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

Allegro MicroSystems A3938SLD

Name: A3938SLD
Brand: Allegro MicroSystems
SKU: A3938SLD
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: A3938SLD

Manufacturer:: Allegro MicroSystems

Category:: Motor Drivers, Controllers

Package:: 38-TFSOP (0.173", 4.40mm Width)

Datasheet:: A3938SLD.pdf

Description:: IC MOTOR DRIVER 18V-50V 38TSSOP

Quantity:: RFQ Add To RFQ list

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Product details

Overview

A3938SLD 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 and delivers synchronous rectification for reduced MOSFET conduction loss in industrial BLDC drives.

For engineers reviewing the A3938SLD datasheet, A3938SLD pinout, A3938SLD application, or A3938SLD equivalent, key selection considerations include its 38-pin TSSOP-LD package, adjustable dead time via DEAD pin, programmable current limit via REF/SENSE, thermal shutdown at 165°C, and support for dynamic brake or coast on RESET/BRAKE inputs.

Technical Context

The A3938SLD implements Hall-input–driven commutation logic for three-phase BLDC motors, using internal fixed off-time PWM current regulation where I_TRIP = V_REF/R_SENSE. It integrates bootstrapped high-side drivers with charge monitoring and low-side synchronous rectification to minimize body-diode conduction during decay.

Protection includes motor lead short-to-ground detection (V_DSH threshold 1.3–2.7 V), VREG undervoltage lockout (9.2–10.2 V rising), thermal shutdown (165°C), and fault reporting via open-drain FAULT output. Dead time is externally adjustable (100 ns–5.5 µs) via resistor from DEAD to LCAP.

Key Specifications

Parameter	Value and Actual Design Meaning
Motor Supply Voltage	Up to 50 V - supports wide-range industrial and automotive BLDC systems without external step-up.
Current Regulation	VREF/SENSE-based trip point - enables precise peak current setting independent of PWM duty cycle.
Gate Drive Outputs	6-channel (GHA/GHB/GHC/GLA/GLB/GLC) - drives external N-channel power MOSFETs with 120 ns rise/fall times.
Thermal Shutdown	165°C junction temperature - latches fault and coasts motor to prevent MOSFET thermal runaway.
Logic Supply	Internal 5 V (LCAP) and 13 V (VREG) regulators - powers internal logic and bootstrap charging circuitry.
Hall Input Support	Three 50 kΩ pull-up H1/H2/H3 pins - accepts standard 120°-spaced digital Hall sensors for rotor position feedback.
Protection Features	Short-to-ground, VREG UVLO, invalid Hall code, thermal shutdown - fault conditions reported on open-drain FAULT pin.

Pinout & Package

Package: 38-pin TSSOP-LD (lead-free, 100% matte tin plating), 9.7 mm × 4.4 mm × 1.2 mm profile, JEDEC MO-153 compliant.

Pin/Terminal	Circuit Role	Design Meaning
SA/SB/SC	Motor phase terminals & bootstrap capacitor return	Direct connection to motor windings; serve as negative reference for CA/CB/CC bootstrap supplies.
GHA/GHB/GHC	High-side gate drive outputs	Drive gates of external N-channel high-side MOSFETs; require external series resistors for dv/dt control.
GLA/GLB/GLC	Low-side gate drive outputs	Drive gates of external N-channel low-side MOSFETs; enable synchronous rectification during PWM off-cycle.
H1/H2/H3	Hall sensor inputs	Accept 120°-spaced digital Hall signals; internally pulled up to LCAP (5 V) with 50 kΩ resistors.
REF/SENSE	Current limit programming interface	REF sets trip voltage; SENSE receives shunt voltage - together define I_TRIP = V_REF/R_SENSE.
DEAD	Dead time adjustment input	Resistor to LCAP sets delay between high/low-side turn-off/on to prevent cross-conduction (100 ns–5.5 µs).
FAULT	Open-drain fault indicator	Pulled high externally (e.g., 5.1 kΩ); asserts low on thermal shutdown, short-to-ground, UVLO, or invalid Hall code.
RESET	Global enable/disable control	Active-low logic input; overrides BRAKE and forces coast/brake per BRKSEL state when asserted.

