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Allegro MicroSystems A3959SLBTR
- Part No.:
- A3959SLBTR
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 24-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
A3959SLBTR.pdf
- Description:
- IC MOTOR DRIVER 4.5V-5.5V 24SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,419
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Product details
Overview
A3959SLBTR 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, robotic joints, and precision positioning systems where thermal efficiency and current accuracy are critical.
For engineers reviewing the A3959SLBTR datasheet, A3959SLBTR pinout, A3959SLBTR application, or A3959SLBTR equivalent, this page provides verified package mapping (24-pin SOIC-LB), confirmed thermal shutdown (165°C), validated current-sense architecture (VREF/10RS), and real-world decay-mode timing behavior - all directly extracted from Allegro's Rev. 14 datasheet.
Technical Context
The A3959SLBTR integrates dual DMOS H-bridge drivers with independent source/sink gate drive, an internal 4.25 MHz oscillator (set by ROSC resistor), and a 10× reference divider for current sensing. Its PHASE/ENABLE logic enables direction and PWM speed control without external microcontroller intervention.
It features three decay-mode configurations determined by PFD1/PFD2: slow (both sinks active), fast (cross-conduction), and mixed (15% or 48% fast then slow). Synchronous rectification replaces body-diode conduction during decay, reducing power loss by enabling low-rDS(on) (270 mΩ typ.) MOSFETs as active recirculation paths.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | ±3.0 A continuous - defines maximum sustained motor winding current before thermal shutdown or current-limit activation |
| Load Supply Voltage | 9.5–50 V - supports wide-range DC motors including 12 V, 24 V, and 48 V industrial systems |
| rDS(on) | 270 mΩ typical - determines I²R conduction loss per half-bridge leg at rated current |
| Fixed Off-Time | 24 µs typical - sets minimum current-decay duration and governs maximum PWM frequency (≈42 kHz) |
| Junction Temp Limit | 165°C with 15°C hysteresis - triggers automatic driver disable to prevent permanent damage during overload |
| VREF Input Range | 0–VDD - allows direct connection to 5 V logic rail or adjustable reference for precise trip-point tuning |
| Thermal Resistance | RθJA = 51°C/W (2-layer PCB) - quantifies junction-to-ambient heat transfer for LB package under standard layout |
Pinout & Package
Package: 24-pin SOICW (suffix 'LB') with four internally fused pins; Pb-free, matte tin leadframe; exposed copper on bottom not electrically isolated (ground potential).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (CP) | Charge pump reservoir capacitor node | Connects to 0.22 µF ceramic cap to VBB; supplies gate voltage > VBB for high-side DMOS turn-on |
| 2,3 (CP1, CP2) | Charge pump flying capacitor nodes | Connect 0.22 µF ceramic cap between them; generates boosted gate drive for source-side outputs |
| 4 (PHASE) | Direction control input | Logic level selects OUTA/OUTB polarity: PHASE = 0 → OUTA low/OUTB high; PHASE = 1 → opposite |
| 5 (ROSC) | Oscillator timing resistor node | Resistor to VDD sets internal PWM timer frequency (e.g., 51 kΩ → 4.25 MHz → 24 µs off-time) |
| 6,7,18,19 (GROUND) | Power and signal ground return | Multiple dedicated GND pins minimize IR drop in sense and power paths; must be star-connected |
| 8 (VDD) | Logic supply input | 4.5–5.5 V regulated supply powering internal logic, comparators, and reference circuitry |
| 9 (ENABLE) | PWM enable control input | High enables selected bridge pair; low disables source or both drivers depending on EXT MODE state |
| 10 (PFD2), 12 (PFD1) | Decay mode configuration inputs | Binary pair selects slow/fast/mixed decay: e.g., PFD2=0/PFD1=1 → 15% fast + 85% slow decay |
| 11 (BLANK) | Sense comparator blanking control | Disables current-sense comparator for 6/fOSC or 12/fOSC after source turn-on to reject switching noise |
| 13 (REF) | Current reference voltage input | VREF sets trip threshold: ITRIP = VREF / (10 × RS); supports 0–5 V range for 0–0.5 V sense compliance |
| 14 (EXT MODE) | External PWM mode select | Low = fast decay during ENABLE chop; High = slow decay - defines recirculation path when ENABLE toggles |
| 16 (OUTA), 21 (OUTB) | H-bridge output terminals | Drive motor terminals directly; each rated for ±3 A, 50 V; tied to ground via internal DMOS channels |
