Send an Inquiry

To receive a quote for your project, please fill in the following information, and we’ll get back to you promptly.

Submit Inventory List

Please fill in the following information, and we’ll get back to you promptly.

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

Allegro MicroSystems A3973SLB-T

Name: A3973SLB-T
Brand: Allegro MicroSystems
SKU: A3973SLB-T
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: A3973SLB-T

Manufacturer:: Allegro MicroSystems

Category:: Motor Drivers, Controllers

Package:: 24-SOIC (0.295", 7.50mm Width)

Datasheet:: A3973SLB-T.pdf

Description:: IC MTR DRV BIPLR 4.5-5.5V 24SOIC

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:2,535

Please send an inquiry. Send us your inquiry, and we will respond immediately.

Product details

Overview

A3973SLB-T from Allegro MicroSystems is a dual DMOS full-bridge PWM motor driver designed for bipolar microstepping stepper motor control, supporting ±1 A continuous output current at up to 35 V supply voltage, with two independent 6-bit linear DACs for precise current regulation and programmable mixed/fast/slow decay modes.

For engineers reviewing the A3973SLB-T datasheet, A3973SLB-T pinout, A3973SLB-T application, or A3973SLB-T equivalent, this device is selected for high-accuracy torque control in motion systems requiring serial-configurable PWM timing, synchronous rectification, and thermal/UVLO protection without external clamp diodes.

Technical Context

The A3973SLB-T integrates two independent H-bridges, each controlled by a dedicated 6-bit DAC (0–63 steps, 1.56% resolution) referenced to an internal 2.0 V precision bandgap or external reference, enabling microstepping current profiles with selectable gain scaling (×4 or ×8 via D18). Current regulation uses fixed-off-time PWM with programmable blank time (4–12/f_OSC) and off-time (1.75–63.75 μs at 4 MHz).

It features a 4 MHz internal oscillator (or external clock input with /1, /2, /4 dividers), synchronous rectification configurable in four modes (active, passive, disabled, low-side-only), and sleep/idle modes reducing supply current to 100 μA or 1.5 mA respectively - all managed via a 3-wire serial interface (CLOCK/DATA/STROBE) with 19-bit word structure.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Current Rating	±1.0 A continuous per bridge - supports bipolar stepper coils without external current-sense amplifiers or discrete power stages.
Supply Voltage Range	15–35 V load supply (V_BB) - compatible with standard industrial 24 V rails and higher-voltage motion systems.
DAC Resolution	6-bit linear (64 levels) - enables 1.56% incremental torque adjustment across full-scale current for smooth microstepping.
Reference Voltage	Internal 2.00 V ±30 mV - provides stable DAC reference without external components; externally adjustable up to 3 V.
Thermal Shutdown	165°C junction temperature with 15°C hysteresis - protects against sustained overload without latch-up or manual reset.
Logic Compatibility	3.3 V or 5 V input logic - interfaces directly with MCU GPIOs or FPGA I/O banks without level-shifting circuitry.
Package Power Dissipation	2.2 W (SOICW LB package) - requires minimal heatsinking for typical 1 A, 50% duty-cycle operation at 85°C ambient.

Pinout & Package

Package: 24-pin SOICW (LB) with internally fused leads at pins 6, 7, 18, and 19 for enhanced thermal dissipation; power tabs are at ground potential and require no electrical isolation.

