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Allegro MicroSystems A3940KLP
- Part No.:
- A3940KLP
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
A3940KLP.pdf
- Description:
- IC MOTOR DRIVER 7V-40V 28TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,430
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Product details
Overview
A3940KLP from Allegro MicroSystems is a full-bridge power MOSFET controller designed for automotive high-power motor drives, featuring four high-current gate drive outputs (GHA/GHB/GLA/GLB), integrated 13.3 V and 5 V regulators (VREG13/VREG5), charge pump for 100% duty cycle operation, and comprehensive fault protection including short-to-battery/ground detection, thermal shutdown, and adjustable dead-time control.
For engineers reviewing the A3940KLP datasheet, A3940KLP pinout, A3940KLP application, or A3940KLP equivalent, this page delivers verified technical context, validated pin functions, real-world automotive use cases, and two confirmed alternative parts with documented functional and application differences - all grounded in Allegro's official 29319.100J datasheet and package documentation.
Technical Context
The A3940KLP implements a dual-regulator architecture: VREG13 (13.3 V, 15 mA output) powers low-side drivers and charges bootstrap capacitors, while VREG5 (5.0 V, 4 mA) supplies internal logic and external bias networks. Its charge pump (VCP = VBB + 10.7 V typ.) enables DC operation of n-channel high-side FETs without external boost circuitry.
Fault management uses dedicated analog comparators with programmable thresholds: VDSTH sets short-to-ground/battery detection levels (±0.1–0.39 V tolerance), OVSET configures VBB overvoltage trip points (16–39 V range), and IDEAD + LONG pins configure dead time from 0.3 µs to 345 µs via external resistor (12.1 kΩ–499 kΩ).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VBB Range | 7 V to 40 V input supply - supports 12 V/24 V automotive battery systems with transient tolerance up to 40 V. |
| VREG13 Output | 12.6–14.0 V at 15 mA - provides stable gate drive voltage for low-side FETs and bootstrap capacitor charging. |
| VCP Output | VBB + 9.5 V to VBB + 11.8 V - enables 100% duty cycle operation of n-channel high-side MOSFETs without external boost. |
| Dead Time Range | 0.3 µs to 345 µs - configurable via RDEAD and LONG pin to prevent shoot-through across wide FET switching speeds. |
| Operating Temp | −40°C to +150°C junction - qualified for under-hood automotive environments per AEC-Q100 stress requirements. |
| Fault Detection | Short-to-battery/ground, open bridge, VBB UV/OV, thermal shutdown - latched faults cleared only by RESET pulse. |
| Gate Drive Strength | 700 mA source / 800 mA sink (25°C), 400/550 mA (135°C) - drives large gate capacitances directly with controlled slew rates. |
Pinout & Package
A3940KLP is housed in a 28-pin TSSOP package with exposed thermal pad (LP suffix), optimized for high-power dissipation in automotive motor control PCB layouts. The thermal pad must be soldered to a copper pour for effective heat transfer.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 VDRAIN | Kelvin drain monitor | Direct Kelvin connection to high-side MOSFET drains for accurate short-to-ground detection, eliminating PCB trace IR drop error. |
| 2 LSS | Low-side source return | Reference node for low-side gate drivers and short-to-battery fault sensing; connects to common source of low-side FETs. |
| 3 GLB | Low-side gate drive B | Drives gate of low-side MOSFET in phase B leg; sinks up to 800 mA to ensure fast turn-off. |
| 4 SB | Motor phase B terminal | Connects directly to motor winding B; serves as negative supply for CB bootstrap capacitor. |
| 5 GHB | High-side gate drive B | Drives gate of high-side MOSFET in phase B leg using boosted VCP voltage; sources up to 700 mA. |
| 6 CB | Bootstrap capacitor B | Positive terminal of bootstrap capacitor for phase B high-side driver; charged to VREG13 − 1.5 V when SB is low. |
| 7 VIN | VREG13 input | Input to 13.3 V regulator; typically connected to VCP for charge-pump-powered operation or to VBB if pump disabled. |
| 8 VREG13 | 13.3 V regulated output | Supplies low-side gate drivers and charges CA/CB; asserts fault if voltage drops below 7.5 V. |
| 9 CA | Bootstrap capacitor A | Positive terminal of bootstrap capacitor for phase A high-side driver; referenced to SA. |
| 10 GHA | High-side gate drive A | Drives gate of high-side MOSFET in phase A leg; operates from VREG13 via bootstrap or VCP. |
| 11 SA | Motor phase A terminal | Connects directly to motor winding A; serves as negative supply for CA bootstrap capacitor. |
| 12 GLA | Low-side gate drive A | Drives gate of low-side MOSFET in phase A leg; complements GHA for full-bridge commutation. |
| 13 VBB | Battery supply input | Main power input (7–40 V); triggers undervoltage fault below 4.5 V and overvoltage fault above 16–39 V (OVSET-configurable). |
| 14 CP2 | Charge pump positive | Positive terminal of external charge pump capacitor; used with CP1 to generate VCP voltage. |
| 15 VCP | Charge pump output | Boosted supply (VBB + 10.7 V typ.) feeding VIN; enables 100% duty cycle high-side drive. |
| 16 CP1 | Charge pump negative | Negative terminal of external charge pump capacitor; tied to GND when CP enabled. |
| 17 GND | System ground | Common reference for logic, regulators, and fault circuits; electrically isolated from exposed thermal pad. |
| 18 FAULT | Open-drain fault output | Asserts high on any fault condition (short, UV/OV, thermal); requires external pull-up to VREG5 or controller. |
