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Allegro MicroSystems A3977KLP-T
- Part No.:
- A3977KLP-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
A3977KLP-T.pdf
- Description:
- IC MTR DRV BIPOLR 3-5.5V 28TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,941
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Product details
Overview
A3977KLP-T 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 fixed off-time PWM current regulation with automatic mixed/fast/slow decay selection, and operates from a 3.0–5.5 V logic supply. It is used in precision motion control systems such as industrial automation actuators and medical infusion pumps.
For engineers reviewing the A3977KLP-T datasheet, A3977KLP-T pinout, A3977KLP-T application, or A3977KLP-T equivalent, key selection criteria include its 28-pin TSSOP-LP package with exposed thermal pad, ±2.5 A drive capability, microstep resolution control via MS1/MS2, synchronous rectification for reduced power dissipation, and built-in thermal shutdown and UVLO protection.
Technical Context
The A3977KLP-T integrates dual N-channel DMOS H-bridges with a digital translator that converts STEP/DIR inputs into precise phase current waveforms. Its current regulation uses fixed off-time PWM with blanking time (700–1200 ns) and adjustable decay mode selection via PFD voltage thresholds (0.21×VDD and 0.6×VDD).
It implements automatic decay mode detection: slow decay for increasing DAC steps, fast/mixed decay for decreasing steps-reducing BEMF-induced current distortion. Internal synchronous rectification replaces external Schottky diodes, lowering power loss, while charge pump (CP1/CP2/VCP) enables high-side gate drive above VBB.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | ±2.5 A continuous - supports bipolar stepper motors up to 2.5 A per phase without external current amplification |
| Load Supply Voltage | 8–35 V - compatible with common industrial 12 V, 24 V, and 36 V motor rails |
| Logic Supply Range | 3.0–5.5 V - interfaces directly with 3.3 V or 5 V microcontrollers without level shifting |
| Microstep Resolution | Full / Half / Quarter / Eighth step - selected by MS1/MS2 logic inputs; enables 1.8° motor to achieve 0.225° step angle |
| RDS(on) (Source/Sink) | 0.28 Ω / 0.22 Ω typical - minimizes conduction loss and thermal rise at rated current |
| Thermal Shutdown | 165°C with 15°C hysteresis - protects against sustained overload or poor heatsinking |
| Fixed Off-Time | 30–46 µs (typical 38 µs) - sets minimum current decay duration; adjustable via RC1/RC2 timing network |
Pinout & Package
The A3977KLP-T is housed in a 28-pin thin-shrink small-outline package (TSSOP-LP) with an exposed thermal pad for enhanced heat dissipation. Total height is <1.2 mm, and the package is lead-free with 100% matte tin plating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SENSE1, SENSE2 | Current sense inputs | Connect to low-side sense resistors (RS); maximum 0.5 V input limits ITRIP = VREF/(8×RS) |
| OUT1A/OUT1B/OUT2A/OUT2B | H-bridge outputs | Drive two independent motor windings; each bridge supports ±2.5 A bidirectional current |
| STEP, DIR, MS1, MS2 | Translator control inputs | STEP advances one microstep; DIR sets rotation direction; MS1/MS2 select resolution per truth table |
| PFD | Decay mode control | Voltage threshold sets fast/slow/mixed decay: <0.21×VDD → fast, >0.6×VDD → slow, between → mixed |
| HOME | Logic output | Active-low signal indicating translator home state (initial position after power-up or RESET) |
| ENABLE, SLEEP | Power control | ENABLE (active-low) disables outputs; SLEEP (active-low) reduces quiescent current to 20 µA |
| VBB1/VBB2 | Motor supply inputs | Independent load supplies for each H-bridge; decoupling >47 µF electrolytic required near pins |
| VCP, CP1, CP2 | Charge pump network | VCP is reservoir node; CP1/CP2 require 0.22 µF ceramic caps to generate gate drive >VBB |
| AGND, PGND | Analog & power ground | Must be connected externally at star point under thermal pad to minimize noise and IR drop |
Key Features
| Feature | Design Value |
|---|---|
| Integrated translator | Eliminates need for external sequencer or microcontroller firmware to generate phase currents - STEP/DIR interface only |
| Automatic decay mode selection | Reduces current waveform distortion caused by motor back-EMF, improving step accuracy and reducing audible noise |
| Synchronous rectification | Replaces body diode conduction with low-RDS(on) MOSFET paths during decay, cutting power loss vs. discrete diodes |
| Home state initialization | Power-up or RESET forces known initial winding current polarity and DAC level - ensures repeatable startup position |
| Comprehensive protection | Includes thermal shutdown (165°C), UVLO (2.45–2.95 V enable threshold), and crossover-current prevention |
Applications
| Industrial CNC Positioning | Medical Infusion Pumps |
|---|---|
Use Scenario: Precise linear actuation of tool carriages using 1.8° hybrid stepper motors. IC Role / Device Role / Timing Role: Bipolar stepper driver with microstepping translator and current regulation - controls phase current magnitude and polarity per step command. Use Value: Eighth-step mode enables 0.225° resolution; ±2.5 A drive sustains torque at high acceleration; thermal shutdown prevents fault propagation during jam conditions. | Use Scenario: Controlled delivery of IV fluids via peristaltic or syringe-based stepper-driven mechanisms. IC Role / Device Role / Timing Role: Motor driver with deterministic startup (HOME output) and low-noise current decay - ensures accurate volumetric dosing and silent operation. Use Value: Mixed-decay mode minimizes audible motor whine; SLEEP mode reduces standby power to 20 µA for battery-powered portables. |
| Automated Laboratory Equipment | 3D Printer Extruder Control |
