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Allegro MicroSystems A3964SLB-T
- Part No.:
- A3964SLB-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
A3964SLB-T.pdf
- Description:
- IC MOTOR DRIVER BIPOLAR 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,337
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Product details
Overview
A3964SLB-T from Allegro MicroSystems is a dual full-bridge PWM motor driver IC designed for bipolar stepper motor current control via fixed off-time PWM regulation. It delivers ±800 mA continuous output current per bridge, supports up to 30 V load supply voltage, and integrates precision 2.5 V reference, internal clamp diodes, thermal shutdown, and crossover-current protection - enabling compact, robust motion control in industrial automation and precision positioning systems.
For engineers reviewing the A3964SLB-T datasheet, A3964SLB-T pinout, A3964SLB-T application, or A3964SLB-T equivalent, key selection considerations include its 20-pin SOIC (LB) package with internally fused power pins, user-configurable RC-based off-time and blanking window, PHASE/ENABLE logic interface for bidirectional control, and ±800 mA current capability with integrated protection features.
Technical Context
The A3964SLB-T implements two independent full-bridge drivers with saturated sink/source outputs, each controlled by dedicated PHASE and ENABLE inputs. Its internal fixed off-time PWM current regulator compares sensed voltage across external RS resistors against a user-set VREF(IN), derived from the internal 2.5 V reference, to maintain peak current at ITRIP ≈ VREF(IN)/RS.
Off-time (tOFF = RT × CT) and comparator blanking are jointly set by the same external RC network - CT = 1000 pF and RT = 30 kΩ yields nominal tOFF = 30 μs and blanking sufficient to suppress false trips from switching transients and diode reverse recovery. Crossover-current protection enforces dead time during PHASE transitions, and UVLO disables outputs when VCC drops below 4.4 V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | ±800 mA continuous per bridge - defines maximum sustained torque delivery without external heatsinking under TA ≤ 85°C. |
| Load Supply Voltage | Up to 30 V (abs max 33 V) - supports common industrial motor rails including 24 V DC systems. |
| Reference Voltage | 2.50 V ±2% (2.45–2.55 V) - enables accurate, temperature-stable current limit setting via external resistor divider. |
| PWM Off-Time | 30 μs typical (27–33 μs) with RT = 30 kΩ, CT = 1000 pF - sets minimum current decay interval and regulates low-current ripple. |
| Thermal Shutdown | 165°C junction activation with 15°C hysteresis - protects against sustained overload or poor PCB thermal design. |
| Logic Supply Range | 4.75–5.25 V - requires stable 5 V rail; UVLO ensures safe disable below 4.4 V. |
| Sense Voltage Limit | 1.0 V max on SENSE1/SENSE2 - constrains RS selection to avoid comparator saturation (e.g., RS ≥ 1.25 Ω for ITRIP = 800 mA). |
Pinout & Package
Package: 20-pin SOICW (suffix LB), lead-free with 100% matte tin plating; pins 5, 6, 15, and 16 internally fused for enhanced thermal conduction to PCB ground plane.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 7, 8, 9, 10, 11, 12, 13, 14, 17, 18, 19, 20 | Ground | Common return for logic, sense, and load supplies - all 16 pins tied internally to GND for low-impedance thermal and electrical path. |
| 5, 6, 15, 16 | Fused Power Ground | Internally fused GND connections optimized for high-current sink paths - reduce IR drop and improve thermal dissipation from output drivers. |
| VBB (Pin 1) | Motor Supply Input | High-side power rail for both bridges (up to 30 V); must be decoupled with ≥47 μF electrolytic capacitor near the pin. |
| VCC (Pin 2) | Logic Supply Input | 5 V ±5% digital supply; powers internal logic, reference, and comparators - subject to UVLO at 4.4 V. |
| OUT1A/OUT1B (Pins 18/17) | Bridge 1 Output Terminals | Drive one winding of a bipolar stepper motor; configured as H-bridge with source/sink capability per PHASE/ENABLE state. |
| OUT2A/OUT2B (Pins 12/11) | Bridge 2 Output Terminals | Drive second stepper winding independently; identical electrical specs and protection to Bridge 1. |
| SENSE1/SENSE2 (Pins 19/13) | Current Sense Inputs | Differential inputs monitoring voltage across external RS resistors - limited to 1.0 V max to prevent comparator saturation. |
| PHASE1/PHASE2 (Pins 16/15) | Polarity Control Inputs | Set current direction per bridge (H/L = forward/reverse); PWM-capable for linear speed/torque control in brushed DC mode. |
| ENABLE1/ENABLE2 (Pins 9/8) | Bridge Enable Inputs | Active-low enables - high state disables both drivers; propagation delay <3.2 μs ensures fast response to fault conditions. |
