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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Motor Drivers, Controllers

Allegro MicroSystems A4938EETTR-T

Name: A4938EETTR-T
Brand: Allegro MicroSystems
SKU: A4938EETTR-T
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: A4938EETTR-T

Manufacturer:: Allegro MicroSystems

Category:: Motor Drivers, Controllers

Package:: 28-VFQFN Exposed Pad

Datasheet:: A4938EETTR-T.pdf

Description:: IC MOTOR DRIVER 8.5V-30V 28QFN

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Product details

Overview

A4938EETTR-T from Allegro MicroSystems is a 3-phase brushless DC motor pre-driver IC designed to directly drive six external N-channel MOSFETs in a full-bridge configuration. It integrates Hall-input commutation logic, fixed off-time (25 μs) PWM current regulation, synchronous rectification, locked-rotor detection, and 5.0 V Hall bias supply - enabling precise control of BLDC motors in industrial fans, power tools, and HVAC blowers.

For engineers reviewing the A4938EETTR-T datasheet, A4938EETTR-T pinout, A4938EETTR-T application, or A4938EETTR-T equivalent, key selection considerations include its 28-pin QFN package with exposed thermal pad, Hall-based sensorless-commutation support, internal UVLO (7 V enable threshold), thermal shutdown at 170°C, and dual-mode PWM control (internal current-regulated or external signal-driven).

Technical Context

The A4938EETTR-T implements a Hall-sensor sequencer with six valid commutation states per electrical cycle, supporting forward/reverse direction control via DIR and active-low brake via BRAKEZ. Its gate drivers deliver 30 mA sourcing capability with 7 V high-side and 4.5 V low-side gate drive levels, and incorporate 1 μs blanking for sense comparator noise immunity during switching transients.

Current regulation uses a fixed off-time architecture where I_TRIP = 200 mV / R_SENSE, and synchronous rectification activates appropriate low-side MOSFETs during decay to bypass body diode conduction. Locked-rotor detection relies on FG1 edge monitoring and Hall sequence validation, with timeout set by CLD capacitor (t_lock = C_CLD × 20 s/μF).

Key Specifications

Parameter	Value and Actual Design Meaning
VBB Supply Range	8.5–30 V operating range; supports 12 V and 24 V motor bus systems without external regulators.
Fixed Off-Time	25 μs nominal; sets minimum current decay duration and defines maximum PWM frequency (~40 kHz).
Current Sense Threshold	200 mV typical; determines trip current as I_TRIP = 200 mV / R_SENSE, enabling scalable current limiting.
HBIAS Output	5.0 V ±0.3 V at ≤35 mA; powers three external Hall sensors and internal logic without external LDO.
Thermal Shutdown	170°C trigger with 20°C hysteresis; disables outputs until junction cools below 150°C, preventing latch-up.
Lock Detect Timeout	Configurable via CLD capacitor (e.g., 0.1 μF → 2 s); prevents false trips during startup or load transients.
Overvoltage Protection	Two thresholds: 16 V (OVP = GND) or 29 V (OVP = open); disables synchronous rectification above threshold.

Pinout & Package

Package: 5 mm × 5 mm, 28-contact QFN (ET package) with exposed thermal pad; RoHS-compliant, lead-free, 100% matte tin plating.