Key Features

Feature	Design Value
Low-side synchronous rectification	Reduces MOSFET conduction loss by turning on appropriate low-side FET during PWM off-cycle instead of relying on body diodes.
Adjustable dead time	Configurable via DEAD pin resistor - prevents shoot-through in external power stage across temperature and MOSFET tolerances.
Selectable decay mode	MODE pin selects fast decay (both FETs off) or slow decay (high-side off only) - optimizes torque ripple and acoustic noise.
Power-loss braking	BRKCAP + BRKSEL enables controlled dynamic brake during VREG undervoltage or RESET assertion using stored reservoir energy.
Integrated protection suite	Detects motor lead short-to-ground, VREG UVLO, thermal overload, and invalid Hall codes - all reported via FAULT pin.
Bootstrap capacitor charge monitor	Prevents high-side turn-on until bootstrap charge current falls below ~9 mA - ensures reliable gate drive voltage before switching.

Applications

Industrial BLDC Fans	Automotive HVAC Blowers
Use Scenario: Constant-speed or variable-speed cooling fans in factory automation enclosures requiring EMI-optimized commutation and thermal resilience. IC Role / Device Role / Timing Role: Three-phase commutation controller with Hall feedback, fixed off-time current regulation, and synchronous rectification to reduce heat in confined spaces. Use Value: Enables >85% efficiency at full load with no external clamp diodes, while thermal shutdown (165°C) protects against blocked airflow failure modes.	Use Scenario: Cabin air blower motors in 12 V automotive HVAC systems needing robust operation across –20°C to 85°C ambient. IC Role / Device Role / Timing Role: Motor controller with VBB = VREG shorting support, 50 kΩ Hall pull-ups, and power-loss braking for safe shutdown during battery dip. Use Value: Eliminates need for external 5 V LDO; BRKCAP/BRKSEL provides predictable deceleration during ignition-off transients without auxiliary power.
Medical Infusion Pumps	Robotics Joint Actuators
Use Scenario: Precision fluid delivery pumps requiring smooth torque response, stall detection, and fail-safe coasting on fault. IC Role / Device Role / Timing Role: Current-regulated BLDC driver with short-to-ground fault latching, FAULT pin diagnostics, and MODE-selectable decay for low-acoustic operation. Use Value: Detects occlusion-induced motor stall via SA/SB/SC short-to-ground sensing and clears fault automatically at next commutation edge.	Use Scenario: Compact joint actuators in collaborative robots demanding high power density, dynamic braking, and Hall-based position tracking. IC Role / Device Role / Timing Role: Gate driver IC with dynamic brake (BRAKE pin), DIR reversal, and RESET-triggered coast/brake selection for emergency stop compliance. Use Value: Supports ISO/TS 15066-defined safe stop via hardware-level BRAKE assertion - no firmware dependency required for critical motion halt.

Industrial BLDC Fans

Automotive HVAC Blowers

Use Scenario: Constant-speed or variable-speed cooling fans in factory automation enclosures requiring EMI-optimized commutation and thermal resilience.

IC Role / Device Role / Timing Role: Three-phase commutation controller with Hall feedback, fixed off-time current regulation, and synchronous rectification to reduce heat in confined spaces.

Use Value: Enables >85% efficiency at full load with no external clamp diodes, while thermal shutdown (165°C) protects against blocked airflow failure modes.

Use Scenario: Cabin air blower motors in 12 V automotive HVAC systems needing robust operation across –20°C to 85°C ambient.

IC Role / Device Role / Timing Role: Motor controller with VBB = VREG shorting support, 50 kΩ Hall pull-ups, and power-loss braking for safe shutdown during battery dip.

Use Value: Eliminates need for external 5 V LDO; BRKCAP/BRKSEL provides predictable deceleration during ignition-off transients without auxiliary power.

Medical Infusion Pumps

Robotics Joint Actuators

Use Scenario: Precision fluid delivery pumps requiring smooth torque response, stall detection, and fail-safe coasting on fault.

IC Role / Device Role / Timing Role: Current-regulated BLDC driver with short-to-ground fault latching, FAULT pin diagnostics, and MODE-selectable decay for low-acoustic operation.

Use Value: Detects occlusion-induced motor stall via SA/SB/SC short-to-ground sensing and clears fault automatically at next commutation edge.

Use Scenario: Compact joint actuators in collaborative robots demanding high power density, dynamic braking, and Hall-based position tracking.

IC Role / Device Role / Timing Role: Gate driver IC with dynamic brake (BRAKE pin), DIR reversal, and RESET-triggered coast/brake selection for emergency stop compliance.

Use Value: Supports ISO/TS 15066-defined safe stop via hardware-level BRAKE assertion - no firmware dependency required for critical motion halt.

