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Allegro MicroSystems A3940KLW
- Part No.:
- A3940KLW
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 28-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
A3940KLW.pdf
- Description:
- IC MOTOR DRIVER 7V-40V 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,644
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Product details
Overview
A3940KLW from Allegro MicroSystems is a full-bridge power MOSFET controller designed for automotive high-power motor drive applications. It delivers four high-current gate drive outputs, supports 100% duty cycle operation via integrated charge pump, and provides motor lead short-to-battery/short-to-ground fault detection with programmable dead-time adjustment. It operates across –40°C to +150°C junction temperature and drives n-channel MOSFETs in electric power steering and HVAC blower systems.
For engineers reviewing the A3940KLW datasheet, A3940KLW pinout, A3940KLW application, or A3940KLW equivalent, key selection criteria include bootstrap-capable high-side drive, VBB overvoltage threshold adjustability (via OVSET), thermal shutdown at 172°C, and compatibility with 7–40 V battery supply rails in safety-critical automotive subsystems.
Technical Context
The A3940KLW implements dual independent half-bridge gate drivers with synchronous rectification control and programmable dead-time logic using external resistor (IDEAD) and LONG pin selection. Its charge pump (VCP = VBB + 10.7 V typical) enables DC operation of high-side n-MOSFETs without external boost circuitry.
Fault protection integrates Kelvin-connected VDRAIN monitoring for short-to-ground detection, LSS-referenced short-to-battery sensing, and VREG13/VBB undervoltage/overvoltage comparators with user-adjustable thresholds. All fault states assert open-drain FAULT output and force coast mode (GHx = GLx = 0).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VBB Supply Range | 7 V to 40 V - supports 12 V and 24 V automotive battery systems with overvoltage trip points adjustable from 16 V to 39 V via OVSET pin |
| Junction Temp Range | –40°C to +150°C - qualified for under-hood automotive environments including EPS and transmission control units |
| Gate Drive Outputs | Four: GHA/GLA & GHB/GLB - each capable of 700 mA source / 800 mA sink pulsed current at 25°C for driving large n-MOSFET gates |
| Dead Time Adjustment | 0.3 µs to 345 µs - set by RDEAD (12.1 kΩ–499 kΩ) and LONG pin to prevent shoot-through during phase transitions |
| VREG13 Output | 13.3 V ±0.7 V - powers low-side drivers and charges bootstrap capacitors; dropout voltage ≤0.7 V at 15 mA load |
| Fault Detection Latency | 1.7 µs noise filter - ensures robust operation in EMI-heavy vehicle electrical systems without false triggering |
| Thermal Shutdown | 172°C ±12°C - latched fault with 12°C hysteresis prevents thermal cycling during overload conditions |
Pinout & Package
A3940KLW is housed in a 28-pin wide-body SOIC package with gull-wing leads, optimized for automotive PCB layouts requiring thermal reliability and creepage clearance. The exposed pad is not internally connected to GND per datasheet specification.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VDRAIN (1) | Kelvin sense node | Direct connection to high-side MOSFET drains enables accurate short-to-ground detection independent of PCB trace resistance |
| LSS (2) | Low-side source reference | Common return for GLA/GLB drivers and short-to-battery monitor reference - must tie to low-side MOSFET sources |
| GHB (5) / GHA (10) | High-side gate drive outputs | Drive n-MOSFET gates with VCP-supplied voltage; require external series resistors to control slew rate and EMI |
| GLB (3) / GLA (12) | Low-side gate drive outputs | Sink current into low-side MOSFET gates; referenced to LSS, not GND - critical for accurate short-to-battery sensing |
| OVSET (19) | Analog threshold input | Resistor-divider voltage from VREG5 sets VBB overvoltage trip point (16–39 V range); floating disables protection |
| VDSTH (28) | Fault threshold input | Configures short-to-ground/short-to-battery detection level (0.3–3.0 V range); determines VSTG(th) and VSTB(th) thresholds |
| FAULT (18) | Open-drain diagnostic output | Asserts logic high on any fault condition; requires external pull-up to VREG5 and interfaces directly with MCU GPIO interrupt pins |
| RESET (24) | Asynchronous control input | Logic low forces coast mode, clears latched faults, and reduces quiescent current to 1.0 µA - used for system-level fault recovery |
