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Allegro MicroSystems A3940KLWTR
- Part No.:
- A3940KLWTR
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 28-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
A3940KLWTR.pdf
- Description:
- IC MOTOR DRIVER 7V-40V 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,033
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Product details
Overview
A3940KLWTR 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 A3940KLWTR datasheet, A3940KLWTR pinout, A3940KLWTR application, or A3940KLWTR equivalent, this page delivers verified technical context, validated pin functions, confirmed protection features, real-world automotive use cases, and two documented alternative parts with precise functional and application-level differences.
Technical Context
The A3940KLWTR integrates dual high-side gate drivers with bootstrap and charge-pump circuitry enabling continuous DC operation of n-channel MOSFETs, even at low battery input (7 V). Its VREG13 regulator supplies 13.3 V ±0.7 V at up to 15 mA to drive low-side gates and charge bootstrap capacitors, while VREG5 delivers 5.0 V ±0.5 V for internal logic and external bias networks.
Fault management includes latched short-to-ground and short-to-battery detection using VDSTH-configurable thresholds, non-latched VBB undervoltage (5.25 V trip) and overvoltage (adjustable from 19.6 V to 36.4 V), thermal shutdown at 172°C, and noise-filtered open-drain FAULT output. Dead time is programmable from 0.3 µs to 345 µs via IDEAD current and LONG control pin.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VBB Range | 7 V to 40 V - supports full 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 gate drivers and charges bootstrap capacitors without external supply. |
| VCP Output | VBB + 9.5 V to VBB + 11.8 V - enables 100% duty cycle high-side drive for n-MOSFETs without external boost. |
| Dead Time Range | 0.3 µs to 345 µs - prevents shoot-through across wide MOSFET switching speed range via RDEAD and LONG pin. |
| TJ Operating Range | –40°C to +150°C - qualified for under-hood automotive environments per AEC-Q100 stress requirements. |
| Fault Detection Latency | 1.7 µs noise filter + 2 dead times - ensures accurate short-circuit detection after PWM transitions settle. |
| Thermal Shutdown | 172°C with 12°C hysteresis - protects against sustained overload while allowing recovery without power cycle. |
Pinout & Package
A3940KLWTR is supplied in a 28-pin wide-body SOIC package (KLW) with standard 0.050″ lead pitch and exposed thermal pad not internally connected to GND. The package supports industrial reflow and meets JEDEC MS-013 standards.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VDRAIN (1) | Kelvin drain monitor | Provides isolated high-side drain voltage sensing for accurate short-to-ground fault detection; eliminates PCB trace IR drop error. |
| LSS (2) | Low-side source return | Reference node for low-side MOSFET source terminals and short-to-battery fault monitoring. |
| GLB (3) | Low-side gate driver B | Sinks up to 800 mA (25°C) to turn on external n-MOSFET; ON resistance ≤6.0 Ω at 135°C ensures robust drive at high temp. |
| SB (4) | Motor phase B connection | Direct interface to motor winding B; also negative terminal for CB bootstrap capacitor and reference for high-side driver. |
| GHB (5) | High-side gate driver B | Sources up to 700 mA (25°C); uses VREG13 as supply; requires external series resistor to control slew rate and EMI. |
| CB (6) | Bootstrap capacitor B | Charged to VREG13 – 1.5 V when SB is low; lifts GHB gate above VBATT during high-side conduction. |
| VIN (7) | VREG13 input | Accepts VCP (charge-pump output) or direct VBB ≥11 V; enables flexible power architecture with or without charge pump. |
| VREG13 (8) | 13 V regulated output | Powers low-side drivers and charges CA/CB; dropout ≤0.7 V at 15 mA ensures stability under load. |
| CA (9) | Bootstrap capacitor A | Paired with SA; same function as CB but for phase A high-side driver GHA. |
| GHA (10) | High-side gate driver A | Matches GHB in specs; enables bidirectional full-bridge control with independent phase A/B timing. |
| SA (11) | Motor phase A connection | Direct interface to motor winding A; negative terminal for CA and reference for GHA floating supply. |
| GLA (12) | Low-side gate driver A | Matches GLB in specs; complements GHA for complete phase A low/high-side control. |
| VBB (13) | Battery supply input | Main power rail; monitored for UV (5.25 V) and OV (user-adjustable 19.6–36.4 V); faults asserted if out of range. |
| CP2 (14) | Charge pump positive | Connects to positive side of external charge-pump capacitor; used only when VCP regulation required below VBB+11 V. |
| VCP (15) | Charge pump output | Regulated at VBB+10.7 V typical; supplies VIN to VREG13; enables 100% duty cycle without external boost IC. |
| CP1 (16) | Charge pump negative | Connects to negative side of external charge-pump capacitor; left open if charge pump disabled. |
| GND (17) | Common ground | Logic and supply return; electrically isolated from exposed thermal pad in KLW package. |
| FAULT (18) | Open-drain fault indicator | Asserts high on any fault (latched or non-latched); pulls low internally during sleep; requires external pull-up to VREG5. |
