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Allegro MicroSystems A5931GESTR-3-T
- Part No.:
- A5931GESTR-3-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 24-WFQFN Exposed Pad
- Datasheet:
-
A5931GESTR-3-T.pdf
- Description:
- BLDC SENSORLESS SINUSOIDAL DRIVE
- Quantity:
- Payment:
- Shipping:
Inventory:3,805
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Product details
Overview
A5931GESTR-3-T from Allegro MicroSystems is a discontinued three-phase sensorless fan driver IC designed for high-speed server fans, delivering sinusoidal modulation (24.4 kHz typical), closed-loop speed control with EEPROM-configurable speed curves, and integrated 3 A MOSFET drivers (210 mΩ RDS(ON) at 25°C). It eliminates Hall sensors and external microcontrollers in thermal management systems.
For engineers reviewing the A5931GESTR-3-T datasheet, A5931GESTR-3-T pinout, A5931GESTR-3-T application, or A5931GESTR-3-T equivalent, key selection considerations include its QFN-24 ES package, I²C interface (0x55), FG/RD open-drain outputs, SPD PWM input, and discontinuation status requiring transition planning to A89331GETSR.
Technical Context
The A5931GESTR-3-T implements sensorless back-EMF detection for commutation without position sensors, using charge-pump-driven gate drivers and configurable linear phase advance (up to 11° at 20,000 rpm). Its closed-loop control loop uses a 9-bit speed demand derived from PWM duty cycle (0.1–100 kHz range) and supports dual-slope speed curve profiles via EEPROM.
Protection architecture includes lock detection with programmable tOFF, overcurrent protection (6.5 A typical), thermal shutdown (165°C trip), VBB UVLO (4.3 V), and shorted-load monitoring. Standby mode is activated by holding SPD low beyond programmed lock-off time, and RD output signals rotor faults per EEPROM-defined RPM thresholds (RDHIGH/RDLOW).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 5–16 V DC - supports standard 12 V server fan rails with 18 V absolute max rating |
| Motor Phase Current | 3000 mA - enables direct drive of high-airflow server fans without external power stages |
| Driver RDS(ON) | 210 mΩ (typ, 25°C) - minimizes conduction loss and thermal rise in compact QFN package |
| PWM Input Frequency | 0.1–100 kHz - accommodates legacy and modern MCU-generated fan control signals |
| I²C Address | 0x55 - allows daisy-chaining multiple units on shared bus with unique register mapping |
| Operating Temperature | –40°C to +105°C - qualified for industrial-grade server chassis environments |
| Thermal Resistance | RθJA = 45°C/W - requires exposed pad soldering to PCB copper for reliable 3 A operation |
Pinout & Package
The A5931GESTR-3-T is housed in a 24-contact, 4 mm × 4 mm × 0.75 mm QFN package with exposed thermal pad (ES suffix), Pb-free with 100% matte-tin leadframe plating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FG | Open-drain speed feedback / I²C SDA | Delivers two pulses per mechanical revolution; doubles as bidirectional data line for EEPROM programming |
| SPD | PWM speed demand input / I²C SCL | Accepts 0–100% duty cycle signal; repurposed as clock line during serial configuration |
| RD | Open-drain rotor lock indicator | Asserts high on detected stall or underspeed condition per EEPROM-configured RPM thresholds |
| DIR | Direction control logic input | High = A→B→C sequence; low = A→C→B; internal 100 kΩ pull-up requires external GND/VREF tie for noise immunity |
| OUTA/OUTB/OUTC | Three-phase motor terminals | Drive wye- or delta-connected BLDC fans; CTAP provides optional common connection for wye motors |
| VBB (Pins 8 & 11) | Power supply input | Dual VBB pins reduce IR drop and improve current sharing across 12 V rail |
| LSS (Pins 6 & 13) | Low-side source return | Provides dedicated return path for sink-side MOSFETs to minimize ground bounce |
| GND (Pin 23) | System ground reference | Primary ground connection; must be tied to exposed thermal pad for thermal and electrical integrity |
Key Features
| Feature | Design Value |
|---|---|
| Sinusoidal modulation | 24.4 kHz fixed-frequency drive reduces audible noise and mechanical vibration vs trapezoidal alternatives |
| EEPROM-configurable speed curve | Full 9-bit resolution speed profile (MINSPD to MAXSPD) programmed once, eliminating runtime MCU overhead |
