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Allegro MicroSystems A3977SLPTR
- Part No.:
- A3977SLPTR
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
A3977SLPTR.pdf
- Description:
- IC MTR DRV BIPOLR 3-5.5V 28TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,149
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Product details
Overview
A3977SLPTR from Allegro MicroSystems is a bipolar stepper motor driver IC with integrated translator, supporting full-, half-, quarter-, and eighth-step microstepping modes. It delivers ±2.5 A output current at up to 35 V, features automatic mixed/fast/slow decay mode selection, and operates with 3.0–5.5 V logic supply - enabling precise motion control in compact industrial positioning systems.
For engineers reviewing the A3977SLPTR datasheet, A3977SLPTR pinout, A3977SLPTR application, or A3977SLPTR equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, and two confirmed alternative drivers for motor control system migration or sourcing flexibility.
Technical Context
The A3977SLPTR integrates dual N-channel DMOS H-bridges with fixed off-time PWM current regulation, where trip current is set by external sense resistors and VREF (ITRIPmax = VREF / 8 × RS). Its on-chip translator eliminates phase sequencing logic, advancing one step per STEP pulse while MS1/MS2 configure resolution per Table 1.
Decay mode is dynamically selected: slow decay for rising DAC steps, and PFD-voltage-controlled fast/mixed decay for falling steps - reducing audible noise and improving current waveform fidelity. Synchronous rectification (enabled via SR pin) replaces body-diode conduction with low-RDS(on) MOSFET paths during decay, cutting power dissipation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | ±2.5 A continuous - supports NEMA 17–23 stepper motors without external heatsinking under typical PCB thermal conditions. |
| Load Supply Voltage | 8–35 V - compatible with 12 V and 24 V industrial DC bus rails. |
| Logic Supply Range | 3.0–5.5 V - interoperable with 3.3 V and 5 V microcontrollers without level shifting. |
| RDS(on) (Source/Sink) | 0.28 Ω / 0.22 Ω typical - limits conduction loss to ≤1.4 W per bridge at 2.5 A, enabling high-efficiency operation. |
| Microstep Resolution | Full / Half / Quarter / Eighth - selectable via MS1/MS2 pins; eighth-step yields 1.8° motor → 0.225° mechanical resolution. |
| Fixed Off-Time | 30–46 µs (typ.) - sets minimum PWM period; adjustable via RC1/RC2 timing networks for optimal current regulation stability. |
| Thermal Shutdown | 165°C junction with 15°C hysteresis - protects against sustained overload or poor heatsinking without latch-up. |
Pinout & Package
Package: 28-pin TSSOP (LP suffix), 9.7 mm × 4.4 mm × 1.2 mm max height, with exposed thermal pad for enhanced PCB heat transfer.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SENSE1 / SENSE2 | Current sense inputs | Connect to low-side sense resistors for Bridge 1 and Bridge 2; voltage must not exceed 0.5 V DC. |
| OUT1A / OUT1B / OUT2A / OUT2B | H-bridge outputs | Drive bipolar stepper motor windings; each pair forms one full-bridge (Phase A/B); rated for 35 V, ±2.5 A. |
| STEP / DIR / MS1 / MS2 | Translator control inputs | STEP advances one microstep; DIR sets rotation direction; MS1/MS2 select resolution (Table 1); all TTL/CMOS compatible. |
| PFD | Percent Fast Decay control | Voltage threshold (0.21×VDD to 0.6×VDD) selects fast/mixed/slow decay for improved current waveform fidelity. |
| HOME | Logic output indicator | Active-low signal indicating translator home state (initial position after power-up or RESET). |
| ENABLE / SLEEP | Power control inputs | ENABLE (active-low) disables outputs; SLEEP (active-low) reduces quiescent current to 20 µA and shuts down charge pump/VREG. |
| VBB1 / VBB2 | Motor supply inputs | Independent load supplies for each H-bridge; decouple with ≥47 µF electrolytic capacitors near pins. |
| VCP / CP1 / CP2 | Charge pump network | VCP is reservoir node; CP1/CP2 require 0.22 µF ceramic caps to generate >VBB gate drive for high-side N-MOSFETs. |
| AGND / PGND | Analog & power ground | Must be connected externally at single point near thermal pad - critical for accurate current sensing and thermal performance. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated translator | Eliminates need for microcontroller-based phase sequencing - STEP/DIR interface reduces firmware overhead and simplifies motion control in resource-constrained systems. |
