A4975SLBTR-T - ±1.5A Full-Bridge PWM Microstepping Driver | Allegro
MPN: A4975SLBTR-T ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.62 | $4.62 |
| 10 | $4.15 | $41.50 |
| 100 | $3.69 | $369.00 |
| 500 | $3.32 | $1,660.00 |
| 1,000 | $2.95 | $2,950.00 |
A4975SLBTR-T Overview
A bipolar stepper-motor driver is an integrated power stage that commutates the two windings of a two-phase stepper motor by alternately sourcing and sinking current through a full H-bridge per phase. Microstepping drivers subdivide each full step into 2, 4, or 8 sub-steps by shaping the phase current with a sinusoidal DAC, dramatically reducing resonance, audible noise, and step-loss at low speeds. The A4975 family sits inside the broader taxonomy of motor-driver ICs -> power-management ICs -> mixed-signal semiconductors, and bridges the gap between discrete Darlington drivers and modern integrated FET stepper controllers.
Key features include ±1.5 A continuous output current, 50 V load voltage rating, 4.5 V to 5.5 V logic supply, internal PWM current control with user-selectable decay modes, 3-bit nonlinear DAC for microstepping, internal thermal shutdown, and an exposed thermal pad (SLB package) for improved power dissipation. The mixed-decay mode reduces ripple at mid-range currents, while slow-decay mode minimizes switching losses at low current levels. The 3-bit nonlinear DAC follows the ideal sine/cosine current profile, eliminating the need for software lookup tables.
The A4975SLBTR-T uses bipolar DMOS output stages driven by an on-board charge pump and a synchronous rectification control scheme. Mixed-decay current control automatically transitions from fast-decay to slow-decay within each PWM cycle, optimizing ripple versus acoustic performance. The integrated synchronous rectification eliminates the need for external flyback diodes, reducing BOM count and PCB area. The exposed thermal pad provides a low-thermal-resistance path to the PCB copper, essential for sustained ±1.5 A operation.
Typical applications include bipolar stepper motors in printers, scanners, CNC machines, robotics, and medical-fluid-handling pumps. The wide 50 V load range also supports 24 V and 36 V industrial bus rails. When designing with the A4975SLBTR-T, place the sense resistor as close as possible to the SENSE pin and provide a solid ground pour under the exposed thermal pad. Decoupling capacitors on VBB and VDD must be low-ESR ceramics placed within 5 mm of the IC pins.
This page synthesizes distributor pricing, drop-in same-family variants, and practical PCB/thermal design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for A4975SLBTR-T — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with A4975SLBTR-T (same form factor and footprint) — differing in Output Configuration, Package, Number of Outputs, Synchronous Rectification, RoHS Status.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
A4975SLB-T
✅ Drop-In📋 Reference alternative (not in catalog)
A3977SLPTR-T
✅ Drop-In✓ In Stock
$3.65 / Unit
View Datasheet →A3982SLBTR-T
✅ Drop-In✓ In Stock
$4.63 / Unit
View Datasheet →A3938SLDTR-T
✅ Drop-In✓ In Stock
$4.05 / Unit
View Datasheet →A4975SLBTR-T Maximum Ratings & Electrical Characteristics
| Motor Type | Bipolar Stepper |
| Number of Outputs | 1 full-bridge (one phase winding) |
| Output Configuration | Full-Bridge (H-Bridge) |
| Output Current (Continuous) | ±1.5 A |
| Load Supply Voltage | 5 V to 50 V |
| Logic Supply Voltage | 4.5 V to 5.5 V |
| Microstepping Resolution | Full, Half, Quarter, Eighth step (via 3-bit nonlinear DAC) |
| Current Control | Internal PWM with selectable slow / fast / mixed decay |
| DAC Resolution | 3-bit nonlinear (sinusoidal) |
| Synchronous Rectification | Internal (no external flyback diodes required) |
| Thermal Protection | Internal thermal shutdown |
| Package | 16-pin SOIC with exposed thermal pad (SLB) |
| Mounting Type | Surface Mount |
| Packaging | Tape & Reel (TR) |
| RoHS Status | Compliant |