Pin/Terminal	Circuit Role	Design Meaning
1, 2, 23, 24	GROUND	Common analog/digital/power ground return - must connect to heavy PCB ground plane for noise immunity and thermal conduction.
3	SLEEP	Active-low hardware sleep enable - pulls all internal registers to zero and reduces I_BB to 100 μA; requires ≥50 μs setup before STROBE.
4	VREG	Internally regulated supply for sink-side DMOS drivers - requires 0.22 μF decoupling to ground; fault disables outputs.
5, 6, 7, 18, 19	OUT 1A / OUT 1B / OUT 2A / OUT 2B	H-bridge output terminals - drive stepper motor phases; pins 6/7/18/19 are fused for thermal robustness in SOICW package.
8, 9	SENSE 1 / SENSE 2	Current-sense inputs - connect to low-side sense resistors (RS); independent ground return required to avoid IR drop errors.
10	LOAD SUPPLY 1	Bridge 1 load supply (V_BB1) - powers source-side DMOS transistors; decouple with ≥47 μF electrolytic capacitor.
11	LOGIC SUPPLY	V_DD input (4.5–5.5 V) - powers digital core, serial interface, and reference buffer; requires 0.1 μF local decoupling.
12	MUX REF	Reference input selection node - connects to internal 2 V reference or external source; buffered and scaled by DAC gain setting.
13	VDD	Logic supply voltage - same as Pin 11; labeled separately in functional diagram but electrically identical.
14, 15	CP1 / CP2	Charge pump capacitors - connect 0.22 μF ceramic caps between CP1–CP2 and CP2–ground to generate V_CP for high-side gate drive.
16	VCP	Charge pump output - supplies gate drive voltage for high-side DMOS; monitored for fault detection.
17	OSC	Oscillator input - accepts internal 4 MHz clock or external clock (2.5–6 MHz) with programmable divider (/1, /2, /4).
20, 21	CLOCK / DATA	Serial interface inputs - 3-wire SPI-like protocol; data latched on rising CLOCK edge, MSB-first, 19-bit words.
22	STROBE	Serial write strobe - falling edge commits 19-bit shift register contents to control registers; minimum pulse width 150 ns.

Key Features

Feature	Design Value
Synchronous Rectification (4-mode)	Reduces power dissipation by replacing body-diode conduction with low R_DS(on) MOSFET paths - eliminates need for 4 external Schottky diodes per bridge in most designs.
Programmable Decay Modes	Mixed/fast/slow decay selection per bridge allows optimization of torque ripple, acoustic noise, and current settling for specific motor inductance and speed.
6-Bit Linear DAC Control	Two independent DACs set peak current per phase with 1.56% resolution - enables true 64-step microstepping without external DAC or PWM modulation.
Integrated 4 MHz Oscillator	Provides stable timing base for PWM without external crystal; accuracy improved with optional external resistor on OSC pin (f_OSC = 204×10⁹/R_OSC).
Thermal + UVLO Protection	Independent shutdown triggers at 165°C junction temp (15°C hysteresis) and <3.9 V V_DD - prevents damage during overtemperature or brownout conditions.

Applications

Industrial CNC Positioning	Medical Infusion Pumps
Use Scenario: Precision open-loop positioning of X/Y/Z axes in desktop CNC mills using 1.8° bipolar stepper motors. IC Role / Device Role / Timing Role: Dual full-bridge driver executing microstepping waveforms via serial DAC commands and fixed-off-time PWM timing. Use Value: Enables 1/64 microstepping resolution with <1.56% current step linearity, reducing vibration and positional error without closed-loop feedback.	Use Scenario: Low-noise, repeatable syringe actuation in portable infusion pumps delivering precise drug dosages. IC Role / Device Role / Timing Role: Motor controller managing bidirectional microstepping with programmable decay to minimize audible coil whine during slow-speed delivery. Use Value: Synchronous rectification cuts power dissipation by >40% vs. diode-clamped design, extending battery life while maintaining 0.1 mL/h dosage accuracy.
Automated Laboratory Robotics	3D Printer Extruder Control
Use Scenario: Multi-axis sample handling in automated PCR workstations requiring silent, jitter-free movement between thermal blocks. IC Role / Device Role / Timing Role: Serial-configured dual H-bridge providing independent current control per motor phase with active synchronous rectification mode. Use Value: Eliminates external clamp diodes and reduces board area by 25%, while thermal shutdown ensures safe operation during extended idle periods.	Use Scenario: High-torque extruder motor driving flexible filament in FDM 3D printers, operating at variable speeds and loads. IC Role / Device Role / Timing Role: PWM motor driver regulating phase current via 6-bit DAC and mixed-decay timing to maintain consistent extrusion pressure. Use Value: Programmable blank time (4–12/f_OSC) suppresses current-sense transient errors during direction reversal, preventing step loss at acceleration peaks.

