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Allegro MicroSystems A3940KLW-T
- Part No.:
- A3940KLW-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 28-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
A3940KLW-T.pdf
- Description:
- IC MOTOR DRIVER 7V-40V 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,034
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Product details
Overview
A3940KLW-T 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. Used in electric power steering (EPS), HVAC blower, and seat actuator systems.
For engineers reviewing the A3940KLW-T datasheet, A3940KLW-T pinout, A3940KLW-T application, or A3940KLW-T equivalent, this page delivers verified technical context, validated pin functions, confirmed protection features, and real-world automotive use cases - all grounded in Allegro's official documentation and electrical specifications.
Technical Context
The A3940KLW-T integrates dual high-side gate drivers with bootstrap and charge-pump circuitry enabling DC operation of n-channel MOSFETs, plus dual low-side drivers with synchronous rectification support. Its fault monitoring uses Kelvin-connected VDRAIN and LSS references to detect short-to-battery and short-to-ground conditions with user-configurable VDSTH threshold voltage.
Dead time is programmable via IDEAD current (12 kΩ–499 kΩ resistor to GND) and LONG logic input, yielding adjustable shoot-through prevention from 0.3 µs to 345 µs. Thermal shutdown activates at TJ = 172°C with 12°C hysteresis, and undervoltage/overvoltage protection operates across VBB = 4.5–39 V with user-adjustable overvoltage trip via OVSET.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VBB Range | 7 V to 40 V - supports wide automotive battery range including cold-crank (7 V) and load-dump (40 V) conditions. |
| VREG13 Output | 12.6–14.0 V at 15 mA - powers low-side drivers and charges bootstrap capacitors; dropout ≤0.7 V ensures stable operation down to VIN = 11 V. |
| VCP Output | VBB + 9.5 V to VBB + 11.8 V - enables 100% duty cycle high-side drive without external boost supply. |
| Dead Time Range | 0.3 µs to 345 µs - configurable via RDEAD and LONG pin to match MOSFET switching speed and prevent cross-conduction. |
| Fault Detection | Short-to-ground, short-to-battery, open-bridge, VBB UV/OV, thermal shutdown - all asserted on open-drain FAULT pin with noise filtering (1.7 µs). |
| Operating Temp | −40°C to +135°C ambient (TJ up to +150°C) - qualified for under-hood automotive environments. |
| Gate Drive Strength | 700 mA source / 800 mA sink (25°C), 400/550 mA at 135°C - drives large gate capacitances with controlled slew rate via external resistors. |
Pinout & Package
Package: 28-pin wide-body SOIC (KLW), Pb-free with 100% matte-tin leadframe plating. Exposed thermal pad not internally connected to GND.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 VDRAIN | Kelvin drain monitor | Direct connection to high-side MOSFET drains for accurate short-to-ground detection; eliminates PCB trace IR drop error. |
| 2 LSS | Low-side source return | Reference node for low-side fault sensing and GLx driver return; connects to common low-side MOSFET sources. |
| 3 GLB | Low-side gate drive B | Drives gate of low-side MOSFET in phase B leg; 800 mA sink capability supports fast turn-off. |
| 4 SB | Motor phase B terminal | Connects directly to motor winding B; also negative supply for CB bootstrap capacitor. |
| 5 GHB | High-side gate drive B | Drives gate of high-side MOSFET in phase B leg; bootstrapped or charge-pump powered for 100% duty cycle. |
| 6 CB | Bootstrap cap 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 linear regulator; typically tied to VCP or VBB ≥11 V to sustain high-side gate drive. |
| 8 VREG13 | 13.3 V regulated output | Powers low-side drivers and charges CA/CB; fault asserted if voltage drops below 7.5 V. |
| 9 CA | Bootstrap cap A | Positive terminal of bootstrap capacitor for phase A high-side driver; identical function to CB. |
| 10 GHA | High-side gate drive A | Drives gate of high-side MOSFET in phase A leg; synchronized with PHASE and ENABLE logic. |
| 11 SA | Motor phase A terminal | Connects directly to motor winding A; also 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 rail (7–40 V); powers VREG5, internal logic, and supplies VCP charge pump. |
| 14 CP2 | Charge pump positive | Connects to positive side of external charge pump capacitor; used only when charge pump enabled. |
| 15 VCP | Charge pump output | Regulated boost voltage (VBB + ~11 V); supplies VIN to sustain high-side drive during 100% duty cycle. |
| 16 CP1 | Charge pump negative | Connects to negative side of external charge pump capacitor; left open if charge pump disabled. |
| 17 GND | Common ground | Logic and supply return; electrically connected to exposed thermal pad in KLW package. |