| Integrated charge pump | Enables 100% duty-cycle capability for high-side drivers without external bootstrap components |
| Programmable deceleration time | SpeedFeedbackClamp register adjusts coast-down rate to prevent abrupt stops and bearing stress |
| Lock detection with restart | tOFF-programmable auto-recovery after rotor stall, avoiding manual reset in unattended systems |
| Shorted-load protection | Monitors VDS across all drivers; shuts down within 640 ns on overcurrent, preventing latch-up failure |
Applications
| Server Fan Thermal Control | Network Switch Cooling |
|---|---|
Use Scenario: High-density 1U/2U rack servers requiring silent, vibration-free airflow at 15,000–30,000 RPM under variable thermal load. IC Role / Device Role / Timing Role: Primary motor controller executing sensorless commutation, closed-loop speed regulation, and fault reporting via RD/FG. Use Value: Eliminates Hall sensors and MCU firmware, reducing BOM cost and board space while meeting ASHRAE A-class acoustic requirements. |
Use Scenario: Carrier-grade Ethernet switches with multi-zone thermal management and hot-swap fan modules. IC Role / Device Role / Timing Role: Standalone fan driver with I²C configurability for per-module speed tuning and real-time telemetry via FG pulse count. Use Value: Enables field-upgradable speed curves without hardware change; RD output integrates directly into switch supervisor IC fault registers. |
| Storage Enclosure Ventilation | Industrial PC Active Cooling |
Use Scenario: JBOD enclosures with up to 24 hot-swap drives generating localized heat gradients across front-to-back airflow paths. IC Role / Device Role / Timing Role: Three-phase driver managing differential pressure requirements across redundant fan trays using DIR-controlled airflow reversal. Use Value: DIR pin enables automatic airflow direction switching during maintenance; soft-start prevents inrush-induced voltage sag on shared 12 V rail. |
Use Scenario: Fan-cooled ruggedized IPCs deployed in factory automation with wide ambient temperature swings (–40°C to +105°C). IC Role / Device Role / Timing Role: Embedded thermal actuator providing closed-loop response to CPU/GPU temperature sensors via analog SPD input. Use Value: Standby mode reduces idle power to <100 µA; thermal shutdown (165°C) protects against enclosure overheating failures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar three-phase sensorless fan driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| A89331GETSR | Successor device with enhanced EMI performance, extended temperature range (–40°C to +125°C), and updated EEPROM map; same QFN-24 ES package. | Supports next-generation server platforms requiring higher junction temperature margin and lower radiated emissions. | Recommended for new designs; migration path documented in Allegro AN-1234. |
| MP6532GQ-Z | Monolithic 3-phase driver with integrated current sense; lacks EEPROM and I²C, requiring external MCU for closed-loop control. | Suitable for cost-sensitive applications where firmware control already exists and Hall-less operation is secondary to integration density. | Consider only if existing MCU infrastructure supports real-time BEMF processing and speed curve interpolation. |
Compared with A5931GESTR-3-T, A89331GETSR offers lifecycle continuity and improved thermal robustness, while MP6532GQ-Z trades configurability for silicon area savings-making A89331GETSR the only drop-in replacement for legacy A5931-3 designs requiring zero layout changes.
Availability
A5931GESTR-3-T is available at Aetrix Electronics and suitable for server thermal management, network equipment cooling, and industrial PC ventilation requiring stable component supply despite end-of-life status.
Supply support for A5931GESTR-3-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 sensing and power IC solutions, specializing in motion control, energy-efficient power conversion, and precision current sensing.
The A5931GESTR-3-T belongs to Allegro's fan driver product line, engineered specifically for high-reliability, low-noise thermal management in datacenter and telecom infrastructure where sensorless operation and EEPROM customization reduce system complexity.
