Allegro MicroSystems A3969SETTR-T

Overview

A3969SETTR-T from Allegro MicroSystems is a dual full-bridge PWM motor driver IC designed to control both windings of a two-phase bipolar stepper motor. It delivers ±650 mA continuous output current per bridge, supports 30 V load supply voltage, and integrates fixed-frequency PWM current regulation with user-selectable blanking window. Used in precision motion control systems such as industrial automation actuators and medical lab equipment positioning stages.

For engineers reviewing the A3969SETTR-T datasheet, A3969SETTR-T pinout, A3969SETTR-T application, or A3969SETTR-T equivalent, key selection criteria include its Satlington® sink drivers for low saturation voltage at high current, thermal shutdown with 15°C hysteresis, and RC-timed 25 kHz oscillator for ripple-current control in stepper winding current regulation.

Technical Context

The A3969SETTR-T implements two independent H-bridge outputs with phase/enable logic control per bridge, enabling bipolar stepper microstepping via external timing components (RT = 56 kΩ, CT = 680 pF). Its internal PWM latch resets on current-sense comparator trip (VREF/4 threshold), with blanking time t_blank = 1900 × CT (1.3 μs typical) to suppress switching transients.

Each bridge features crossover-current protection, UVLO (2.75–3.0 V enable threshold), ground-clamp and flyback diodes, and thermal shutdown at 165°C. The Satlington® sink structure achieves 0.3–1.3 V saturation voltage across 400–650 mA load current while maintaining Darlington-level peak current capability.

Key Specifications

Pinout & Package

Package: 28-pin QFN (5 mm × 5 mm, 0.90 mm height) with exposed thermal pad; RoHS-compliant, matte tin leadframe plating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TB6600HG and DRV8825, the A3969SETTR-T provides optimal balance of integration (internal PWM, blanking, protection), thermal robustness (2°C/W R_θJT), and 3.3 V logic compatibility-making it ideal for space-constrained industrial motion modules where reliability trumps ultra-fine microstepping.

Availability

A3969SETTR-T is available at Aetrix Electronics and suitable for industrial CNC positioning, medical diagnostic imaging stage control, lab automation liquid handling, and automated test equipment fixture motion requiring stable component supply despite end-of-life status.

Supply support for A3969SETTR-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 ICs, specializing in motion control, current sensing, and motor driver solutions for industrial and automotive markets.

The A3969 product line was engineered for cost-effective, thermally robust bipolar stepper motor control in space-constrained embedded systems-emphasizing integration of protection, current regulation, and 3.3 V logic compatibility without external support components.

FAQ

What is the maximum continuous output current supported by the A3969SETTR-T?

The A3969SETTR-T supports ±650 mA continuous output current per H-bridge under specified thermal conditions (T_A ≤ 85°C, 4-layer PCB). This rating assumes proper heatsinking via the exposed thermal pad and adherence to the 32°C/W junction-to-ambient thermal resistance specification. Peak current capability is ±750 mA, but sustained operation above ±650 mA risks thermal shutdown activation unless ambient temperature and PCB layout are optimized.

How does the A3969SETTR-T implement current regulation without an external microcontroller?

The A3969SETTR-T uses an internal fixed-frequency PWM current-control circuit that operates autonomously. It compares the voltage across external sense resistors (connected to SENSE1/SENSE2) against a trip threshold derived from the REF input voltage (V_TRIP = V_REF/4). When current reaches the trip point, the source driver turns off; current recirculates through the sink driver and internal diodes until the oscillator resets the latch. No external controller is needed for basic current-regulated operation.

What is the purpose of the RC pin on the A3969SETTR-T, and how is it configured?

The RC pin on the A3969SETTR-T connects to an external RC timing network (RT resistor to VCC, CT capacitor to GND) that sets both the internal oscillator frequency and the current-sense comparator blanking window. With RT = 56 kΩ and CT = 680 pF, the device achieves ~25 kHz PWM frequency and ~1.3 μs blanking time. This configuration prevents false triggering during H-bridge switching transients and defines the fundamental current regulation timing for the A3969SETTR-T.

Does the A3969SETTR-T require special power-up sequencing?

No, the A3969SETTR-T does not require special power-up sequencing. Its internal circuitry is designed for robust startup under normal operating conditions. Both VBB (motor supply) and VCC (logic supply) can be ramped independently within their absolute maximum ratings. Internal UVLO circuitry ensures functional reset occurs only after VCC exceeds 2.75 V, and thermal protection remains inactive until junction temperature reaches 165°C-allowing safe initialization without external sequencing logic for the A3969SETTR-T.

What package type and thermal characteristics define the A3969SETTR-T's mounting requirements?

The A3969SETTR-T uses a 28-pin QFN package (5 mm × 5 mm, 0.90 mm height) with an exposed thermal pad. Its thermal performance is characterized by R_θJA = 32°C/W (on 4-layer JEDEC board) and R_θJT = 2°C/W, enabling up to 3.9 W power dissipation at 25°C ambient. Successful mounting requires soldering the thermal pad to a dedicated copper area with ≥4 thermal vias (0.3 mm diameter) connecting to inner ground/power planes-critical for maintaining junction temperature below 150°C during continuous ±650 mA operation of the A3969SETTR-T.