| 18 FAULT | Open-drain fault indicator | Asserted high during any fault condition; requires external pull-up to VREG5 or controller; causes automatic coast. |
| 19 OVSET | VBB overvoltage threshold | Analog input (0–0.9 V) setting VBB OV trip point: 16–39 V range; 0.45 V → 24–30.5 V, 0.9 V → 32.5–39 V. |
| 20 VREG5 | 5 V regulated output | Powers internal logic, thermal sensor, and external resistor networks (OVSET, VDSTH); short-circuit protected to 28 mA. |
| 21 MODE | Decay mode select | Logic input: MODE = 1 → slow decay (braking), MODE = 0 → fast decay (coast); internal 50 kΩ pull-down. |
| 22 SR | Synchronous rectification | Enables active low-side conduction during off-time to reduce power loss; internal 50 kΩ pull-down. |
| 23 ENABLE | Driver enable control | Logic "1" enables PHASE-based PWM control; logic "0" disables outputs; internal 50 kΩ pull-down. |
| 24 PHASE | Direction control | PHASE = 1 → current SA→SB (forward), PHASE = 0 → SB→SA (reverse); internal 50 kΩ pull-down. |
| 25 RESET | Reset/sleep control | Logic "1" enables device; logic "0" clears latched faults and enters ultra-low-power sleep mode (<1 µA). |
| 26 LONG | Dead time scaling | Selects long (K=32) or short (K=1) dead time multiplier; used with RDEAD to set tDEAD = K(18.8RDEAD + 50) + 90 ns. |
| 27 IDEAD | Dead time current set | Analog current input (4–167 µA) set by resistor to GND; determines base dead time before LONG scaling. |
| 28 VDSTH | Fault threshold reference | DC voltage (0.3–3.0 V) setting short-to-ground/battery detection threshold; referenced to LSS or VDRAIN. |
Key Features
| Feature | Design Value |
|---|---|
| Charge-pump boosted gate drive | Enables true 100% duty cycle operation of n-channel high-side MOSFETs without external boost supply. |
| Programmable dead-time cross-conduction protection | Adjustable from 0.3 µs to 345 µs via RDEAD and LONG pin - matches diverse MOSFET switching speeds. |
| Kelvin VDRAIN fault sensing | Eliminates PCB trace resistance error in short-to-ground detection, enabling precise VDSTH threshold setting. |
| Synchronous rectification support | Reduces conduction losses during PWM off-time by actively turning on low-side FETs instead of freewheeling. |
| Multi-level fault diagnostics | Distinguishes short-to-battery, short-to-ground, open-bridge, VBB UV/OV, and thermal shutdown - each asserted on FAULT pin. |
Applications
| Electric Power Steering (EPS) | HVAC Blower Motor Control |
|---|---|
|
Use Scenario: Driving dual-phase brushless DC motor in column-assist EPS system requiring high torque at low speed and fault resilience during road shock events. IC Role / Device Role / Timing Role: Full-bridge gate driver controlling four external n-channel MOSFETs; manages direction (PHASE), braking (MODE), and fault response (FAULT) in real time. Use Value: Integrated short-to-ground/battery detection on VDRAIN/LSS prevents false trips during transient voltage spikes; 172°C thermal shutdown protects against motor stall overheating. |
Use Scenario: Controlling high-current 12 V blower motor in automotive HVAC system with variable-speed demand and EMI-sensitive cabin environment. IC Role / Device Role / Timing Role: Gate driver IC providing PWM-controlled full-bridge commutation, synchronous rectification (SR), and programmable dead time to minimize shoot-through EMI. Use Value: VREG5-powered OVSET/VDSTH resistor networks ensure stable fault thresholds across temperature; 5 V logic interface simplifies MCU integration. |
| Automotive Seat Actuator | Active Suspension Damping Control |
|
Use Scenario: Positioning heavy vehicle seats using bidirectional 24 V DC motor with strict functional safety requirements for stall and wiring fault detection. IC Role / Device Role / Timing Role: Full-bridge controller managing motor direction (PHASE), decay mode (MODE), and fault reporting (FAULT) with latch-clear on RESET pulse. Use Value: Latched fault behavior allows diagnostic logging before reset; programmable VDSTH (0.3–3.0 V) enables precise short detection across varied motor winding resistances. |
Use Scenario: Driving compact high-bandwidth damping actuators in semi-active suspension, demanding rapid PWM response and thermal robustness near engine bay. IC Role / Device Role / Timing Role: High-side/lower-side gate driver with charge-pump (VCP) and bootstrap (CA/CB) supporting 22.5 kHz PWM switching and 100% duty cycle hold. Use Value: VCP ripple <500 mV ensures stable high-side gate voltage during high-frequency PWM; 135°C ambient rating sustains operation in under-hood thermal zones. |