| Automatic decay mode selection | Dynamically chooses fast/mixed/slow decay per step transition - minimizes current distortion from BEMF, improving torque linearity and reducing motor vibration/noise. |
| Synchronous rectification | Replaces body-diode conduction with active MOSFET paths during decay - cuts power loss by ~30% vs. diode-only recirculation, lowering thermal load. |
| Home state initialization | Power-up or RESET forces known initial DAC levels and polarity (Step #1 in Table 2), ensuring repeatable motor start position without homing routine. |
| Comprehensive protection | Includes UVLO (2.7 V threshold), thermal shutdown (165°C), crossover-current prevention, and blanking-timed current-sense comparator - enables robust operation in unregulated environments. |
Applications
| Industrial CNC Positioning | Medical Infusion Pumps |
|---|---|
Use Scenario: Precision linear actuation in desktop CNC mills and 3D printer extruders requiring sub-millimeter repeatability. IC Role / Device Role / Timing Role: Dual-H-bridge driver with microstepping translator - directly converts STEP pulses into controlled winding currents with minimal host CPU involvement. Use Value: Eighth-step resolution (0.225°) and automatic decay optimization reduce positional error and resonance, enabling smooth, quiet motion at low speeds without mechanical dampers. | Use Scenario: Accurate syringe plunger advancement in battery-powered portable infusion devices with strict EMI and power budget constraints. IC Role / Device Role / Timing Role: Low-quiescent-current stepper driver with SLEEP mode - maintains motor hold torque only when needed, extending battery life between charges. Use Value: 20 µA sleep current and synchronous rectification cut average system power by >40% vs. legacy drivers, meeting IEC 60601-1 portable device efficiency targets. |
| Automated Test Equipment (ATE) | Lab Automation Stage Control |
Use Scenario: High-speed indexing of probe cards and wafer handlers where rapid, repeatable angular positioning is required between test cycles. IC Role / Device Role / Timing Role: Translator-based stepper controller - accepts 500 kHz STEP commands to achieve fast acceleration/deceleration profiles without jitter. Use Value: 500 kHz maximum STEP frequency and <1 µs pulse timing allow ≤2 ms full-step transitions, enabling ≤100 ms full 360° rotation for high-throughput test sequences. | Use Scenario: Microscope stage focusing and XY translation in research-grade optical systems demanding sub-micron stability and zero backlash. IC Role / Device Role / Timing Role: Bipolar stepper driver with HOME output - provides deterministic startup position and eliminates need for external limit switches or encoders. Use Value: Active HOME signal confirms initial state after power cycle, enabling immediate closed-loop-like repeatability without calibration routines or additional sensors. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar stepper motor driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TB6600HG | Higher 4.5 A rating, but requires external phase sequencing logic and lacks integrated translator. | Better for high-torque motors (>2.5 A), but increases MCU firmware complexity and PCB layout effort. | Choose TB6600HG only if higher current and external control flexibility outweigh translator convenience. |
| DRV8825 | Lower 2.2 A rating, same 28-pin TSSOP package, includes built-in translator and decay control - but no HOME output or PFD-adjustable mixed decay. | Suitable for cost-sensitive consumer motion systems where deterministic home state is non-critical. | Prefer DRV8825 for simpler, lower-power designs where A3977SLPTR's HOME and precision decay tuning are unnecessary. |
Compared with TB6600HG and DRV8825, the A3977SLPTR uniquely combines ±2.5 A drive capability, translator simplicity, HOME state signaling, and PFD-voltage-tuned mixed decay - making it optimal for industrial and medical systems requiring deterministic startup, low-noise operation, and minimal host processor load.
Availability
A3977SLPTR is available at Aetrix Electronics and suitable for industrial CNC positioning, medical infusion pumps, automated test equipment, lab automation stages, and precision motion control systems requiring stable component supply across long production lifecycles.
