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

Allegro MicroSystems A3938SLDTR

Name: A3938SLDTR
Brand: Allegro MicroSystems
SKU: A3938SLDTR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: A3938SLDTR

Manufacturer:: Allegro MicroSystems

Category:: Motor Drivers, Controllers

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

Datasheet:: A3938SLDTR.pdf

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

Quantity:: RFQ Add To RFQ list

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Product details

Overview

A3938SLDTR 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 BLDC motors in industrial pumps, HVAC blowers, and power tools.

For engineers reviewing the A3938SLDTR datasheet, A3938SLDTR pinout, A3938SLDTR application, or A3938SLDTR equivalent, key selection criteria include synchronous rectification support, adjustable dead time via DEAD pin, selectable fast/slow decay modes, motor lead short-to-ground protection, and thermal shutdown at 165°C.

Technical Context

The A3938SLDTR implements Hall-input commutation logic for 120°-spaced sensors and integrates bootstrap high-side drivers with charge current monitoring. Its internal fixed off-time PWM current control uses external RC network on RC pin to set t_OFF (10–50 µs), while REF and SENSE pins configure peak current limit via I_TRIP = V_REF/R_SENSE.

Protection architecture includes latched motor lead short-to-ground detection (cleared per commutation), VREG undervoltage lockout (9.1–10.2 V trip), thermal shutdown (165°C, 10°C hysteresis), and fault reporting via open-drain FAULT pin. Synchronous rectification enables low-side-only conduction during PWM off-cycle to reduce MOSFET body diode losses.

Key Specifications

Parameter	Value and Actual Design Meaning
Motor Supply Voltage	Up to 50 V - supports wide-range BLDC motor operation without external step-up regulation.
Peak Current Limit	User-set via REF voltage and external sense resistor - enables precise torque control and overcurrent protection.
Fixed Off-Time Range	10–50 µs via external RT/CT on RC pin - determines PWM current regulation frequency and avoids audible noise.
Dead Time Adjustment	100 ns to 5.5 µs via resistor from DEAD to LCAP - prevents cross-conduction in external N-MOSFET half-bridges.
Thermal Shutdown	165°C junction temperature with 10°C hysteresis - ensures safe operation under overload or poor heatsinking.
VREG Output	13 V ±0.6 V at –10 mA - powers low-side drivers and bootstrap charge circuit; requires 10 µF decoupling capacitor.
LCAP Reference	5.0 V ±0.25 V - supplies internal logic, DEAD pin bias, and FAULT pull-up reference.

Pinout & Package

Package: 38-pin TSSOP (LD), lead-free, 100% matte tin plated leadframe, 0.5 mm pitch, JEDEC MO-153 BD-1 compliant.

Pin/Terminal	Circuit Role	Design Meaning
SA/SB/SC	Motor phase terminals & bootstrap capacitor negatives	Direct connection to motor windings; serve as return paths for floating high-side gate drivers.
GHA/GHB/GHC	High-side gate drive outputs	Drive N-channel MOSFET gates with 11.6 V typical output; require external series resistors for dv/dt control.
GLA/GLB/GLC	Low-side gate drive outputs	Drive N-channel MOSFET gates with VREG − 0.5 V typical; enable synchronous rectification during off-cycle.
H1/H2/H3	Hall sensor inputs	120°-spaced commutation inputs with internal 50 kΩ pull-ups to LCAP; detect invalid codes (000/111) for fault triggering.
REF/SENSE	Current limit comparator inputs	Set peak winding current using I_TRIP = V_REF/R_SENSE; SENSE blanked during switching transients to avoid false trips.
DEAD	Dead time adjustment input	Analog input setting high-side to low-side turn-off delay; resistor to LCAP sets 100 ns–5.5 µs range to prevent shoot-through.
FAULT	Open-drain fault indicator	Pulled high externally (e.g., 5.1 kΩ) to signal thermal shutdown, VREG UVLO, Hall error, or short-to-ground faults.
VREG/LCAP	Regulated supplies	VREG = 13 V output for gate drivers; LCAP = 5 V reference for logic and analog functions - both require local decoupling.