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 thermal performance, improved VCP regulation stability, and extended VBB UV lockout (4.5 V → 5.0 V). | Supports higher ambient temperatures and tighter battery UV margins; recommended for new designs targeting ASIL-B compliance. | Select A3941KLPTR-T for new designs requiring production longevity and improved fault margin; A3940KLW-T remains valid for legacy repair or existing inventory use. |
| TLE9201SG | Infineon automotive H-bridge driver with integrated current sense, SPI interface, and ASIL-B ready diagnostics - no external VDSTH/OVSET resistor networks required. | Offers digital configuration and embedded diagnostics but requires MCU firmware integration; lacks direct Kelvin VDRAIN monitoring. | Choose TLE9201SG when system-level functional safety certification (ISO 26262) and programmable diagnostics are mandatory; A3940KLW-T suits analog-control architectures with minimal MCU overhead. |
Compared with A3941KLPTR-T, the A3940KLW-T offers identical pinout and core functionality but lacks updated thermal derating and tighter UV thresholds; versus TLE9201SG, it provides simpler analog configuration and Kelvin-sensed fault detection but no embedded diagnostics or current measurement.
Availability
A3940KLW-T is available at Aetrix Electronics and suitable for electric power steering, HVAC blower, and seat actuator applications requiring stable component supply despite its discontinued status for new designs.
Supply support for A3940KLW-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 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 control, delivering robust full-bridge gate driving with integrated fault protection and thermal resilience for under-hood deployment.
FAQ
Is the A3940KLW-T still available for purchase?
Yes, A3940KLW-T is available through Aetrix Electronics for legacy design support, repair, and replacement. Although Allegro discontinued new design-in as of December 2016, Aetrix maintains traceable inventory with documented lot history and full datasheet compliance verification for the A3940KLW-T.
What is the key difference between A3940KLW-T and A3941KLPTR-T?
The A3941KLPTR-T is the designated replacement for the A3940KLW-T, offering identical pinout and function with improved thermal shutdown margin (172°C vs. same), tighter VBB undervoltage lockout (5.0 V min), and enhanced VCP regulation stability. The A3940KLW-T remains fully functional but lacks these refinements.
Can the A3940KLW-T drive both high-side and low-side n-channel MOSFETs without external level shifters?
Yes, the A3940KLW-T integrates a charge pump (VCP) and bootstrap circuitry (CA/CB) to generate gate voltages above VBB, enabling direct drive of high-side n-channel MOSFETs. Low-side drivers (GLA/GLB) operate referenced to LSS, eliminating need for level shifters in either half-bridge leg.
How does the A3940KLW-T detect short-to-ground faults?
The A3940KLW-T uses Kelvin-connected VDRAIN to monitor high-side drain-to-source voltage and LSS as reference for low-side detection. When GHx is active, VDRAIN-to-VSX voltage is compared to VDSTH; when GLx is active, VSX-to-LSS voltage is compared. Fault assertion occurs if measured voltage exceeds VDSTH ± tolerance band.
What package type does the A3940KLW-T use, and is thermal pad connected to GND?
The A3940KLW-T uses a 28-pin wide-body SOIC package (KLW suffix). Its exposed thermal pad is electrically connected to GND per Allegro's mechanical drawings and thermal test data, enabling effective heat dissipation when soldered to a thermally optimized PCB land pattern.
A3940KLW-T 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-T FAQ
1.How can I place an order for A3940KLW-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A3940KLW-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 A3940KLW-T reliable?
The price and inventory of A3940KLW-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3940KLW-T is usually 5 days.
3.What payment methods are accepted for A3940KLW-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3940KLW-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3940KLW-T?
A3940KLW-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3940KLW-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 A3940KLW-T?
For technical support, including A3940KLW-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3940KLW-T requirements.
6.How does Aetrix verify that A3940KLW-T is sourced from the original manufacturer or authorized distributors?
All A3940KLW-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 A3940KLW-T meets industry standards.
7.What is the process for return or replacement of A3940KLW-T?
All A3940KLW-T units undergo pre-shipment inspection (PSI). If there is an issue with A3940KLW-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 A3940KLW-T part is unused and in its original packaging.
Return procedure for A3940KLW-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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