Number
A4938EETTR-T
Description
IC DC MOTOR PREDRIVER 3PH 28-QFN
Manufacturer
Allegro Microsystems Inc
Datasheet

Specifications of A4938EETTR-T

Applications
DC Motor Controller, Brushless (BLDC), 3 Phase
Number Of Outputs
1
Voltage - Supply
8.5 V ~ 30 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
28-VFQFN Exposed Pad
Operating Temperature Classification
Industrial
Motor Controller Type
Motor Driver
Operating Supply Voltage (min)
8.5V
Operating Supply Voltage (max)
30V
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Current - Output
-
Voltage - Load
-
Lead Free Status / Rohs Status
Supplier Unconfirmed
Other names
620-1383-2
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)
A4938-DS
Approximate Scale 1:1
System
Control
Logic
0.1 μF
V
IN
3-Phase Brushless DC Motor Pre-Driver
OVP
FG
BRAKEZ
ENABLE
DIR
CLD
GND
Typical Application
HBIAS
HA+ HA– HB+ HB– HC+ HC–
0.1 μF
A4938
CP1
CP2 VCP
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
Continued on the next page…
SENSE
GHA
GHC
GHB
GLA
GLB
GLC
VBB
SA
SB
SC
0.1 μF
2 kΩ
V
M
IN
0.1 μF
A4938

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A4938EETTR-T Summary of contents

Page 1

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 ...

Page 2

... Description (continued) shutdown with hysteresis, undervoltage lockout, and dead time protection. Special power-up sequencing is not required. Operating temperature range is –40°C to 85°C. Selection Guide Part Number A4938EETTR-T 1500 pieces per reel Absolute Maximum Ratings Characteristics Load Supply Voltage Motor Phase Output ...

Page 3

A4938 0.1 μF Lock CLD Detect HBIAS 2 kΩ HA+ 0.1 μF HALL HA- Commun- HB+ ication HALL Logic HB- HC+ HALL HC- FG1 BRAKEZ System DIR Logic ENABLE V IN GND Terminal List Number Name 1 HA+ Hall input ...

Page 4

A4938 ELECTRICAL CHARACTERISTICS Characteristics Supply Voltage Range Motor Supply Current HBIAS HBIAS Current Limit Control Logic Logic Input Voltage Logic Input Pull-Up Input Pin Glitch Reject ENABLE Standby Pulse Propagation Delay HBIAS Wake-up Delay, Standby Mode Gate Drive High-Side Gate ...

Page 5

A4938 ELECTRICAL CHARACTERISTICS Characteristics Hall Logic Hall Input Current Common Mode Input Range AC Input Voltage Range Hall Thresholds Hall Threshold Hysteresis Pulse Reject Filter FG FG Output Saturation Voltage FG Leakage Current *Typical data are for initial design estimations ...

Page 6

A4938 Logic States Table (See timing charts, below Don’t Care (can 0 high impedance Condition – – – – Forward D – ...

Page 7

A4938 Power-up and Standby Modes Timing Diagram VBB Charge Pump HBIAS Voltage ENABLE Power-up and Standby Modes Timing Diagram VBB V +7 Charge Pump 7.5 V HBIAS Voltage ENABLE 3-Phase Brushless DC Motor Pre-Driver V BBUV Standby Mode ...

Page 8

A4938 Load current is regulated by an internal Current Regulation fixed off-time PWM control circuit. When the outputs of the full bridge are turned on, current increases in the motor winding until it reaches a value given by: ...

Page 9

A4938 holding ENABLE high for longer than 3 ms. Note that the state of BRAKEZ does not affect Standby mode. The internal charge pump is used to generate a Charge Pump supply above V to drive the high-side MOSFETs. The ...

Page 10

A4938 29X 0.08 C +0.05 0.25 –0.07 +0.20 0.55 –0. Copyright ©2010, Allegro MicroSystems, Inc. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such de par tures from the detail spec ...

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