Use Scenario: Sample handling robotics requiring repeatable angular positioning of grippers or rotary stages. IC Role / Device Role / Timing Role: Translator-based stepper driver with DIR/STEP interface - accepts simple pulse trains from low-resource controllers. Use Value: No phase tables or complex firmware needed; HOME output confirms known start position before motion sequence begins. | Use Scenario: Fine-grained filament feed control in FDM 3D printers where microstep smoothness affects surface finish. IC Role / Device Role / Timing Role: High-fidelity current regulator with adjustable fixed off-time - maintains consistent microstep torque across speed range. Use Value: RDS(on) of 0.22 Ω (sink) and 0.28 Ω (source) limits self-heating; exposed thermal pad enables stable operation at 2.5 A in compact enclosures. |
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 voltage rating (44 V), but no integrated translator; requires external step/direction sequencing logic | Used where microcontroller handles microstepping math; lacks HOME output and automatic decay selection | Choose when system already implements translation in firmware and needs higher bus voltage headroom |
| DRV8825 | Lower max current (2.2 A), same 28-pin TSSOP package; includes indexer but no PFD-controlled mixed decay | Common in hobbyist 3D printers; lacks synchronous rectification and has higher RDS(on) (0.35 Ω typical) | Choose for cost-sensitive, lower-current designs where decay mode flexibility is not critical |
Compared with TB6600HG and DRV8825, the A3977KLP-T uniquely combines translator-based simplicity, ±2.5 A drive, PFD-adjustable mixed decay, and synchronous rectification - making it optimal for industrial and medical systems requiring deterministic startup, low acoustic noise, and minimal MCU overhead.
Availability
A3977KLP-T is available at Aetrix Electronics and suitable for industrial CNC positioning, medical infusion pumps, automated laboratory equipment, and 3D printer extruder control requiring stable component supply across long production lifecycles.
Supply support for A3977KLP-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 and manufacturer of high-performance magnetic sensing and power IC solutions, founded in 1985 and headquartered in Manchester, NH.
The A3977 product line targets precision motion control applications, delivering integrated stepper drivers with on-chip translators, robust protection, and thermally optimized packaging for industrial, medical, and instrumentation systems.
FAQ
What is the maximum motor supply voltage supported by the A3977KLP-T?
The A3977KLP-T supports a load supply voltage (VBB) range of 8 V to 35 V, with absolute maximum rating at 35 V. Operation above 35 V risks permanent damage. For reliable long-term use, design margins should keep VBB ≤33 V under transient conditions, especially with inductive kickback from stepper windings.
How does the A3977KLP-T implement microstepping without external sequencing logic?
The A3977KLP-T contains a fully integrated translator that interprets STEP and DIR inputs to generate internal DAC commands and H-bridge switching sequences. With MS1 and MS2 set, each rising edge on STEP automatically advances the motor one microstep - eliminating need for external phase tables or microcontroller-based waveform generation.
What is the function of the PFD pin on the A3977KLP-T?
The PFD (Percent Fast Decay) pin on the A3977KLP-T sets the decay mode behavior during current reduction steps. A voltage <0.21×VDD selects fast decay; >0.6×VDD selects slow decay; voltages between select mixed decay - enabling optimization of torque linearity, noise, and power dissipation per application.
Does the A3977KLP-T require external Schottky diodes for flyback protection?
No, the A3977KLP-T does not require external Schottky diodes due to its internal synchronous rectification circuitry. When enabled (SR = low), it actively turns on low-RDS(on) MOSFETs during decay to replace body diode conduction - reducing power loss and heat generation compared to passive diode solutions.
What thermal management considerations apply to the A3977KLP-T in continuous 2.5 A operation?
In continuous ±2.5 A operation, the A3977KLP-T requires proper thermal design: solder the exposed thermal pad to a multilayer PCB ground plane with ≥6 thermal vias, use ≥47 µF bulk capacitance at VBB pins, and maintain ambient temperature ≤85°C. With RθJA = 28°C/W, junction temperature must stay below 150°C - derate current if heatsinking is insufficient.
A3977KLP-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tube
- 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:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-TSSOP-EP
A3977KLP-T FAQ
1.How can I place an order for A3977KLP-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A3977KLP-T 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 A3977KLP-T reliable?
The price and inventory of A3977KLP-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3977KLP-T is usually 5 days.
3.What payment methods are accepted for A3977KLP-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3977KLP-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3977KLP-T?
A3977KLP-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3977KLP-T 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 A3977KLP-T?
For technical support, including A3977KLP-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3977KLP-T requirements.
6.How does Aetrix verify that A3977KLP-T is sourced from the original manufacturer or authorized distributors?
All A3977KLP-T 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 A3977KLP-T meets industry standards.
7.What is the process for return or replacement of A3977KLP-T?
All A3977KLP-T units undergo pre-shipment inspection (PSI). If there is an issue with A3977KLP-T, 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 A3977KLP-T part is unused and in its original packaging.
Return procedure for A3977KLP-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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