Key Features

Feature	Design Value
Synchronous rectification	Enables low-side-only conduction during PWM off-cycle - reduces MOSFET power loss and eliminates need for external clamp diodes.
Adjustable dead time	Configurable 100 ns–5.5 µs delay between high-side and low-side switching - prevents cross-conduction across all operating conditions.
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 target motor load.
Power-loss braking	BRKCAP + BRKSEL enables dynamic braking during VREG undervoltage or RESET assertion - maintains controlled stop even during supply collapse.
Hall input protection	Detects invalid 000/111 Hall codes and triggers coast mode - prevents erratic commutation due to noisy or failed sensors.

Applications

Industrial Pumps	HVAC Blowers
Use Scenario: Constant-pressure variable-speed pump in commercial plumbing systems. IC Role / Device Role / Timing Role: Three-phase BLDC controller managing Hall-based commutation and real-time current limiting. Use Value: Enables smooth speed ramping, overcurrent protection during dry-run events, and reduced EMI via adjustable dead time and decay mode.	Use Scenario: High-efficiency centrifugal blower in rooftop HVAC units. IC Role / Device Role / Timing Role: Motor driver coordinating PWM speed control, thermal monitoring, and short-circuit protection on motor leads. Use Value: Supports fan safety shutdown on motor stall, minimizes power loss via synchronous rectification, and maintains stable operation across 24–48 V supply range.
Power Tools	Automated Gate Operators
Use Scenario: Cordless drill requiring high-torque startup and rapid direction reversal. IC Role / Device Role / Timing Role: BLDC controller executing DIR-driven commutation reversal and BRAKE-triggered dynamic stopping. Use Value: Delivers instant torque response via internal current regulation, prevents MOSFET shoot-through during direction change using programmable dead time.	Use Scenario: Residential garage door opener with obstacle detection and soft-start/stop. IC Role / Device Role / Timing Role: Motor controller implementing coast/brake selection (BRKSEL), fault-latched short-to-ground detection, and regulated gate drive. Use Value: Ensures safe emergency stop via power-loss braking, protects against wiring faults with motor lead monitoring, and sustains reliable operation over temperature extremes.

Industrial Pumps

HVAC Blowers

Use Scenario: Constant-pressure variable-speed pump in commercial plumbing systems.

IC Role / Device Role / Timing Role: Three-phase BLDC controller managing Hall-based commutation and real-time current limiting.

Use Value: Enables smooth speed ramping, overcurrent protection during dry-run events, and reduced EMI via adjustable dead time and decay mode.

Use Scenario: High-efficiency centrifugal blower in rooftop HVAC units.

IC Role / Device Role / Timing Role: Motor driver coordinating PWM speed control, thermal monitoring, and short-circuit protection on motor leads.

Use Value: Supports fan safety shutdown on motor stall, minimizes power loss via synchronous rectification, and maintains stable operation across 24–48 V supply range.

Power Tools

Automated Gate Operators

Use Scenario: Cordless drill requiring high-torque startup and rapid direction reversal.

IC Role / Device Role / Timing Role: BLDC controller executing DIR-driven commutation reversal and BRAKE-triggered dynamic stopping.

Use Value: Delivers instant torque response via internal current regulation, prevents MOSFET shoot-through during direction change using programmable dead time.

Use Scenario: Residential garage door opener with obstacle detection and soft-start/stop.

IC Role / Device Role / Timing Role: Motor controller implementing coast/brake selection (BRKSEL), fault-latched short-to-ground detection, and regulated gate drive.

Use Value: Ensures safe emergency stop via power-loss braking, protects against wiring faults with motor lead monitoring, and sustains reliable operation over temperature extremes.

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
MP6532GQ-Z	Integrated 3-phase gate drivers with 60 V rating; no internal Hall logic - requires external MCU for commutation.	Lacks native Hall sensor interface; suited for field-oriented control (FOC) systems with position sensing via encoder or resolver.	Choose MP6532GQ-Z when implementing closed-loop FOC or needing higher voltage margin; retain A3938SLDTR for Hall-based sensorless simplicity.
STSPIN32F0A	Embedded 32-bit ARM Cortex-M0 MCU with integrated gate drivers and hardware FOC engine; supports Hall, encoder, and sensorless BEMF sensing.	Provides full motor control firmware stack and digital current regulation - eliminates need for external microcontroller.	Choose STSPIN32F0A for compact, self-contained BLDC solutions; select A3938SLDTR when leveraging existing MCU infrastructure and prioritizing analog current control precision.

