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Allegro MicroSystems A3974SED-T
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- Part No.:
- A3974SED-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 44-LCC (J-Lead)
- Datasheet:
-
A3974SED-T.pdf
- Description:
- IC MOTOR DRIVER 4.5V-5.5V 44PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:2,439
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Product details
Overview
A3974SED-T from Allegro MicroSystems is a DMOS dual full-bridge PWM motor driver IC designed for bidirectional current control of two DC motors in industrial and embedded motion systems. It delivers ±1.5 A output current per bridge, supports up to 50 V load supply voltage, and features programmable slow/fast/mixed current-decay modes via 3-wire serial interface - enabling precise torque and speed regulation in robotic actuators and automated valves.
For engineers reviewing the A3974SED-T datasheet, A3974SED-T pinout, A3974SED-T application, or A3974SED-T equivalent, key selection criteria include its 44-pin PLCC package with fused ground pins, synchronous rectification capability eliminating external clamp diodes, thermal shutdown at 165°C, and support for external ENABLE-based PWM chopping alongside internal fixed-off-time current regulation.
Technical Context
The A3974SED-T integrates two independent DMOS H-bridges with dedicated sense inputs (SENSE1/SENSE2), reference buffers (REF1/REF2), and gate drivers powered by an internal charge pump (CP/CP1/CP2) and VREG regulator. Each bridge supports configurable decay modes (slow, fast, mixed) and synchronous rectification controlled via serial bits D11–D12 and D17.
Its serial interface uses CLOCK/DATA/STROBE signals to load two 20-bit words configuring blank time, off-time (5-bit), fast-decay time (4-bit), phase, enable logic, and Gm range (D16). Internal protection includes UVLO on VDD (4.2 V threshold), thermal shutdown with 15°C hysteresis, crossover-current protection, and fault detection on CP and VREG rails.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | ±1.5 A continuous per bridge - enables driving medium-power DC motors without external current amplification. |
| Load Supply Voltage | 15–50 V - supports wide-range industrial power rails including 24 V and 48 V systems. |
| rDS(on) | 0.315 Ω (sink), 0.5 Ω (source) - minimizes conduction loss and heat generation during high-current operation. |
| Current Regulation | Fixed off-time PWM with programmable 1.75–63.75 μs off-time - provides stable current control across variable motor back-EMF. |
| Thermal Shutdown | 165°C junction temperature with 15°C hysteresis - protects against sustained overload or poor heatsinking without latch-up. |
| Serial Interface | 3-wire (CLOCK/DATA/STROBE), 20-bit word length - allows real-time reconfiguration of decay mode, blank time, and reference scaling without MCU GPIO overhead. |
| Synchronous Rectification | Active, passive, low-side-only, or disabled - reduces power dissipation by replacing body-diode conduction with low-rDS(on) MOSFET paths. |
Pinout & Package
The A3974SED-T is housed in a 44-pin plastic leaded chip carrier (PLCC) with internally fused ground pins (pins 1, 2, 11–13, 22–24, 33–35, 44) for enhanced thermal dissipation. The fused pins are at ground potential and require no electrical isolation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (pins 1,2,11–13,22–24,33–35,44) | Power and logic ground reference | Fused ground terminals provide low-impedance return path and improved heat spreading across PCB ground plane. |
| OUT1A / OUT1B / OUT2A / OUT2B | H-bridge output terminals | Drive motor windings in forward/reverse direction; each pair forms one full-bridge with ±1.5 A capability. |
| SENSE1 / SENSE2 | Current-sense input for bridge 1 and 2 | Connects to low-side sense resistor; enables closed-loop current regulation using VREF/RS ratio. |
| REF1 / REF2 | Analog reference input for current trip threshold | Sets ITRIP = VREF/(5×RS) or VREF/(10×RS) depending on D16 bit - allows fine-tuning of motor stall current. |
| ENABLE1 / ENABLE2 | External PWM enable control inputs | Supports external microcontroller-generated PWM for speed/torque control independent of internal timer. |
| CLOCK / DATA / STROBE | 3-wire serial interface inputs | Enable dynamic configuration of decay mode, blank time, and off-time without requiring dedicated SPI peripheral. |
