Allegro MicroSystems A3966SLBTR

Overview

A3966SLBTR from Allegro MicroSystems is a dual full-bridge PWM motor driver IC designed to control both windings of a bipolar stepper motor. It delivers ±650 mA continuous output current per bridge, supports up to 30 V load supply voltage, and integrates fixed-frequency PWM current regulation with user-selectable blanking via external RC timing network. It is used in precision motion control systems such as industrial automation actuators and medical lab equipment positioning stages.

For engineers reviewing the A3966SLBTR datasheet, A3966SLBTR pinout, A3966SLBTR application, or A3966SLBTR equivalent, key selection criteria include its Satlington® sink drivers for low saturation voltage at high current, internal thermal shutdown with 15 °C hysteresis, crossover-current protection, and compatibility with 16-pin SOICW (LB) PCB layouts requiring ground-plane thermal coupling through pins 4 and 13.

Technical Context

The A3966SLBTR implements two independent full-bridge channels, each with PHASE/ENABLE logic control and internal PWM current regulation based on a fixed-frequency oscillator set by external RT–CT components. Current sensing uses a dedicated comparator with 18 mA offset error and blanking windows triggered on source turn-on or PHASE/ENABLE transitions.

Each bridge features Satlington® sink outputs delivering ≤0.5 V saturation at +400 mA and ≤1.3 V at +650 mA, alongside source drivers with 1.7–2.1 V saturation. Protection includes UVLO (4.1–4.6 V enable threshold), thermal shutdown at 165 °C, and built-in ground-clamp/flyback diodes - eliminating need for external flyback components.

Key Specifications

Pinout & Package

Package: 16-pin SOICW (suffix LB), with pins 4 and 13 internally fused to the die pad for enhanced thermal conduction to PCB ground plane. RoHS-compliant, 100% matte tin leadframe plating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TB6600HG and DRV8825, the A3966SLBTR provides a cost-optimized, fully integrated solution for mid-current bipolar stepper control where analog current setting, thermal robustness in SOICW, and minimal external components are prioritized over ultra-high current or advanced microstepping.

Availability

A3966SLBTR is available at Aetrix Electronics and suitable for industrial CNC positioning, medical fluid pump actuation, automated lab sample handling, and 3D printer extruder motion requiring stable component supply and long-term production continuity.

Supply support for A3966SLBTR 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 Hall-effect sensors, motor drivers, and power ICs, headquartered in Manchester, NH.

The A3966 product line targets cost-sensitive, thermally constrained bipolar stepper motor applications in industrial automation, medical devices, and instrumentation - emphasizing integration, thermal resilience, and analog programmability over digital configurability.

FAQ

What is the maximum continuous output current per bridge of the A3966SLBTR?

The A3966SLBTR supports ±650 mA continuous output current per full-bridge channel under TA ≤ 85 °C with adequate PCB copper area. Peak current capability is ±750 mA, but sustained operation above 650 mA requires thermal derating based on ambient temperature and heatsinking. The A3966SLBTR achieves this with Satlington® sink drivers that limit VCE(sat) to ≤0.5 V at 400 mA, reducing power loss and junction temperature rise.

How does the A3966SLBTR implement current regulation without an external microcontroller?

The A3966SLBTR uses an internal fixed-frequency PWM current-control circuit that compares sensed winding current (via external RS resistor) against a trip threshold derived from VREF/4. When current reaches ITRIP = VREF/(4×RS), the source driver turns off; current recirculates through the sink driver and internal clamp diode until the oscillator resets the latch. This autonomous regulation loop eliminates need for MCU-based current feedback in the A3966SLBTR.

Can the A3966SLBTR drive unipolar stepper motors?

No, the A3966SLBTR is specifically designed for two-phase bipolar stepper motors and cannot drive unipolar steppers. Its dual full-bridge architecture provides bidirectional current control per winding (OUT1A/OUT1B and OUT2A/OUT2B), which is incompatible with the center-tapped winding topology of unipolar motors. Attempting to use the A3966SLBTR with unipolar motors will result in incorrect phase excitation and loss of torque.

What is the purpose of pins 4 and 13 on the A3966SLBTR package?

Pins 4 and 13 of the A3966SLBTR are internally fused to the die pad and serve exclusively as thermal conduction paths to the PCB ground plane - they carry no electrical signal. These pins must be soldered to a large copper pour or thermal pad to dissipate up to 1.87 W of package power dissipation at TA = 25 °C. Leaving them unconnected severely limits safe operating current and risks thermal shutdown during continuous 650 mA operation.

Does the A3966SLBTR require external flyback diodes for inductive load protection?

No, the A3966SLBTR integrates internal ground-clamp and flyback diodes for each output transistor, eliminating the need for external diodes. These diodes provide recirculation paths during current decay when ENABLE is asserted or PHASE changes state. This integration reduces bill-of-materials count, PCB area, and layout complexity - a key design advantage confirmed in the A3966SLBTR functional block diagram and absolute maximum ratings table.