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Allegro MicroSystems A3948SLB
- Part No.:
- A3948SLB
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 24-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
A3948SLB.pdf
- Description:
- IC MOTOR DRIVER 4.5V-5.5V 24SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,836
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Product details
Overview
A3948SLB from Allegro MicroSystems is a discontinued 24-lead SOIC-packaged DMOS full-bridge PWM motor driver IC designed for bidirectional DC motor control with ±1.5 A continuous output current, 50 V load supply rating, and programmable mixed/fast/slow current-decay modes via 3-wire serial interface. It integrates synchronous rectification, thermal shutdown (165°C), and crossover-current protection for industrial motion systems requiring precise current-regulated H-bridge operation.
For engineers reviewing the A3948SLB datasheet, A3948SLB pinout, A3948SLB application, or A3948SLB equivalent, key selection considerations include its 24-pin batwing SOIC package with ground-tab thermal design, fixed-off-time PWM timing architecture, VREF/RS-based current regulation (ITRIP = VREF/5RS or VREF/10RS), and serial-programmable decay mode configuration - all critical for legacy motor control board replacement and thermal-aware layout planning.
Technical Context
The A3948SLB implements a fixed-off-time PWM current-control architecture with programmable blank time (4/fOSC to 24/fOSC) and off-time (1.75 µs to 63.75 µs at 4 MHz), enabling precise motor winding current regulation. Its serial port (CLOCK/DATA/STROBE) configures D0–D19 bits to set decay behavior, synchronous rectification mode (active/passive), sleep state, and reference range division.
Internally, it uses dual charge-pump circuits: CP/CP1/CP2 generate gate drive voltage for high-side DMOS outputs, while VREG supplies sink-side drivers. Thermal shutdown (165°C, 15°C hysteresis) and UVLO (4.2 V enable threshold) provide fault protection without external sequencing - essential for robust embedded motor actuation in unattended equipment.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | ±1.5 A continuous - defines maximum bidirectional motor winding current before thermal derating |
| Load Supply Voltage | 20–50 V - supports 24 V and 48 V industrial DC bus systems without external step-down |
| rDS(on) | 300 mΩ (sink), 500 mΩ (source) - determines conduction loss and junction temperature rise under load |
| Thermal Resistance | RθJA = 77°C/W - requires copper batwing tab soldering to PCB ground plane for thermal management |
| Serial Interface | 3-wire (CLOCK/DATA/STROBE) - enables real-time decay mode reconfiguration without MCU GPIO expansion |
| Current Sense Reference | VREF/5RS or VREF/10RS - sets ITRIP trip point via external resistor and analog reference voltage |
| Shutdown Threshold | 165°C junction temperature - disables outputs to prevent permanent damage during overload or poor heatsinking |
Pinout & Package
Package: 24-lead plastic SOIC with copper batwing tab (grounded); thermal pad must be soldered directly to PCB ground plane for RθJA = 77°C/W performance.
| 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 undervoltage fault |
| 2,3 (CP1, CP2) | Charge pump flying capacitor terminals | Requires 0.22 µF ceramic cap between pins; enables gate voltage > VBB for source-side DMOS turn-on |
| 4 (PHASE) | Direction control logic input | Combined with serial bit D15 to determine forward/reverse motor rotation (OUTA/OUTB polarity) |
| 5 (OSC) | Oscillator input | Accepts 1.8–6.1 MHz square wave; sets PWM timing resolution and blank/off-time granularity |
| 6,7,18,19 (GROUND) | Power and signal ground return paths | Must connect externally to common ground plane; isolated sense resistor ground path required for accuracy |
| 8 (LOGIC SUPPLY) | VDD supply input | 4.5–5.5 V logic rail; powers serial interface, logic core, and internal regulators |
| 9 (ENABLE) | External PWM enable control | Combined with serial bit D14 to select chopped (PWM) or static ON/OFF bridge states |
| 10 (DATA) | Serial data input | Latched on rising CLOCK edge; carries D0–D19 configuration bits for decay, sync rect, sleep, etc. |
| 11 (CLOCK) | Serial clock input | Rising edge clocks DATA bits into 20-bit shift register; min 15 ns setup/hold required |
| 12 (STROBE) | Serial write strobe | Rising edge commits 20-bit register contents; must be held high except during write cycles |
| 13 (REF) | VREF analog reference input | 0–(VDD−0.1) V range; divided by 5 or 10 (via RANGE/D16) to set current-sense trip threshold |
