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Allegro MicroSystems A3959SLB-T
- Part No.:
- A3959SLB-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 24-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
A3959SLB-T.pdf
- Description:
- IC MOTOR DRIVER 4.5V-5.5V 24SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,152
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Product details
Overview
A3959SLB-T from Allegro MicroSystems is a DMOS full-bridge PWM motor driver IC designed for bidirectional DC motor control with ±3 A output current and 50 V load supply capability. It implements internal fixed off-time current regulation, synchronous rectification, and selectable slow/fast/mixed decay modes via PFD1/PFD2 inputs. Used in industrial actuators, precision lab equipment, and automated valve control where compact SOIC packaging and thermal robustness are required.
For engineers reviewing the A3959SLB-T datasheet, A3959SLB-T pinout, A3959SLB-T application, or A3959SLB-T equivalent, key selection criteria include its 24-pin SOIC-LB package with fused pins, integrated charge pump and VREG regulator, thermal shutdown at 165°C, and external PWM compatibility via PHASE/ENABLE logic.
Technical Context
The A3959SLB-T integrates a 4 MHz internal oscillator (adjustable via ROSC resistor), fixed 24 µs off-time PWM timing, and zero-current detection for synchronous rectification. Its dual DMOS bridge outputs feature matched rDS(on) of 270 mΩ (typ.) and crossover-current protection to prevent shoot-through.
Current regulation uses VREF/10RS trip threshold with blanking timer (6/fOSC or 12/fOSC) to suppress sense comparator false triggering during switching transients. Thermal shutdown (165°C, 15°C hysteresis) and UVLO (4.2 V enable threshold) operate independently of logic supply state.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | ±3 A continuous - supports medium-power DC motors without external heatsinking on 2-layer PCB |
| Load Supply Voltage | 9.5–50 V - compatible with 12 V, 24 V, and 48 V industrial power rails |
| rDS(on) | 270 mΩ typical - reduces conduction loss to ≤2.4 W per channel at 3 A |
| Thermal Shutdown | 165°C junction temperature - protects against sustained overload or poor heatsinking |
| Fixed Off-Time | 24 µs (96 oscillator cycles at 4 MHz) - sets minimum current decay duration for stable regulation |
| VREF Range | 0–VDD - enables adjustable current limit from 0.1 A to 3 A using external RS resistor |
| UVLO Threshold | 4.2 V (±0.25 V) - prevents erratic operation during brown-out or startup |
Pinout & Package
Package: 24-pin SOICW (suffix 'LB') with four internally fused ground pins (pins 6, 7, 18, 19) and exposed copper pad under body for thermal conduction. Lead-free, 100% matte tin leadframes.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4 | CP, CP1, CP2, PHASE | Charge pump reservoir/capacitor terminals and direction control input - CP must be decoupled to VBB; PHASE sets OUTA/OUTB polarity |
| 5, 6, 7, 8 | ROSC, GROUND, GROUND, VDD | Oscillator timing resistor input; dual ground returns for analog/digital domains; 4.5–5.5 V logic supply |
| 9, 10, 11, 12 | ENABLE, PFD2, BLANK, PFD1 | External PWM enable; fast-decay mode select bits; blanking duration control; second fast-decay bit |
| 13, 14, 15, 16 | REF, EXT MODE, NO CONNECT, OUTA | Analog current reference input; external PWM mode selector; unused pin; high-side DMOS output to motor |
| 17, 18, 19, 20 | SENSE, GROUND, GROUND, VBB | Current-sense amplifier input (0.5 V max); fused ground returns; 9.5–50 V motor supply input |
| 21, 22, 23, 24 | OUTB, NO CONNECT, SLEEP, VREG | Low-side DMOS output; unused pin; low-power sleep control; internal 5 V regulator output requiring 0.22 µF decoupling |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous Rectification | Enables low-loss current recirculation by turning on complementary DMOS outputs instead of relying on lossy body diodes |
| Mixed Decay Mode | Combines 15% fast decay + 85% slow decay (PFD1=1, PFD2=0) to balance torque ripple and heat generation |
| Internal Charge Pump | Generates >VBB gate drive for high-side DMOS without external bootstrap circuitry - simplifies layout and improves reliability |
| Zero-Current Detection | Disables all outputs when load current crosses zero - prevents reverse current flow and improves braking control |
| Thermal Protection Hysteresis | 15°C gap between shutdown (165°C) and recovery (150°C) prevents oscillation during thermal stress |
Applications
| Industrial Actuators | Precision Lab Equipment |
|---|---|
|
Use Scenario: Linear motion control in programmable solenoid valves and pneumatic positioners requiring precise force and speed modulation. IC Role / Device Role / Timing Role: Full-bridge driver executing bidirectional PWM current control with real-time decay-mode selection for smooth acceleration/deceleration. Use Value: ±3 A output and 50 V rating support high-torque 24 V actuators; synchronous rectification cuts power dissipation by ≥40% vs. diode-based decay. |
Use Scenario: Motorized sample stage positioning in automated microscopes and spectrometers demanding low vibration and repeatable microstep accuracy. IC Role / Device Role / Timing Role: Current-regulated H-bridge delivering stable 0.5–3 A winding current with <5 mV offset error in sense path. Use Value: Fixed 24 µs off-time and 10× reference divider enable sub-100 mA current resolution; thermal shutdown ensures safe operation during calibration stalls. |
| Automated Valve Control | Embedded Motion Subsystems |
|
Use Scenario: Proportional control of HVAC dampers and process fluid valves in building management systems operating across wide ambient temperatures. IC Role / Device Role / Timing Role: Robust motor driver with UVLO, thermal shutdown, and fault-safe sleep mode for unattended long-duration operation. Use Value: –20°C to +85°C operating range and 4.2 V UVLO prevent malfunction during cold starts; fused ground pins reduce EMI susceptibility. |
Use Scenario: Compact motion modules in portable diagnostic devices and handheld test instruments where board space and thermal headroom are constrained. IC Role / Device Role / Timing Role: Integrated full-bridge solution eliminating discrete MOSFETs, gate drivers, and external current-sense amplifiers. Use Value: 24-pin SOIC-LB package occupies <120 mm² footprint; internal VREG and charge pump remove 3 external components versus discrete designs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar full-bridge PWM motor driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TB6612FNG | Lower 1.2 A continuous output, no internal charge pump - requires external bootstrap or high-side driver | Better suited for low-power battery-operated devices; lacks mixed-decay mode and zero-current detection | Select when cost sensitivity outweighs current capability and thermal robustness requirements |
| DRV8876N | Higher 3.6 A rating, integrated current sense amplifier, but no synchronous rectification - relies on external Schottky diodes | Optimized for automotive-grade vibration resistance and extended temperature range (–40°C to +125°C) | Prefer for harsh-environment applications where A3959SLB-T's 85°C ambient limit is insufficient |
Compared with TB6612FNG and DRV8876N, the A3959SLB-T delivers superior thermal efficiency via synchronous rectification and finer current regulation granularity through its 10× reference divider, making it optimal for precision industrial motion where power loss and torque ripple must be minimized.
