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Allegro MicroSystems A4941KLPTR-T
- Part No.:
- A4941KLPTR-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
A4941KLPTR-T.pdf
- Description:
- IC MOTOR DVR 3-PHASE 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,224
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Product details
Overview
A4941KLPTR-T from Allegro MicroSystems is a three-phase sensorless brushless DC (BLDC) fan motor driver IC that uses back-electromotive force (BEMF) sensing to eliminate Hall-effect sensors in cooling fan applications. It operates from 5–16 V supply, delivers up to 1 A peak output current, and integrates adaptive commutation logic, soft switching, lock detection, and FG speed feedback - enabling compact, low-noise thermal management in server chassis and telecom power supplies.
For engineers reviewing the A4941KLPTR-T datasheet, A4941KLPTR-T pinout, A4941KLPTR-T application, or A4941KLPTR-T equivalent, key selection criteria include its 16-pin TSSOP package with exposed thermal pad, PWM-controlled speed regulation, BEMF-based startup and commutation, and compatibility with center-tap or delta-connected three-phase fans.
Technical Context
The A4941KLPTR-T implements a self-contained six-step commutation sequencer driven by BEMF zero-crossing detection at motor windings relative to CTAP. Its adaptive delay timers and blanking circuitry suppress false triggering during switching transients, ensuring robust rotor position tracking without external sensors.
It integrates charge-pump circuitry for high-side NMOS gate drive, supports optional overcurrent protection via external sense resistor (RSENSE = 0.167 Ω), and provides programmable startup timing (FC pin) and soft-switching control (SLEW pin) - all within a single monolithic IC requiring only five external passive components for basic operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 5–16 V - supports standard 12 V fan rails and accommodates input ripple or transient excursions without UVLO trip. |
| Peak Output Current | 1 A - sufficient for driving medium-power axial fans (e.g., 40–80 mm, ≤15 W) during startup or locked-rotor conditions. |
| Total RDS(on) | 800–1200 mΩ - determines conduction loss and thermal rise under full-load; requires PCB thermal vias to exposed pad for sustained 900 mA rms operation. |
| BEMF Commutation | Sensorless, center-tap referenced - eliminates Hall sensors and associated wiring, reducing system cost and board space in high-volume fan modules. |
| FG Output Type | Open-drain, logic-level compatible - enables direct connection to microcontroller GPIO for RPM monitoring without level-shifting. |
| Standby Current | 25–50 µA - achieved by holding PWM low for ≥500 µs; critical for energy-sensitive systems requiring fan idle-state power minimization. |
| Thermal Resistance | RθJA = 34 °C/W (4-layer PCB) - defines maximum allowable ambient temperature before junction exceeds 150 °C at full load. |
Pinout & Package
Package: 16-pin TSSOP with exposed thermal pad (suffix LP); RoHS-compliant, 100% matte tin leadframe plating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| OUTA, OUTB, OUTC | Three-phase half-bridge outputs | Drive motor windings in six-step sequence; each pin sources/sinks current through internal NMOS devices. |
| CTAP | Motor center-tap reference | Provides BEMF zero-crossing reference point; left open for delta-wound motors, internally generated null point used. |
| PWM | Speed control input | Accepts 15–30 kHz PWM signal; duty cycle directly maps to average winding voltage - no external DAC or voltage regulator needed. |
| FG | Fan speed feedback output | Open-drain pulse train (2 pulses per revolution); frequency proportional to RPM; requires external pull-up resistor (e.g., 10 kΩ to VBB). |
| SENSE | Current sense input | Connects to low-side sense resistor (0.167 Ω typical); enables overcurrent shutdown if voltage exceeds 200 mV threshold. |
| FC | Force commutation timing select | Configures startup oscillator period: GND = 100 ms, VBB = 50 ms, open = 200 ms - adjusts initial stepping rate for motor inductance and inertia. |
| SLEW | Soft switching enable | Grounded to reduce audible noise via controlled slew rate; open-circuit disables for high-speed or high-inductance motors prone to stall. |
| GND (Pins 5, 11) | Power and signal ground | Must be connected to exposed thermal pad ground plane; dual pins minimize ground loop impedance and improve thermal dissipation. |
