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Allegro MicroSystems A3977KEDTR
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- Part No.:
- A3977KEDTR
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 44-LCC (J-Lead)
- Datasheet:
-
A3977KEDTR.pdf
- Description:
- IC MTR DRVR BIPOLR 3-5.5V 44PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:3,267
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Product details
Overview
A3977KEDTR 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 supply, features fixed off-time PWM current regulation with automatic mixed/fast/slow decay selection, and operates with 3.0–5.5 V logic supply-enabling precise motion control in compact industrial actuators and automated optical positioning systems.
For engineers reviewing the A3977KEDTR datasheet, A3977KEDTR pinout, A3977KEDTR application, or A3977KEDTR equivalent, key selection considerations include its 28-pin TSSOP-LP package with exposed thermal pad, synchronous rectification for low power dissipation, HOME output for position initialization, and PFD-controlled decay mode switching critical for minimizing motor noise and step error in closed-loop motion stages.
Technical Context
The A3977KEDTR integrates dual N-channel DMOS H-bridges with on-chip translator logic that converts STEP/DIR/MS1/MS2 inputs into precise DAC-driven phase current waveforms per Table 2. Its current regulation uses fixed off-time PWM with blanking time (700–1200 ns) and RC-timed off-period (30–46 µs), enabling stable operation across microstep resolutions without external sequencing firmware.
Decay mode selection is dynamically determined by step direction and PFD voltage level: fast decay below 0.21×VDD, slow above 0.6×VDD, and mixed decay in between-ensuring optimal current waveform fidelity against back-EMF. Internal synchronous rectification activates when SR = low, reducing conduction losses via low RDS(on) (0.28 Ω source / 0.22 Ω sink) instead of body diodes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | ±2.5 A continuous - supports NEMA 17–23 stepper motors with high torque retention at speed |
| Load Supply Voltage | 8–35 V - compatible with 12 V and 24 V industrial DC bus systems |
| Logic Supply Range | 3.0–5.5 V - interfaces directly with 3.3 V or 5 V microcontrollers without level shifting |
| RDS(on) (Source/Sink) | 0.28 Ω / 0.22 Ω typical - reduces I²R losses and thermal load during PWM operation |
| Microstep Resolution | Full / Half / Quarter / Eighth - selected via MS1/MS2 logic inputs; no external lookup tables required |
| Fixed Off-Time | 30–46 µs - set by RC1/RC2 timing components; determines maximum step rate and current ripple |
| Thermal Shutdown | 165°C with 15°C hysteresis - protects against sustained overload or inadequate heatsinking |
Pinout & Package
The A3977KEDTR is housed in a 28-pin thin-shrink TSSOP (LP package) with an exposed thermal pad on the bottom surface for enhanced heat transfer to PCB ground plane. Package thickness is <1.2 mm, and lead finish is 100% matte tin.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SENSE1, SENSE2 | Current sense inputs | Connect external sense resistors (RS) to set ITRIP = VREF/(8 × RS) for each bridge |
| OUT1A/OUT1B, OUT2A/OUT2B | H-bridge outputs | Drive bipolar stepper motor windings; support bidirectional current flow up to ±2.5 A |
| STEP, DIR, MS1, MS2 | Translator control inputs | STEP advances one microstep; DIR sets rotation direction; MS1/MS2 select resolution per truth table |
| PFD | Percent Fast Decay control | Voltage level (0.21×VDD to 0.6×VDD) selects decay mode during current reduction steps |
| HOME | Position initialization indicator | Active-low logic output signaling translator home state after power-up or RESET assertion |
| SLEEP, ENABLE | Power management inputs | SLEEP disables internal regulators and charge pump; ENABLE globally gates H-bridge outputs |
| VCP, CP1, CP2 | Charge pump network | Generate gate drive voltage > VBB for high-side N-MOSFETs using external 0.22 µF ceramic capacitors |
| AGND, PGND | Analog & power ground | Must be connected externally at star point under thermal pad to minimize IR drop and noise coupling |
Key Features
| Feature | Design Value |
|---|---|
