Allegro MicroSystems A3983SLP

Overview

A3983SLP from Allegro MicroSystems is a DMOS bipolar stepper motor driver IC with integrated translator, designed for full-, half-, quarter-, and eighth-step microstepping control of up to ±2 A per phase at 35 V supply. It features automatic mixed/slow decay mode selection, synchronous rectification, and fixed off-time PWM current regulation. Used in precision motion control systems such as medical pumps and automated lab equipment.

For engineers reviewing the A3983SLP datasheet, A3983SLP pinout, A3983SLP application, or A3983SLP equivalent, key selection criteria include its 24-pin TSSOP-LP package with exposed thermal pad, 30 μs typical fixed off-time, ±2 A output drive, VREF-based current programming, and translator-enabled single-pulse step interface.

Technical Context

The A3983SLP implements dual N-channel DMOS full-bridge outputs with independent current regulation per phase using external sense resistors (RS1/RS2) and a DAC-controlled trip threshold derived from VREF. Its translator interprets STEP/DIR/MS1/MS2 inputs to sequence microstep current profiles without external sequencing logic.

Chopping control dynamically selects Slow or Mixed decay based on direction of current change per phase - Slow decay for increasing current, Mixed decay (31.25% fast + remainder slow) for decreasing current - reducing audible noise and improving step accuracy. Synchronous rectification minimizes power dissipation by replacing body diode conduction with low-R_DS(ON) FET switching during decay.

Key Specifications

Pinout & Package

Package: 24-pin TSSOP with exposed thermal pad (suffix LP), 7.80 × 4.40 mm footprint, 1.2 mm max height, lead-free with 100% matte tin plating. Thermal pad must be soldered to PCB ground plane with thermal vias for R_θJA = 28°C/W performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TB6600HG and DRV8825, the A3983SLP uniquely combines translator simplicity, automatic decay adaptation, and synchronous rectification - delivering lower audible noise, higher step accuracy, and reduced power dissipation in space-constrained 24 V industrial motion systems.

Availability

A3983SLP is available at Aetrix Electronics and suitable for medical infusion pumps, industrial CNC positioning, automated laboratory analyzers, and 3D printer extruder control requiring stable component supply and long-term production continuity.

Supply support for A3983SLP 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, founded in 1989 and headquartered in Worcester, Massachusetts.

The A3983 belongs to Allegro's DMOS stepper driver product line, engineered specifically for cost-sensitive, space-constrained motion control applications requiring integrated translation, robust protection, and minimal external components.

FAQ

What is the maximum motor supply voltage supported by the A3983SLP?

The A3983SLP supports a motor supply voltage (VBB) up to 35 V, with absolute maximum rating specified at 35 V. Operation above 35 V risks permanent damage. The device maintains full functionality across 8–35 V, making it suitable for 12 V, 24 V, and 32 V industrial DC bus systems. Always observe the 0.5 V maximum sense voltage limit when sizing current-sense resistors for high-VBB operation.

How does the A3983SLP determine whether to use Slow or Mixed decay mode?

The A3983SLP determines decay mode per phase by comparing the DAC output level before and after each STEP input. If the new DAC level is higher, Slow decay is selected; if lower, Mixed decay (31.25% fast decay followed by slow decay) is used. This real-time decision occurs independently for each full-bridge and is implemented entirely in hardware - no software or configuration is required. The A3983SLP datasheet confirms this behavior in the Functional Description section.

Can the A3983SLP operate with a 3.3 V logic supply?

Yes, the A3983SLP accepts a logic supply (VDD) from 3.0 V to 5.5 V, so 3.3 V operation is fully supported and within specification. Input thresholds scale with VDD (e.g., VIN(1) ≥ 0.7×VDD), ensuring reliable logic-level recognition. However, VCP and charge pump operation depend on VBB, not VDD - so motor supply must still meet minimum 8 V requirement regardless of logic voltage. The A3983SLP electrical characteristics table explicitly lists 3.0 V as the minimum VDD.

What is the purpose of the exposed thermal pad on the A3983SLP package?

The exposed thermal pad on the A3983SLP's 24-pin TSSOP-LP package provides a low-thermal-resistance path from the die to the PCB ground plane. When soldered directly to a copper area with thermal vias, it reduces R_θJA to 28°C/W (per JEDEC 4-layer board standard), enabling continuous ±2 A operation without external heatsinking. The pad must be connected to GND (pins 13 and 24) externally - failure to do so risks thermal runaway and premature device failure. The A3983SLP package drawing and Application Layout section detail required PCB land pattern and via placement.

Does the A3983SLP require external Schottky diodes for flyback protection?

No, the A3983SLP does not require external Schottky diodes due to its integrated synchronous rectification feature. During current decay, the IC actively turns on appropriate low-R_DS(ON) DMOS FETs to recirculate motor current, bypassing body diodes and reducing power loss. This eliminates conduction losses associated with external diodes and simplifies layout. The A3983SLP datasheet states: "synchronous rectification … can eliminate the need for external Schottky diodes in many applications."