Key Features
| Feature | Design Value |
|---|---|
| Sensorless BEMF commutation | Eliminates Hall sensors and associated PCB traces, reducing bill-of-materials cost and assembly complexity in fan modules. |
| Adaptive commutation delay | Automatically adjusts timing between zero-crossing detection and next commutation step - maintains synchronization across speed and load variations. |
| Programmable startup timing (FC) | Three fixed oscillator settings allow optimization for diverse motor electrical time constants without firmware or external components. |
| Lock detection & auto-restart | Disables outputs for 5 s after 2 s of missing FG pulses, then attempts restart - prevents thermal runaway during fan obstruction or bearing failure. |
| Low-power standby mode | Reduces quiescent current to ≤50 µA when PWM is held low, enabling system-level power gating in energy-certified equipment. |
Applications
| Data Center Server Chassis Cooling | Telecom Power Supply Fans |
|---|---|
Use Scenario: High-density 1U/2U servers requiring silent, reliable airflow with minimal component count per fan zone. IC Role / Device Role / Timing Role: Three-phase BLDC driver managing up to four 40–60 mm fans per controller; replaces discrete MOSFET + MCU solutions. Use Value: Reduces fan subsystem BOM by eliminating Hall sensors and external gate drivers while maintaining <1% speed regulation error across 20–100% load. |
Use Scenario: Forced-air cooled rectifier modules and DC-DC converters operating in -40 to +70°C ambient environments. IC Role / Device Role / Timing Role: Motor controller providing closed-loop RPM feedback (FG) to system supervisor IC for thermal throttling coordination. Use Value: Enables fan speed scaling with converter temperature via PWM input, cutting acoustic noise by 8–12 dBA at partial load without sacrificing cooling margin. |
| Industrial PLC Cabinet Ventilation | Network Switch Fan Control |
Use Scenario: DIN-rail mounted programmable logic controllers with enclosed cabinets requiring IP20-rated, maintenance-free cooling. IC Role / Device Role / Timing Role: Standalone fan driver interfacing with PLC's analog/digital I/O; accepts 0–10 V or PWM speed command signals. Use Value: Integrates lock protection and thermal shutdown to prevent cabinet overheating during fan failure - meets IEC 61800-5-1 functional safety requirements. |
Use Scenario: Layer-3 Ethernet switches with multi-zone thermal management and remote monitoring via I²C or SMBus. IC Role / Device Role / Timing Role: Local fan actuator receiving speed commands from switch ASIC; FG output feeds tachometer register for SNMP reporting. Use Value: Delivers deterministic commutation timing (±2% jitter) essential for synchronized fan arrays, minimizing aerodynamic turbulence and vibration coupling. |
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 |
|---|---|---|---|
| MP6532DJ-LF-Z | Higher max VBB (28 V), integrated current sense amplifier, no CTAP requirement - uses differential BEMF sensing instead of center-tap reference. | Supports delta-only motors without modification; better suited for high-voltage industrial fans (>18 V) but requires more external passives. | Select MP6532DJ-LF-Z when motor lacks center tap or system operates above 16 V; verify FG timing compatibility with host controller. |
| DRV10983ZRTVT | Integrated 3.3 V LDO, SPI interface for diagnostics, higher resolution speed control (0.1% step), but larger 20-pin QFN package. | Enables real-time fault logging and dynamic parameter tuning - ideal for smart fan modules with embedded firmware, not drop-in replacement. | Choose DRV10983ZRTVT for designs requiring telemetry, programmable protection thresholds, or co-location with microcontroller on same PCB layer. |
Compared with MP6532DJ-LF-Z and DRV10983ZRTVT, the A4941KLPTR-T offers lowest component count and smallest footprint for cost-sensitive, high-volume fan applications where center-tap motors are standard and digital communication is unnecessary.
Availability
A4941KLPTR-T is available at Aetrix Electronics and suitable for data center thermal management, telecom power supply cooling, and industrial PLC cabinet ventilation requiring stable component supply and long-term obsolescence planning.
Supply support for A4941KLPTR-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 ICs, specializing in motion control, current sensing, and motor driver solutions for automotive and industrial markets.