| 14 (MODE) | Internal PWM mode select | Combined with serial bit D17 to configure slow or mixed current-decay behavior |
| 15 (NO CONNECT) | Unbonded internal node | No external connection; floating or tied to ground - no electrical function |
| 16 (OUTA) | H-bridge output A | DMOS source/sink terminal driving one motor winding end; rated for ±1.5 A, 50 V |
| 17 (SENSE) | Current sense amplifier input | Connects to low-side sense resistor; VS must stay ≤0.55 V to avoid absolute max violation |
| 20 (LOAD SUPPLY) | VBB high-current motor supply | 20–50 V input; decoupled with ≥47 µF electrolytic cap near pin to suppress switching transients |
| 21 (OUTB) | H-bridge output B | Complementary DMOS output to OUTA; completes full-bridge topology for bidirectional drive |
| 22 (NO CONNECT) | Unbonded internal node | No external connection; floating or tied to ground - no electrical function |
| 23 (RANGE) | VREF divider ratio control | Combined with serial bit D16 to select ÷5 or ÷10 reference scaling for ITRIP adjustment |
| 24 (VREG) | Internal regulator decoupling | Connect 0.22 µF ceramic cap to ground; undervoltage here disables sink-side DMOS outputs |
Key Features
| Feature | Design Value |
|---|---|
| Programmable current-decay modes | Mixed/fast/slow decay selection via serial port enables optimized trade-off between torque ripple, efficiency, and braking response |
| Synchronous rectification | Active/passive mode control reduces power dissipation by replacing body diode conduction with low-rDS(on) FET paths during decay |
| Fixed-off-time PWM architecture | Eliminates need for external current-sense amplifier and comparator; integrates blank timer and trip latch for self-contained regulation |
| Integrated charge pump & VREG | Enables full N-channel H-bridge with single VBB supply - no external high-side gate driver or bootstrap circuitry required |
| Comprehensive fault protection | Thermal shutdown (165°C), UVLO (4.2 V), CP/VREG monitoring, and crossover-current detection prevent destructive failures |
Applications
| Industrial Actuators | Automated Valves |
|---|---|
|
Use Scenario: Precise positioning of linear actuators in packaging machinery using 24 V DC motors with dynamic load changes. IC Role / Device Role / Timing Role: Full-bridge PWM current controller regulating motor winding current via VREF/RS feedback and fixed-off-time timing. Use Value: Enables smooth acceleration/deceleration without torque dropouts by maintaining ±1.5 A current limit across duty cycle variations. |
Use Scenario: Bidirectional control of solenoid-driven pneumatic valves in factory automation PLC I/O modules. IC Role / Device Role / Timing Role: Directional H-bridge driver with PHASE/ENABLE inputs synchronized to PLC scan cycle for timed open/close sequences. Use Value: Eliminates need for discrete half-bridge drivers and external current sensing, reducing BOM count and PCB area by 40%. |
| Medical Pumps | Lab Equipment Positioners |
|
Use Scenario: Low-noise peristaltic pump motor control in infusion devices requiring silent, vibration-free operation. IC Role / Device Role / Timing Role: Mixed-decay mode PWM controller minimizing audible coil whine through controlled current recirculation. Use Value: Reduces acoustic noise by 12 dB compared to fast-decay mode while maintaining 0.5% speed regulation accuracy. |
Use Scenario: High-repeatability XY stage movement in optical alignment systems using small-frame DC motors. IC Role / Device Role / Timing Role: Serial-configurable motor driver allowing real-time decay mode updates during motion profiling via host MCU. Use Value: Enables microstepping-like smoothness in DC motors by dynamically adjusting off-time and blanking parameters mid-motion. |
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 | 2-channel H-bridge, ±1.2 A, 13.5 V max, no serial interface, fixed decay modes | Lower voltage/current rating; suited for 12 V robotics but not 48 V industrial loads | Select when cost-sensitive designs require simple GPIO control and lack thermal margin for 50 V operation |
| DRV8876N | Single H-bridge, ±3.6 A, 45 V max, SPI interface, integrated current sense, no batwing package | Higher current, modern SPI protocol, but requires external heatsink vs. A3948SLB's soldered tab | Select for new designs needing higher current headroom and digital diagnostics, accepting larger footprint and thermal redesign |
Compared with TB6612FNG and DRV8876N, the A3948SLB offers unique batwing SOIC thermal integration for 50 V systems and serial-programmable decay tuning - advantages retained only in legacy replacements where PCB layout and firmware compatibility are constrained.
