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Allegro MicroSystems A5947KLPTR-B-T
- Part No.:
- A5947KLPTR-B-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
A5947KLPTR-B-T.pdf
- Description:
- THREE PHASE SENSORLESS SINUSOIDA
- Quantity:
- Payment:
- Shipping:
Inventory:6,873
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Product details
Overview
A5947KLPTR-B-T from Allegro MicroSystems is a three-phase sensorless sinusoidal fan driver IC designed for low-noise, low-vibration cooling in automotive and industrial fans. It integrates closed-loop speed control, EEPROM-configurable speed curves, I²C interface, and on-chip 3.3 V/20 mA linear regulator. Key specs include 24 kHz PWM motor frequency, 510 mΩ typical RDS(ON) at 25°C, and AEC-Q100 qualification for –40°C to +125°C operation.
For engineers reviewing the A5947KLPTR-B-T datasheet, A5947KLPTR-B-T pinout, A5947KLPTR-B-T application, or A5947KLPTR-B-T equivalent, this page delivers verified technical context, validated pin functions, real-world fan control use cases, and two confirmed alternative fan drivers with documented functional and application-level differences.
Technical Context
The A5947KLPTR-B-T implements sensorless back-EMF detection for rotor position estimation, enabling sinusoidal commutation without Hall sensors. Its closed-loop speed control uses a 9-bit SPD input (PWM duty or analog voltage) converted via internal ADC and mapped to motor output via EEPROM-defined speed curves.
It features dual-mode operation: default EEPROM-driven speed profile mode or direct I²C register control (slave address 0x55). Protection includes lock detection with programmable tLOCK, overcurrent (3.0 A trip), overvoltage (19 V or 38 V selectable), thermal shutdown (165°C), and slew rate control via EEPROM SLEW register.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Motor Drive Type | Sensorless three-phase sinusoidal commutation - eliminates Hall sensors and reduces audible noise/vibration |
| Supply Voltage Range | VBB = 4 V to 40 V - supports 12 V and 24 V fan systems with undervoltage lockout at 3.85 V or 8.65 V |
| Motor PWM Frequency | 24.5 kHz typical - enables high-frequency switching to minimize EMI and audible coil whine |
| RDS(ON) (Total) | 510 mΩ typ @ 25°C - ensures low conduction loss and thermal efficiency at full load |
| Speed Input Interface | PWM duty cycle (34 Hz–65 kHz) or analog voltage (0.7 V–2.49 V) - configurable via EEPROM SPDSEL bit |
| EEPROM Capacity | 32 × 16-bit words - stores speed curve parameters, protection thresholds, startup timing, and direction logic |
| I²C Interface | Fast-mode (400 kHz), 7-bit address 0x55 - enables real-time speed demand (Reg 165), fault readback (Reg 147), and die temperature monitoring (Reg 138) |
| Operating Temperature | –40°C to +125°C (Range K) - qualified per AEC-Q100 Grade 0 for under-hood automotive applications |
Pinout & Package
Package: 20-lead TSSOP with exposed thermal pad (LP package), JEDEC MO-153ACT compliant. Thermal resistance RθJA = 34°C/W on 2-layer PCB with 1-in² copper.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1) | Ground reference | Primary power and signal return path; connects to PCB ground plane and exposed thermal pad |
| n/c (Pins 2,3,8,13,14,16) | No connect | Internally unconnected; must be left floating or tied to GND per layout guidelines |
| CP1, CP2, VCP (Pins 4,5,6) | Charge pump circuit | Supports high-side gate drive; requires external 0.1 µF X7R capacitors between CP1–CP2 and CP2–VCP |
| VBB (Pin 7) | Main power supply | Input for 4–40 V motor supply; powers internal regulators, gate drivers, and logic |
| OUTA/B/C (Pins 9,11,12) | Motor phase outputs | Three half-bridge outputs driving BLDC fan windings; each rated for 3.6 A peak current |
| LSS (Pin 10) | Low-side source | Common source node for all low-side MOSFETs; connects to motor star point or sense resistor |
| VREF (Pin 15) | Reference voltage output | Stable 3.3 V ±3% @ 20 mA - powers external sensors or level-shifters; includes UVLO and OCL protection |
| TEST (Pin 17) | Startup status indicator | Open-drain output: low during motor off, high at end of open-loop startup sequence |
| nFAULT (Pin 18) | Fault reporting | Active-low open-drain flag for VBB UVLO/OVLO, thermal shutdown, lock, VCP UVLO, or OCP events |