| VREG / CP / CP1 / CP2 | Internal regulator and charge pump nodes | VREG powers sink-side drivers; CP/CP1/CP2 generate >VBB gate drive for source-side DMOS - requires 0.22 μF ceramic decoupling. |
| SLEEP / OSC | Low-power mode control and oscillator input | SLEEP disables all circuitry except UVLO; OSC accepts 2.9–6.1 MHz square wave for timing base of PWM cycles. |
Key Features
| Feature | Design Value |
|---|---|
| Programmable current-decay modes | Slow, fast, and mixed decay selectable per bridge via serial interface - optimizes torque ripple and audible noise for specific motor inductance. |
| Synchronous rectification | Eliminates need for four external Schottky diodes per bridge in active mode - reduces BOM cost and board area while cutting conduction losses by >40% vs. body diodes. |
| Independent bridge control | Separate ENABLE, REF, and SENSE inputs for each bridge - enables asymmetric operation such as driving one motor at full torque while idling the other. |
| Thermal and electrical protection | Integrated thermal shutdown (165°C), UVLO on VDD and charge pump, and crossover-current protection - prevents latch-up and destructive failure under fault conditions. |
| Low-power sleep mode | Draws ≤100 μA in SLEEP state with serial register reset - suitable for battery-powered portable equipment requiring extended standby time. |
Applications
| Industrial Valve Actuation | Robotic Joint Control |
|---|---|
|
Use Scenario: Precise bidirectional positioning of pneumatic/hydraulic valves in process automation systems. IC Role / Device Role / Timing Role: Dual full-bridge driver regulating current through two solenoid coils to achieve proportional flow control. Use Value: Programmable mixed-decay mode minimizes coil current overshoot during rapid direction reversal, improving valve response time and repeatability. |
Use Scenario: Torque-controlled articulation of multi-axis robotic arms in collaborative manufacturing cells. IC Role / Device Role / Timing Role: Motor driver executing closed-loop current control using external encoder feedback and internal PWM timer. Use Value: Synchronous rectification reduces heat generation in compact joints, allowing higher duty cycle operation without forced cooling. |
| Automated Test Equipment (ATE) | Medical Infusion Pumps |
|
Use Scenario: High-accuracy motion control of probe positioning stages and fixture actuators in semiconductor test handlers. IC Role / Device Role / Timing Role: Dual-bridge controller managing stepper-like microstepping via external PWM and internal current regulation. Use Value: Independent ENABLE inputs allow synchronized start/stop of dual-axis movement with sub-millisecond timing resolution. |
Use Scenario: Silent, low-heat motor actuation in portable infusion pumps delivering precise drug dosing. IC Role / Device Role / Timing Role: Full-bridge driver implementing smooth ramp-up/ramp-down profiles to prevent bolus delivery errors. Use Value: Fast-decay mode selection eliminates audible motor whine during low-speed operation critical for patient comfort. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual full-bridge motor driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| A3992 | Successor device with identical pinout, enhanced thermal performance (RθJA = 18°C/W), and extended operating temperature range (–40°C to 125°C). | Supports new designs requiring longer product lifecycle and wider ambient operating range; retains full software compatibility with A3974SED-T. | Select A3992 for new designs where long-term availability and extended temperature operation are required. |
| TB9051FTG | 3-phase brushless DC driver with integrated current sensing and 12-bit ADC; lacks dual independent full-bridge topology and serial programming interface. | Targets BLDC commutation rather than discrete DC motor control; requires different control firmware and external current sense amplifiers for DC use. | Consider TB9051FTG only when migrating to sensorless BLDC motors and redesigning control architecture. |
Compared with A3974SED-T, the A3992 offers drop-in replacement capability with improved thermal metrics and extended temperature rating, while the TB9051FTG serves a fundamentally different motor type and control paradigm - making A3992 the preferred upgrade path for existing A3974SED-T users.
