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

Allegro MicroSystems A3938SEQTR

Name: A3938SEQTR
Brand: Allegro MicroSystems
SKU: A3938SEQTR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: A3938SEQTR

Manufacturer:: Allegro MicroSystems

Category:: Motor Drivers, Controllers

Package:: 32-LCC (J-Lead)

Datasheet:: A3938SEQTR.pdf

Description:: IC MOTOR DRIVER 18V-50V 32PLCC

Quantity:: RFQ Add To RFQ list

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Inventory:1,965

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Product details

Overview

A3938SEQTR from Allegro MicroSystems is a three-phase brushless DC motor controller IC with integrated high-current N-channel MOSFET gate drivers, 50 V motor supply capability, internal 5 V logic regulator (LCAP), and fixed off-time PWM current control. It supports Hall sensor–based 120° commutation for industrial BLDC motors in HVAC blowers, power tools, and automated door actuators.

For engineers reviewing the A3938SEQTR datasheet, A3938SEQTR pinout, A3938SEQTR application, or A3938SEQTR equivalent, key selection criteria include its synchronous rectification architecture, adjustable dead time via DEAD pin, selectable fast/slow decay modes, and motor lead short-to-ground protection with latched fault clearing.

Technical Context

The A3938SEQTR implements a Hall-input–driven commutation engine with internal logic that sequences six-step switching across three half-bridge phases. Its fixed off-time current regulation uses external RC network on RC pin to set t_OFF between 10 µs and 50 µs, while peak current is set by V_REF/R_SENSE equation.

It integrates bootstrapped high-side drivers with charge monitoring, low-side synchronous rectification (single low-side FET ON during decay), and comprehensive protection: VREG undervoltage lockout (9.1–10.2 V threshold), thermal shutdown at 165°C, and motor lead short-to-ground detection via V_DSH > 2.0 V on SA/SB/SC.

Key Specifications

Parameter	Value and Actual Design Meaning
Motor Supply Voltage	Up to 50 V - enables direct interface with 24 V and 48 V industrial bus systems without external step-up.
Peak Current Limit	Set by V_REF/R_SENSE - allows precise torque control and overcurrent protection using standard shunt resistors.
Fixed Off-Time Range	10–50 µs via RC network - determines minimum PWM frequency and current ripple; avoids audible noise when >10 µs.
Dead Time Adjustment	100 ns to 5.5 µs via resistor from DEAD to LCAP - prevents shoot-through in external N-MOSFET half-bridges.
VREG Output	12.4–13.6 V at –10 mA - powers low-side drivers and bootstrap charge circuit; requires ≥10 µF ceramic capacitor.
Thermal Shutdown	165°C junction temperature with 10°C hysteresis - disables outputs and asserts FAULT until reset or cooldown.
Logic Supply (LCAP)	4.75–5.25 V at –3 mA - powers internal logic, FAULT pull-down, and DEAD/RESET/BRKSEL bias networks.

Pinout & Package

Package: 38-pin TSSOP (LD), lead-free, 100% matte tin plated leadframe; 9.7 mm × 6.4 mm footprint, 1.2 mm max height.

Pin/Terminal	Circuit Role	Design Meaning
SA/SB/SC	Motor phase terminals & bootstrap return	Direct connection to motor windings; negative reference for CA/CB/CC bootstrap capacitors.
GHA/GHB/GHC	High-side gate drive outputs	Drive N-channel MOSFET gates with 11.6 V typical output; require external series gate resistors for dv/dt control.
GLA/GLB/GLC	Low-side gate drive outputs	Drive N-channel MOSFET sources; support synchronous rectification by turning on single low-side FET during decay.
H1/H2/H3	Hall sensor inputs	120°-spaced digital inputs with 50 kΩ internal pull-ups to LCAP; detect invalid codes (000/111) and trigger coast fault.
REF/SENSE	Current limit reference & sense inputs	REF sets trip point (I_TRIP = V_REF/R_SENSE); SENSE receives shunt voltage with 0.91 µs blanking after PWM off.
DEAD	Dead time adjustment input	Analog pin biased by resistor to LCAP; sets delay between high/low-side turn-off and next turn-on to prevent cross-conduction.
FAULT	Open-drain fault indicator	Pulled high externally (e.g., 5.1 kΩ) to indicate thermal shutdown, VREG UVLO, Hall error, or short-to-ground - only short-to-ground fault is latched per commutation.

