Allegro MicroSystems A3988SJP-T

Overview

A3988SJP-T from Allegro MicroSystems is a quad DMOS full-bridge PWM motor driver IC designed to control up to two bipolar stepper motors or four DC motors in industrial motion systems. It delivers 1.2 A per bridge at up to 36 V, features fixed 30 µs off-time PWM current regulation with mixed decay mode, and supports full/half/quarter-step microstepping via 2-bit nonlinear DACs. Its 48-pin LQFP package with exposed thermal pad enables high-power motor control in compact embedded drives.

For engineers reviewing the A3988SJP-T datasheet, A3988SJP-T pinout, A3988SJP-T application, or A3988SJP-T equivalent, this page provides verified technical context, validated pin functions, confirmed thermal performance (R_θJA = 23 °C/W), real-world step sequencing behavior, and direct alternative options for dual-stepper or quad-DC motor control designs.

Technical Context

The A3988SJP-T integrates four independent N-channel DMOS full bridges with synchronous rectification and mixed-decay PWM current control. Each bridge uses a dedicated VREFx input and SENSEx terminal to set peak current via external sense resistors, enabling precise torque control across microstepping modes.

Its internal charge pump (CP1/CP2/VCP) generates gate drive voltage above VBB to fully enhance high-side MOSFETs, while protection circuitry includes thermal shutdown (T_J = 165 °C), UVLO on both VBB (7.6 V threshold) and VDD (2.8 V), and crossover-current prevention with 425 ns typical delay.

Key Specifications

Pinout & Package

The A3988SJP-T is supplied in a 48-pin LQFP package (7 mm × 7 mm) with exposed thermal pad for enhanced heat dissipation. Nominal height is 1.60 mm; lead-free with 100% matte tin plating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with A3988SJP-T, A5988GJPTR-1-T enables higher step rates and torque but requires revalidation of current sense timing; A3988SJP-T retains superior microstepping granularity and independent phase control, making it preferred for precision motion where step smoothness outweighs raw speed.

Availability

A3988SJP-T is available at Aetrix Electronics and suitable for industrial CNC positioning, medical infusion pumps, automated test equipment, and 3D printer extruder control requiring stable component supply and long-term production continuity.

Supply support for A3988SJP-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, headquartered in Manchester, NH, with over 40 years of motion control innovation.

The A3988 product line delivers integrated quad-bridge motor drivers for precision stepper and DC motor control in space-constrained industrial and medical systems, emphasizing thermal efficiency, noise reduction, and flexible microstepping.

FAQ

What is the maximum motor supply voltage supported by the A3988SJP-T?

The A3988SJP-T supports a maximum continuous load supply voltage of 36 V, with a pulsed rating of 38 V for durations under 1 µs. In typical applications such as CNC stages or infusion pumps, it operates reliably at 32 V motor bus voltage with proper decoupling (100 µF bulk + 0.1 µF ceramic per VBB pin). Exceeding 36 V continuously risks permanent damage to the DMOS output stages.

How does the A3988SJP-T implement microstepping, and what resolutions are supported?

The A3988SJP-T implements microstepping using 2-bit nonlinear DACs and fixed off-time PWM current regulation, supporting full-step, half-step, and quarter-step modes via PHASEx, I0x, and I1x logic inputs per bridge. Quarter-step resolution achieves 1.8°/4 = 0.45° mechanical step angle for standard 1.8° stepper motors. The device does not support eighth- or sixteenth-step modes natively; finer resolution requires external indexer or VREF modulation.

Can the A3988SJP-T drive both stepper and DC motors simultaneously?

Yes, the A3988SJP-T can drive up to two stepper motors, four DC motors, or one stepper plus two DC motors simultaneously. Each of its four full bridges operates independently: stepper control uses PHASEx/I0x/I1x sequencing, while DC motor control configures I0x/I1x as enable and PHASEx as direction. This flexibility allows mixed-motor systems-e.g., a 3D printer using steppers for X/Y axes and DC motors for cooling fans-on a single A3988SJP-T.

What thermal design practices are required for reliable A3988SJP-T operation at 1.2 A per bridge?

For reliable A3988SJP-T operation at 1.2 A per bridge, the exposed thermal pad must be soldered to a solid copper ground plane with ≥6 thermal vias (0.3 mm diameter) connecting to inner ground layers. Use a 4-layer PCB per JEDEC standards to achieve R_θJA = 23 °C/W. Ambient temperature must stay ≤70 °C; at 85 °C ambient, derate current to ~0.9 A per bridge to maintain T_J < 150 °C. Avoid routing high-current traces over the thermal pad area.

Does the A3988SJP-T require external components for charge pump operation?

Yes, the A3988SJP-T requires two external capacitors for charge pump operation: a 0.1 µF ceramic capacitor between CP1 and CP2, and a 0.1 µF ceramic capacitor between VCP and VBBx (VBB1 or VBB2). These capacitors must be placed within 3 mm of their respective pins using short, wide traces. Omitting either capacitor causes high-side driver failure, resulting in partial bridge operation or excessive heating. No resistors or inductors are needed in the charge pump circuit.