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Allegro MicroSystems A3958SLB
- Part No.:
- A3958SLB
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 24-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
A3958SLB.pdf
- Description:
- IC MOTOR DRIVER 4.5V-5.5V 24SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,997
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Product details
Overview
A3958SLB 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 internal charge pump for high-side gate drive. Used in precision motion control systems requiring programmable current decay and low-power dissipation during PWM operation.
For engineers reviewing the A3958SLB datasheet, A3958SLB pinout, A3958SLB application, or A3958SLB equivalent, this page provides verified technical context on its serial interface configuration, thermal protection behavior, SOICW package constraints, and functional distinctions versus newer Allegro motor drivers.
Technical Context
The A3958SLB integrates a 3-wire serial interface (CLOCK/DATA/STROBE) to configure 20-bit control registers governing blank time, fixed off-time (5-bit, adjustable 1.75–63.75 μs at 4 MHz), fast-decay duration (4-bit), synchronous rectification mode (active/passive/disabled), and sleep enable. Its internal charge pump generates gate voltage >VBB for source-side DMOS drivers, while VREG supplies sink-side logic.
Current regulation uses external sense resistor (RS) and reference voltage (VREF), with trip threshold set by RANGE pin and D16 bit to divide VREF by 5 or 10. Thermal shutdown activates at 165°C with 15°C hysteresis; UVLO disables outputs below 3.9 V on VDD. The LB package has RθJA = 77°C/W on minimal copper, limiting continuous power dissipation to 1.6 W at TA = 25°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | ±2 A continuous - supports medium-power DC motors without external heatsinking under moderate duty cycles. |
| Load Supply Voltage | 20–50 V - compatible with 24 V and 48 V industrial motor rails; withstands transients up to 50 V. |
| rDS(on) | 270 mΩ typical - reduces conduction loss and self-heating during high-current PWM phases. |
| Thermal Shutdown | 165°C activation with 15°C hysteresis - protects against sustained overload but requires external thermal management in SOICW layout. |
| Serial Interface | 3-wire (CLOCK/DATA/STROBE), 20-bit register map - enables precise tuning of decay timing, blanking, and rectification without hardware changes. |
| Synchronous Rectification | Configurable active/passive/disabled via D11/D12 - cuts power dissipation by replacing body diode conduction with low-rDS(on) FET paths during decay. |
| Package | 24-pin SOICW (LB suffix), internally fused pins - surface-mount compatible with standard reflow profiles; exposed thermal pad not present. |
Pinout & Package
Package: 24-pin SOICW (suffix 'LB'), lead-free with 100% matte tin leadframe. Power pins (VBB, OUTA, OUTB, GROUND) are at ground potential and require no electrical isolation. Thermal resistance: RθJA = 77°C/W (minimal copper), RθJT = 6°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (CP) | Charge pump reservoir capacitor connection | Connects 0.22 μF ceramic cap to VBB; failure causes high-side driver disable due to insufficient gate voltage. |
| 2,3 (CP1, CP2) | Charge pump flying capacitor terminals | Requires 0.22 μF ceramic cap between them; critical for generating >VBB gate drive voltage for source-side DMOS. |
| 4 (PHASE) | Direction control input | Combined with D15 bit to determine forward/reverse motor state; logic-level compatible with 5 V microcontrollers. |
| 5 (OSC) | Oscillator input | Accepts 2.9–6.1 MHz square wave; sets base timing for PWM off-time, blank time, and decay intervals. |
| 6,7 (GROUND) | Power ground return | Dedicated low-impedance path for motor current return; must be routed separately from logic ground to avoid sensing error. |
| 8 (VDD) | Logic supply input | 4.5–5.5 V regulated supply; UVLO triggers below 3.9 V, resetting serial register to all zeros. |
| 9 (ENABLE) | External PWM enable input | Combined with D14 bit to select chopped (PWM) or latched (ON/OFF) bridge operation; supports external speed control. |
| 10 (DATA) | Serial data input | Latched on rising CLOCK edge; must meet 15 ns setup/10 ns hold timing relative to CLOCK and STROBE. |
| 11 (CLOCK) | Serial clock input | Rising edge clocks DATA bits into 20-bit shift register; minimum pulse width 50 ns high/low. |
| 12 (STROBE) | Serial write strobe | Rising edge commits 20-bit register contents; must be held high except during write cycles. |
| 13 (REF) | Current reference input | 0–2.6 V analog input; combined with RS and RANGE/D16 to set ITRIP = VREF/(5×RS) or VREF/(10×RS). |
| 14 (MODE) | PWM decay mode selection | Combined with D17 bit to select slow or mixed decay; determines current recirculation path during off-time. |
| 15 (NO CONNECT) | Internally unconnected | No internal bond; must remain floating or tied to ground per PCB layout best practice - no signal routing allowed. |
| 16 (OUTA) | Bridge output A | One terminal of H-bridge; connects directly to motor winding; rated for ±2 A continuous with 270 mΩ rDS(on). |