Compared with MP6532GQ-Z and STSPIN32F0A, the A3938SLDTR delivers dedicated Hall-commutated gate driving with minimal external components, making it optimal for cost-sensitive, high-reliability BLDC systems where deterministic analog current limiting and robust fault handling are critical.

Availability

A3938SLDTR is available at Aetrix Electronics and suitable for industrial pumps, HVAC blowers, and power tools requiring stable component supply, long-term lifecycle support, and traceable sourcing for production programs.

Supply support for A3938SLDTR 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 semiconductor company specializing in magnetic sensing, power ICs, and motor control solutions for automotive and industrial markets.

The A3938 product line delivers highly integrated three-phase BLDC controllers targeting cost-effective, robust motor drives in appliances, power equipment, and building automation - emphasizing Hall-based simplicity, analog current regulation, and comprehensive fault protection.

FAQ

What is the maximum motor supply voltage supported by the A3938SLDTR?

The A3938SLDTR supports a maximum motor supply voltage (VBB) of 50 V, as specified in its Absolute Maximum Ratings. This allows direct integration with common 24 V and 48 V BLDC motor systems without intermediate regulation. Operation above 50 V risks permanent damage. For 12 V applications, VBB must be shorted to VREG while maintaining VREG ≤ 15 V to avoid overstress.

How does the A3938SLDTR implement current limiting, and what external components are required?

The A3938SLDTR uses internal fixed off-time PWM current control. Peak current is set by I_TRIP = V_REF/R_SENSE, requiring an external sense resistor (R_SENSE) in the motor phase return path and a precision voltage source on the REF pin. The SENSE pin connects to the low-side of R_SENSE, and blanking via RC network prevents false triggering during switching transients.

Can the A3938SLDTR drive N-channel MOSFETs exclusively, and how is high-side drive achieved?

Yes, the A3938SLDTR is designed specifically for N-channel-only external MOSFETs. High-side drive is enabled via integrated bootstrap circuitry: CA/CB/CC pins connect to bootstrap capacitors charged to ~VREG when SA/SB/SC go low. When those outputs swing high, the capacitors lift gate drive voltage above VBB, allowing full enhancement of high-side N-MOSFETs without P-channel devices or isolated supplies.

What fault conditions trigger the open-drain FAULT pin on the A3938SLDTR?

The FAULT pin activates (pulled low) for five confirmed conditions: invalid Hall code (000 or 111), VREG undervoltage (below 9.1 V), thermal shutdown (TJ > 165°C), motor lead short-to-ground (V_DSH > 2.0 V on active high-side), and bootstrap charge failure (I_CX < –9 mA). Only short-to-ground is latched per commutation; others clear automatically when condition resolves.

Does the A3938SLDTR support dynamic braking, and how is it configured?

Yes, the A3938SLDTR supports two dynamic braking modes. Standard braking is activated by asserting the BRAKE pin (drives all low-side FETs ON, high-sides OFF). Power-loss braking is triggered by VREG undervoltage or RESET rising edge when BRKSEL = 1, using the BRKCAP reservoir capacitor to sustain gate drive during supply collapse - enabling controlled stop even during brownout events.

A3938SLDTR Specifications

Product attributes: Attribute value

Manufacturer:: Allegro MicroSystems

Series:: -

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

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:: 38-TSSOP

A3938SLDTR FAQ

1.How can I place an order for A3938SLDTR through Aetrix?

Please submit a Request for Quotation (RFQ) for A3938SLDTR 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 A3938SLDTR reliable?

The price and inventory of A3938SLDTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3938SLDTR is usually 5 days.

3.What payment methods are accepted for A3938SLDTR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3938SLDTR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for A3938SLDTR?

A3938SLDTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your A3938SLDTR 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 A3938SLDTR?

For technical support, including A3938SLDTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3938SLDTR requirements.

6.How does Aetrix verify that A3938SLDTR is sourced from the original manufacturer or authorized distributors?

All A3938SLDTR 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 A3938SLDTR meets industry standards.

7.What is the process for return or replacement of A3938SLDTR?

All A3938SLDTR units undergo pre-shipment inspection (PSI). If there is an issue with A3938SLDTR, 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 A3938SLDTR part is unused and in its original packaging.

Return procedure for A3938SLDTR:

1.Submit a request within 90 days.

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

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