Supply support for A3977SLPTR 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 Manchester, NH.
The A3977 product line targets cost-sensitive yet precision-demanding motion control applications - delivering integrated stepper drivers that reduce system-level design complexity while maintaining robust thermal and electrical protection.
FAQ
What is the maximum step rate supported by the A3977SLPTR?
The A3977SLPTR supports a maximum STEP input frequency of 500 kHz, as specified in its electrical characteristics table. This allows rapid microstep sequencing - for example, at eighth-step mode, 500 kHz enables up to 62,500 full-step-equivalent positions per second. Real-world achievable rate depends on motor inductance, supply voltage, and decay mode configuration; always verify timing margins using the 1.0 µs minimum STEP pulse width and 200 ns data setup/hold requirements from the datasheet.
Does the A3977SLPTR require external Schottky diodes?
No, the A3977SLPTR does not require external Schottky diodes due to its integrated synchronous rectification feature. When the SR pin is held low, the device actively turns on appropriate low-RDS(on) MOSFETs during current decay, replacing body-diode conduction and reducing power loss. External diodes are only needed if SR is disabled (SR = high) for specialized power dissipation routing - a rare case typically reserved for extreme thermal constraints.
How does the A3977SLPTR handle thermal overload?
The A3977SLPTR includes internal thermal shutdown circuitry that disables all DMOS outputs when junction temperature reaches 165°C, with 15°C hysteresis. Once temperature falls below 150°C, normal operation resumes automatically. This protection is independent of external circuitry and activates even during SLEEP mode. For reliable operation, ensure RθJA ≤ 28°C/W via proper PCB copper area, thermal vias under the exposed pad, and adequate airflow - especially at >2 A continuous load.
Can the A3977SLPTR drive unipolar stepper motors?
No, the A3977SLPTR is designed exclusively for bipolar stepper motors. Its dual full-bridge architecture drives current bidirectionally through each winding - a requirement for bipolar operation. Unipolar motors require center-tapped windings and separate phase switching, which the A3977SLPTR does not support. Attempting to connect a unipolar motor will result in incorrect phasing, reduced torque, or potential damage due to improper current paths.
What is the purpose of the HOME output on the A3977SLPTR?
The HOME output on the A3977SLPTR is an active-low logic signal that indicates when the internal translator is in its predefined initial state - occurring at power-up, after RESET assertion, or upon exit from SLEEP mode. It corresponds to Step #1 in Table 2 (100% Phase 1 current, 0% Phase 2 current). This signal enables deterministic motor startup without external homing sensors, allowing systems to resume known position immediately after reset or power cycle - critical for medical and industrial safety-critical motion control.
A3977SLPTR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Motor Type - Stepper:
- Bipolar
- Motor Type - AC, DC:
- -
- Function:
- Driver - Fully Integrated, Control and Power Stage
- Output Configuration:
- Half Bridge (4)
- Interface:
- Logic
- Technology:
- DMOS
- Step Resolution:
- 1, 1/2, 1/4, 1/8
- Applications:
- General Purpose
- Current - Output:
- 2.5A
- Voltage - Supply:
- 3V ~ 5.5V
- Voltage - Load:
- 8V ~ 35V
- Operating Temperature:
- -20°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-TSSOP-EP
A3977SLPTR FAQ
1.How can I place an order for A3977SLPTR through Aetrix?
Please submit a Request for Quotation (RFQ) for A3977SLPTR on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for A3977SLPTR reliable?
The price and inventory of A3977SLPTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3977SLPTR is usually 5 days.
3.What payment methods are accepted for A3977SLPTR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3977SLPTR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3977SLPTR?
A3977SLPTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3977SLPTR order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for A3977SLPTR?
For technical support, including A3977SLPTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3977SLPTR requirements.
6.How does Aetrix verify that A3977SLPTR is sourced from the original manufacturer or authorized distributors?
All A3977SLPTR products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that A3977SLPTR meets industry standards.
7.What is the process for return or replacement of A3977SLPTR?
All A3977SLPTR units undergo pre-shipment inspection (PSI). If there is an issue with A3977SLPTR, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The A3977SLPTR part is unused and in its original packaging.
Return procedure for A3977SLPTR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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