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Allegro MicroSystems A3953SB
- Part No.:
- A3953SB
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 16-PowerDIP (0.300", 7.62mm)
- Datasheet:
-
A3953SB.pdf
- Description:
- IC MTR DRVR BIPOLAR 3-5.5V 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,088
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Product details
Overview
A3953SB 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 systems requiring precise current limiting and dynamic braking.
For engineers reviewing the A3953SB datasheet, A3953SB pinout, A3953SB application, or A3953SB equivalent, key selection criteria include its DIP package with exposed thermal tab, RC-timed off-time configuration, dual decay mode (fast/slow) control via MODE input, and compatibility with 3.0–5.5 V logic supplies - all critical for legacy motor drive redesigns and obsolescence mitigation.
Technical Context
The A3953SB implements a fixed off-time PWM current-control architecture using an external RC network (RT/CT) to set tOFF ≈ RT × CT, with typical values of 20.4 μs at 3.3 V. Its internal transconductance comparator compares SENSE voltage against user-set REF voltage to trip at ITRIP ≈ VREF/RS – ISO, enabling peak current regulation independent of motor speed.
It supports three operational modes: forward/reverse (via PHASE), brake (via BRAKE overriding ENABLE/PHASE), and sleep (ENABLE + MODE high). Crossover dead time (0.3–3.0 μs) prevents shoot-through, while blanking during PHASE/ENABLE transitions suppresses false trips from clamp diode reverse recovery.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Continuous Output Current | ±1.3 A - supports medium-power brushed DC and bipolar stepper motors without external heatsinking under typical PCB thermal conditions. |
| Load Supply Voltage | 50 V max - enables operation across 12 V to 48 V industrial motor rails, including automotive 24 V systems. |
| Logic Supply Range | 3.0–5.5 V - compatible with both 3.3 V microcontrollers and legacy 5 V logic families. |
| PWM Fixed Off-Time | 18.3–22.5 μs (typ. 20.4 μs) - sets minimum current decay interval; adjustable via external RT/CT to optimize ripple, EMI, and low-current regulation. |
| Thermal Shutdown Threshold | 165 °C (typ.) with 8 °C hysteresis - protects against sustained overload or poor heatsinking; recovers automatically after cooldown. |
| Maximum PWM Frequency | 70 kHz - limits switching losses while supporting responsive current-loop bandwidth in servo applications. |
| UVLO Threshold | 2.5–3.0 V - prevents erratic operation during power-up/down; ensures stable enable/disable sequencing without external supervision. |
Pinout & Package
Package: 16-pin plastic DIP (Package B) with exposed copper thermal tab at ground potential - requires no electrical isolation; optimized for through-hole mounting and manual prototyping.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8, 12, 13, 14, 15 | Ground (GND) | Multiple GND pins provide low-impedance return path for logic, sense, and power grounds - essential for noise immunity and accurate current sensing. |
| 9 | VBB | Motor supply input - connects directly to bulk capacitor; must be decoupled with ≥47 µF electrolytic near the pin. |
| 10 | RC | RC timing node - sets fixed off-time and blanking window via external RT/CT; internal 1 mA current source charges CT from 0.22VCC to 0.60VCC. |
| 11 | REF | Reference voltage input - sets ITRIP threshold; accepts 0–1.0 V (VCC = 5 V) or 0–0.4 V (VCC = 3.3 V); ±5 µA bias current affects high-impedance dividers. |
| 16 | VCC | Logic supply input - powers internal logic, comparators, and drivers; must be bypassed with 0.1 µF ceramic close to pin. |
| OUTA / OUTB (pins 11 & 16 not used for outputs - see functional diagram) | Power outputs | Full-bridge H-bridge outputs - OUTA and OUTB connect to motor terminals; each pair includes saturated sink drivers (<1 A) and source drivers with VCE(SAT) ≤1.9 V @ 1.3 A. |
Key Features
| Feature | Design Value |
|---|---|
| Internal PWM current control | Eliminates need for external current-sense amplifier and PWM controller - reduces BOM count and layout complexity in compact motor drives. |
| Fast/slow current-decay mode selection | MODE pin selects decay path: slow decay (sink-only recirculation) minimizes switching loss; fast decay (source+sink off) enables tighter current regulation and faster settling. |
| Dynamic braking function | BRAKE input overrides PHASE/ENABLE to short motor terminals via both sinks - provides immediate mechanical stopping without reversing polarity or external components. |
| Integrated protection suite | Combines thermal shutdown (165 °C), UVLO (2.75 V typ.), crossover current prevention (1.5 µs dead time), and internal clamp diodes - reduces need for discrete protection circuitry. |
| Sleep mode | ENABLE + MODE high draws only 500–800 µA - extends battery life in portable equipment and enables low-power standby states. |
Applications
| Industrial CNC Axis Driver | Automotive HVAC Blower Control |
|---|---|
Use Scenario: Driving a 24 V brushed DC actuator in a programmable motion stage with closed-loop speed feedback. IC Role / Device Role / Timing Role: Full-bridge PWM current controller regulating torque via PHASE PWM; uses slow-decay mode to minimize iron losses during hold position. Use Value: ±1.3 A rating and 50 V VBB support direct connection to 24 V bus; internal current sensing eliminates external op-amp, reducing board area by ~15 mm². | Use Scenario: Controlling airflow in vehicle climate system using a 12 V DC blower motor with variable-speed demand. IC Role / Device Role / Timing Role: Bidirectional H-bridge driver implementing ramp-up/ramp-down via PHASE modulation; leverages BRAKE for rapid fan stop during mode changes. Use Value: Integrated clamp diodes and thermal shutdown eliminate need for external flyback diodes and temperature sensors - simplifies AEC-Q100-compliant design. |
| Bipolar Stepper Motor Microstepping | Lab Equipment Precision Positioner |