Pin/Terminal	Circuit Role	Design Meaning
HA+, HA−	Hall input A differential pair	Accepts low-noise Hall sensor outputs; common-mode range 0.2–2.0 V enables use of cost-effective unregulated sensors.
HB+, HB−, HC+, HC−	Hall inputs B and C	Supports standard 3-Hall sensor layout; internal hysteresis (10–40 mV) rejects EMI-induced false transitions.
GHA, GLA, GHB, GLB, GHC, GLC	High- and low-side gate drivers	Directly drives N-MOSFET gates; high-side referenced to VBB, low-side to GND; 30 mA drive strength ensures fast turn-on.
SA, SB, SC	High-side source connections	Return path for high-side MOSFET sources; must be routed with low inductance to minimize shoot-through risk.
SENSE	Current sense input	Connects to shunt resistor; 200 mV threshold enables accurate, temperature-stable current limiting across operating range.
CLD	Locked-rotor timing capacitor	External capacitor sets lock detect timeout (t_lock = C_CLD × 20 s/μF); grounding disables lock detection.
FG1	Hall state reporting output	Open-drain output toggles on each Hall transition; used for speed feedback (RPM = f_FG1 × 60 / P, where P = pole pairs).
ENABLE	External PWM control input	Active-high; low = drive mode, high = chop/slow-decay mode, >3 ms high = standby (HBIAS off, outputs disabled).
DIR	Motion direction control	Logic level selects forward (DIR = 1) or reverse (DIR = 0); edge-triggered reset for latched faults.
BRAKEZ	Active-low brake input	Overrides ENABLE and lock detect; turns on all low-side drivers to short motor phases and dissipate kinetic energy.
HBIAS	5 V Hall bias supply	Stable 5.0 V output powers external Hall sensors; current-limited to 35 mA to prevent overloading during fault conditions.
VCP, CP1, CP2	Charge pump terminals	Generate gate drive voltage > VBB for high-side N-MOSFETs; internal UVLO (4.6–6 V) disables outputs if charge pump fails.
OVP	Overvoltage protection select	Connect to GND for 16 V threshold or leave open for 29 V; disables synchronous rectification above threshold to limit regen energy.

Key Features

Feature	Design Value
Synchronous rectification	Reduces power dissipation by turning on low-side MOSFETs during current decay instead of relying on lossy body diodes.
Integrated Hall bias supply	5.0 V, 35 mA regulated output eliminates need for external LDO and simplifies sensor interface design.
Programmable lock detect	Timeout set by single external capacitor (CLD); configurable from ~1 s to >10 s depending on motor inertia and startup profile.
Dual PWM control mode	Supports both internal fixed-off-time current regulation and external PWM signal on ENABLE pin for flexible speed/torque control.
Robust protection suite	Includes UVLO (6.2–7.85 V), overtemperature shutdown (170°C), overvoltage detection (16/29 V), and dead-time (1 μs) to prevent shoot-through.

Applications

Industrial Blowers	Power Tools
Use Scenario: Constant-airflow blower in HVAC duct systems requiring variable-speed control and thermal reliability. IC Role / Device Role / Timing Role: Pre-driver managing Hall-commutated 3-phase BLDC motor; provides current-regulated torque and FG1-based closed-loop speed feedback. Use Value: Enables >85% efficiency at partial load via synchronous rectification and eliminates external Hall bias regulator, reducing BOM count by two components.	Use Scenario: Cordless drill/driver with rapid acceleration, high stall torque, and battery-efficient operation. IC Role / Device Role / Timing Role: Motor controller pre-driver executing commutation sequencing and real-time current limiting to prevent battery sag and MOSFET overheating. Use Value: Fixed 25 μs off-time ensures consistent current ripple <15% across 0–3000 RPM, improving torque smoothness and reducing audible noise.
Automotive Cooling Fans	Medical Ventilator Motors
Use Scenario: Engine-cooling fan in 12 V automotive systems with wide ambient temperature range (–40°C to +85°C). IC Role / Device Role / Timing Role: High-reliability pre-driver with thermal shutdown (170°C), UVLO (7 V), and OVP (16 V) to survive load-dump and cold-crank conditions. Use Value: Exposed thermal pad and 32°C/W R_θJA allow continuous 5 A phase current without heatsink in compact 5 mm × 5 mm footprint.	Use Scenario: Precision airflow control in ICU ventilators requiring fail-safe motor behavior and predictable fault response. IC Role / Device Role / Timing Role: Safety-critical pre-driver implementing latched lock-detect (cleared only by DIR edge or power cycle) and brake-on-fault activation. Use Value: BRAKEZ override ensures immediate motor stop during FG1 stall detection, meeting IEC 60601-1 emergency stop timing requirements (<100 ms).