Key Features
| Feature | Design Value |
|---|---|
| Charge-pump boosted high-side drive | Enables true 100% duty cycle operation without external boost IC - eliminates need for external diode/capacitor bootstrap networks |
| Programmable dead-time logic | Two-range adjustment (short/long) via RDEAD + LONG pin prevents shoot-through across wide MOSFET gate charge ranges (Qg = 20–200 nC) |
| Kelvin-connected VDRAIN monitoring | Removes PCB trace IR drop error from short-to-ground detection - improves fault threshold accuracy to ±0.1 V over temperature |
| Synchronous rectification control | SR pin enables body-diode conduction replacement with active low-side FET turn-on - reduces heat generation in PWM decay modes |
| Automotive-grade thermal shutdown | 172°C trip with 12°C hysteresis ensures safe operation during sustained overload while avoiding nuisance shutdowns in hot under-hood environments |
Applications
| Electric Power Steering (EPS) | HVAC Blower Motor Control |
|---|---|
Use Scenario: High-torque bidirectional motor control in column-assist or rack-assist EPS modules operating at 12 V nominal battery voltage with transient surges up to 40 V. IC Role / Device Role / Timing Role: Full-bridge gate driver controlling four external n-MOSFETs; manages PWM timing, dead-time insertion, and real-time fault response within <2 µs latency. Use Value: Integrated VDRAIN Kelvin sensing and programmable OVSET enable reliable short-circuit detection during assist transients without external analog front-end components. | Use Scenario: Variable-speed cabin air blower in premium automotive platforms requiring quiet operation, smooth acceleration, and ASIL-B compliance. IC Role / Device Role / Timing Role: Gate driver with synchronous rectification (SR) support and fast/slow decay mode selection (MODE pin) to minimize audible motor whine and reduce MOSFET switching losses. Use Value: VREG13-regulated 13.3 V supply ensures stable high-side gate voltage across battery dips to 7 V - maintaining torque delivery during cranking events. |
| Transmission Valve Actuator | Seat/Mirror Positioning Motor |
Use Scenario: Precision proportional control of solenoid valves in 8-speed automatic transmissions where duty cycle linearity and thermal robustness are critical. IC Role / Device Role / Timing Role: Full-bridge controller executing microsecond-accurate PWM with adjustable dead time to prevent shoot-through during rapid direction reversal. Use Value: Thermal shutdown at 172°C protects against coil overheating during stall conditions - eliminating need for external thermistors or software-based thermal modeling. | Use Scenario: Compact, low-noise actuators for power seats and mirrors in luxury vehicles requiring silent operation and long-term reliability. IC Role / Device Role / Timing Role: Motor driver implementing coast/brake/fast-decay modes via PHASE/ENABLE/MODE inputs to eliminate mechanical backlash and position overshoot. Use Value: Fault diagnostic output (FAULT pin) provides immediate hardware-level indication of open-load or short-circuit conditions - enabling fail-safe ECU responses without polling delays. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar full-bridge gate driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| A3941KLPTR-T | Successor device with enhanced ESD rating (±8 kV HBM), updated thermal shutdown threshold (165°C), and improved VREG13 load regulation (±2 mV vs. ±5 mV) | Qualified for newer automotive platforms requiring ISO 10605 compliance and tighter supply regulation in ADAS-related motor subsystems | Select A3941KLPTR-T for new designs requiring extended lifecycle support and higher ESD immunity; A3940KLW remains viable for legacy repair and obsolescence management |
| TLE9201SG | Integrated high-/low-side drivers with embedded current sense amplifier; lacks programmable dead time and Kelvin VDRAIN sensing | Better suited for compact single-package solutions where board space is constrained but fault diagnostics are less stringent | Choose TLE9201SG only when current measurement integration outweighs need for precision short-circuit localization - not a drop-in replacement |
Compared with A3940KLW, A3941KLPTR-T offers higher ESD robustness and tighter regulation for next-gen automotive ECUs, while TLE9201SG trades off diagnostic precision for monolithic integration - neither matches A3940KLW's Kelvin-sensed fault localization capability.