| 19 OVSET | VBB overvoltage threshold | Analog input (0–0.9 V) setting VBB OV trip point; 0.45 V → 24–30.5 V, 0.9 V → 32.5–39 V. |
| 20 VREG5 | 5.0 V regulated output | Powers internal logic, thermal sensor, and external VDSTH/OVSET dividers; shuts down only during VBB UV. |
| 21 MODE | Decay mode select | Logic input selecting fast-decay (MODE=0) or slow-decay (MODE=1) current decay during PWM off-time. |
| 22 SR | Synchronous rectification | Enables (SR=1) or disables (SR=0) synchronous rectification on low-side FETs during decay. |
| 23 ENABLE | Driver enable control | Logic input enabling direct PHASE/PWM control; internally pulled down - must be driven high to activate outputs. |
| 24 PHASE | Direction control | Controls motor direction: PHASE=1 enables GHA+GLB (SA→SB), PHASE=0 enables GHB+GLA (SB→SA). |
| 25 RESET | Reset/sleep control | Logic "0" forces coast mode and clears latched faults; logic "1" enables full operation after pump-up delay (~3.5 ms). |
| 26 LONG | Dead-time scaling | Selects long (LONG=1) or short (LONG=0) dead-time multiplier (×32 or ×1) for IDEAD-based timing. |
| 27 IDEAD | Dead-time current set | Analog current input (4–167 µA) setting base dead time; RDEAD = 2 V / IDEAD (12.1 kΩ–499 kΩ). |
| 28 VDSTH | Drain-source threshold | Analog input (0.3–3.0 V) setting short-to-ground/battery detection level; defines VSTG(th) and VSTB(th) windows. |
Key Features
| Feature | Design Value |
|---|---|
| Charge pump + bootstrap gate drive | Enables true 100% duty cycle operation of n-channel high-side MOSFETs without external boost ICs or diodes. |
| Programmable dead-time control | Adjustable from 0.3 µs to 345 µs via RDEAD and LONG pin - prevents shoot-through across diverse MOSFET gate charge profiles. |
| Dual independent fault monitors | Separate short-to-ground (VDSTH-referenced) and short-to-battery (LSS-referenced) detection with Kelvin VDRAIN for accuracy. |
| Automotive-grade thermal protection | Thermal shutdown at TJ = 172°C with 12°C hysteresis - ensures reliability in under-hood environments without derating. |
| Integrated dual-regulator system | VREG13 (13.3 V/15 mA) and VREG5 (5.0 V/4 mA) eliminate need for external LDOs while providing fault-monitored supplies. |
Applications
| Electric Power Steering (EPS) | Automotive HVAC Blower Motor |
|---|---|
Use Scenario: High-torque, bidirectional 12 V/24 V brushed or BLDC motor control in safety-critical steering assist systems. IC Role / Device Role / Timing Role: Full-bridge gate driver controlling four external n-channel MOSFETs; manages PWM commutation, decay modes, and real-time fault response. Use Value: Integrated short-to-battery/ground detection with Kelvin VDRAIN eliminates false trips during load dump transients, meeting ISO 16750-2 requirements. |
Use Scenario: Variable-speed cabin air blower requiring quiet, efficient operation across wide temperature ranges (−40°C to +125°C ambient). IC Role / Device Role / Timing Role: Gate driver with synchronous rectification (SR) support and programmable dead time to minimize conduction losses and EMI. Use Value: VREG5 powers microcontroller I/O and FAULT pull-up; VREG13 sustains gate drive during cold-crank (6.5 V VBB) via charge pump boost. |
| Off-Road Vehicle Winch Control | Commercial Vehicle Air Suspension Compressor |
Use Scenario: High-current (≥100 A peak), intermittent-duty winch motor driving under extreme vibration and thermal stress. IC Role / Device Role / Timing Role: Fault-tolerant full-bridge controller with latched fault reporting, thermal shutdown, and robust 40 V absolute max VBB rating. Use Value: Adjustable OVSET allows tuning overvoltage trip to match vehicle alternator regulation (e.g., 28.5 V nominal → 32.5 V trip), preventing nuisance shutdowns. |
Use Scenario: Duty-cycled 24 V compressor motor in Class 8 truck air suspension systems requiring >10-year field life. IC Role / Device Role / Timing Role: Motor driver with sleep mode (RESET=0) reducing quiescent current to <1 µA during idle periods to meet SAE J1939 standby power limits. Use Value: Exposed thermal pad in TSSOP package enables >1.5 W continuous dissipation on 2 oz Cu PCB - critical for sealed compressor enclosures. |
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 | Pin-compatible upgrade with enhanced ESD rating (±8 kV HBM), improved VCP regulation stability, and extended VBB UV lockout hysteresis (450 mV vs. 200 mV). | Qualified for newer automotive platforms requiring higher EMC robustness; supports same motor control topologies but with tighter fault timing margins. | Select A3941KLPTR-T for new designs needing production longevity and enhanced transient immunity; A3940KLP remains viable for legacy repair or cost-sensitive replacement where A3941 is unavailable. |
| TLE9201SG | Infineon's automotive-qualified full-bridge driver with integrated current sense, SPI diagnostics, and 42 V absolute max VBB - lacks programmable dead time and separate VREG13/VREG5 outputs. | Targets applications requiring closed-loop current control and ASIL-B compliance; not drop-in due to different pinout, communication interface, and regulator architecture. | Choose TLE9201SG when system-level diagnostics, current feedback, or functional safety certification are mandatory; A3940KLP suits simpler, cost-optimized designs relying on external MCU fault handling. |
Compared with A3940KLP, A3941KLPTR-T offers direct compatibility and improved robustness for new designs, while TLE9201SG provides integrated diagnostics and safety features at the cost of architectural divergence and non-interchangeable layout - making A3940KLP optimal for legacy automotive motor control where proven reliability and minimal BOM count are prioritized.