Availability
A3974SED-T is available at Aetrix Electronics and suitable for industrial valve actuation, robotic joint control, automated test equipment, and medical infusion pump designs requiring stable component supply despite its Last Time Buy status.
Supply support for A3974SED-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 precision power ICs, headquartered in Worcester, Massachusetts.
The A3974SED-T belongs to Allegro's legacy motor driver product line targeting cost-sensitive, thermally demanding DC motor control applications in industrial automation and medical devices.
FAQ
What is the maximum continuous output current supported by the A3974SED-T?
The A3974SED-T supports ±1.5 A continuous output current per bridge under specified thermal conditions. This rating assumes adequate PCB copper area (4-layer JEDEC standard), ambient temperature ≤85°C, and proper decoupling of VREG and CP pins. Exceeding this current without derating may trigger thermal shutdown at 165°C junction temperature.
Does the A3974SED-T require external Schottky diodes for flyback protection?
No, the A3974SED-T does not require external Schottky diodes in most applications due to its integrated synchronous rectification feature. When enabled, it uses the low rDS(on) of internal DMOS transistors to recirculate current during decay, reducing power loss and eliminating external diode BOM cost - provided the selected decay mode (active or low-side-only) matches the motor winding characteristics.
How is current regulation implemented in the A3974SED-T?
The A3974SED-T implements current regulation using a fixed off-time PWM scheme that compares the voltage across an external sense resistor (RS) to a scaled reference voltage (VREF/5 or VREF/10 based on D16). When the sensed current reaches the trip threshold, the source driver turns off for a programmable off-time period, after which the current recirculates via synchronous rectification or body diodes depending on decay mode configuration.
Can the A3974SED-T be used in new designs despite its Last Time Buy status?
No - the A3974SED-T is designated Last Time Buy with a final order deadline of April 30, 2010, and is obsolete for new design-in. Allegro explicitly recommends transitioning to the A3992 for new applications. Aetrix Electronics maintains limited legacy stock for existing customer support but does not endorse A3974SED-T in newly developed products.
What package type and thermal characteristics does the A3974SED-T use?
The A3974SED-T uses a 44-pin plastic leaded chip carrier (PLCC) with internally fused ground pins (pins 1, 2, 11–13, 22–24, 33–35, 44) for enhanced thermal conduction. Its thermal resistance is RθJA = 22°C/W (4-layer JEDEC board) and RθJT = 6°C/W, enabling reliable operation up to 85°C ambient when mounted on a properly designed PCB with sufficient copper pour and ground plane area.
A3974SED-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 44-LCC (J-Lead)
- 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 (4)
- Interface:
- Serial
- Technology:
- DMOS
- Step Resolution:
- -
- Applications:
- General Purpose
- Current - Output:
- 1.5A
- Voltage - Supply:
- 4.5V ~ 5.5V
- Voltage - Load:
- 15V ~ 50V
- Operating Temperature:
- -20°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 44-PLCC (16.59x16.59)
A3974SED-T FAQ
1.How can I place an order for A3974SED-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A3974SED-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 A3974SED-T reliable?
The price and inventory of A3974SED-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3974SED-T is usually 5 days.
3.What payment methods are accepted for A3974SED-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3974SED-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3974SED-T?
A3974SED-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3974SED-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 A3974SED-T?
For technical support, including A3974SED-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3974SED-T requirements.
6.How does Aetrix verify that A3974SED-T is sourced from the original manufacturer or authorized distributors?
All A3974SED-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 A3974SED-T meets industry standards.
7.What is the process for return or replacement of A3974SED-T?
All A3974SED-T units undergo pre-shipment inspection (PSI). If there is an issue with A3974SED-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 A3974SED-T part is unused and in its original packaging.
Return procedure for A3974SED-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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