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Allegro MicroSystems A3958SB-T
- Part No.:
- A3958SB-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 24-PowerDIP (0.300", 7.62mm)
- Datasheet:
-
A3958SB-T.pdf
- Description:
- IC MOTOR DRIVER 4.5V-5.5V 24DIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,865
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Product details
Overview
A3958SB-T from Allegro MicroSystems is a DMOS full-bridge PWM motor driver IC designed for bidirectional DC motor control with ±2 A continuous output current and 50 V load supply capability. It implements fixed-off-time current regulation via serial-programmable decay modes (slow, fast, mixed), synchronous rectification, and integrated thermal/UVLO protection. Used in precision motion control systems requiring programmable current decay and low-power dissipation.
For engineers reviewing the A3958SB-T datasheet, A3958SB-T pinout, A3958SB-T application, or A3958SB-T equivalent, key selection criteria include its 24-pin DIP package with exposed thermal tabs, serial 3-wire interface (CLOCK/DATA/STROBE), internal charge pump for high-side drive, and configurable braking via slow-decay + synchronous rectification mode.
Technical Context
The A3958SB-T integrates a 24-pin DIP-packaged DMOS H-bridge with independent source/sink drivers (rDS(on) = 270 mΩ typ), internal 4–6 MHz oscillator, and programmable blank time (4/fOSC to 24/fOSC) to suppress current-sense comparator false triggering during switching transients. Its serial interface configures 19-bit control register including off-time (D2–D6), fast-decay time (D7–D10), and decay-mode selection (D13/D17).
Current regulation uses external sense resistor RS and reference voltage VREF, with trip threshold set to VREF/5RS or VREF/10RS depending on RANGE logic level and D16 bit. Synchronous rectification operates in active/passive modes (D11/D12) to replace body diode conduction, reducing power loss during decay phases without requiring external Schottky diodes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | ±2 A continuous - supports medium-power DC motors without external heatsinking under typical PCB thermal conditions. |
| Load Supply Voltage | 20–50 V - compatible with 24 V and 48 V industrial motor buses. |
| rDS(on) | 270 mΩ typical - limits conduction loss to ≤1.08 W per channel at 2 A, enabling efficient thermal design. |
| Serial Interface | 3-wire (CLOCK/DATA/STROBE) - enables real-time configuration of decay mode, blank time, and off-time without MCU GPIO overhead. |
| Thermal Shutdown | 165°C with 15°C hysteresis - protects against sustained overload while allowing brief peak-current operation. |
| Synchronous Rectification | Configurable active/passive mode - replaces lossy body diodes with low-RDS(on) FET paths during current recirculation. |
| UVLO Threshold | 4.2 V (typ) with 0.1 V hysteresis - prevents erratic operation during brown-out or incomplete power-up sequences. |
Pinout & Package
Package: 24-pin plastic DIP with exposed thermal tabs (suffix 'B'); lead-free, 100% matte tin leadframe; power pins at ground potential, no electrical isolation required.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CP | Charge pump reservoir capacitor connection | Connects 0.22 μF ceramic cap to VBB; supplies gate voltage >VBB for high-side DMOS drive. |
| CP1 & CP2 | Charge pump flying capacitor terminals | Connect 0.22 μF ceramic cap between CP1–CP2; generates boosted gate drive voltage. |
| PHASE | Direction control input | Combined with D15 bit to determine forward/reverse motor rotation (OUTA/OUTB polarity). |
| ENABLE | Bridge enable/chop control | When programmed via D14, enables external PWM chopping in fast or slow decay mode. |
| SENSE | Current sense resistor return | Connects to low-side of external RS; feeds current-sense comparator for ITRIP regulation. |
| OUTA / OUTB | H-bridge output terminals | Drive motor terminals directly; each rated for ±2 A continuous, 50 V max, with 270 mΩ rDS(on). |
| VBB | Motor supply input | Accepts 20–50 V DC; decoupled with ≥47 μF electrolytic capacitor placed near pin. |
| VREG | Internal regulator output | Supplies sink-side DMOS gates; requires 0.22 μF decoupling capacitor to ground. |
Key Features
| Feature | Design Value |
|---|---|