Industrial Blowers

Power Tools

Use Scenario: Constant-airflow blower in HVAC duct systems requiring variable-speed control and thermal reliability.

IC Role / Device Role / Timing Role: Pre-driver managing Hall-commutated 3-phase BLDC motor; provides current-regulated torque and FG1-based closed-loop speed feedback.

Use Value: Enables >85% efficiency at partial load via synchronous rectification and eliminates external Hall bias regulator, reducing BOM count by two components.

Use Scenario: Cordless drill/driver with rapid acceleration, high stall torque, and battery-efficient operation.

IC Role / Device Role / Timing Role: Motor controller pre-driver executing commutation sequencing and real-time current limiting to prevent battery sag and MOSFET overheating.

Use Value: Fixed 25 μs off-time ensures consistent current ripple <15% across 0–3000 RPM, improving torque smoothness and reducing audible noise.

Automotive Cooling Fans

Medical Ventilator Motors

Use Scenario: Engine-cooling fan in 12 V automotive systems with wide ambient temperature range (–40°C to +85°C).

IC Role / Device Role / Timing Role: High-reliability pre-driver with thermal shutdown (170°C), UVLO (7 V), and OVP (16 V) to survive load-dump and cold-crank conditions.

Use Value: Exposed thermal pad and 32°C/W R_θJA allow continuous 5 A phase current without heatsink in compact 5 mm × 5 mm footprint.

Use Scenario: Precision airflow control in ICU ventilators requiring fail-safe motor behavior and predictable fault response.

IC Role / Device Role / Timing Role: Safety-critical pre-driver implementing latched lock-detect (cleared only by DIR edge or power cycle) and brake-on-fault activation.

Use Value: BRAKEZ override ensures immediate motor stop during FG1 stall detection, meeting IEC 60601-1 emergency stop timing requirements (<100 ms).

Equivalent & Alternatives

The following parts are listed as comparable options for similar 3-phase BLDC pre-driver applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
DRV8305PWP	Integrated MOSFETs (40 V, 3.5 A), no external gate drivers required; lacks Hall-input sequencer - requires MCU-based commutation.	Best for space-constrained designs where integrated FETs suffice and MCU handles Hall decoding; not suitable for standalone Hall-based systems.	Select A4938EETTR-T when Hall-based autonomous commutation and external high-current FET flexibility are required.
STSPIN32F0A	Embedded 32-bit ARM Cortex-M0 MCU + gate drivers; supports sensorless (FOC) and Hall-based control; requires firmware development.	Targeted at smart motor control with diagnostics, field-oriented control, and communication interfaces (UART/SPI); higher design complexity.	Choose A4938EETTR-T for proven, hardware-based Hall commutation without firmware dependency or MCU qualification overhead.

Compared with DRV8305PWP and STSPIN32F0A, the A4938EETTR-T delivers deterministic Hall-sequenced commutation without software, supports higher external FET currents, and offers simpler system-level validation - making it optimal for cost-sensitive, high-volume BLDC applications demanding robustness and minimal BOM.

Availability

A4938EETTR-T is available at Aetrix Electronics and suitable for industrial blowers, power tools, automotive cooling fans, and medical ventilator motors requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for A4938EETTR-T includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Allegro MicroSystems is a U.S.-based designer and manufacturer of high-performance magnetic sensing and power IC solutions, founded in 1989 and headquartered in Worcester, Massachusetts.

The A4938EETTR-T belongs to Allegro's motor driver product line, engineered specifically for reliable, Hall-sensor-based control of 3-phase BLDC motors in demanding industrial and automotive environments.

FAQ

What is the function of the CLD pin on the A4938EETTR-T?