Key Features

Feature	Design Value
Low-side synchronous rectification	Enables single low-side FET conduction during PWM off-cycle - reduces MOSFET body diode losses and eliminates need for external clamp diodes.
Adjustable dead time	Configurable 100 ns–5.5 µs delay via DEAD pin resistor - ensures safe commutation timing across MOSFET parameter variations and temperature drift.
Selectable decay mode	MODE pin selects fast decay (both FETs off) or slow decay (high-side off only) - optimizes current ripple and acoustic noise for specific motor inductance.
Power-loss braking	BRKCAP + BRKSEL enable dynamic braking during VREG undervoltage or RESET assertion - uses 4.7 µF reservoir cap to sustain 6.5 V gate drive for 300 ms.
Integrated 5 V logic regulator	LCAP pin delivers stable 5 V ±2.5% at –3 mA - powers internal logic, Hall bias, and FAULT/DEAD/RESET interfaces without external LDO.

Applications

Industrial HVAC Blower	Power Tool Motor Control
Use Scenario: Constant-air-volume blower in commercial rooftop units requiring quiet, efficient speed regulation under variable static pressure. IC Role / Device Role / Timing Role: Three-phase BLDC controller managing Hall-based commutation, fixed off-time current limiting, and synchronous rectification to reduce heat in compact enclosures. Use Value: Enables >85% efficiency at partial load via low R_DS(on) gate drive and body-diode loss elimination, reducing heatsink size and acoustic noise.	Use Scenario: Cordless drill/driver with variable-speed trigger and electronic brake for rapid stop and safety compliance. IC Role / Device Role / Timing Role: Motor controller executing fast/slow decay selection, dynamic braking via BRAKE pin, and stall detection through short-to-ground monitoring on SA/SB/SC. Use Value: Provides immediate motor stop (<100 ms) using low-side short-circuit braking, while thermal shutdown prevents battery drain during jam events.
Automated Door Actuator	Conveyor Belt Drive
Use Scenario: Low-voltage (24 V) linear actuator for hospital swing doors needing smooth start/stop, position repeatability, and EMI-safe operation. IC Role / Device Role / Timing Role: BLDC driver using DIR and PWM inputs for bidirectional motion control, MODE pin for decay tuning, and FAULT output for system-level diagnostics. Use Value: Delivers <±1% speed regulation via internal current loop and eliminates mechanical brake wear through controlled electronic deceleration.	Use Scenario: Medium-power (300–500 W) conveyor system in packaging line requiring robust overcurrent response and continuous duty cycle operation. IC Role / Device Role / Timing Role: Gate driver with VREG undervoltage lockout, thermal shutdown, and motor lead short-to-ground protection - all latched or auto-cleared per commutation. Use Value: Prevents catastrophic failure during belt jam by detecting SA/SB/SC short-to-ground within 10 µs and disabling affected high-side FETs only.

Industrial HVAC Blower

Power Tool Motor Control

Use Scenario: Constant-air-volume blower in commercial rooftop units requiring quiet, efficient speed regulation under variable static pressure.

IC Role / Device Role / Timing Role: Three-phase BLDC controller managing Hall-based commutation, fixed off-time current limiting, and synchronous rectification to reduce heat in compact enclosures.

Use Value: Enables >85% efficiency at partial load via low R_DS(on) gate drive and body-diode loss elimination, reducing heatsink size and acoustic noise.

Use Scenario: Cordless drill/driver with variable-speed trigger and electronic brake for rapid stop and safety compliance.

IC Role / Device Role / Timing Role: Motor controller executing fast/slow decay selection, dynamic braking via BRAKE pin, and stall detection through short-to-ground monitoring on SA/SB/SC.

Use Value: Provides immediate motor stop (<100 ms) using low-side short-circuit braking, while thermal shutdown prevents battery drain during jam events.

Automated Door Actuator

Conveyor Belt Drive

Use Scenario: Low-voltage (24 V) linear actuator for hospital swing doors needing smooth start/stop, position repeatability, and EMI-safe operation.

IC Role / Device Role / Timing Role: BLDC driver using DIR and PWM inputs for bidirectional motion control, MODE pin for decay tuning, and FAULT output for system-level diagnostics.

Use Value: Delivers <±1% speed regulation via internal current loop and eliminates mechanical brake wear through controlled electronic deceleration.

Use Scenario: Medium-power (300–500 W) conveyor system in packaging line requiring robust overcurrent response and continuous duty cycle operation.

IC Role / Device Role / Timing Role: Gate driver with VREG undervoltage lockout, thermal shutdown, and motor lead short-to-ground protection - all latched or auto-cleared per commutation.

Use Value: Prevents catastrophic failure during belt jam by detecting SA/SB/SC short-to-ground within 10 µs and disabling affected high-side FETs only.

Equivalent & Alternatives

The following parts are listed as comparable options for similar three-phase BLDC motor controller applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
STSPIN32F0A	Integrated 32-bit ARM Cortex-M0 MCU + gate drivers; requires firmware programming; no Hall-only mode; 65 V max V_BB.	Best for designs needing closed-loop field-oriented control (FOC), not basic Hall-commutated trapezoidal drive.	Select when sensorless or FOC is required; avoid if drop-in Hall-based replacement is needed.
DRV8313	Three-phase gate driver only (no Hall logic or current regulation); requires external MCU; 60 V max V_BB; no integrated VREG or LCAP.	Suitable for systems with existing motion controller MCU; lacks A3938SEQTR's self-contained commutation and protection features.	Choose when full design flexibility and external current sensing/control are preferred over integrated simplicity.