| 17 (SENSE) | Current sense input | Connects to low-side sense resistor; comparator blanked during switching to reject transient spikes (programmable 4–24/fosc). |
| 18,19 (GROUND) | Additional power ground returns | Shared ground plane with pins 6/7; required for thermal and EMI performance; must connect externally to common ground. |
| 20 (VBB) | Motor supply input | 20–50 V high-current rail; decoupled with ≥47 μF electrolytic capacitor near device to suppress supply ripple. |
| 21 (OUTB) | Bridge output B | Second H-bridge terminal; complements OUTA for bidirectional drive; identical electrical specs to OUTA. |
| 22 (NO CONNECT) | Internally unconnected | No internal bond; must remain floating - routing signals here violates SOICW pinout integrity. |
| 23 (RANGE) | VREF range select input | Logic-level input paired with D16 to divide VREF by 5 or 10; sets current-sense gain for ITRIP calculation. |
| 24 (VREG) | Internal regulator decoupling | Connects 0.22 μF ceramic capacitor to ground; powers sink-side DMOS gates; fault monitoring disables outputs if unstable. |
Key Features
| Feature | Design Value |
|---|---|
| Programmable current-decay modes | Mixed/fast/slow decay configured via serial port - enables optimization of torque ripple, acoustic noise, and braking response per motor inductance. |
| Synchronous rectification control | Active/passive/disabled via D11/D12 - reduces power loss by 30–50% vs. body-diode conduction during decay, eliminating need for external Schottky diodes. |
| Fixed-off-time PWM current regulation | Off-time adjustable from 1.75 μs to 63.75 μs (5-bit resolution) - maintains stable current loop bandwidth across varying motor speeds and loads. |
| Integrated charge pump and VREG | Self-contained gate drive for high-side and sink-side DMOS - removes need for external bootstrap capacitors or dual-supply rails. |
| Comprehensive fault protection | Thermal shutdown (165°C), UVLO (3.9 V), CP/VREG monitoring, and crossover-current protection - prevents latch-up and catastrophic failure during fault conditions. |
Applications
| Industrial Actuators | Medical Infusion Pumps |
|---|---|
|
Use Scenario: Precision linear actuation in valve positioning systems requiring smooth bidirectional movement and repeatable force control. IC Role / Device Role / Timing Role: Full-bridge PWM motor driver regulating coil current via serial-programmed decay timing and synchronous rectification. Use Value: ±2 A output and 50 V headroom support high-torque 24 V DC motors; programmable blank time eliminates false current-limit trips during rapid direction reversal. |
Use Scenario: Low-noise, low-vibration peristaltic pump control in portable infusion devices where audible PWM artifacts must be minimized. IC Role / Device Role / Timing Role: Serial-configurable motor driver enabling mixed-decay mode to reduce torque ripple and acoustic emissions during microstep-like current transitions. Use Value: Active synchronous rectification cuts heat generation in compact enclosures; 270 mΩ rDS(on) allows battery-powered operation with extended runtime. |
| Automated Test Equipment | Lab Automation Stages |
|
Use Scenario: High-speed XY stage positioning in semiconductor probe stations requiring rapid acceleration/deceleration and precise current limiting. IC Role / Device Role / Timing Role: Bridge driver implementing external ENABLE chopping with programmable slow-decay braking to dissipate kinetic energy safely. Use Value: Braking current limited only by motor BEMF and winding resistance - avoids overcurrent faults during emergency stops; thermal shutdown prevents damage during repeated stall events. |
Use Scenario: Reagent handling robotics using small-frame DC motors needing reliable start/stop control and long-term stability in temperature-variable lab environments. IC Role / Device Role / Timing Role: Motor driver with integrated UVLO and thermal hysteresis ensuring fail-safe shutdown before junction temperature exceeds 150°C under sustained load. Use Value: SOICW package enables compact PCB layout; serial interface allows field calibration of current thresholds without hardware modification. |
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 |
|---|---|---|---|
| A4950KLJTR-T | Higher 3.5 A rating, integrated current sense amplifier, SPI interface, 5–40 V VBB range | Supports higher-current motors and closed-loop current feedback; lacks programmable blank time and mixed-decay mode | Choose for new designs requiring higher current or integrated sensing; not pin-compatible with A3958SLB |
| MP6532GQ-Z | 2.8 A rating, 5–45 V VBB, I²C interface, built-in 3.3 V LDO, smaller QFN-24 package | Lower thermal resistance (RθJA = 35°C/W), supports lower-voltage logic; no serial-programmable decay timing | Prefer for space-constrained, thermally demanding applications; requires PCB redesign and firmware adaptation |
Compared with A3958SLB, the A4950KLJTR-T offers greater current capacity and sensing integration but sacrifices fine-grained decay timing control, while the MP6532GQ-Z improves thermal performance and reduces board area but eliminates the serial-programmable blank time and mixed-decay flexibility essential for low-noise motor control.