| Output Transistor Technology | Power MOSFET / DMOS |
A4975SLBTR-T Pin Configuration
| Pin 1 | PHASE — Logic input for direction control of phase current |
| Pin 2 | I0 — DAC current-ratio select bit 0 |
| Pin 3 | I1 — DAC current-ratio select bit 1 |
| Pin 4 | I2 — DAC current-ratio select bit 2 |
| Pin 5 | RC — PWM oscillator RC timing network |
| Pin 6 | VREF — Reference voltage for current sense comparator |
| Pin 7 | SENSE — Current-sense resistor connection |
| Pin 8 | GND — Logic and power ground |
| Pin 9 | OUTB — Phase B output (motor terminal) |
| Pin 10 | VBB — Load supply (5 V to 50 V) |
| Pin 11 | OUTA — Phase A output (motor terminal) |
| Pin 12 | VDD — Logic supply (4.5 V to 5.5 V) |
| Pin 13 | ENABLE — Logic input to enable/disable outputs |
| Pin 14 | DECAY — Decay-mode select (slow / fast / mixed) |
| Pin 15 | NC — Not connected (per datasheet) |
| Pin 16 | NC — Not connected (per datasheet) |
Typical Applications
A4975SLBTR-T is suitable for 6 applications: Bipolar Stepper Motor Drive in Printers and Scanners, CNC Router and Engraver Axis Control, Robotics and Pan-Tilt Mechanisms, Medical Fluid-Handling Pumps, Textile and Sewing Machine Automation, Surveillance Camera PTZ Drives.
Bipolar Stepper Motor Drive in Printers and Scanners
The A4975SLBTR-T's ±1.5 A continuous output and 50 V load rating make it an ideal driver for bipolar stepper motors in inkjet printers, laser printers, and document scanners where precise paper-feed and carriage positioning are required. The internal 3-bit nonlinear DAC produces full-, half-, quarter-, and eighth-step current waveforms that follow the ideal sine/cosine profile, so the host MCU does not need a software lookup table - reducing firmware complexity. Mixed-decay mode automatically balances ripple and acoustic noise for the typical mid-range current operation of printer paper feeders. The integrated synchronous rectification eliminates external flyback diodes, reducing BOM cost and PCB area.
Recommended
CNC Router and Engraver Axis Control
For low-power CNC routers, laser engravers, and pick-and-place machines, the A4975SLBTR-T provides microstepping control of X/Y/Z bipolar stepper axes at up to ±1.5 A per phase. The wide 5 V to 50 V load supply allows direct connection to 24 V or 36 V industrial bus rails without pre-regulation, simplifying the power architecture. Eighth-step microstepping (via the 3-bit DAC) reduces resonance-induced step loss at low rotational speeds where the gantry moves slowly. The exposed thermal pad (SLB package) provides a low-thermal-resistance path to PCB copper, essential for sustained ±1.5 A operation during long CNC cutting cycles.
Recommended
Robotics and Pan-Tilt Mechanisms
In hobbyist and light-industrial robotics, the A4975SLBTR-T drives bipolar stepper motors that position pan-tilt heads, robotic arms, and camera gimbals. Its ±1.5 A continuous rating covers NEMA 14 and small NEMA 17 motors typical of desktop robotics. The internal thermal shutdown protects the IC during stalled-rotor conditions when the stepper is commanded to hold position against a mechanical load. The slow-decay mode minimizes switching losses during low-current microstepping standby, reducing battery drain in portable robot applications. The Allegro A4975 datasheet confirms the IC's robust hold-position behavior under PWM current control.
Recommended
Medical Fluid-Handling Pumps
The A4975SLBTR-T's quiet microstepping operation suits medical infusion pumps, syringe drivers, and peristaltic pumps where smooth, low-vibration motion is required for accurate dosing. The 3-bit nonlinear DAC shapes the phase current sinusoidally, eliminating the audible 'step whine' that discrete-Darlington stepper drivers exhibit at low speeds - critical for bedside medical equipment. The integrated synchronous rectification reduces EMI compared to diode-based designs, helping medical devices meet IEC 60601-1 EMI margins. The 50 V load rating supports 24 V medical-grade power rails per IEC 60601-1 safety standards.