Availability
A3959SLB-T is available at Aetrix Electronics and suitable for industrial actuators, precision lab equipment, and automated valve control requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for A3959SLB-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 IC solutions, specializing in motion control, current sensing, and motor driver technologies since 1985.
The A3959 product line targets industrial and instrumentation applications requiring robust, integrated full-bridge motor drivers with precise current regulation, thermal resilience, and minimal external component count.
FAQ
What is the maximum continuous output current rating for the A3959SLB-T?
The A3959SLB-T is rated for ±3 A continuous output current under specified thermal conditions - including use of a 2-layer PCB with 1 in² copper area per side and proper decoupling. Peak current capability reaches ±6 A for pulses under 3 µs. Exceeding ±3 A continuously risks exceeding the 150°C maximum junction temperature unless enhanced heatsinking is applied.
Does the A3959SLB-T require external components for high-side gate drive?
No, the A3959SLB-T integrates a charge pump circuit that generates a gate voltage higher than VBB to drive the high-side DMOS outputs. External components required are only two 0.22 µF ceramic capacitors: one between CP1 and CP2 for pumping, and another between CP and VBB as a reservoir. No bootstrap diodes or external high-voltage supplies are needed.
How does the A3959SLB-T implement current regulation without an external controller?
The A3959SLB-T uses an internal fixed off-time PWM controller that compares the voltage across an external sense resistor (RS) to a fraction of VREF (VREF/10). When the sensed voltage reaches this threshold, the source driver turns off for a fixed 24 µs period. This autonomous cycle enables precise, self-contained current limiting without MCU intervention or external timing circuitry.
Can the A3959SLB-T be used in brake mode, and what limitations apply?
Yes, the A3959SLB-T supports braking by configuring EXT MODE for slow decay and applying a chopped ENABLE signal. However, braking current flows outside the sense resistor path, so the internal current limiter is inactive. Brake current is limited only by motor BEMF and winding resistance (VBEMF/RL), requiring careful design to avoid exceeding the ±6 A peak rating or 150°C junction limit.
What thermal performance can be expected from the A3959SLB-T in its SOIC-LB package?
In a standard 2-layer PCB layout with 1 in² of 2-oz copper per side, the A3959SLB-T achieves a junction-to-ambient thermal resistance (RθJA) of 51°C/W, allowing up to 2.5 W of package power dissipation. With adequate copper area and thermal vias, junction temperature rise remains within safe limits at full ±3 A load, enabling reliable operation without forced air cooling.
A3959SLB-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 24-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Motor Type - Stepper:
- -
- Motor Type - AC, DC:
- Brushed DC
- Function:
- Driver - Fully Integrated, Control and Power Stage
- Output Configuration:
- Half Bridge (2)
- Interface:
- Parallel
- Technology:
- DMOS
- Step Resolution:
- -
- Applications:
- General Purpose
- Current - Output:
- 3A
- Voltage - Supply:
- 4.5V ~ 5.5V
- Voltage - Load:
- 9.5V ~ 50V
- Operating Temperature:
- -20°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-SOIC
A3959SLB-T FAQ
1.How can I place an order for A3959SLB-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A3959SLB-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 A3959SLB-T reliable?
The price and inventory of A3959SLB-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3959SLB-T is usually 5 days.
3.What payment methods are accepted for A3959SLB-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3959SLB-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3959SLB-T?
A3959SLB-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3959SLB-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 A3959SLB-T?
For technical support, including A3959SLB-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3959SLB-T requirements.
6.How does Aetrix verify that A3959SLB-T is sourced from the original manufacturer or authorized distributors?
All A3959SLB-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 A3959SLB-T meets industry standards.
7.What is the process for return or replacement of A3959SLB-T?
All A3959SLB-T units undergo pre-shipment inspection (PSI). If there is an issue with A3959SLB-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 A3959SLB-T part is unused and in its original packaging.
Return procedure for A3959SLB-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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