| Programmable current-decay modes | Slow, fast, or mixed decay selected via serial bits D13/D17 - enables optimal torque ripple/noise trade-off per motor type. |
| Synchronous rectification control | Active/passive mode selectable via D11/D12 - eliminates body-diode conduction loss, reducing heat by up to 40% vs. passive decay. |
| Fixed-off-time PWM timer | Off-time adjustable from 1.75 μs to 63.75 μs (4 MHz OSC) via D2–D6 - sets current regulation frequency independently of MCU clock. |
| Integrated protection circuitry | Thermal shutdown (165°C), UVLO (4.2 V), and crossover-current protection - eliminates need for external fault monitoring circuitry. |
| Low-noise current sensing | Blank time programmable (4/fOSC–24/fOSC) and dedicated SENSE ground path - rejects switching transients, ensuring accurate ITRIP regulation. |
Applications
| Industrial CNC Axis Control | Automated Guided Vehicle (AGV) Drive |
|---|---|
Use Scenario: Precise speed and direction control of stepper-less DC servo axes in milling and lathe machines. IC Role / Device Role / Timing Role: Full-bridge PWM driver regulating motor current via serial-configured mixed-decay mode to minimize torque ripple at low speeds. Use Value: Enables smooth microstepping-equivalent motion without encoder feedback, leveraging programmable off-time and blank time for stable current regulation. | Use Scenario: Bidirectional traction motor control in battery-powered AGVs navigating warehouse environments. IC Role / Device Role / Timing Role: Motor driver implementing regenerative braking via slow-decay + synchronous rectification mode during ENABLE chopping. Use Value: Recirculates braking energy through low-rDS(on) FETs instead of dissipating it in body diodes, extending battery runtime by ~12% in stop-start cycles. |
| Medical Infusion Pump Actuation | Robotic Joint Actuator |
Use Scenario: Low-noise, low-vibration motor control for syringe-driven infusion pumps requiring silent operation in patient rooms. IC Role / Device Role / Timing Role: PWM current controller using fast-decay mode during acceleration and slow-decay during steady-state flow to reduce audible coil whine. Use Value: Serial-programmable decay timing allows tuning to motor inductance/resonance, eliminating 12–18 kHz acoustic noise common in fixed-decay drivers. | Use Scenario: Compact joint motor driver in collaborative robots where thermal density and EMI must be minimized. IC Role / Device Role / Timing Role: H-bridge driver with synchronous rectification enabled and active-mode zero-current detection to prevent reverse current during rapid direction reversal. Use Value: Prevents uncontrolled back-EMF-induced current reversal during dynamic maneuvers, improving position accuracy and reducing mechanical stress on gear trains. |
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 current rating; no serial interface; fixed decay modes only; 5 V logic supply only. | Suitable for low-power robotics but lacks programmable off-time and thermal performance for 2 A industrial loads. | Select A3958SB-T when precise current regulation, thermal robustness, or serial configurability is required. |
| DRV8876N | Higher 3.6 A rating; integrated current sense amplifier; SPI interface; no exposed thermal tab in HTSSOP package. | Better for high-current, space-constrained designs but requires more complex layout and lacks DIP thermal management simplicity. | Select A3958SB-T for legacy-compatible DIP footprint, proven thermal performance on single-layer PCBs, and simplified current-sense implementation. |
Compared with TB6612FNG and DRV8876N, the A3958SB-T offers superior thermal resistance (40°C/W vs. >60°C/W for surface-mount alternatives) and deterministic current regulation via serial-programmable blank time and off-time-critical for noise-sensitive medical and precision industrial motion systems.
Availability
A3958SB-T is available at Aetrix Electronics and suitable for industrial CNC axis control, automated guided vehicle (AGV) drive, medical infusion pump actuation, and robotic joint actuator applications requiring stable component supply and long-term obsolescence planning.
Supply support for A3958SB-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 sensors and power ICs, headquartered in Worcester, Massachusetts.
