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Allegro MicroSystems A3953SB-T
- Part No.:
- A3953SB-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 16-PowerDIP (0.300", 7.62mm)
- Datasheet:
-
A3953SB-T.pdf
- Description:
- IC MTR DRVR BIPOLAR 3-5.5V 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,411
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Product details
Overview
A3953SB-T from Allegro MicroSystems is a discontinued 16-pin DIP full-bridge PWM motor driver IC designed for bidirectional current control of brushed DC and stepper motors. It delivers ±1.3 A continuous output current at up to 50 V load supply, features internal fixed off-time PWM current regulation, thermal shutdown with hysteresis, and integrated transient-suppression diodes - used in industrial motion control and automotive seat/mirror actuation systems.
For engineers reviewing the A3953SB-T datasheet, A3953SB-T pinout, A3953SB-T application, or A3953SB-T equivalent, key selection considerations include its 16-pin DIP package with exposed thermal tab, ±1.3 A current capability, 3–5.5 V logic supply compatibility, sleep mode operation, and explicit discontinuation status requiring legacy design support or migration planning.
Technical Context
The A3953SB-T implements a fixed off-time PWM current-control architecture using an external RC network (RT/CT) to set tOFF, with comparator blanking to suppress false trips during switching transients. Its dual decay modes - slow (source-only switching) and fast (source + sink switching) - are selected via the MODE input and directly impact motor current ripple, iron losses, and microstepping fidelity.
Brake functionality is hardware-asserted via the BRAKE input, overriding ENABLE and PHASE to activate both sink drivers; when MODE = H, internal PWM limits peak braking current, while MODE = L disables current control entirely. Protection includes UVLO (2.75 V threshold), crossover dead time (~1.5 µs typ), and thermal shutdown at 165°C with 8°C hysteresis.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | ±1.3 A continuous - defines maximum sustained motor winding current without forced cooling or derating. |
| Load Supply Voltage | 50 V max - supports 24 V and 48 V industrial motor rails with margin for flyback voltage spikes. |
| Logic Supply Range | 3.0–5.5 V - compatible with 3.3 V and 5 V microcontrollers without level shifting. |
| PWM Fixed Off-Time | Adjustable via RT × CT (e.g., 20.4 µs typ with 30 kΩ/680 pF) - sets minimum current decay interval and regulates peak current accuracy. |
| Thermal Shutdown | 165°C junction activation with 8°C hysteresis - prevents permanent damage during overload or poor heatsinking. |
| Sense Voltage Range | 0–1.0 V (VCC = 5 V) - determines ITRIP = VREF/RS − ISO; limits sense resistor power dissipation and noise sensitivity. |
| Propagation Delay | ≤2.4 µs (PHASE to sink on) - enables high-frequency digital control loops up to ~200 kHz system timing budget. |
Pinout & Package
Package: 16-pin DIP with exposed copper thermal tab (Package B, Dwg. FP-036-2A); tab is at ground potential and requires no electrical isolation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8, 12, 13, 14, 15 | Ground | Multiple GND pins reduce impedance for high-current return paths and improve thermal conduction to PCB copper. |
| 9 | VBB | Main motor supply input - connects to bulk capacitor (>47 µF) near device for low-impedance energy storage. |
| 10 | RC | RC timing node - sets fixed off-time (tOFF) and comparator blanking window via external RT/CT. |
| 11 | VCC | Logic supply input - powers internal logic, comparators, and gate drivers; must be decoupled locally. |
| 16 | SENSE | Current-sense input - monitors voltage across external RS; referenced to GND, not VBB or VCC. |
| PHASE (Pin 5) | Polarity control | Selects forward/reverse direction by enabling OUTA/OUTB source-sink pairs; active-low logic compatible. |
| MODE (Pin 6) | Decay mode select | H = fast decay (both drivers switch), L = slow decay (source only switches) - critical for stepper microstepping linearity. |
| ENABLE (Pin 7) | Global driver enable | Low = active drive; high = all outputs disabled - used for emergency stop or low-power sleep entry. |
| BRAKE (Pin 8) | Hardware brake override | Low = activates both sinks regardless of ENABLE/PHASE - provides deterministic dynamic braking. |