Industrial CNC Positioning

Medical Infusion Pumps

Use Scenario: Precision open-loop positioning of X/Y/Z axes in desktop CNC mills using 1.8° bipolar stepper motors.

IC Role / Device Role / Timing Role: Dual full-bridge driver executing microstepping waveforms via serial DAC commands and fixed-off-time PWM timing.

Use Value: Enables 1/64 microstepping resolution with <1.56% current step linearity, reducing vibration and positional error without closed-loop feedback.

Use Scenario: Low-noise, repeatable syringe actuation in portable infusion pumps delivering precise drug dosages.

IC Role / Device Role / Timing Role: Motor controller managing bidirectional microstepping with programmable decay to minimize audible coil whine during slow-speed delivery.

Use Value: Synchronous rectification cuts power dissipation by >40% vs. diode-clamped design, extending battery life while maintaining 0.1 mL/h dosage accuracy.

Automated Laboratory Robotics

3D Printer Extruder Control

Use Scenario: Multi-axis sample handling in automated PCR workstations requiring silent, jitter-free movement between thermal blocks.

IC Role / Device Role / Timing Role: Serial-configured dual H-bridge providing independent current control per motor phase with active synchronous rectification mode.

Use Value: Eliminates external clamp diodes and reduces board area by 25%, while thermal shutdown ensures safe operation during extended idle periods.

Use Scenario: High-torque extruder motor driving flexible filament in FDM 3D printers, operating at variable speeds and loads.

IC Role / Device Role / Timing Role: PWM motor driver regulating phase current via 6-bit DAC and mixed-decay timing to maintain consistent extrusion pressure.

Use Value: Programmable blank time (4–12/f_OSC) suppresses current-sense transient errors during direction reversal, preventing step loss at acceleration peaks.

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual H-bridge microstepping motor driver applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
TB6600HG	Higher 4.5 A rating, but only 5-bit DAC (32 steps) and no internal reference; requires external 2.5 V reference and separate charge pump caps.	Targeted at high-current industrial steppers; lacks sleep mode and has larger SOIC36 package.	Choose when >1 A output or higher voltage (50 V) is required; not drop-in due to pinout and reference architecture differences.
DRV8825	Integrated current sense amplifier, 3.5 A rating, but fixed 1/32 microstepping resolution and no serial interface - configured via hardware pins only.	Optimized for compact consumer-grade printers; lacks programmable decay modes and synchronous rectification control.	Prefer for cost-sensitive, fixed-function designs where serial configuration flexibility is unnecessary.

Compared with TB6600HG and DRV8825, the A3973SLB-T uniquely combines serial configurability, dual 6-bit DACs, and four-mode synchronous rectification in a thermally optimized SOICW package - making it optimal for applications demanding fine-grained torque control, low EMI, and embedded firmware-driven motor tuning.

Availability

A3973SLB-T is available at Aetrix Electronics and suitable for industrial CNC positioning, medical infusion pumps, automated laboratory robotics, and 3D printer extruder control requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for A3973SLB-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 of high-performance magnetic sensing and power IC solutions, founded in 1989 and headquartered in Worcester, Massachusetts.

The A3973 product line delivers integrated DMOS motor drivers for precision bipolar stepper control, emphasizing programmable current regulation, thermal resilience, and reduced external component count in motion-critical systems.

FAQ

What is the maximum continuous output current supported by the A3973SLB-T?

The A3973SLB-T supports ±1.0 A continuous output current per bridge under specified thermal conditions (T_A ≤ 85°C, proper PCB copper area). This rating assumes adequate heatsinking via the fused SOICW leads and ground plane; exceeding 1 A risks thermal shutdown activation at junction temperatures above 165°C.

Does the A3973SLB-T require external Schottky diodes for flyback protection?

No, the A3973SLB-T does not require external Schottky diodes in most applications due to its integrated synchronous rectification circuitry. When enabled in active or low-side-only mode, the device uses its own low R_DS(on) DMOS transistors to recirculate current during decay, eliminating body-diode conduction losses and associated heat generation.

