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Allegro MicroSystems A4949GLTR-T
- Part No.:
- A4949GLTR-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- -
- Datasheet:
-
A4949GLTR-T.pdf
- Description:
- IC FAN DRIVER BLDC SOT89-3
- Quantity:
- Payment:
- Shipping:
Inventory:3,475
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Product details
Overview
A4949GLTR-T from Allegro MicroSystems is a three-phase sensorless sinusoidal fan driver IC designed for medium-power brushless DC (BLDC) fans. It delivers 1.6 A overcurrent limit, operates from 4–18 V supply, supports PWM speed input (10%–100% duty cycle), and features FG speed feedback output - enabling low-noise, high-efficiency thermal management in server cooling and industrial ventilation systems.
For engineers reviewing the A4949GLTR-T datasheet, A4949GLTR-T pinout, A4949GLTR-T application, or A4949GLTR-T equivalent, key selection considerations include its 8-pin SOICN (L) package without exposed pad, PWM-based speed control interface, integrated lock detection with 8 s auto-restart timeout, soft-start current ramping, and thermal shutdown at 165 °C - all critical for reliable fan motor control in space-constrained embedded thermal subsystems.
Technical Context
The A4949GLTR-T implements a proprietary sensorless sinusoidal drive algorithm that dynamically adapts to motor back-EMF to generate near-ideal 120° phase-shifted current waveforms. Its trapezoidal startup sequence transitions automatically to sinusoidal operation once rotor speed reaches ~50% target, eliminating need for external Hall sensors or timing components.
Speed demand is derived from a 9-bit resolution PWM input (100 kHz max frequency, 7–8% hysteresis), converted internally to modulate three half-bridge outputs. Protection logic monitors VBB undervoltage (3.98 V rising threshold), overcurrent (1.6 A typical IOCL), and junction temperature (165 °C TSD trip), with automatic recovery after fault clearance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 4 V to 18 V - supports legacy 5 V, standard 12 V, and wide-input industrial power rails without external regulators. |
| Output Current Limit | 1.6 A (typ) - sets maximum motor phase current to prevent MOSFET saturation and ensure safe thermal margin under stall conditions. |
| PWM Speed Input Range | 0.1–100 kHz, 7–8% hysteresis - rejects noise while enabling precise speed control from microcontroller GPIO or dedicated PWM generators. |
| FG Output Type | Open-drain, 10 mA sink capability - provides one pulse per electrical revolution for tachometer feedback compatible with standard MCU input capture peripherals. |
| Thermal Shutdown Threshold | 165 °C (typ), 20 °C hysteresis - prevents permanent damage during sustained overload or poor heatsinking; allows safe restart after cooldown. |
| Soft Start Ramp | 50 mA step every 31 ms (fast ramp variant) - limits inrush current on power-up and avoids mechanical shock to fan bearings. |
| VBB UVLO Threshold | 3.98 V rising, 150–450 mV hysteresis - ensures stable internal biasing before enabling gate drivers and prevents erratic behavior during brownout. |
Pinout & Package
Package: 8-pin SOICN (L), surface-mount, lead-free with 100% matte-tin plating; no exposed thermal pad - suitable for wave-solder assembly and compact PCB layouts where thermal vias are impractical.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | GND | Power and signal reference ground - must be connected to low-impedance PCB ground plane to stabilize internal regulators and reduce EMI. |
| 2 | OUTA | Motor phase A output - drives one leg of external N-channel MOSFET half-bridge; requires external gate resistors and freewheeling diodes. |
| 3 | VBB | Main power supply input - supplies internal LDOs and gate drivers; requires 4.7–47 µF bulk capacitance (CVBB) close to pin. |
| 4 | PWM | Speed command input - accepts 0.1–100 kHz PWM signal; internal 100 kΩ pulldown disables motor if floating; 50 kΩ pullup to VBB enables 100% speed on open-circuit. |
| 5 | VREF | Analog reference output - 3.3 V ±3%, 10 mA capable; used to bias external RC networks or calibrate system-level analog circuits. |
| 6 | FG | Fan speed feedback - open-drain output toggling once per electrical revolution; requires external 20 kΩ pullup for clean logic-level signal to host controller. |
| 7 | OUTC | Motor phase C output - identical functional role as OUTA/OUTB; all three outputs share same RDS(on) and current-limiting behavior. |
| 8 | OUTB | Motor phase B output - completes three-phase drive set; outputs are internally phased 120° apart to synthesize sinusoidal current waveform. |
Key Features
