Allegro MicroSystems A4986SESTR-T

Overview

A4986SESTR-T from Allegro MicroSystems is a dual DMOS full-bridge stepper motor driver with parallel input interface, rated for 35 V load supply and ±2 A output current per bridge. It supports full/half/quarter-step microstepping via integrated 2-bit nonlinear DACs and fixed off-time PWM current regulation using mixed decay mode to reduce audible noise and power dissipation. It is used in precision motion control systems such as 3D printer extruder drives and CNC stepper axes.

For engineers reviewing the A4986SESTR-T datasheet, A4986SESTR-T pinout, A4986SESTR-T application, or A4986SESTR-T equivalent, key selection criteria include its QFN-24 package with exposed thermal pad, 30 µs typical fixed off-time, synchronous rectification, and integrated short-to-ground and shorted-load protection - all critical for compact, thermally constrained stepper driver designs.

Technical Context

The A4986SESTR-T implements two independent N-channel DMOS full-bridges controlled by parallel logic inputs (PH1/PH2, IN0x/IN1x), each regulated by fixed off-time PWM with blanking (≈1 µs) and mixed decay (31.25% fast + 68.75% slow). Current limiting is set via external sense resistors and a 2-bit DAC that scales peak current to 33%, 66%, or 100% of ITripMAX = VREF/(8 × RS).

Internal circuitry includes a charge pump (CP1/CP2) for high-side gate drive, a 7 V VREG regulator for sink-side FETs, undervoltage lockout on VDD (2.8 V threshold), thermal shutdown at 165 °C with 15 °C hysteresis, and crossover-current protection. Sleep mode draws <10 µA and disables outputs, charge pump, and regulators.

Key Specifications

Pinout & Package

Package: 24-contact QFN (ES), 4 mm × 4 mm × 0.75 mm, with exposed thermal pad (lead-free, matte tin plating). Designed for high-density PCB layouts and enhanced thermal dissipation via direct pad soldering and thermal vias.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TB6600HG and DRV8825, the A4986SESTR-T delivers superior thermal efficiency in compact QFN-24 due to lower R_DS(ON), synchronous rectification, and mixed decay - making it optimal for space-constrained, noise-sensitive, and thermally demanding stepper applications where reliability under wiring faults is essential.

Availability

A4986SESTR-T is available at Aetrix Electronics and suitable for 3D printer motion control, CNC milling axis drivers, and automated lab equipment requiring stable component supply, consistent thermal performance, and long-term production continuity.

Supply support for A4986SESTR-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 and manufacturer of high-performance magnetic sensing and power IC solutions, headquartered in Manchester, NH.

The A4986SESTR-T belongs to Allegro's DMOS full-bridge motor driver product line, engineered specifically for cost-sensitive, thermally constrained stepper motor applications in industrial automation and precision instrumentation.

FAQ

What is the maximum continuous output current supported by the A4986SESTR-T?

The A4986SESTR-T is rated for ±2 A continuous output current per full-bridge under specified thermal conditions. This rating assumes proper PCB layout with the exposed thermal pad soldered to a multi-layer ground plane and thermal vias. Derating is required above 85 °C ambient or with inadequate copper area - actual sustainable current depends on layout, airflow, and VBB voltage. The A4986SESTR-T achieves this with 320–430 mΩ R_DS(ON) and synchronous rectification to minimize power loss.

Does the A4986SESTR-T support microstepping, and how is it configured?

Yes, the A4986SESTR-T supports full-step, half-step, and quarter-step microstepping via its integrated 2-bit nonlinear DACs. Configuration is performed using parallel logic inputs: PH1/PH2 select phase polarity, while IN0x/IN1x set the current scaling percentage (33%, 66%, or 100% of ITripMAX) for each bridge. No external indexer or clock is needed - step resolution is determined solely by the logic state sequence applied to these pins. The A4986SESTR-T does not include an internal step clock generator.

How does the mixed decay mode in the A4986SESTR-T improve motor performance?

The A4986SESTR-T's mixed decay mode applies fast decay for 31.25% of the fixed off-time and slow decay for the remainder. This reduces audible motor whine, improves step accuracy by minimizing current overshoot during direction changes, and lowers power dissipation compared to pure fast or slow decay. The feature is fully internal - no external configuration is required. It works in conjunction with synchronous rectification to further cut losses, making the A4986SESTR-T especially effective in low-speed, high-resolution stepper applications.

What protection features are built into the A4986SESTR-T?

The A4986SESTR-T integrates short-to-ground protection (latched disable until SLEEP is toggled), shorted-load protection (repetitive off-time cycling), thermal shutdown (165 °C trip with 15 °C hysteresis), undervoltage lockout on VDD (2.8 V rising threshold), crossover-current protection, and internal UVLO. It also includes blanking (~1 µs) to prevent false overcurrent trips during switching transients. These protections operate autonomously without external components - a key differentiator from discrete or less-integrated alternatives like the A4986SESTR-T's closest functional peers.

Can the A4986SESTR-T operate from a 3.3 V logic supply?

Yes, the A4986SESTR-T supports 3.3 V logic supply on its VDD pin, with guaranteed operation from 3.0 V to 5.5 V. Input thresholds are ratiometric (V_IN(1) ≥ 0.7 × VDD, V_IN(0) ≤ 0.3 × VDD), and input hysteresis (5–19% of VDD) enhances noise immunity. All logic inputs - including PH1, PH2, IN01, IN11, IN02, IN12, and SLEEP - are fully compatible with 3.3 V microcontrollers without level shifting. This makes the A4986SESTR-T suitable for modern low-voltage embedded systems.