Allegro MicroSystems A3973SLBTR-T

Overview

A3973SLBTR-T from Allegro MicroSystems is a dual DMOS full-bridge PWM motor driver designed for bipolar microstepping stepper motors, supporting ±1 A continuous output current and 35 V load supply voltage. It integrates two 6-bit linear DACs for precise torque control, programmable mixed/fast/slow current-decay modes, and synchronous rectification to eliminate external clamp diodes in most applications - used in industrial CNC motion controllers and precision lab automation stages.

For engineers reviewing the A3973SLBTR-T datasheet, A3973SLBTR-T pinout, A3973SLBTR-T application, or A3973SLBTR-T equivalent, key selection considerations include its 24-pin SOICW-LB package with four internally fused leads, serial 3-wire interface (CLOCK/DATA/STROBE), internal 4 MHz oscillator, 2 V precision reference, and thermal shutdown at 165°C with 15°C hysteresis.

Technical Context

The A3973SLBTR-T implements fixed-off-time PWM current regulation using two independent 6-bit DACs (each controlling one H-bridge), with selectable current decay modes (mixed, fast, slow) programmed via 19-bit serial words. Its internal oscillator (4 MHz typical) drives programmable blank time (4–12/f_OSC) and off-time (1.75–63.75 μs) counters.

Synchronous rectification is configurable via two serial bits into Active, Passive, Disabled, or Low-Side-Only modes - enabling low-R_DS(on) recirculation paths that reduce power dissipation by replacing external Schottky diodes. Current sensing uses dedicated SENSE1/SENSE2 inputs referenced to ground, with trip threshold I_TRIP = V_DAC/(Range × R_S), where Range is 4 or 8 per D18 bit.

Key Specifications

Pinout & Package

Package: 24-pin SOICW (LB) with four internally fused leads (pins 6, 7, 18, 19) for enhanced thermal dissipation; power tabs at ground potential - no electrical isolation required.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TB6600HG and DRV8825, the A3973SLBTR-T uniquely combines serial configurability, dual independent 6-bit DACs, and four synchronous rectification modes - making it optimal for applications needing adaptive current profiling and EMI-sensitive layouts, despite its lower current ceiling.

Availability

A3973SLBTR-T is available at Aetrix Electronics and suitable for industrial CNC positioning, lab automation stages, 3D printer extruder control, and medical imaging gantry drive applications requiring stable component supply and long-term production continuity.

Supply support for A3973SLBTR-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 sensors and power ICs, founded in 1989 and headquartered in Worcester, Massachusetts.

The A3973 product line targets precision motion control in industrial and medical equipment, emphasizing integrated current regulation, thermal robustness, and flexible microstepping implementation without external timing components.

FAQ

What is the maximum continuous output current supported by the A3973SLBTR-T?

The A3973SLBTR-T supports ±1.0 A continuous output current per bridge under specified thermal conditions (T_A ≤ 85°C, adequate PCB copper). This rating assumes use of the LB package's four fused leads for thermal enhancement and proper decoupling of VREG and VCP pins with 0.22 μF capacitors. Exceeding this current may trigger thermal shutdown at 165°C junction temperature.

Does the A3973SLBTR-T require an external oscillator, or does it have an internal clock source?

The A3973SLBTR-T includes a 4 MHz internal oscillator usable without external components - the OSC pin is shorted to ground in default configuration. For higher timing precision, an external clock (2.5–6.0 MHz) can be applied to the OSC pin, with internal dividers (÷1, ÷2, ÷4) selectable via serial bits D12–D13. The internal oscillator's frequency tolerance is process-dependent unless a precision resistor is added between OSC and VDD.

How does the A3973SLBTR-T implement microstepping control?

The A3973SLBTR-T achieves microstepping through two independent 6-bit linear DACs (one per H-bridge), each setting current magnitude in 1.56% increments of full scale. Combined with programmable phase bits (D13/D14) and decay-mode selection (D15/D16), it supports full-step, half-step, and fractional microstepping up to 1/64. Current levels are updated dynamically via the 3-wire serial interface without interrupting motor operation.

Can the A3973SLBTR-T operate with 3.3 V logic-level control signals?

Yes, the A3973SLBTR-T accepts 3.3 V or 5 V logic-level inputs on CLOCK, DATA, STROBE, and SLEEP pins - its logic input voltage range is –0.3 V to VDD + 0.3 V, and VDD operates from 4.5 V to 5.5 V. Input thresholds are defined at 2.0 V (logic high) and 0.8 V (logic low), ensuring reliable recognition of 3.3 V CMOS signals even with VDD = 5.0 V.

What thermal protection features are built into the A3973SLBTR-T?

The A3973SLBTR-T incorporates junction-temperature-based thermal shutdown at 165°C (typical) with 15°C hysteresis, plus undervoltage lockout (UVLO) that disables outputs if VDD drops below 3.9 V. These protections operate independently of the serial interface and remain active in sleep mode. No special power-up sequencing is required - the device resets safely on VDD ramp-up.