Allegro MicroSystems A3967SLBTR

Overview

A3967SLBTR from Allegro MicroSystems is a bipolar stepper motor driver IC with integrated translator, supporting full-, half-, quarter-, and eighth-step microstepping modes, ±750 mA output current per bridge, 30 V load supply rating, and automatic mixed/fast/slow current-decay mode selection for reduced audible noise and improved step accuracy in motion control systems.

For engineers reviewing the A3967SLBTR datasheet, A3967SLBTR pinout, A3967SLBTR application, or A3967SLBTR equivalent, this page delivers verified electrical parameters, thermal characteristics, truth-table-based resolution control, fixed off-time PWM timing, and real-world implementation guidance for embedded motor control designs.

Technical Context

The A3967SLBTR implements dual full-bridge drive with Satlington® sink drivers and fixed off-time PWM current regulation. Its internal translator converts STEP/DIR/MS1/MS2 logic inputs into precise DAC-controlled phase currents, eliminating need for external sequencing logic or microcontroller-intensive waveform generation.

Current decay mode is dynamically selected per step based on DAC level transitions and PFD voltage (0.21VCC–0.6VCC), enabling mixed-decay operation that mitigates BEMF-induced current distortion. Protection includes thermal shutdown at 165°C (15°C hysteresis), UVLO at 2.7 V (±0.25 V), and crossover-current prevention without special power-up sequencing.

Key Specifications

Pinout & Package

Package: 24-pin SOIC (suffix LB) with internally fused ground pins (6, 7, 18, 19) for enhanced thermal dissipation; lead-free, 100% matte tin plating; θ_JA = 50°C/W (2-layer PCB), 35°C/W (4-layer JEDEC).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bipolar stepper motor driver applications.

Compared with TB6600HG and DRV8825, the A3967SLBTR uniquely integrates translator logic and automatic mixed-decay selection in a thermally robust SOIC package - simplifying design for mid-power embedded motion control where ease of use and noise reduction are critical.

Availability

A3967SLBTR is available at Aetrix Electronics and suitable for 3D printer motion control, CNC axis driving, and automated laboratory instrumentation requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for A3967SLBTR 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 motion control solutions, with over 40 years of innovation in high-reliability analog and mixed-signal devices.

The A3967 product line was designed specifically for cost-effective, low-noise microstepping motor control in resource-constrained embedded systems - prioritizing integration, thermal resilience, and simplified interface over raw current output.

FAQ

What microstep resolutions does the A3967SLBTR support, and how are they selected?

The A3967SLBTR supports full-, half-, quarter-, and eighth-step microstepping modes. Resolution is selected exclusively via the logic states of MS1 and MS2 inputs per the truth table in the datasheet: MS1=L/MS2=L = full step; MS1=H/MS2=L = half step; MS1=L/MS2=H = quarter step; MS1=H/MS2=H = eighth step. These settings take effect on the next STEP pulse. The A3967SLBTR does not support other resolutions such as sixteenth-step or arbitrary interpolation.

How does the A3967SLBTR implement automatic current-decay mode selection?

The A3967SLBTR determines decay mode per step based on whether the DAC output level increases, decreases, or stays the same relative to the prior step - combined with the voltage applied to the PFD pin. If DAC level decreases, decay mode follows PFD thresholds (slow if >0.6VCC, fast if <0.21VCC, mixed in between). If DAC level increases or holds, slow decay is used. This behavior is intrinsic to the A3967SLBTR's internal control logic and requires no external configuration.

What is the purpose of the fused ground pins (6, 7, 18, 19) on the A3967SLBTR package?

The fused ground pins (6, 7, 18, 19) on the A3967SLBTR are internally bonded to the thermal pad of the 24-pin SOIC package, significantly lowering thermal resistance (θ_JA = 50°C/W on 2-layer PCB). This design allows higher continuous current (±750 mA) without exceeding 150°C junction temperature, eliminates need for external thermal vias in many layouts, and ensures stable ground reference for both analog sense paths and power switching nodes.

Can the A3967SLBTR operate with a 3.3 V logic supply while driving a 24 V motor supply?

Yes, the A3967SLBTR supports independent logic and motor supplies: VCC operates from 3.0 V to 5.5 V (fully compatible with 3.3 V microcontrollers), while VBB1/VBB2 accept 4.75 V to 30 V (including 24 V). The device isolates logic and power domains internally - no level shifters needed. Verified operation at VCC = 3.3 V and VBB = 24 V is documented in the Electrical Characteristics table under "Logic Supply Voltage Range" and "Load Supply Voltage Range".

What protection features are built into the A3967SLBTR, and how do they behave during fault conditions?

The A3967SLBTR includes thermal shutdown (activates at 165°C junction temperature, 15°C hysteresis), undervoltage lockout (UVLO triggers below 2.45 V rising, resets above 2.95 V), and crossover-current protection. During thermal fault, all outputs disable until junction cools below 150°C; during UVLO, drivers disable and translator resets to home state. No external components are required - these functions are fully internal to the A3967SLBTR die.