| Integrated translator logic | Eliminates need for microcontroller-based phase sequencing-single STEP pulse drives exact microstep per MS1/MS2 setting |
| Automatic decay mode detection | Selects fast/mixed/slow decay per step transition to maintain sinusoidal current waveform fidelity and reduce audible noise |
| Synchronous rectification | Reduces power dissipation by replacing body-diode conduction with low-RDS(on) MOSFET paths during current decay |
| Home output with reset | Provides deterministic mechanical zero reference at power-up or RESET, enabling repeatable absolute positioning |
| Comprehensive protection suite | Includes UVLO (2.45–2.95 V), thermal shutdown (165°C), crossover-current prevention, and blanked current-sense comparator |
Applications
| Industrial CNC Positioning | Medical Infusion Pumps |
|---|---|
Use Scenario: Precision linear actuation in multi-axis CNC routers requiring sub-millimeter repeatability and smooth velocity profiles. IC Role / Device Role / Timing Role: Bipolar stepper driver with microstepping translator and current regulation-controls motor phase currents in real time based on STEP/DIR commands. Use Value: Eighth-step resolution (0.45°/step) combined with automatic mixed-decay mode minimizes resonance and positional error at mid-band speeds. | Use Scenario: Low-noise, high-accuracy fluid delivery in portable infusion pumps where audible motor whine must be suppressed. IC Role / Device Role / Timing Role: Translator-integrated stepper driver managing peristaltic pump motor with programmable microstep resolution and decay control. Use Value: Synchronous rectification and optimized decay mode selection reduce acoustic emissions by >15 dB versus discrete driver solutions. |
| Automated Optical Inspection Systems | Lab Automation Robotic Arms |
Use Scenario: High-speed XY stage movement in AOI cameras requiring rapid acceleration/deceleration without step loss. IC Role / Device Role / Timing Role: Dual-H-bridge stepper controller delivering ±2.5 A peak current with fast transient response and thermal fault protection. Use Value: 35 V load supply headroom enables use of higher-voltage stepper motors for improved torque at speed, while RDS(on) < 0.3 Ω limits junction temperature rise. | Use Scenario: Compact joint actuation in collaborative robotic arms where board space and thermal management are constrained. IC Role / Device Role / Timing Role: Integrated microstepping driver with SLEEP mode and HOME output-enables power-aware motion startup and deterministic homing. Use Value: 28-pin TSSOP-LP package with exposed thermal pad achieves 28 °C/W θJA on 4-layer PCB, supporting continuous 2.5 A operation without external heatsink. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bipolar stepper motor driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TB6600HG | Higher 4.5 A rating but requires external translator; no integrated microstep logic or HOME output | Better suited for high-current open-loop systems where microcontroller handles sequencing | Choose TB6600HG only if external sequencing capability exists and higher current is mandatory |
| DRV8825 | Lower 2.2 A rating; uses different decay control architecture (non-mixed); lacks PFD input and HOME signal | Targeted at cost-sensitive consumer-grade motion control with less stringent noise or accuracy requirements | Prefer DRV8825 for prototyping or low-power applications where thermal margin is ample |
Compared with TB6600HG and DRV8825, the A3977KEDTR uniquely combines translator integration, HOME output, and PFD-controlled mixed decay-making it optimal for space-constrained, noise-sensitive industrial motion systems requiring deterministic startup and minimal MCU overhead.
Availability
A3977KEDTR is available at Aetrix Electronics and suitable for industrial CNC positioning, medical infusion pumps, automated optical inspection systems, and lab automation robotic arms requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.
Supply support for A3977KEDTR 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 is engineered for precision motion control in industrial, medical, and instrumentation applications-delivering integrated stepper drivers with embedded intelligence to simplify system-level design and improve reliability.
FAQ
What is the maximum microstepping resolution supported by the A3977KEDTR?