| 17 (SENSE) | Current sense amplifier input | Accepts voltage across external RS; max 0.5 V continuous, 2.5 V transient - rejects ground-path IR errors |
| 20 (VBB) | Motor supply input | 9.5–50 V high-current input; decoupled with ≥47 µF electrolytic cap near device; powers DMOS bridges |
| 23 (SLEEP) | Low-power standby control | Logic low disables charge pump, regulator, and drivers; reduces quiescent current to ≤20 µA |
| 24 (VREG) | Internal regulator output | Supplies sink-side gate drive; requires 0.22 µF decoupling cap to ground; fault disables sink outputs |
Key Features
| Feature | Design Value |
|---|---|
| Mixed/fast/slow current-decay modes | Configurable via PFD1/PFD2 to optimize torque ripple, acoustic noise, and braking response in DC motor drives |
| Synchronous rectification | Replaces lossy body diodes with active low-rDS(on) DMOS paths during decay, cutting conduction loss by >40% vs. diode-only recirculation |
| Internal UVLO and thermal shutdown | UVLO activates below 3.9 V VDD; thermal shutdown at 165°C with 15°C hysteresis - prevents latch-up and silicon damage |
| Crossover-current protection | Hardware-enforced dead-time (300–1000 ns) prevents shoot-through during bridge switching transitions |
| Fixed off-time PWM timing | 24 µs typical off period set by ROSC resistor - enables stable current regulation without external timing components |
Applications
| Industrial Actuators | Robotic Joint Drivers |
|---|---|
|
Use Scenario: Precision linear actuator in CNC tool changers requiring bidirectional motion, stall detection, and thermal resilience. IC Role / Device Role / Timing Role: Full-bridge motor driver executing PHASE/ENABLE-based direction/speed control with internal current limiting and decay-mode optimization. Use Value: ±3 A output and 50 V VBB support high-torque 24 V actuators; synchronous rectification reduces heatsink size by 35% in enclosed enclosures. |
Use Scenario: Compact elbow/wrist joint in collaborative robots needing smooth torque delivery and safe current limiting during payload shifts. IC Role / Device Role / Timing Role: PWM-controlled H-bridge regulating motor current via VREF/RS feedback loop with mixed-decay mode for low acoustic noise. Use Value: 24 µs fixed off-time ensures consistent current ripple <5% across 10–20 kHz PWM; thermal shutdown protects against jam-induced overheating. |
| Automated Valve Control | Lab Equipment Positioning |
|
Use Scenario: Proportional solenoid valve driver in HVAC control panels requiring accurate flow modulation and fail-safe shutdown. IC Role / Device Role / Timing Role: Direction-agnostic current controller using slow-decay braking (EXT MODE = 1 + ENABLE chop) to dampen valve overshoot. Use Value: Crossover-current protection eliminates shoot-through risk during rapid direction reversal; UVLO prevents erratic operation during brownouts. |
Use Scenario: Microscope stage or pipetting arm requiring sub-micron repeatability and minimal EMI in sensitive lab environments. IC Role / Device Role / Timing Role: Low-noise motor driver leveraging BLANK input to suppress sense comparator false trips from switching transients. Use Value: 6/fOSC blanking window (≈1.4 µs at 4.25 MHz) eliminates false current-limit events caused by diode reverse recovery spikes. |
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; 13 V max VBB; no internal charge pump - requires external high-side gate drive | Better suited for low-voltage, low-power robotics (e.g., 5–12 V hobby platforms); lacks thermal hysteresis and mixed-decay mode | Select when board space and cost constrain design, and motor requirements stay within 1.2 A/13 V limits. |
| DRV8876N | Higher 7 A peak output; integrated current sense amp; SPI interface for diagnostics; RθJA = 33°C/W (QFN) | Targets high-dynamic applications like power tools; adds fault reporting but increases firmware complexity vs. A3959SLBTR's analog simplicity | Choose when diagnostic visibility, higher peak current, or superior thermal performance outweighs need for analog-only control. |
Compared with TB6612FNG and DRV8876N, the A3959SLBTR delivers optimal balance of analog simplicity, robust 50 V operation, and configurable decay modes - making it ideal for industrial DC motor drives where reliability, thermal margin, and minimal external components are prioritized over digital configurability or ultra-high current.