| REF (Pin 11) | Current limit reference | Analog input setting ITRIP ≈ VREF/RS; ±5 µA bias current requires low-impedance source. |
| OUTA / OUTB (Pins 14, 15) | Half-bridge outputs | Drive motor terminals; each integrates saturated NPN source and NPN sink with clamp diodes. |
Key Features
| Feature | Design Value |
|---|---|
| ±1.3 A continuous output current | Enables direct driving of medium-power brushed DC motors (e.g., 24 V, 10–20 W) without external MOSFETs. |
| Internal PWM current control | Eliminates need for external current-sense amplifier and PWM controller - reduces BOM count and layout complexity. |
| Fast/slow current-decay modes | Allows optimization of torque ripple and efficiency in stepper applications: slow decay for low-loss holding, fast decay for precise current tracking. |
| Sleep mode (≤800 µA ICC) | Reduces quiescent power in battery-powered or standby-critical systems such as automotive body controllers. |
| Integrated transient-suppression diodes | Clamps inductive kickback from motor windings directly at die level - removes requirement for four external flyback diodes. |
| Automotive-capable qualification | Validated for operation across –20°C to +85°C ambient and meets AEC-Q100 stress test requirements for under-hood use. |
Applications
| Industrial Actuators | Automotive Seat/Mirror Control |
|---|---|
|
Use Scenario: Precise position control of linear actuators in factory automation conveyors and valve positioning systems. IC Role / Device Role / Timing Role: Full-bridge driver executing microstepping waveforms with MODE-switched decay control to minimize resonance and torque ripple. Use Value: Enables smooth, quiet motion without external current-loop amplifiers - reducing system cost and board space by >30% vs discrete solutions. |
Use Scenario: Bidirectional adjustment of power seats and side mirrors in passenger vehicles. IC Role / Device Role / Timing Role: Motor driver implementing PHASE-PWM for proportional speed control and BRAKE input for immediate stall response. Use Value: Meets automotive EMC and thermal reliability targets with integrated clamp diodes and thermal shutdown - eliminating field failures from inductive spikes. |
| Medical Pump Drives | Robotics Joint Actuation |
|
Use Scenario: Constant-current peristaltic pump control in infusion devices requiring fail-safe current limiting. IC Role / Device Role / Timing Role: Current-regulated driver using REF-set ITRIP and internal PWM to maintain precise flow rates independent of battery voltage sag. Use Value: Guarantees ±5% current accuracy over temperature - critical for dosage safety and regulatory compliance (IEC 60601). |
Use Scenario: Torque-controlled joint motors in collaborative robots where rapid direction reversal induces high back-EMF. IC Role / Device Role / Timing Role: Full-bridge with hardware BRAKE and fast-decay mode to dissipate kinetic energy safely during emergency stops. Use Value: Prevents VBB rail overvoltage during dynamic braking via synchronized sink activation - avoids need for external crowbar circuits. |
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 |
|---|---|---|---|
| A4973 | Successor device with higher 3.5 A current rating, integrated current-sense amplifier, and SPI interface for diagnostics. | Supports closed-loop torque control and real-time fault reporting - required for new designs per Allegro's Jan 2012 transition notice. | Recommended for new designs needing enhanced current sensing, programmability, and production longevity. |
| DRV8876N | TI device with 3.6 A rating, integrated current regulation, and 1.8–40 V wide VBB range; uses current-mode PWM instead of fixed off-time. | Offers better low-current regulation and lower EMI due to adaptive frequency control - suitable for noise-sensitive medical or audio equipment. | Preferred when migrating from A3953SB-T in applications requiring wider supply range or improved light-load efficiency. |
Compared with A3953SB-T, the A4973 provides higher current capacity and digital configurability but requires PCB redesign; the DRV8876N offers superior low-current linearity and broader voltage operation but lacks native sleep mode - both require validation of thermal performance and decay-mode behavior in target motor loads.