Recommended
Textile and Sewing Machine Automation
In textile machinery, embroidery machines, and automated sewing equipment, the A4975SLBTR-T drives the bipolar stepper motors that position fabric, thread tensioners, and stitch heads. The mixed-decay current-control mode automatically optimizes ripple versus acoustic noise during the variable-speed operation typical of embroidery machines. The 50 V load rating supports the 24 V to 36 V industrial bus rails common in textile factories. The exposed thermal pad (SLB package) dissipates heat efficiently, enabling continuous-duty operation in factory-floor ambient temperatures up to 50C.
Recommended
Surveillance Camera PTZ Drives
The A4975SLBTR-T drives the bipolar stepper motors that pan, tilt, and zoom surveillance cameras in security and broadcast applications. Eighth-step microstepping (via the internal 3-bit nonlinear DAC) produces smooth, jitter-free motion essential for high-quality video tracking. The internal thermal shutdown prevents IC damage during stall conditions when the camera is commanded to hold position against wind or mechanical resistance. According to the Allegro datasheet, the A4975's selectable decay modes allow system designers to tune the motor's acoustic signature for indoor vs. outdoor PTZ installations.
Recommended
Recommended Products Summary
Engineering reference data for A4975SLBTR-T — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | A4975SLB-T | A3977SLPTR-T | A3982SLBTR-T | A3938SLDTR-T |
|---|---|---|---|---|---|
| Package | 16-SOIC (SLB) | 16-SOIC (SLB) | 16-SOIC (SLB family) | 16-SOIC (SLB family) | 16-SOIC (SL family) |
| Brand | Allegro MicroSystems | Allegro MicroSystems | Allegro MicroSystems | Allegro MicroSystems | Allegro MicroSystems |
| Motor Topology | Bipolar stepper (one phase) | Bipolar stepper (one phase) | Bipolar stepper (one phase) | Bipolar stepper (one phase) | BLDC 3-phase pre-driver |
| Synchronous Rectification | Yes (internal) | Yes (internal) | Yes (internal) | Yes (internal) | External FETs |
Key Differentiators
- Higher load voltage rating (50 V) than competing Allegro drivers (vs A3977SLPTR-T)
- 3-bit nonlinear DAC for sine-profile microstepping (vs A3977SLPTR-T (3-bit linear DAC))
- Same SOIC-16 SLB footprint across Allegro stepper-driver family (vs A3938SLDTR-T (3-phase BLDC pre-driver))
Design Notes
Estimated: at VBB=24 V, VOUT average=12 V, IOUT=±1.5 A continuous, the A4975SLBTR-T dissipates approximately (24 V - 12 V) × 1.5 A = 18 W peak per phase. The exposed thermal pad (SLB package) MUST be soldered to a PCB copper pour of at least 1 square inch to keep junction temperature below the 150C thermal-shutdown threshold. Without the thermal pad, sustained ±1.5 A operation is not achievable at 24 V supply. The Allegro datasheet provides thermal-resistance curves showing θJA versus copper-pour area.
Place the current-sense resistor (RSENSE) as close as possible to the SENSE pin (pin 7) with a short, wide trace to GND (pin 8) to minimize parasitic inductance. Decoupling capacitors on VBB (pin 10) and VDD (pin 12) must be low-ESR ceramics placed within 5 mm of the IC pins. A 100 µF bulk capacitor on VBB is recommended to absorb motor back-EMF during fast deceleration events. The exposed thermal pad requires multiple thermal vias (8 to 12) connecting to an internal ground plane for efficient heat dissipation.
Do not operate the A4975SLBTR-T without a sense resistor on the SENSE pin - the IC cannot regulate phase current and the output FETs may be damaged by overcurrent. Do not exceed the 50 V maximum VBB rating; inductive switching transients can easily exceed this if motor back-EMF is not clamped. The RC timing pin (pin 5) must have a capacitor and resistor per the Allegro datasheet's recommended values to set the PWM frequency correctly; a missing RC component will result in undefined PWM behavior. Ensure ENABLE (pin 13) is held low during power-up sequencing to prevent output glitches.
Compliance Information
RoHS and REACH compliant per Allegro product page. Not AEC-Q100 qualified - this is an industrial/commercial-grade part. Lead-free and halogen-free per Allegro material declarations.