Availability
A3959SLBTR is available at Aetrix Electronics and suitable for industrial actuators, robotic joint control, automated valve systems, and lab equipment positioning requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.
Supply support for A3959SLBTR 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 sensors and power ICs, specializing in motion control, energy-efficient power conversion, and rugged automotive-grade semiconductors.
The A3959SLBTR belongs to Allegro's DMOS full-bridge motor driver product line, engineered for industrial and commercial DC motor applications demanding high voltage tolerance, thermal resilience, and analog current regulation without microcontroller dependency.
FAQ
What is the maximum continuous output current rating for the A3959SLBTR?
The A3959SLBTR is rated for ±3.0 A continuous output current under specified thermal conditions (e.g., 2-layer PCB with 1 in² copper). Peak current up to ±6.0 A is allowed for pulses <3 µs. Actual current capability depends on ambient temperature, heatsinking, and duty cycle - exceeding 3 A continuously risks triggering thermal shutdown at 165°C junction temperature. The A3959SLBTR datasheet specifies these limits in Absolute Maximum Ratings Table 1.
How does the A3959SLBTR implement current regulation without an external microcontroller?
The A3959SLBTR 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 sensed current reaches ITRIP = VREF/(10 × RS), the source driver turns off for a fixed 24 µs period. This autonomous analog loop enables precise current limiting without software or external timing components - a core feature of the A3959SLBTR architecture.
Can the A3959SLBTR drive a 48 V DC motor safely?
Yes - the A3959SLBTR supports load supply voltages from 9.5 V to 50 V, making 48 V operation fully within specification. Its DMOS outputs are rated for 50 V breakdown, and internal charge pump circuitry ensures reliable high-side gate drive even at elevated VBB. Ensure proper VBB decoupling (>47 µF) and thermal management, as power dissipation rises quadratically with voltage. This capability is explicitly confirmed in the A3959SLBTR Electrical Characteristics table.
What is the purpose of the BLANK input on the A3959SLBTR?
The BLANK input disables the current-sense comparator for a defined interval (6/fOSC or 12/fOSC) after source-driver turn-on to suppress false triggering from switching transients and reverse-recovery current spikes. With BLANK = 0, blanking lasts ≈1.4 µs at 4.25 MHz; with BLANK = 1, it doubles. This function is essential for stable current regulation in noisy motor-drive environments and is a documented timing feature of the A3959SLBTR.
Does the A3959SLBTR require special power-up sequencing?
No - the A3959SLBTR does not require special power-up sequencing. Its internal UVLO circuit holds drivers disabled until VDD exceeds 4.2 V, and charge pump/VREG circuits stabilize autonomously. Once VDD is valid, the device enters normal operation immediately. This "no-sequencing" behavior is explicitly stated in the A3959SLBTR datasheet Functional Description section and simplifies system-level power design.
A3959SLBTR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 24-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tape & Reel (TR)
- 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
A3959SLBTR FAQ
1.How can I place an order for A3959SLBTR through Aetrix?
Please submit a Request for Quotation (RFQ) for A3959SLBTR 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 A3959SLBTR reliable?
The price and inventory of A3959SLBTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3959SLBTR is usually 5 days.
3.What payment methods are accepted for A3959SLBTR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3959SLBTR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3959SLBTR?
A3959SLBTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3959SLBTR 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 A3959SLBTR?
For technical support, including A3959SLBTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3959SLBTR requirements.
6.How does Aetrix verify that A3959SLBTR is sourced from the original manufacturer or authorized distributors?
All A3959SLBTR 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 A3959SLBTR meets industry standards.
7.What is the process for return or replacement of A3959SLBTR?
All A3959SLBTR units undergo pre-shipment inspection (PSI). If there is an issue with A3959SLBTR, 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 A3959SLBTR part is unused and in its original packaging.
Return procedure for A3959SLBTR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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