| VREF(OUT) (Pin 14) | 2.5 V Reference Output | Stable, buffered 2.5 V source for setting VREF(IN); drives external RA/RB divider with 150–900 μA output current. |
| VREF(IN) (Pin 6) | Reference Input | User-defined trip point for current regulation; typically set to 0.5–2.0 V via resistor divider from VREF(OUT). |
| RC1/RC2 (Pins 4/3) | RC Timing Inputs | Accept external RT/CT networks - single CT sets both off-time and comparator blanking window per bridge. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 2.5 V precision reference | Enables stable, temperature-invariant current limit setting without external voltage sources or trimming. |
| Single RC network for off-time + blanking | Eliminates need for separate filter components on sense inputs - reduces BOM count and layout complexity. |
| Saturated sink drivers with clamp diodes | Minimizes conduction loss (VCE(SAT) ≤ 0.6 V @ 500 mA) and provides inherent flyback path without external diodes. |
| Internal thermal shutdown + UVLO | Automatically disables outputs at TJ = 165°C or VCC < 4.4 V - prevents latch-up and irreversible damage under fault conditions. |
| Internally fused ground pins (5,6,15,16) | Improves thermal resistance (RθJA = 61°C/W) and current-handling capacity for high-duty-cycle stepper hold applications. |
Applications
| Industrial Stepper Positioning | Lab Equipment Motion Control |
|---|---|
|
Use Scenario: Open-loop positioning of X-Y stages in CNC milling accessories and automated test fixtures requiring precise 1.8° step resolution. IC Role / Device Role / Timing Role: Dual full-bridge driver executing microstepping-compatible PHASE/ENABLE sequencing to control two-phase bipolar stepper windings. Use Value: ±800 mA per phase sustains holding torque at standstill; fixed off-time PWM maintains consistent current regulation across ambient temperatures from –20°C to 85°C. |
Use Scenario: Precision syringe pump actuation in analytical instruments where repeatable fluid displacement depends on smooth, jitter-free motor rotation. IC Role / Device Role / Timing Role: Current-regulated H-bridge delivering constant-phase current to minimize torque ripple and acoustic noise during low-speed operation. Use Value: RC-configurable blanking window (set by CT) suppresses false overcurrent trips during commutation, ensuring uninterrupted microstep execution. |
| Embedded Robotics Actuation | Medical Device Motor Control |
|
Use Scenario: Joint actuation in collaborative robotic arms using NEMA 17 stepper motors with 3 mH winding inductance and 2.5 Ω DCR. IC Role / Device Role / Timing Role: Dual-bridge driver implementing slow-decay PWM mode to sustain bidirectional torque while minimizing heat generation in space-constrained enclosures. Use Value: Internal thermal shutdown (165°C) and crossover-current protection prevent driver latch-up during rapid direction reversals or stall events. |
Use Scenario: Linear actuator control in portable infusion pumps requiring fail-safe current limiting and EMI-optimized switching behavior. IC Role / Device Role / Timing Role: Safety-critical motor driver enforcing strict 1.0 V sense voltage ceiling and UVLO lockout to prevent uncontrolled motor run-away. Use Value: 30 V absolute max VBB rating accommodates battery-backed 24 V systems; lead-free SOIC package meets RoHS and medical-grade soldering requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual full-bridge PWM motor driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TB6600HG | Higher 4.5 A peak current, external current-sense amplifier required; no integrated 2.5 V reference or blanking control. | Better suited for high-torque NEMA 23+ steppers; lacks single-RC timing simplicity and internal protection integration of A3964SLB-T. | Select when >1 A per phase is needed and board space allows discrete sensing and thermal management. |
| DRV8825 | Microstepping support up to 1/32, integrated indexer, lower 2.2 A max current; uses internal current DAC instead of analog VREF(IN) comparison. | Optimized for microstepping-centric applications like 3D printer axes; lacks the A3964SLB-T's analog programmability and high-voltage (30 V) capability. | Prefer for systems requiring onboard step/direction logic and fine position resolution, not raw analog current control. |
Compared with TB6600HG and DRV8825, the A3964SLB-T offers unique value in analog-configurable, thermally robust bipolar stepper control at 30 V with minimal external components - ideal for industrial motion subsystems where reliability, voltage headroom, and design simplicity outweigh microstepping granularity.