| SPD (Pin 19) | Speed demand input / I²C clock | Accepts PWM duty or analog voltage; doubles as I²C SCL line when serial mode enabled |
| FG (Pin 20) | Speed feedback / I²C data | Open-drain tachometer output (30 × RPM); doubles as I²C SDA line during serial communication |
| PAD (Exposed) | Thermal & electrical ground | Must be soldered to large PCB copper area with ≥4 thermal vias for reliable thermal dissipation |
Key Features
| Feature | Design Value |
|---|---|
| Sinusoidal modulation | Reduces torque ripple and acoustic noise vs. trapezoidal drive - critical for quiet HVAC and cabin fans |
| EEPROM-configurable speed curve | Enables application-specific fan profiles (linear, staircase, dual-slope) without MCU firmware changes |
| I²C serial control interface | Allows runtime speed adjustment, fault diagnostics, and parameter tuning without reprogramming EEPROM |
| Integrated 3.3 V linear regulator | Eliminates need for external LDO; supplies internal logic and external peripherals up to 20 mA |
| Programmable slew rate control | Adjusts dv/dt on OUTA/B/C to reduce EMI and prevent false overvoltage triggering during fast transients |
| Lock detection with restart timeout | Automatically disables outputs for tLOCK (default 5 s) on rotor stall, then resumes normal startup |
Applications
| Automotive Engine Cooling Fan | Industrial Server Rack Fan |
|---|---|
Use Scenario: Regulated cooling for turbocharged engine bays where vibration and acoustic noise must meet OEM NVH targets. IC Role / Device Role / Timing Role: Primary three-phase BLDC motor controller performing sensorless commutation, closed-loop RPM regulation, and thermal fault management. Use Value: Eliminates Hall sensors and MCU, reducing BOM cost and board space while meeting AEC-Q100 Grade 0 requirements for 125°C ambient. | Use Scenario: High-reliability 24 V server cooling with dynamic speed response to CPU thermal load and remote monitoring via I²C. IC Role / Device Role / Timing Role: Standalone fan driver executing EEPROM-defined speed-vs-temperature curves and reporting faults via FG/nFAULT pins. Use Value: Enables precise thermal management without host processor intervention; I²C allows real-time speed override and die temperature readback (Reg 138). |
| Medical Imaging System Fan | Telecom Power Amplifier Cooling |
Use Scenario: Ultra-quiet airflow for MRI or CT scanner enclosures where audible noise disrupts patient experience. IC Role / Device Role / Timing Role: Sinusoidal drive IC delivering smooth torque and minimal vibration across 10–100% speed range. Use Value: 24 kHz PWM frequency and sine-wave modulation suppress mechanical resonance and acoustic emissions below human hearing threshold. | Use Scenario: Forced-air cooling of GaN-based RF power amplifiers requiring rapid thermal response and overtemperature shutdown coordination. IC Role / Device Role / Timing Role: Motor controller with integrated thermal shutdown (165°C TJ) and VBB overvoltage lockout (38 V option) for 48 V telecom systems. Use Value: Direct thermal coupling to heatsink via exposed pad and fast-acting TSD protection prevent GaN device destruction during transient overload. |
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 |
|---|---|---|---|
| MP6532GQ-Z | Integrated gate drivers only; requires external MCU for speed control and EEPROM-like configuration; no on-chip 3.3 V regulator | Best suited for designs already using a host microcontroller with custom fan algorithms and separate LDO | Select MP6532GQ-Z when system-level flexibility and multi-fan synchronization via MCU are prioritized over standalone operation. |
| DRV10983ZRTVT | Includes Hall sensor interface and supports both sensorless and sensored modes; lacks I²C interface and EEPROM; lower RDS(ON) (320 mΩ) | Preferred for applications needing fallback to Hall-based operation or tighter torque control at low speed | Choose DRV10983ZRTVT when robust low-speed startup or hybrid sensor/sensorless operation is required, and I²C diagnostics are not needed. |
Compared with MP6532GQ-Z and DRV10983ZRTVT, the A5947KLPTR-B-T uniquely combines standalone EEPROM-based speed profiling, integrated 3.3 V regulator, and I²C diagnostics in a single AEC-Q100-qualified package-reducing system complexity for automotive and high-reliability industrial fans.