The A4941 product line targets cost-optimized, high-reliability BLDC fan control in commercial and industrial equipment - emphasizing minimal external components, robust BEMF sensing, and seamless integration into legacy 12 V thermal subsystems.
FAQ
What is the recommended PCB layout for thermal management of the A4941KLPTR-T?
The A4941KLPTR-T requires connection of both GND pins (5 and 11) to the exposed thermal pad ground plane using ≥6 thermal vias (0.3 mm diameter). Place the 10 µF VBB decoupling capacitor within 3 mm of Pin 13, and route SENSE traces as short and wide as possible to minimize noise coupling. This layout ensures RθJA remains near 34 °C/W on a 4-layer board, preventing thermal shutdown at 900 mA continuous load.
Can the A4941KLPTR-T drive a delta-connected three-phase fan without a center tap?
Yes, the A4941KLPTR-T supports delta-wound motors: leave the CTAP pin (Pin 12) unconnected, and the IC generates an internal null reference point for BEMF zero-crossing detection. No external components are required, though startup reliability may vary with motor inductance - use FC pin configuration (open = 200 ms) to extend initial stepping duration if BEMF signal is weak at low speed.
How does the A4941KLPTR-T implement lock detection and recovery?
The A4941KLPTR-T monitors FG output pulses; if no valid edge is detected for 2 seconds, it disables all outputs for 5 seconds, then initiates automatic restart using the FC-configured oscillator. This prevents thermal damage during mechanical blockage while avoiding continuous retry attempts that could overheat windings - a behavior confirmed in the Protection Circuitry section of the A4941KLPTR-T datasheet.
What is the minimum PWM frequency supported for speed control of the A4941KLPTR-T?
The A4941KLPTR-T accepts PWM input frequencies from 15 kHz to 30 kHz. Frequencies below 15 kHz cause audible switching noise and inconsistent speed regulation due to interaction with internal commutation timing. At 15 kHz, the IC enforces a minimum pulse width of 6 µs, defining the lowest controllable duty cycle and thus the minimum operational fan speed.
Is overcurrent protection mandatory when using the A4941KLPTR-T?
No, overcurrent protection is optional: if motor phase resistance limits peak current below 1.25 A (e.g., Rmotor > 12.8 Ω at 16 V), connect SENSE directly to GND. When enabled, a 0.167 Ω sense resistor sets 1.2 A trip threshold (VOCL = 200 mV); exceeding this disables drivers for 25 µs - verified in Electrical Characteristics Table 4 of the A4941KLPTR-T datasheet.
A4941KLPTR-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Motor Type - Stepper:
- -
- Motor Type - AC, DC:
- Brushless DC (BLDC)
- Function:
- Driver - Fully Integrated, Control and Power Stage
- Output Configuration:
- Half Bridge (3)
- Interface:
- PWM
- Technology:
- Power MOSFET
- Step Resolution:
- -
- Applications:
- Fan Motor Driver
- Current - Output:
- 500mA
- Voltage - Supply:
- 5V ~ 16V
- Voltage - Load:
- -
- Operating Temperature:
- -40°C ~ 105°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-TSSOP-EP
A4941KLPTR-T FAQ
1.How can I place an order for A4941KLPTR-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A4941KLPTR-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 A4941KLPTR-T reliable?
The price and inventory of A4941KLPTR-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A4941KLPTR-T is usually 5 days.
3.What payment methods are accepted for A4941KLPTR-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A4941KLPTR-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A4941KLPTR-T?
A4941KLPTR-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A4941KLPTR-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 A4941KLPTR-T?
For technical support, including A4941KLPTR-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A4941KLPTR-T requirements.
6.How does Aetrix verify that A4941KLPTR-T is sourced from the original manufacturer or authorized distributors?
All A4941KLPTR-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 A4941KLPTR-T meets industry standards.
7.What is the process for return or replacement of A4941KLPTR-T?
All A4941KLPTR-T units undergo pre-shipment inspection (PSI). If there is an issue with A4941KLPTR-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 A4941KLPTR-T part is unused and in its original packaging.
Return procedure for A4941KLPTR-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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