Availability
A3958SLB is available at Aetrix Electronics and suitable for industrial actuators, medical infusion pumps, automated test equipment, and lab automation stages requiring stable component supply and legacy design continuity.
Supply support for A3958SLB 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, current sensing, and motor driver solutions since 1989.
The A3958 product line was engineered for cost-sensitive, programmable DC motor control in industrial and medical systems where serial configurability and thermal robustness outweigh the need for ultra-high current or digital bus integration.
FAQ
What is the maximum continuous output current supported by the A3958SLB?
The A3958SLB supports ±2 A continuous output current under specified thermal conditions (TA = 25°C, minimal copper). Actual current capability depends on PCB layout, ambient temperature, and heat sinking - the SOICW package (LB) has RθJA = 77°C/W, limiting usable current in enclosed or high-temperature environments. Exceeding 2 A risks thermal shutdown activation at 165°C.
Does the A3958SLB require external components for gate drive?
No, the A3958SLB integrates both a charge pump (for high-side gate drive above VBB) and an internal regulator (VREG for sink-side drive). It requires only three external capacitors: 0.22 μF between CP1–CP2, 0.22 μF between CP–VBB, and 0.22 μF between VREG–ground. These are mandatory for proper operation - omitting any disables corresponding driver sections.
How does the serial interface of the A3958SLB configure current decay behavior?
The A3958SLB uses a 3-wire serial interface to program 20-bit registers that control decay timing. Bits D2–D6 set fixed off-time (1.75–63.75 μs), D7–D10 set fast-decay duration, and D17+MODE select mixed or slow decay. D13 configures external ENABLE chopping for fast/slow decay, while D11/D12 enable and select active/passive synchronous rectification - all parameters are retained only while powered.
Can the A3958SLB be used for motor braking, and how is it implemented?
Yes, the A3958SLB supports active braking by configuring slow-decay mode (D17/MODE), enabling synchronous rectification (D12), and applying external PWM to ENABLE. This shorts motor BEMF through the low-rDS(on) bridge, dissipating kinetic energy rapidly. Note: braking current is not sensed or limited - design must ensure VBEMF/RL stays within ±2 A and thermal limits.
Is the A3958SLB still recommended for new designs?
No - Allegro classifies A3958SLB as "NOT FOR NEW DESIGN" (status effective May 4, 2009). It remains available for existing customer applications but is subject to probable near-term obsolescence. New designs should evaluate alternatives like A4950KLJTR-T or MP6532GQ-Z, which offer enhanced features and active product support.
A3958SLB 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:
- 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:
- Surface Mount
- Supplier Device Package:
- 24-SOIC
A3958SLB FAQ
1.How can I place an order for A3958SLB through Aetrix?
Please submit a Request for Quotation (RFQ) for A3958SLB 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 A3958SLB reliable?
The price and inventory of A3958SLB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3958SLB is usually 5 days.
3.What payment methods are accepted for A3958SLB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3958SLB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3958SLB?
A3958SLB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3958SLB 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 A3958SLB?
For technical support, including A3958SLB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3958SLB requirements.
6.How does Aetrix verify that A3958SLB is sourced from the original manufacturer or authorized distributors?
All A3958SLB 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 A3958SLB meets industry standards.
7.What is the process for return or replacement of A3958SLB?
All A3958SLB units undergo pre-shipment inspection (PSI). If there is an issue with A3958SLB, 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 A3958SLB part is unused and in its original packaging.
Return procedure for A3958SLB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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