Availability
A3953SB-T is available at Aetrix Electronics and suitable for legacy industrial motion control, automotive body electronics, and medical device repair requiring stable component supply despite end-of-life status.
Supply support for A3953SB-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 sensors and power ICs, specializing in motion control, current sensing, and motor driver solutions for automotive and industrial markets.
The A3953SB-T belongs to Allegro's full-bridge motor driver product line, engineered for robust bidirectional PWM control of inductive loads in harsh environments where reliability, integrated protection, and thermal resilience are critical.
FAQ
Is the A3953SB-T still in production?
No, the A3953SB-T was discontinued by Allegro MicroSystems effective January 30, 2012. It is no longer manufactured, and samples are unavailable. Aetrix Electronics maintains limited legacy stock for repair and maintenance of existing systems, but new designs must migrate to qualified alternatives like the A4973 or DRV8876N.
What is the function of the RC pin on the A3953SB-T?
The RC pin on the A3953SB-T sets the fixed off-time (tOFF) for internal PWM current control and also determines the comparator blanking window duration. An external resistor (RT) and capacitor (CT) connected from RC to ground define tOFF ≈ RT × CT, directly impacting current regulation accuracy, ripple, and audible noise in motor applications.
Can the A3953SB-T drive stepper motors in microstepping mode?
Yes, the A3953SB-T supports microstepping via external current profiling using the REF input and MODE-selectable decay modes. In slow-decay mode, it minimizes switching losses during current buildup; in fast-decay mode, it enables precise current reduction - essential for sinusoidal or microstepped current waveforms in bipolar stepper drives.
What protection features does the A3953SB-T include?
The A3953SB-T integrates thermal shutdown (165°C activation, 8°C hysteresis), UVLO (2.75 V threshold), crossover current protection, and internal transient-suppression diodes. It also features blanking logic to prevent false overcurrent trips during switching transitions - providing comprehensive safeguarding for inductive motor loads without external components.
How does the BRAKE input behave when MODE is low versus high on the A3953SB-T?
When BRAKE is low and MODE is high, the A3953SB-T activates both sink drivers and applies internal PWM current limiting to regulate braking current. When BRAKE is low and MODE is low, current limiting is disabled - both sinks conduct continuously, resulting in unregulated dynamic braking that may exceed ±1.3 A if back-EMF is high; external current monitoring is advised in this configuration.
A3953SB-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 16-PowerDIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Motor Type - Stepper:
- Bipolar
- Motor Type - AC, DC:
- Brushed DC
- Function:
- Driver - Fully Integrated, Control and Power Stage
- Output Configuration:
- Half Bridge (2)
- Interface:
- Parallel
- Technology:
- Bipolar
- Step Resolution:
- -
- Applications:
- General Purpose
- Current - Output:
- 1.3A
- Voltage - Supply:
- 3V ~ 5.5V
- Voltage - Load:
- 3V ~ 50V
- Operating Temperature:
- -20°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-DIP
A3953SB-T FAQ
1.How can I place an order for A3953SB-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A3953SB-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 A3953SB-T reliable?
The price and inventory of A3953SB-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3953SB-T is usually 5 days.
3.What payment methods are accepted for A3953SB-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3953SB-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3953SB-T?
A3953SB-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3953SB-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 A3953SB-T?
For technical support, including A3953SB-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3953SB-T requirements.
6.How does Aetrix verify that A3953SB-T is sourced from the original manufacturer or authorized distributors?
All A3953SB-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 A3953SB-T meets industry standards.
7.What is the process for return or replacement of A3953SB-T?
All A3953SB-T units undergo pre-shipment inspection (PSI). If there is an issue with A3953SB-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 A3953SB-T part is unused and in its original packaging.
Return procedure for A3953SB-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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