Availability
A3964SLB-T is available at Aetrix Electronics and suitable for industrial automation, lab instrumentation, embedded robotics, and medical device motion control requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.
Supply support for A3964SLB-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 sensing and power ICs, headquartered in Worcester, Massachusetts, with deep expertise in motion control, current sensing, and automotive-grade reliability.
The A3964SLB-T belongs to Allegro's legacy dual full-bridge motor driver product line, engineered specifically for cost-sensitive, thermally demanding bipolar stepper applications in industrial and instrumentation markets - emphasizing analog configurability, integrated protection, and SOICW thermal performance.
FAQ
What is the maximum continuous output current supported by the A3964SLB-T?
The A3964SLB-T supports ±800 mA continuous output current per bridge at TA ≤ 85°C with adequate PCB copper area. This rating assumes proper thermal management - exceeding this current without heatsinking risks activation of the 165°C thermal shutdown circuit. The A3964SLB-T does not support higher peak currents beyond its specified continuous rating.
How is current limiting configured on the A3964SLB-T?
Current limiting on the A3964SLB-T is set by the voltage applied to the VREF(IN) pin, which is typically derived from the internal 2.5 V reference using an external resistor divider (RA/RB). The peak current is calculated as ITRIP ≈ VREF(IN)/RS, where RS is the external sense resistor. The A3964SLB-T requires RS to be selected so that the sense voltage stays within 0–1.0 V.
Does the A3964SLB-T support microstepping?
The A3964SLB-T does not natively support microstepping. It is a dual full-bridge driver with PHASE/ENABLE logic inputs - microstepping must be implemented externally via controller-generated PWM waveforms on PHASE and ENABLE. Unlike dedicated microstepping drivers such as the DRV8825, the A3964SLB-T provides analog current regulation but no onboard indexer or fractional step logic.
What package type is used for the A3964SLB-T, and why are some pins fused?
The A3964SLB-T uses a 20-pin SOICW (suffix LB) package with internally fused pins 5, 6, 15, and 16. These fused ground pins provide lower thermal resistance (RθJA = 61°C/W) and improved current-handling capacity for high-duty-cycle applications. The fusion enhances thermal dissipation into the PCB ground plane without requiring external thermal pads or vias.
Can the A3964SLB-T operate from a 3.3 V logic supply?
No - the A3964SLB-T requires a logic supply (VCC) between 4.75 V and 5.25 V. Operation below 4.75 V triggers UVLO, disabling outputs when VCC falls below 4.4 V. A 3.3 V rail cannot power the A3964SLB-T directly; level-shifting or a dedicated 5 V LDO is required for compatibility with 3.3 V controllers.
A3964SLB-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- 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:
- Parallel
- Technology:
- Bipolar
- Step Resolution:
- -
- Applications:
- General Purpose
- Current - Output:
- 800mA
- Voltage - Supply:
- 4.75V ~ 5.25V
- Voltage - Load:
- 5V ~ 30V
- Operating Temperature:
- -20°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
A3964SLB-T FAQ
1.How can I place an order for A3964SLB-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A3964SLB-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 A3964SLB-T reliable?
The price and inventory of A3964SLB-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3964SLB-T is usually 5 days.
3.What payment methods are accepted for A3964SLB-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3964SLB-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3964SLB-T?
A3964SLB-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3964SLB-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 A3964SLB-T?
For technical support, including A3964SLB-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3964SLB-T requirements.
6.How does Aetrix verify that A3964SLB-T is sourced from the original manufacturer or authorized distributors?
All A3964SLB-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 A3964SLB-T meets industry standards.
7.What is the process for return or replacement of A3964SLB-T?
All A3964SLB-T units undergo pre-shipment inspection (PSI). If there is an issue with A3964SLB-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 A3964SLB-T part is unused and in its original packaging.
Return procedure for A3964SLB-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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