Availability
A3940KLW is available at Aetrix Electronics and suitable for electric power steering, HVAC blower control, and transmission actuator applications requiring stable component supply amid automotive production cycles.
Supply support for A3940KLW 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 power ICs, specializing in automotive and industrial motion control solutions since 1989.
The A3940 product line was engineered specifically for high-reliability automotive motor drive systems requiring robust fault diagnostics, wide input voltage tolerance, and extended temperature operation - targeting EPS, HVAC, and chassis actuation markets.
FAQ
What is the maximum allowable VBB voltage for continuous operation of the A3940KLW?
The A3940KLW supports continuous operation up to 40 V on the VBB pin. Absolute maximum rating is +40 V; exceeding this risks permanent damage. Overvoltage protection triggers at user-configurable thresholds between 16 V and 39 V via the OVSET pin, but the device itself remains functional up to 40 V regardless of OVSET setting. Always observe derating guidelines in the datasheet for sustained high-temperature operation.
Does the A3940KLW support 100% duty cycle operation, and how is it implemented?
Yes, the A3940KLW supports true 100% duty cycle operation through its integrated charge pump circuit. The VCP output supplies VBB + 10.7 V (typical) to the VREG13 regulator, which then powers the high-side gate drivers. This eliminates reliance on bootstrap capacitor recharge during low-duty-cycle intervals - enabling continuous high-side FET conduction required in applications like electric parking brakes and holding torque scenarios.
How does the VDRAIN pin improve short-to-ground fault detection accuracy in the A3940KLW?
The VDRAIN pin provides a Kelvin connection directly to the high-side MOSFET drains, bypassing PCB trace resistance that would otherwise introduce voltage measurement error. This allows the A3940KLW to compare drain-to-source voltage against the VDSTH threshold with ±0.1 V accuracy over temperature - critical for distinguishing actual shorts from normal voltage drops during high-current transients in EPS and transmission valve applications.
Can the A3940KLW drive both N-channel and P-channel MOSFETs in the same bridge configuration?
No, the A3940KLW is designed exclusively for n-channel MOSFETs in both high-side and low-side positions. Its gate drive architecture relies on bootstrapped high-side supply (via CA/CB) and charge-pump boosted VCP voltage - incompatible with p-channel high-side configurations. Attempting to use p-channel devices will result in improper turn-on behavior and potential shoot-through due to mismatched threshold control.
What happens to the A3940KLW gate drive outputs during thermal shutdown?
During thermal shutdown, the A3940KLW asserts the FAULT pin high and disables both VREG13 and VREG5 regulators. As VREG13 collapses below 4 V, the GHx and GLx outputs transition to high-impedance (Z) state - effectively removing gate drive from all external MOSFETs. This is a latched condition requiring either removal of thermal stress or a RESET = 0 pulse to clear and resume operation.
A3940KLW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 28-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Motor Type - Stepper:
- -
- Motor Type - AC, DC:
- Brushed DC
- Function:
- Controller - Commutation, Direction Management
- Output Configuration:
- Pre-Driver - Half Bridge (2)
- Interface:
- Parallel
- Technology:
- Power MOSFET
- Step Resolution:
- -
- Applications:
- -
- Current - Output:
- -
- Voltage - Supply:
- 7V ~ 40V
- Voltage - Load:
- -
- Operating Temperature:
- -40°C ~ 135°C (TA)
- Grade:
- Automotive
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-SOIC
A3940KLW FAQ
1.How can I place an order for A3940KLW through Aetrix?
Please submit a Request for Quotation (RFQ) for A3940KLW 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 A3940KLW reliable?
The price and inventory of A3940KLW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3940KLW is usually 5 days.
3.What payment methods are accepted for A3940KLW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3940KLW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3940KLW?
A3940KLW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3940KLW 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 A3940KLW?
For technical support, including A3940KLW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3940KLW requirements.
6.How does Aetrix verify that A3940KLW is sourced from the original manufacturer or authorized distributors?
All A3940KLW 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 A3940KLW meets industry standards.
7.What is the process for return or replacement of A3940KLW?
All A3940KLW units undergo pre-shipment inspection (PSI). If there is an issue with A3940KLW, 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 A3940KLW part is unused and in its original packaging.
Return procedure for A3940KLW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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