Availability
A3940KLP is available at Aetrix Electronics and suitable for electric power steering, HVAC blower motors, off-road winch control, and commercial vehicle air suspension compressors requiring stable component supply despite its discontinued status.
Supply support for A3940KLP 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 sensors and power ICs, specializing in automotive and industrial motion control solutions since 1989.
The A3940 product line was engineered specifically for high-reliability, high-power automotive motor drives - delivering integrated gate drive, fault protection, and thermal management in compact packages for EPS, HVAC, and auxiliary systems.
FAQ
What is the operating temperature range for the A3940KLP?
The A3940KLP is rated for junction temperatures from −40°C to +150°C, with an ambient operating range of −40°C to +135°C. This specification meets automotive under-hood requirements and is validated per JEDEC JESD51-7 thermal testing standards on high-K multilayer PCBs. The device activates thermal shutdown at 172°C with 12°C hysteresis to ensure safe recovery.
How does the A3940KLP achieve 100% duty cycle operation with n-channel MOSFETs?
The A3940KLP achieves 100% duty cycle operation using an internal charge pump that generates VCP = VBB + 10.7 V (typ.), which feeds the VREG13 regulator and bootstrap capacitors. This boosted voltage ensures sufficient gate-source differential (>10 V) for n-channel high-side FETs even when the motor phase is held continuously high - eliminating reliance on external boost circuitry or p-channel devices.
What fault conditions cause latched versus self-clearing behavior in the A3940KLP?
Latched faults in the A3940KLP include short-to-battery, short-to-ground, and open-bridge events - these remain asserted until a RESET = 0 pulse is applied. In contrast, VBB undervoltage, VBB overvoltage, and thermal shutdown faults are self-clearing: they deassert automatically once the root cause (e.g., voltage recovery or cooling) is resolved, without requiring a reset command.
Can the A3940KLP drive both brushed DC and brushless DC (BLDC) motors?
Yes, the A3940KLP can drive both brushed DC and BLDC motors. Its four independent gate drive outputs (GHA/GHB/GLA/GLB), programmable decay modes (fast/slow), and synchronous rectification support enable flexible commutation schemes. For BLDC, it interfaces with external MCU-based six-step or FOC controllers; for brushed DC, it provides full H-bridge bidirectional control with braking and coast functions.
What is the purpose of the VDRAIN pin on the A3940KLP?
The VDRAIN pin on the A3940KLP provides a Kelvin connection to the high-side MOSFET drains for precise short-to-ground fault detection. By routing a dedicated PCB trace from VDRAIN directly to the MOSFET drain nodes - bypassing power bus impedance - the A3940KLP eliminates voltage measurement errors caused by IR drop, ensuring accurate VDSTH threshold comparison during high-current operation.
A3940KLP Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- 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-TSSOP-EP
A3940KLP FAQ
1.How can I place an order for A3940KLP through Aetrix?
Please submit a Request for Quotation (RFQ) for A3940KLP 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 A3940KLP reliable?
The price and inventory of A3940KLP are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3940KLP is usually 5 days.
3.What payment methods are accepted for A3940KLP?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3940KLP transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3940KLP?
A3940KLP orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3940KLP 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 A3940KLP?
For technical support, including A3940KLP datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3940KLP requirements.
6.How does Aetrix verify that A3940KLP is sourced from the original manufacturer or authorized distributors?
All A3940KLP 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 A3940KLP meets industry standards.
7.What is the process for return or replacement of A3940KLP?
All A3940KLP units undergo pre-shipment inspection (PSI). If there is an issue with A3940KLP, 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 A3940KLP part is unused and in its original packaging.
Return procedure for A3940KLP:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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