Availability
A5947KLPTR-B-T is available at Aetrix Electronics and suitable for automotive engine cooling, industrial server rack thermal management, and medical imaging system fan control requiring stable component supply, AEC-Q100 compliance, and long-term production continuity.
Supply support for A5947KLPTR-B-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 automotive-grade reliability.
The A5947 product line is engineered specifically for intelligent, low-noise, sensorless BLDC fan control in demanding environments - emphasizing vibration reduction, configurability, and integration to replace MCU-based fan subsystems.
FAQ
What is the maximum motor supply voltage supported by the A5947KLPTR-B-T?
The A5947KLPTR-B-T supports a VBB supply range of 4 V to 40 V. Its absolute maximum rating is 40 V, and overvoltage protection triggers at either 19 V or 38 V depending on EEPROM OVPOPT and VBBOV settings. Operation above 40 V risks permanent damage. The A5947KLPTR-B-T is commonly used with 12 V and 24 V fan systems.
Does the A5947KLPTR-B-T require external Hall sensors for motor commutation?
No, the A5947KLPTR-B-T performs sensorless commutation using back-EMF detection and sinusoidal drive - eliminating the need for Hall sensors, associated wiring, and mounting space. This reduces system cost and improves reliability in dusty or high-vibration environments where Hall sensors may fail. The A5947KLPTR-B-T is explicitly designed for Hall-less fan applications.
How is speed controlled on the A5947KLPTR-B-T - via PWM, analog voltage, or I²C?
Speed on the A5947KLPTR-B-T can be controlled via three methods: (1) PWM duty cycle on SPD pin (34 Hz–65 kHz), (2) analog voltage (0.7–2.49 V) on SPD pin, or (3) direct I²C write to register 165. The mode is selected via EEPROM SPDSEL bit. All methods map to a 9-bit demand value (0–511) that determines motor output duty. The A5947KLPTR-B-T defaults to PWM mode at power-up.
What protection features are integrated into the A5947KLPTR-B-T?
The A5947KLPTR-B-T integrates lock detection with restart timeout, overcurrent protection (3.0 A trip), VBB overvoltage/undervoltage lockout, VCP undervoltage detection, thermal shutdown (165°C), and motor output short-circuit monitoring. Faults are reported via nFAULT pin and readable via I²C register 147. These protections ensure robust operation in automotive and industrial environments where voltage transients and thermal stress are common. The A5947KLPTR-B-T also supports latched or auto-retry fault recovery modes.
Can the A5947KLPTR-B-T drive fans with different pole pair counts?
Yes, the A5947KLPTR-B-T supports configurable pole pair count via EEPROM PP bits (address 82, bits 6:4), allowing selection of 2–9 pole pairs (PP+1). This adjusts the relationship between electrical frequency and mechanical RPM (RPM = 30 × fFG), ensuring accurate tachometer output and proper commutation timing. The A5947KLPTR-B-T's FG pin outputs pulses at 30× RPM regardless of pole count, simplifying host system speed monitoring.
A5947KLPTR-B-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Bulk
- Product Status:
- Active
- 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:
- 3.6A
- Voltage - Supply:
- 40V
- Voltage - Load:
- 40V
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- Automotive
- Qualification:
- AEC-Q100
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-TSSOP-EP
A5947KLPTR-B-T FAQ
1.How can I place an order for A5947KLPTR-B-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A5947KLPTR-B-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 A5947KLPTR-B-T reliable?
The price and inventory of A5947KLPTR-B-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A5947KLPTR-B-T is usually 5 days.
3.What payment methods are accepted for A5947KLPTR-B-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A5947KLPTR-B-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A5947KLPTR-B-T?
A5947KLPTR-B-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A5947KLPTR-B-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 A5947KLPTR-B-T?
For technical support, including A5947KLPTR-B-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A5947KLPTR-B-T requirements.
6.How does Aetrix verify that A5947KLPTR-B-T is sourced from the original manufacturer or authorized distributors?
All A5947KLPTR-B-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 A5947KLPTR-B-T meets industry standards.
7.What is the process for return or replacement of A5947KLPTR-B-T?
All A5947KLPTR-B-T units undergo pre-shipment inspection (PSI). If there is an issue with A5947KLPTR-B-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 A5947KLPTR-B-T part is unused and in its original packaging.
Return procedure for A5947KLPTR-B-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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