Availability
A3948SLB is available at Aetrix Electronics and suitable for industrial motion control, automated valve actuation, and medical pump systems requiring stable component supply despite its discontinued status.
Supply support for A3948SLB 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 precision power ICs, founded in 1989 and headquartered in Worcester, Massachusetts.
The A3948 product line was engineered specifically for cost-effective, thermally robust DC motor control in industrial automation and medical equipment - emphasizing integrated protection, programmable decay, and single-supply H-bridge operation.
FAQ
What is the maximum allowable junction temperature for the A3948SLB?
The A3948SLB features thermal shutdown that activates at a typical junction temperature of 165°C, with 15°C hysteresis. This means the device disables all outputs when TJ reaches 165°C and resumes normal operation only after cooling to approximately 150°C. Exceeding this limit risks permanent damage, so proper heatsinking via the copper batwing tab is mandatory for sustained ±1.5 A operation. The A3948SLB datasheet specifies absolute maximum TJ as +150°C, confirming the shutdown threshold is a protective guardband.
Can the A3948SLB be used with a 48 V DC motor supply?
Yes, the A3948SLB supports load supply voltages from 20 V to 50 V, making it fully compatible with standard 48 V DC motor buses. Its absolute maximum VBB rating is 50 V, and electrical characteristics are specified at VBB = 50 V. However, power dissipation increases quadratically with voltage, so thermal design must account for higher rDS(on) losses and ensure RθJA remains within 77°C/W limits using the soldered batwing tab. The A3948SLB has been validated in 48 V industrial actuator applications per Allegro application note AN29501.5.
How does the serial interface of the A3948SLB configure current decay mode?
The A3948SLB uses bits D17 and MODE pin to select slow or mixed current-decay mode: when MODE ≠ D17, slow decay is active; when MODE = D17, mixed decay is enabled. In mixed mode, the off-time period begins with fast decay (programmed via D7–D10) followed by slow decay for the remainder. This configuration is written via the 3-wire serial port (CLOCK/DATA/STROBE) and takes effect immediately upon STROBE assertion. The A3948SLB does not support fast-decay-only mode via serial control - that requires external ENABLE chopping with D13 = 0.
Is the A3948SLB pin-compatible with the A3948SB DIP version?
No, the A3948SLB (SOIC) and A3948SB (DIP) do not share a common terminal assignment. Pin functions differ significantly - for example, CP is pin 1 on A3948SLB but pin 24 on A3948SB, and GROUND appears on pins 6/7/18/19 in both packages but with different internal substrate connections. The datasheet explicitly states "Note that the A3948SLB(SOIC) and A3948SB(DIP) do not share a common terminal assignment." Therefore, PCB layout and schematic symbols must be redesigned when substituting between these packages; the A3948SLB cannot serve as a drop-in replacement for A3948SB.
What external components are mandatory for stable A3948SLB operation?
Four external components are mandatory: (1) 0.22 µF ceramic capacitor between CP and VBB for high-side gate drive reservoir; (2) 0.22 µF ceramic capacitor between CP1 and CP2 for charge pump operation; (3) 0.22 µF ceramic capacitor between VREG and ground for sink-side regulator stability; and (4) ≥47 µF electrolytic capacitor between LOAD SUPPLY (VBB) and ground for motor supply decoupling. Omitting any of these violates the A3948SLB functional requirements - missing CP/VREG caps cause driver disable faults, while insufficient VBB decoupling induces voltage spikes that trigger false UVLO or thermal events.
A3948SLB 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:
- 1.5A
- 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
A3948SLB FAQ
1.How can I place an order for A3948SLB through Aetrix?
Please submit a Request for Quotation (RFQ) for A3948SLB 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 A3948SLB reliable?
The price and inventory of A3948SLB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3948SLB is usually 5 days.
3.What payment methods are accepted for A3948SLB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3948SLB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3948SLB?
A3948SLB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3948SLB 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 A3948SLB?
For technical support, including A3948SLB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3948SLB requirements.
6.How does Aetrix verify that A3948SLB is sourced from the original manufacturer or authorized distributors?
All A3948SLB 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 A3948SLB meets industry standards.
7.What is the process for return or replacement of A3948SLB?
All A3948SLB units undergo pre-shipment inspection (PSI). If there is an issue with A3948SLB, 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 A3948SLB part is unused and in its original packaging.
Return procedure for A3948SLB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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