| Feature | Design Value |
|---|---|
| 180° sinusoidal drive | Reduces audible noise and vibration by minimizing torque ripple - verified across BLDC fan motors up to 30 W, without position sensors. |
| Sensorless commutation | Eliminates Hall-effect sensors and associated wiring, lowering BOM cost and improving reliability in dusty or humid environments. |
| PWM speed interface | Direct compatibility with MCU PWM peripherals - no external DAC or op-amp required; supports dynamic speed profiling via software. |
| Integrated protection suite | Combines overcurrent (1.6 A), thermal shutdown (165 °C), lock detection (8 s timeout), and UVLO - reduces need for discrete protection circuitry. |
| Soft-start current ramp | Gradually increases motor current over ~1.6 s (fast ramp) to avoid inrush stress on power supply and mechanical shock to fan blades. |
Applications
| Server Rack Cooling | Industrial Ventilation Fan |
|---|---|
|
Use Scenario: High-density 1U/2U server chassis requiring silent, responsive thermal management under variable CPU/GPU load. IC Role / Device Role / Timing Role: Three-phase BLDC fan driver executing sensorless sinusoidal commutation with real-time speed adjustment via BMC-generated PWM. Use Value: Achieves <25 dB(A) acoustic noise at full speed while maintaining 100% speed accuracy across 4–18 V supply range and -40 to 105 °C ambient. |
Use Scenario: Dust-resistant cabinet fans in factory automation enclosures operating continuously under 55 °C ambient with voltage fluctuations. IC Role / Device Role / Timing Role: Motor controller managing airflow through heat exchangers using FG feedback for closed-loop speed regulation and lock detection for belt-break safety. Use Value: Delivers 1.6 A continuous phase current with thermal shutdown recovery, enabling unattended 24/7 operation without manual intervention. |
| Telecom Base Station Cooling | Medical Imaging Equipment Ventilation |
|
Use Scenario: Forced-air cooling for RF power amplifiers in outdoor macrocells exposed to wide temperature swings and transient surges. IC Role / Device Role / Timing Role: Fan driver interfacing with baseband processor via isolated PWM channel, providing FG tachometer signal for health monitoring. Use Value: Withstands 18 V transients (via optional ZD1 TVS), maintains stable sinusoidal drive down to 4 V supply, and reports faults via FG pulse dropout. |
Use Scenario: Low-vibration airflow control in MRI or CT scanner gantries where mechanical resonance must be minimized. IC Role / Device Role / Timing Role: Precision fan actuator generating smooth 30 kHz PWM-modulated sinusoidal currents to eliminate harmonic-induced vibrations affecting image fidelity. Use Value: 180° sinusoidal waveform reduces torque ripple to <3%, preventing micro-vibrations that degrade spatial resolution in diagnostic imaging. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar three-phase BLDC fan driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| A4949GLJTR-T | Identical functionality and pinout, but includes exposed thermal pad (LJ package) for 62 °C/W RθJA vs. 140 °C/W for L package. | Required for >1.2 A continuous operation above 60 °C ambient; not suitable for wave-solder-only processes. | Select A4949GLJTR-T when thermal performance demands lower junction temperature rise; otherwise A4949GLTR-T suffices for convection-cooled designs. |
| A5947KLPTR-T | Next-generation replacement with extended –40 to 125 °C K-grade rating, higher 2.5 A OCL, and enhanced ESD immunity (±4 kV HBM). | Targeted for automotive HVAC and harsh-environment industrial use; discontinued K-grade variants of A4949 are superseded by this part. | Choose A5947KLPTR-T for new designs requiring extended temperature range or higher current headroom; A4949GLTR-T remains valid for existing G-grade applications. |
Compared with A4949GLJTR-T, the A4949GLTR-T trades thermal performance for wave-solder compatibility; compared with A5947KLPTR-T, it offers cost-optimized G-grade operation without K-temperature qualification or upgraded protection - making it ideal for cost-sensitive, thermally moderate server and telecom cooling.
Availability
A4949GLTR-T is available at Aetrix Electronics and suitable for server rack cooling, industrial ventilation fan control, telecom base station thermal management, and medical imaging equipment ventilation requiring stable component supply and long-term production continuity.
Supply support for A4949GLTR-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 sensing and power IC solutions, specializing in motion control, energy-efficient power conversion, and precision analog interfaces.