FAQ
Is the A5931GESTR-3-T still in production?
No, the A5931GESTR-3-T is a discontinued product. Allegro MicroSystems ceased production as of September 30, 2024. It should not be purchased for new design applications, and samples are no longer available. Aetrix Electronics maintains limited legacy stock for ongoing production support, but long-term design-in requires transition to the recommended substitution A89331GETSR.
What is the function of the CTAP pin on the A5931GESTR-3-T?
The CTAP pin on the A5931GESTR-3-T is an optional analog input for wye-connected motors, serving as the motor common node. It requires a 2 kΩ series resistor; for delta-wound motors, CTAP must remain open-circuited. This pin enables accurate back-EMF sampling in wye configurations and is unused in delta topologies-leaving it floating avoids unintended current paths.
Can the A5931GESTR-3-T operate without programming its EEPROM?
Yes, the A5931GESTR-3-T operates with factory-default EEPROM settings, including MINSPD = 2000 rpm, SPDSLP1 = 2243, DCON = 97 (10% duty), and closed-loop mode enabled. These defaults support basic functionality but lack application-specific tuning; full performance requires custom EEPROM programming via Allegro's EVB software or I²C commands to registers 65–84.
How does the RD output behave when the A5931GESTR-3-T detects a rotor lock?
When the A5931GESTR-3-T detects a rotor lock, the RD pin asserts high after either two consecutive lock events (LOCKEVT = 0) or after RDBLANK timeout if speed falls below RDLOW (LOCKEVT = 1), per EEPROM configuration. RD remains high until speed exceeds RDHIGH post-RD delay, or until PWM is cycled. The RD function can be disabled entirely by setting RDHIGH = 0 in EEPROM.
What thermal design considerations apply to the A5931GESTR-3-T's QFN-24 ES package?
The A5931GESTR-3-T's QFN-24 ES package requires soldering the exposed thermal pad to ≥1 in² of 2-layer PCB copper to achieve the specified RθJA of 45°C/W. Inadequate pad connection raises junction temperature, risking premature thermal shutdown (165°C trip) under 3 A continuous load. Thermal vias (≥6×0.3 mm diameter) beneath the pad are strongly recommended for sustained operation above 2 A.
A5931GESTR-3-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 24-WFQFN Exposed Pad
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Motor Type - Stepper:
- Multiphase
- Motor Type - AC, DC:
- Brushless DC (BLDC)
- Function:
- Driver - Fully Integrated, Control and Power Stage
- Output Configuration:
- Half Bridge (3)
- Interface:
- Analog, I2C, PWM
- Technology:
- Power MOSFET
- Step Resolution:
- -
- Applications:
- Fan Motor Driver
- Current - Output:
- 3A
- Voltage - Supply:
- 5V ~ 16V
- Voltage - Load:
- 5V ~ 16V
- Operating Temperature:
- -40°C ~ 105°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-QFN (4x4)
A5931GESTR-3-T FAQ
1.How can I place an order for A5931GESTR-3-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A5931GESTR-3-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 A5931GESTR-3-T reliable?
The price and inventory of A5931GESTR-3-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A5931GESTR-3-T is usually 5 days.
3.What payment methods are accepted for A5931GESTR-3-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A5931GESTR-3-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A5931GESTR-3-T?
A5931GESTR-3-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A5931GESTR-3-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 A5931GESTR-3-T?
For technical support, including A5931GESTR-3-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A5931GESTR-3-T requirements.
6.How does Aetrix verify that A5931GESTR-3-T is sourced from the original manufacturer or authorized distributors?
All A5931GESTR-3-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 A5931GESTR-3-T meets industry standards.
7.What is the process for return or replacement of A5931GESTR-3-T?
All A5931GESTR-3-T units undergo pre-shipment inspection (PSI). If there is an issue with A5931GESTR-3-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 A5931GESTR-3-T part is unused and in its original packaging.
Return procedure for A5931GESTR-3-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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