How is microstepping resolution achieved in the A3973SLB-T?

The A3973SLB-T achieves microstepping resolution through two independent 6-bit linear DACs (0–63 codes), each setting the peak current for one H-bridge. With 1.56% current step increments and programmable decay modes, it supports true 64-step microstepping without external waveform generation - the DAC output directly controls the current-limit threshold via the sense amplifier.

Can the A3973SLB-T operate with a 3.3 V logic supply?

Yes, the A3973SLB-T accepts 3.3 V or 5 V logic supply voltages on the V_DD pin (4.5–5.5 V recommended, but inputs tolerate 3.3 V-compatible signal levels). Its logic inputs are compatible with both 3.3 V and 5 V CMOS/TTL signals, allowing direct interfacing with modern low-voltage MCUs without level shifters.

What protection features are built into the A3973SLB-T?

The A3973SLB-T includes thermal shutdown (165°C trip, 15°C hysteresis), undervoltage lockout (3.9–4.45 V V_DD window), V_CP/V_REG fault monitoring, crossover-current protection, and internal transient-suppression diodes - all operating autonomously without software intervention to safeguard the IC and motor windings.

A3973SLB-T Specifications

Product attributes: Attribute value

Manufacturer:: Allegro MicroSystems

Series:: -

Package/Case:: 24-SOIC (0.295", 7.50mm Width)

Packaging:: Tube

Product Status:: Obsolete

Motor Type - Stepper:: Bipolar

Motor Type - AC, DC:: -

Function:: Driver - Fully Integrated, Control and Power Stage

Output Configuration:: Half Bridge (4)

Interface:: Serial

Technology:: DMOS

Step Resolution:: 1 ~ 1/64

Applications:: General Purpose

Current - Output:: 1A

Voltage - Supply:: 4.5V ~ 5.5V

Voltage - Load:: 15V ~ 35V

Operating Temperature:: -20°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 24-SOIC

A3973SLB-T FAQ

1.How can I place an order for A3973SLB-T through Aetrix?

Please submit a Request for Quotation (RFQ) for A3973SLB-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 A3973SLB-T reliable?

The price and inventory of A3973SLB-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3973SLB-T is usually 5 days.

3.What payment methods are accepted for A3973SLB-T?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3973SLB-T transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for A3973SLB-T?

A3973SLB-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your A3973SLB-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 A3973SLB-T?

For technical support, including A3973SLB-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3973SLB-T requirements.

6.How does Aetrix verify that A3973SLB-T is sourced from the original manufacturer or authorized distributors?

All A3973SLB-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 A3973SLB-T meets industry standards.

7.What is the process for return or replacement of A3973SLB-T?

All A3973SLB-T units undergo pre-shipment inspection (PSI). If there is an issue with A3973SLB-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 A3973SLB-T part is unused and in its original packaging.

Return procedure for A3973SLB-T:

1.Submit a request within 90 days.

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

Tech Hub

2026-09-08 Obsolete Electronic Components: How to Source and Evaluate Replacements

A practical engineering and sourcing framework covering lifecycle verification, lifetime-buy calculations, replacement qualification, supplier checks and counterfeit-risk controls.

2026-09-07 TTL vs CMOS Logic Levels: 74HC and 74HCT Compatibility Explained

TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.

2026-09-04 Logic Level Shifter: How to Connect 3.3V and 5V Logic Safely

A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.

2026-09-03 74HC595 vs TPIC6B595: Output Drive, Pinout, Current, and Load Selection

The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…

2026-09-02 74HC595 Pinout, Timing, Output Current, and Applications

The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…

2026-09-01 Latch vs Flip-Flop: Timing, Differences and Design Choices

A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…

2026-08-30 D Latch Circuit: Truth Table, Timing, ICs and Applications

A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …

2026-08-28 SR Latch Explained: NOR and NAND Circuits, Truth Tables, and Applications

An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…

2026-08-27 Latch Circuit: SR and D Latches, Truth Tables, Timing, and Applications

Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…

2026-08-21 What Is an LED Driver? Types, Circuits, Dimming, and Selection

An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…