Compared with STSPIN32F0A and DRV8313, the A3938SEQTR provides standalone Hall-commutated operation without firmware, integrated 5 V logic supply, and autonomous fault handling - making it optimal for cost-sensitive, high-reliability industrial motion where MCU resources are constrained or unavailable.

Availability

A3938SEQTR is available at Aetrix Electronics and suitable for industrial HVAC blowers, power tool motor drives, and automated door actuators requiring stable component supply and long-term production continuity.

Supply support for A3938SEQTR 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 of high-performance magnetic sensors and power ICs, specializing in motion control, energy-efficient power conversion, and automotive-grade reliability.

The A3938 product line delivers integrated three-phase BLDC controllers for industrial and consumer motion systems - designed to replace discrete gate driver + logic solutions with reduced BOM count, simplified layout, and built-in protection.

FAQ

What is the maximum motor supply voltage supported by the A3938SEQTR?

The A3938SEQTR supports a maximum motor supply voltage (V_BB) of 50 V, as specified in its Absolute Maximum Ratings table. This rating applies continuously under normal operating conditions and allows direct interfacing with common 24 V and 48 V industrial power rails. Exceeding 50 V risks permanent damage to internal high-side drivers and bootstrap circuitry.

How does the A3938SEQTR implement current limiting, and what components set the trip threshold?

The A3938SEQTR uses internal fixed off-time PWM current control where the peak load current is determined by I_TRIP = V_REF / R_SENSE. The REF pin accepts an analog voltage (typically 0–1.5 V), and the SENSE pin connects to the low-side shunt resistor. An external resistor divider or DAC sets V_REF, while R_SENSE is placed between PGND and motor return - both values directly define the current limit.

Can the A3938SEQTR operate without external microcontroller intervention?

Yes, the A3938SEQTR operates autonomously as a Hall-commutated BLDC controller. With H1/H2/H3 Hall inputs, DIR, PWM, and MODE pins configured, it executes full six-step commutation, current regulation, fault detection, and braking - all without MCU firmware. It is designed for standalone use in applications where adding a processor adds cost, complexity, or latency.

What protection features does the A3938SEQTR provide, and how are faults signaled?

The A3938SEQTR provides motor lead short-to-ground detection, VREG undervoltage lockout (9.1–10.2 V), thermal shutdown at 165°C, invalid Hall code detection, and bootstrap capacitor charge monitoring. All faults assert the open-drain FAULT pin (pulled high externally). Only short-to-ground is latched per commutation; others clear automatically when the fault condition ends.

What is the function of the BRKCAP and BRKSEL pins on the A3938SEQTR?

The BRKCAP pin connects to a 4.7 µF reservoir capacitor that supplies gate drive voltage during power loss; BRKSEL selects coast (0) or brake (1) behavior upon VREG undervoltage or RESET assertion. When BRKSEL = 1 and a power-loss event occurs, the A3938SEQTR sustains low-side gate drive for ~300 ms using BRKCAP energy - enabling controlled dynamic braking even as main supply collapses.

A3938SEQTR Specifications

Product attributes: Attribute value

Manufacturer:: Allegro MicroSystems

Series:: -

Package/Case:: 32-LCC (J-Lead)

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, PWM

Technology:: Power MOSFET

Step Resolution:: -

Applications:: General Purpose

Current - Output:: -

Voltage - Supply:: 18V ~ 50V

Voltage - Load:: -

Operating Temperature:: -20°C ~ 85°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 32-PLCC (11.43x13.97)

A3938SEQTR FAQ

1.How can I place an order for A3938SEQTR through Aetrix?

Please submit a Request for Quotation (RFQ) for A3938SEQTR 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 A3938SEQTR reliable?

The price and inventory of A3938SEQTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3938SEQTR is usually 5 days.

3.What payment methods are accepted for A3938SEQTR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3938SEQTR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for A3938SEQTR?

A3938SEQTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your A3938SEQTR 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 A3938SEQTR?

For technical support, including A3938SEQTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3938SEQTR requirements.

6.How does Aetrix verify that A3938SEQTR is sourced from the original manufacturer or authorized distributors?

All A3938SEQTR 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 A3938SEQTR meets industry standards.

7.What is the process for return or replacement of A3938SEQTR?

All A3938SEQTR units undergo pre-shipment inspection (PSI). If there is an issue with A3938SEQTR, 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 A3938SEQTR part is unused and in its original packaging.

Return procedure for A3938SEQTR:

1.Submit a request within 90 days.

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

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