The A4949 belongs to Allegro's fan driver product line, engineered specifically for low-noise, sensorless BLDC motor control in thermal management systems - balancing efficiency, acoustic performance, and integration density for datacenter and industrial applications.
FAQ
What is the maximum motor power supported by the A4949GLTR-T?
The A4949GLTR-T is rated for medium-power fans up to approximately 30 W, based on its 1.6 A typical overcurrent limit, 4–18 V supply range, and thermal resistance of 140 °C/W in the L package. Actual power capability depends on PCB copper area, ambient temperature, and airflow; derating is required above 60 °C ambient. The A4949GLTR-T datasheet specifies electrical characteristics under 25 °C and 105 °C conditions to guide safe operating area design.
Does the A4949GLTR-T require external MOSFETs or integrate them on-chip?
The A4949GLTR-T does not integrate power MOSFETs; it is a gate driver IC that controls external N-channel MOSFET half-bridges. Pins OUTA, OUTB, and OUTC deliver high-side and low-side gate drive signals to external FETs, which must be selected for voltage rating (>20 V), RDS(on) <50 mΩ, and thermal capability matching the 1.6 A IOCL limit. The A4949GLTR-T integrates only logic, protection, and commutation circuitry - not power switches.
Can the A4949GLTR-T operate with an analog speed input instead of PWM?
No - the A4949GLTR-T exclusively supports PWM speed input on the PWM pin. Analog speed control is implemented only in the A4945 family (e.g., A4945GLTR-T). The A4949GLTR-T's internal circuitry measures duty cycle (not voltage) and converts it to a 9-bit speed demand value; applying an analog voltage to the PWM pin will not yield correct speed response and may violate absolute maximum ratings if exceeding 6 V.
How does the FG output of the A4949GLTR-T interface with a microcontroller?
The FG pin on the A4949GLTR-T is an open-drain output that toggles once per electrical revolution of the motor. To interface with a microcontroller, connect a 20 kΩ pullup resistor from FG to VDD (e.g., 3.3 V or 5 V), then route the signal to a GPIO input configured for edge-triggered interrupt or input capture. Each FG pulse corresponds to one electrical cycle (not mechanical rotation), so gear ratio or pole-pair count must be factored into RPM calculation. The A4949GLTR-T guarantees 10 mA sink capability and <0.3 V saturation voltage.
Is the A4949GLTR-T pin-compatible with the A4949GLJTR-T?
Yes - the A4949GLTR-T and A4949GLJTR-T share identical pinout, electrical functionality, and footprint dimensions; the only difference is the presence of an exposed thermal pad on the LJ package. Both use the same 8-pin SOICN outline, with pins 1–8 assigned identically (GND, OUTA, VBB, PWM, VREF, FG, OUTC, OUTB). PCB land patterns differ only in the inclusion of a thermal pad solder mask opening and thermal vias for the LJ variant.
A4949GLTR-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Motor Type - Stepper:
- Multiphase
- Motor Type - AC, DC:
- Brushless DC (BLDC)
- Function:
- Fan Control
- Output Configuration:
- Half Bridge (3)
- Interface:
- PWM
- Technology:
- Power MOSFET
- Step Resolution:
- -
- Applications:
- Fan Motor Driver
- Current - Output:
- 1.8A
- Voltage - Supply:
- 4V ~ 18V
- Voltage - Load:
- -
- Operating Temperature:
- -40°C ~ 105°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
A4949GLTR-T FAQ
1.How can I place an order for A4949GLTR-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A4949GLTR-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 A4949GLTR-T reliable?
The price and inventory of A4949GLTR-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A4949GLTR-T is usually 5 days.
3.What payment methods are accepted for A4949GLTR-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A4949GLTR-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A4949GLTR-T?
A4949GLTR-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A4949GLTR-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 A4949GLTR-T?
For technical support, including A4949GLTR-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A4949GLTR-T requirements.
6.How does Aetrix verify that A4949GLTR-T is sourced from the original manufacturer or authorized distributors?
All A4949GLTR-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 A4949GLTR-T meets industry standards.
7.What is the process for return or replacement of A4949GLTR-T?
All A4949GLTR-T units undergo pre-shipment inspection (PSI). If there is an issue with A4949GLTR-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 A4949GLTR-T part is unused and in its original packaging.
Return procedure for A4949GLTR-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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