Allegro MicroSystems A3992SB-T

Overview

A3992SB-T from Allegro MicroSystems is a DMOS dual full-bridge microstepping PWM motor driver IC designed for bipolar stepper motor control in industrial motion systems. It delivers ±1.5 A continuous output current at up to 50 V supply, supports 6-bit linear DAC-based torque control (1.56% resolution), and implements programmable mixed/fast/slow decay modes via serial interface. Used in precision CNC stages and automated lab equipment requiring smooth microstepped motion.

For engineers reviewing the A3992SB-T datasheet, A3992SB-T pinout, A3992SB-T application, or A3992SB-T equivalent, this page provides verified technical context, validated package mapping, confirmed pin functions, real-world thermal performance data, and two documented alternative parts with explicit functional and application-level differences.

Technical Context

The A3992SB-T integrates two independent DMOS full-bridge drivers with synchronous rectification, fixed-off-time PWM timing, and a 4 MHz internal oscillator (or external clock input). Its dual 6-bit linear DACs set per-bridge current levels with ±0.5 LSB accuracy referenced to either internal 2 V or external REF voltage.

Current regulation uses VREF/(Range × RSENSE) scaling, where Range = 4 or 8 (selected via Word 0 D18), enabling precise ITRIPMAX tuning. Protection includes short-to-ground latching (≥2 A OCP threshold), thermal shutdown at 165°C (15°C hysteresis), crossover-current prevention, and UVLO at 4.2 V with 100 mV hysteresis.

Key Specifications

Pinout & Package

Package: 24-pin plastic DIP with dual copper batwing tabs (suffix B), 1.27 mm lead pitch, exposed die pad fused to GND for thermal conduction. Maximum height 5.33 mm. RoHS-compliant, 100% matte tin plating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TB6600HG and DRV8825, the A3992SB-T uniquely provides per-bridge 6-bit DAC control, programmable decay timing, and synchronous rectification - making it the only option among the three that supports adaptive torque profiling and <1 W quiescent dissipation in industrial embedded motion controllers.

Availability

A3992SB-T is available at Aetrix Electronics and suitable for industrial CNC positioning, automated laboratory equipment, medical imaging actuators, and factory automation conveyors requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant through-hole assembly.

Supply support for A3992SB-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 IC solutions, specializing in motion control, current sensing, and automotive safety systems since 1989.

The A3992SB-T belongs to Allegro's DMOS dual full-bridge motor driver product line, engineered specifically for precision bipolar stepper motor control in industrial automation, medical devices, and instrumentation where reliability, thermal resilience, and programmable current regulation are critical.

FAQ

What is the maximum continuous output current supported by the A3992SB-T?

The A3992SB-T supports ±1.5 A continuous output current per bridge under specified thermal conditions (26 °C/W on 4-layer PCB). This rating assumes proper PCB layout with star-grounded sense resistors, adequate copper area for the batwing DIP thermal pad, and ambient temperature ≤85°C. Exceeding this current without enhanced heatsinking risks thermal shutdown activation at 165°C junction temperature.

Does the A3992SB-T require external Schottky diodes for flyback protection?

No, the A3992SB-T does not require external Schottky diodes due to its integrated synchronous rectification circuitry. During current decay, the device actively turns on low-R_DS(on) DMOS transistors to recirculate load current, eliminating body-diode conduction losses. This feature reduces power dissipation by up to 45% compared to discrete diode solutions and removes four external components in typical designs.

How is microstepping resolution controlled on the A3992SB-T?

Microstepping resolution on the A3992SB-T is controlled via two independent 6-bit linear DACs (one per bridge), programmed through its 3-wire serial interface. Each DAC sets current magnitude in 64 discrete steps (1.56% increments of full scale), enabling precise torque control for 1/2-, 1/4-, 1/8-, 1/16-, 1/32-, and 1/64-step modes. The actual step subdivision is determined by external controller sequencing of phase polarity (D13/D14 bits), while DAC values define current amplitude per microstep.

What protection features are built into the A3992SB-T?

The A3992SB-T includes short-to-ground protection (latching ≥2 A OCP), thermal shutdown (165°C typical, 15°C hysteresis), UVLO (4.2 V enable threshold), crossover-current prevention, and shorted-load tolerance. Unlike many competitors, its short-to-ground fault latches until SLEEP is asserted high or VDD is cycled - preventing uncontrolled restart after winding faults. All protections operate without external components.

Can the A3992SB-T operate with a 3.3 V logic supply?

Yes, the A3992SB-T accepts 3.3 V logic signals on its DATA, STROBE, CLOCK, SLEEP, and OSC inputs, as its logic input voltage range is –0.3 V to 7 V. However, the VDD pin itself must be supplied with 4.5–5.5 V to power the internal digital core and regulator. Therefore, a level-shifting interface or separate 5 V rail is required for VDD, while controller GPIOs may directly drive the logic inputs at 3.3 V.