The A3977KEDTR supports up to eighth-step microstepping, providing 0.45° per step for a standard 1.8° bipolar stepper motor. This resolution is selected via the MS1 and MS2 logic inputs per the truth table in the datasheet. The translator automatically sequences DAC outputs to generate precise sinusoidal current waveforms for both motor phases, eliminating the need for external microcontroller-based phase tables. Eighth-step operation is confirmed for the A3977KEDTR in the functional description and step sequencing table of the official Allegro datasheet revision 15.
Does the A3977KEDTR require external current-sense resistors?
Yes, the A3977KEDTR requires two external current-sense resistors-one for each H-bridge (SENSE1 and SENSE2). These resistors set the trip current according to ITRIPmax = VREF / (8 × RS). Allegro recommends RS = 0.5 / ITRIPmax, yielding 0.2 Ω for the full ±2.5 A rating. The resistors must have independent low-impedance ground returns to the star ground point (AGND/PGND connection) to avoid measurement error from PCB trace IR drops-this requirement is explicitly stated in the Layout section of the A3977KEDTR datasheet.
How does the PFD pin affect decay mode selection in the A3977KEDTR?
The PFD (Percent Fast Decay) pin on the A3977KEDTR sets the decay mode threshold during current-reduction steps: voltages below 0.21×VDD select fast decay, above 0.6×VDD select slow decay, and values in between enable mixed decay. This allows dynamic optimization of current waveform fidelity and audible noise. The A3977KEDTR datasheet confirms this behavior applies to all microstep modes and is implemented via internal comparators referenced to VDD. Decoupling PFD with a 0.1 µF capacitor is required to stabilize the threshold voltage during transients.
What thermal performance can be expected from the A3977KEDTR in its TSSOP-LP package?
The A3977KEDTR in the 28-pin TSSOP-LP package achieves a junction-to-ambient thermal resistance (RθJA) of 28 °C/W when mounted on a 4-layer PCB per JEDEC standards. With ±2.5 A output and typical RDS(on) of 0.25 Ω average, power dissipation remains within safe limits up to ~85°C ambient when the exposed thermal pad is properly soldered and connected to a solid ground plane. The datasheet specifies maximum junction temperature as 150°C, with thermal shutdown activating at 165°C and 15°C hysteresis-confirmed in the Absolute Maximum Ratings and Thermal Characteristics sections.
Is the A3977KEDTR pin-compatible with other Allegro stepper drivers like the A3982 or A3983?
No, the A3977KEDTR is not pin-compatible with the A3982 or A3983. While all three are Allegro microstepping drivers, they differ in pin count (A3982/A3983 use 56-pin QFP), pin functions (e.g., A3983 includes nFAULT and nSLEEP with different logic polarity), and internal architecture (A3983 adds indexer mode and different decay control). The A3977KEDTR's 28-pin TSSOP-LP layout and terminal list-including dedicated HOME, PFD, and RC1/RC2 pins-is unique to this family. Substitution would require PCB redesign and firmware adaptation.
A3977KEDTR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 44-LCC (J-Lead)
- 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:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 44-PLCC (16.59x16.59)
A3977KEDTR FAQ
1.How can I place an order for A3977KEDTR through Aetrix?
Please submit a Request for Quotation (RFQ) for A3977KEDTR 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 A3977KEDTR reliable?
The price and inventory of A3977KEDTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3977KEDTR is usually 5 days.
3.What payment methods are accepted for A3977KEDTR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3977KEDTR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3977KEDTR?
A3977KEDTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3977KEDTR 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 A3977KEDTR?
For technical support, including A3977KEDTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3977KEDTR requirements.
6.How does Aetrix verify that A3977KEDTR is sourced from the original manufacturer or authorized distributors?
All A3977KEDTR 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 A3977KEDTR meets industry standards.
7.What is the process for return or replacement of A3977KEDTR?
All A3977KEDTR units undergo pre-shipment inspection (PSI). If there is an issue with A3977KEDTR, 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 A3977KEDTR part is unused and in its original packaging.
Return procedure for A3977KEDTR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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