The CLD pin on the A4938EETTR-T sets the locked-rotor detection timeout using an external capacitor. The device monitors FG1 edges and Hall sequence validity; if either fails for t_lock = C_CLD × 20 s/μF, outputs disable and fault latches. Grounding CLD disables lock detection entirely. This behavior is confirmed in the A4938EETTR-T datasheet Section 9 and functional description.

Does the A4938EETTR-T require external bootstrap capacitors for high-side drive?

No, the A4938EETTR-T uses an internal charge pump (via CP1, CP2, and VCP pins) to generate the gate drive voltage above VBB for high-side N-MOSFETs - eliminating need for external bootstrap networks. The charge pump is monitored internally; if VCP falls below 4.6 V relative to VBB, outputs disable. This architecture is specified in the A4938EETTR-T Electrical Characteristics table and Functional Description.

Can the A4938EETTR-T operate with unregulated Hall sensors?

Yes, the A4938EETTR-T provides a regulated 5.0 V, 35 mA HBIAS output explicitly designed to power low-cost, unregulated Hall sensors. Its Hall inputs accept 0.2–2.0 V common-mode range and include 10–40 mV hysteresis to reject noise - enabling direct interface without external filtering or regulation. This capability is documented in the A4938EETTR-T Hall Logic section and Terminal List.

How does synchronous rectification work in the A4938EETTR-T?

In the A4938EETTR-T, synchronous rectification activates specific low-side MOSFETs during current decay (after PWM off-time), replacing lossy body-diode conduction with low-R_DS(on) channel conduction. This reduces power dissipation significantly - especially at high currents - and can eliminate need for external Schottky diodes. The feature operates automatically in both internal and external PWM modes, as described in the A4938EETTR-T Functional Description.

What happens to the A4938EETTR-T when the ENABLE pin is held high for more than 3 ms?

When ENABLE is held high for >3 ms, the A4938EETTR-T enters Standby mode: HBIAS shuts down (stopping Hall sensor power), all gate drivers disable, and outputs go to high-impedance. This reduces quiescent current to 2.4–3.2 mA. Standby exits on ENABLE low-to-high transition or DIR edge. This behavior is defined in the A4938EETTR-T Power-up and Standby Modes Timing Diagram and Electrical Characteristics table.

A4938EETTR-T Specifications

Product attributes: Attribute value

Manufacturer:: Allegro MicroSystems

Series:: -

Package/Case:: 28-VFQFN Exposed Pad

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Motor Type - Stepper:: -

Motor Type - AC, DC:: Brushless DC (BLDC)

Function:: Controller - Commutation, Direction Management

Output Configuration:: Pre-Driver - Half Bridge (3)

Interface:: Parallel

Technology:: Power MOSFET

Step Resolution:: -

Applications:: General Purpose

Current - Output:: -

Voltage - Supply:: 8.5V ~ 30V

Voltage - Load:: -

Operating Temperature:: -40°C ~ 85°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 28-QFN (5x5)

A4938EETTR-T FAQ

1.How can I place an order for A4938EETTR-T through Aetrix?

Please submit a Request for Quotation (RFQ) for A4938EETTR-T on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for A4938EETTR-T reliable?

The price and inventory of A4938EETTR-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A4938EETTR-T is usually 5 days.

3.What payment methods are accepted for A4938EETTR-T?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A4938EETTR-T transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for A4938EETTR-T?

A4938EETTR-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your A4938EETTR-T order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for A4938EETTR-T?

For technical support, including A4938EETTR-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A4938EETTR-T requirements.

6.How does Aetrix verify that A4938EETTR-T is sourced from the original manufacturer or authorized distributors?

All A4938EETTR-T products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that A4938EETTR-T meets industry standards.

7.What is the process for return or replacement of A4938EETTR-T?

All A4938EETTR-T units undergo pre-shipment inspection (PSI). If there is an issue with A4938EETTR-T, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The A4938EETTR-T part is unused and in its original packaging.

Return procedure for A4938EETTR-T:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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