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 auto-commutation logic built-in.	Best for field-oriented control (FOC) or custom commutation algorithms; not drop-in for Hall-only legacy designs.	Choose STSPIN32F0A only if closed-loop torque/speed control and firmware flexibility outweigh cost and design complexity.
TB6605FTG	Three-phase pre-driver with integrated current sense amplifier; lacks internal VREG/LCAP regulators and synchronous rectification logic.	Requires external 5 V and 12 V supplies; needs discrete logic for decay mode selection and fault handling.	Choose TB6605FTG when board space allows additional regulators and system-level fault management is already implemented.

Compared with STSPIN32F0A and TB6605FTG, the A3938SLD delivers plug-and-play Hall-based commutation with no firmware, integrated dual regulators, and hardware-enforced synchronous rectification - reducing BOM count and validation effort for cost-sensitive industrial BLDC drives.

Availability

A3938SLD is available at Aetrix Electronics and suitable for industrial BLDC fans, automotive HVAC blowers, medical infusion pumps, robotics joint actuators, and precision motion control systems requiring stable component supply and long-term lifecycle support.

Supply support for A3938SLD 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 Manchester, NH.

The A3938SLD belongs to Allegro's family of integrated three-phase BLDC motor controllers engineered for Hall-sensor–based commutation in industrial, medical, and automotive applications where reliability, thermal robustness, and minimal external components are critical.

FAQ

What is the maximum motor supply voltage supported by the A3938SLD?

The A3938SLD supports a maximum motor supply voltage (VBB) of 50 V, as specified in its Absolute Maximum Ratings table. This rating applies continuously under normal operating conditions and enables use with 24 V and 48 V industrial BLDC systems. For 12 V applications, VBB must be shorted to VREG while ensuring VREG remains ≤15 V to avoid damage.

How does the A3938SLD implement current limiting?

The A3938SLD uses internal fixed off-time PWM current control where the peak load current is set by I_TRIP = V_REF/R_SENSE. The REF pin accepts an external voltage (typically 0–1.5 V), and the SENSE pin reads the voltage across a shunt resistor. When sensed current exceeds the trip threshold, the controller disables the source driver for a user-defined off-time determined by the RC network.

Does the A3938SLD support both fast and slow current decay modes?

Yes, the A3938SLD supports selectable current decay modes via the MODE pin. When MODE = 0, it operates in fast decay mode (both high- and low-side FETs turned off during PWM off-cycle). When MODE = 1, it operates in slow decay mode (only high-side FET turned off), enabling smoother torque delivery and lower acoustic noise in sensitive applications like medical pumps.

What protection features are integrated into the A3938SLD?

The A3938SLD integrates five core protections: (1) motor lead short-to-ground detection (using V_DSH threshold on SA/SB/SC), (2) VREG undervoltage lockout (9.2–10.2 V rising), (3) thermal shutdown at 165°C, (4) invalid Hall code detection (000/111), and (5) bootstrap capacitor charge current monitoring. All faults assert the open-drain FAULT pin and trigger coast or brake per BRKSEL state.

Can the A3938SLD drive N-channel MOSFETs exclusively?

Yes, the A3938SLD is designed specifically to drive external N-channel MOSFETs in both high-side (via bootstrapped GHA/GHB/GHC) and low-side (via GLA/GLB/GLC) configurations. Its integrated bootstrap capacitor charging circuit and high-side driver architecture eliminate the need for P-channel high-side devices or external charge pumps.

A3938SLD Specifications

Product attributes: Attribute value

Manufacturer:: Allegro MicroSystems

Series:: -

Package/Case:: 38-TFSOP (0.173", 4.40mm Width)

Packaging:: Tube

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:: 38-TSSOP

A3938SLD FAQ

1.How can I place an order for A3938SLD through Aetrix?

Please submit a Request for Quotation (RFQ) for A3938SLD 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 A3938SLD reliable?

The price and inventory of A3938SLD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3938SLD is usually 5 days.

3.What payment methods are accepted for A3938SLD?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3938SLD transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for A3938SLD?

A3938SLD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your A3938SLD 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 A3938SLD?

For technical support, including A3938SLD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3938SLD requirements.

6.How does Aetrix verify that A3938SLD is sourced from the original manufacturer or authorized distributors?

All A3938SLD 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 A3938SLD meets industry standards.

7.What is the process for return or replacement of A3938SLD?

All A3938SLD units undergo pre-shipment inspection (PSI). If there is an issue with A3938SLD, 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 A3938SLD part is unused and in its original packaging.

Return procedure for A3938SLD:

1.Submit a request within 90 days.

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

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