The A3958SB-T belongs to Allegro's DMOS full-bridge motor driver product line, engineered specifically for robust, programmable PWM control of brushed DC motors in industrial automation, medical equipment, and mobility systems.
FAQ
What is the maximum continuous output current supported by the A3958SB-T?
The A3958SB-T supports ±2 A continuous output current under specified thermal conditions (TA = 25°C, single-layer PCB with 1 in² exposed copper). This rating assumes proper heatsinking via the exposed thermal tabs on the 24-pin DIP package. At higher ambient temperatures or reduced copper area, derating applies per the RθJA = 40°C/W thermal resistance specification. The A3958SB-T maintains this current capability across its full 20–50 V load supply range.
How does the serial interface of the A3958SB-T configure current decay modes?
The A3958SB-T uses a 3-wire serial interface (CLOCK/DATA/STROBE) to program its 19-bit control register. Decay mode is configured via bit D13 (external PWM decay) and bit D17 (internal PWM mode): D13 selects fast/slow decay during ENABLE chopping; D17 selects slow/mixed decay during internal PWM operation. Mixed decay combines fast decay for initial current reduction followed by slow decay for controlled recirculation-programmed independently via D2–D6 (off-time) and D7–D10 (fast-decay time).
Can the A3958SB-T implement regenerative braking, and how is it configured?
Yes, the A3958SB-T supports regenerative braking via slow-decay mode combined with synchronous rectification. To configure: set D13 = 1 (slow decay for external PWM), enable synchronous rectification (D12 = 1), and assert ENABLE chopping. During braking, current recirculates through the low-rDS(on) FETs instead of lossy body diodes, recovering energy into the VBB rail. Note that braking current is not regulated by the internal current-sense loop-designers must ensure VBB capacitance and system impedance limit peak brake current to within ±2 A and 50 V absolute maximum ratings.
What thermal protection features are integrated into the A3958SB-T?
The A3958SB-T integrates thermal shutdown with hysteresis: it disables all outputs when junction temperature reaches 165°C (typical), then re-enables them after cooling by 15°C (hysteresis). This protection operates independently of external circuitry and responds to die temperature-not case or ambient temperature. The 24-pin DIP package's exposed thermal tabs and low RθJT = 6°C/W enable effective heat transfer to the PCB, making the A3958SB-T suitable for applications where forced air cooling is unavailable.
Is the A3958SB-T pin-compatible with other variants in the A3958 family?
The A3958SB-T shares identical pinout and functionality with the A3958SLBTR-T SOIC variant-both use the same 24-pin mapping and serial register structure. However, the DIP ('B') and SOICW ('LB') packages differ mechanically: the DIP has exposed thermal tabs and substrate grounds (pins 6, 7, 18, 19), while the SOICW fuses pins 6 and 7, and 18 and 19 internally. Electrical behavior is identical, but thermal performance differs significantly (RθJA = 40°C/W vs. 77°C/W), requiring separate layout validation for each package.
A3958SB-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 24-PowerDIP (0.300", 7.62mm)
- 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:
- Serial
- Technology:
- DMOS
- Step Resolution:
- -
- Applications:
- General Purpose
- Current - Output:
- 2A
- Voltage - Supply:
- 4.5V ~ 5.5V
- Voltage - Load:
- 20V ~ 50V
- Operating Temperature:
- -20°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 24-DIP
A3958SB-T FAQ
1.How can I place an order for A3958SB-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A3958SB-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 A3958SB-T reliable?
The price and inventory of A3958SB-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3958SB-T is usually 5 days.
3.What payment methods are accepted for A3958SB-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3958SB-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3958SB-T?
A3958SB-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3958SB-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 A3958SB-T?
For technical support, including A3958SB-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3958SB-T requirements.
6.How does Aetrix verify that A3958SB-T is sourced from the original manufacturer or authorized distributors?
All A3958SB-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 A3958SB-T meets industry standards.
7.What is the process for return or replacement of A3958SB-T?
All A3958SB-T units undergo pre-shipment inspection (PSI). If there is an issue with A3958SB-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 A3958SB-T part is unused and in its original packaging.
Return procedure for A3958SB-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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