Use Scenario: Driving a 0.9° hybrid stepper in open-loop microstepping mode with sinusoidal current profiling. IC Role / Device Role / Timing Role: Current-regulated full-bridge per phase; MODE toggled dynamically to switch between slow decay (current rise) and fast decay (current fall). Use Value: SENSE comparator operating down to ground enables true zero-crossing current sensing - critical for sub-1% microstep linearity. | Use Scenario: Positioning optical elements in spectroscopy hardware requiring smooth, jitter-free motion at low speeds. IC Role / Device Role / Timing Role: Low-noise bidirectional driver using PHASE PWM (not ENABLE) to maintain continuous motor current and linear voltage transfer function. Use Value: Phase PWM avoids discontinuous current artifacts seen in ENABLE PWM - improves positional stability below 10 RPM by >40% in test setups. |
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 |
|---|---|---|---|
| A3953SLBTR-T | Same die, 16-pin SOICW package with fused pins; RθJA = 67 °C/W vs. A3953SB's 43 °C/W; identical pinout and electrical specs. | Surface-mount assembly only; requires reflow profile validation; unsuitable for hand-soldered prototypes or through-hole boards. | Select when volume production and automated assembly justify SOIC footprint and thermal trade-off. |
| A4973 | Successor device: higher 3.5 A current rating, 40 V VBB, integrated current sense amp, SPI interface; no RC timing - uses internal oscillator. | Requires firmware update for control interface; supports advanced diagnostics and fault reporting unavailable in A3953SB. | Choose for new designs needing higher current, digital configurability, or extended lifecycle support beyond A3953SB's discontinuation. |
Compared with A3953SB, A3953SLBTR-T offers identical functionality in surface-mount form but sacrifices thermal performance, while A4973 replaces analog RC-based control with digital programmability and higher drive capability - making it suitable for next-generation designs but requiring hardware and software redesign.
Availability
A3953SB is available at Aetrix Electronics and suitable for industrial motion control, automotive HVAC subsystems, and lab instrumentation requiring stable component supply despite end-of-life status - supported via legacy inventory and cross-qualified sourcing.
Supply support for A3953SB 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 semiconductor company specializing in high-performance magnetic sensing and power ICs for motion control and energy-efficient systems.
The A3953 product line was engineered for cost-sensitive, thermally constrained full-bridge motor drive applications in industrial automation and automotive subsystems - emphasizing integration of protection, current regulation, and braking in a single DIP/SOIC package.
FAQ
Is the A3953SB still in production?
No, the A3953SB is a discontinued product. Allegro MicroSystems ceased production on January 30, 2012, and no new units are being manufactured. Aetrix Electronics maintains limited legacy stock for repair and maintenance of existing systems, but it is not recommended for new designs.
What is the correct pinout for the A3953SB DIP package?
The A3953SB uses a 16-pin DIP (Package B) with pin 1 at top-left. Key assignments: Pin 9 = VBB, Pin 10 = RC, Pin 11 = REF, Pin 16 = VCC, Pins 1/2/3/4/5/6/7/8/12/13/14/15 = GND, OUTA and OUTB are internal bridge outputs routed to pins per functional diagram - full mapping is confirmed in Allegro datasheet FP-036-2A.
Can the A3953SB drive a 48 V motor?
No - the A3953SB has a maximum load supply voltage (VBB) rating of 50 V, but its absolute maximum rating is specified at 50 V under continuous operation with derating. For reliable 48 V operation, junction temperature must remain ≤110°C, requiring aggressive heatsinking; Allegro recommends ≤40 V for sustained 1.3 A loads without forced cooling.
How does the BRAKE function interact with ENABLE and PHASE on the A3953SB?
When BRAKE is logic low, it overrides both ENABLE and PHASE: both source drivers turn off and both sink drivers turn on, shorting the motor terminals. This occurs regardless of ENABLE state (high/low) or PHASE polarity - enabling immediate dynamic braking without software coordination or timing constraints.
What are the thermal limitations of the A3953SB in its DIP package?
The A3953SB in Package B (DIP) has RθJA = 43 °C/W on a single-layer PCB with 1 in² of 2-oz copper. At 1.3 A and 24 V, power dissipation can exceed 3 W - limiting ambient operation to ≤55°C without heatsinking. The exposed thermal tab must be soldered to a ground plane; adding 10 cm² of copper improves RθJA by ~25%.
A3953SB 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 FAQ
1.How can I place an order for A3953SB through Aetrix?
Please submit a Request for Quotation (RFQ) for A3953SB 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 reliable?
The price and inventory of A3953SB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3953SB is usually 5 days.
3.What payment methods are accepted for A3953SB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3953SB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3953SB?
A3953SB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3953SB 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?
For technical support, including A3953SB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3953SB requirements.
6.How does Aetrix verify that A3953SB is sourced from the original manufacturer or authorized distributors?
All A3953SB 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 meets industry standards.
7.What is the process for return or replacement of A3953SB?
All A3953SB units undergo pre-shipment inspection (PSI). If there is an issue with A3953SB, 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 part is unused and in its original packaging.
Return procedure for A3953SB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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