| OVSET (19) | VBB overvoltage threshold | Analog input (0–0.9 V) sets VBB OV trip point; 0.45 V → 28 V, 0.9 V → 36.4 V; sourced from VREG5 divider. |
| VREG5 (20) | 5 V regulated output | Powers internal logic, thermal sensor, and external VDSTH/OVSET dividers; short-circuit protected to 28 mA. |
| MODE (21) | Decay mode select | Logic 0 = fast decay (both HS/LS off), Logic 1 = slow decay (HS off only); determines motor current recirculation path. |
| SR (22) | Synchronous rectification | Logic 1 enables LS FET conduction during HS off time to reduce conduction loss; improves efficiency in PWM modes. |
| ENABLE (23) | Driver enable | Logic 1 activates PHASE-controlled outputs; logic 0 forces coast (all drivers off); internal 50 kΩ pull-down. |
| PHASE (24) | Direction control | Logic 1 → current SA→SB (forward), Logic 0 → SB→SA (reverse); defines bridge diagonal activation sequence. |
| RESET (25) | Reset/sleep control | Logic 0 clears latched faults and enters ultra-low-power sleep (<1 µA); logic 1 wakes device after VCP pump-up (~3.5 ms). |
| LONG (26) | Dead-time scaling | Logic 0 = short dead time (0.3–11 µs), Logic 1 = long dead time (8.3–345 µs); scales RDEAD-based IDEAD current. |
| IDEAD (27) | Dead-time current set | Analog input (2 V reference); 12 kΩ–499 kΩ to GND sets IDEAD from 4 µA to 167 µA, directly controlling tdead. |
| VDSTH (28) | Drain-source threshold | Analog input (0.3–3.0 V) sets short-to-ground/short-to-battery detection level; referenced to LSS or VDRAIN. |
Key Features
| Feature | Design Value |
|---|---|
| Charge-pump boosted gate drive | Delivers VCP = VBB + 10.7 V typical, enabling 100% duty cycle n-MOSFET control without external boost converter. |
| Programmable dead-time cross-conduction prevention | Adjustable from 0.3 µs to 345 µs via RDEAD and LONG pin-supports wide MOSFET gate charge and switching speed range. |
| Motor lead short-circuit diagnostics | Detects short-to-battery and short-to-ground on both phases using VDSTH-configurable thresholds and Kelvin VDRAIN sensing. |
| Automotive-grade thermal protection | Thermal shutdown at 172°C with 12°C hysteresis ensures reliability in under-hood environments without false trips. |
| Integrated dual LDO regulators | VREG13 (13.3 V/15 mA) and VREG5 (5.0 V/4 mA) eliminate need for external bias supplies and simplify BOM. |
Applications
| Electric Power Steering (EPS) | HVAC Blower Motor Control |
|---|---|
|
Use Scenario: Bidirectional 12 V/24 V brushed or brushless motor control in column-assist or rack-assist EPS modules. IC Role / Device Role / Timing Role: Full-bridge gate driver controller managing high-current n-MOSFET half-bridges with real-time fault monitoring and thermal protection. Use Value: Enables fail-safe coast-on-fault response, supports ASIL-B diagnostic coverage via latched FAULT output and VDSTH threshold tuning. |
Use Scenario: Variable-speed HVAC blower motor drive in passenger cabin climate control systems. IC Role / Device Role / Timing Role: PWM-controlled full-bridge driver delivering up to 30 A peak motor current with synchronous rectification for efficiency. Use Value: Reduces conduction losses by >15% vs. freewheeling diodes via SR control, extends motor life through precise dead-time management. |
| Engine Cooling Fan Control | Active Grille Shutter Actuation |
|
Use Scenario: High-torque radiator cooling fan drive requiring robust overvoltage protection during load dump events. IC Role / Device Role / Timing Role: Gate driver with user-adjustable VBB OVSET (up to 36.4 V) and thermal shutdown to survive 40 V transients. Use Value: Eliminates need for external TVS or OV clamp circuits, reducing system cost and board space by 30%. |
Use Scenario: Precision position control of multi-vane active grille shutters using small brushed DC motors. IC Role / Device Role / Timing Role: Low-quiescent current full-bridge controller with sleep mode (<1 µA) and wake-on-ENABLE for energy-efficient actuation. Use Value: Meets OEM 100 µA standby current targets via RESET-controlled sleep, extending vehicle battery life during parking mode. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar full-bridge MOSFET controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| A3941KLPTR-T | Pin-compatible upgrade with enhanced VBB OV tolerance (up to 45 V), improved thermal shutdown accuracy (±5°C), and faster FAULT propagation (1.2 µs vs. 2.0 µs). | Supports 48 V mild-hybrid systems and higher ambient temperature zones where A3940KLWTR's 40 V VBB max and 172°C shutdown are limiting. | Select A3941KLPTR-T for new designs targeting extended voltage range, tighter thermal margins, or ISO 26262 ASIL-B compliance. |
| TLE9201SG | Integrated high-/low-side drivers with embedded current sense, no external bootstrap/charge-pump components required; 40 V absolute max VBB. | Reduces external component count by ~12 parts (capacitors, resistors, diodes) but lacks programmable dead time and Kelvin VDRAIN sensing. | Choose TLE9201SG for cost-sensitive, space-constrained applications where integrated current sensing outweighs diagnostic flexibility. |
Compared with A3940KLWTR, A3941KLPTR-T offers higher voltage resilience and tighter thermal control for next-gen automotive platforms, while TLE9201SG trades configurability for integration density-making A3940KLWTR optimal for legacy 12 V/24 V systems requiring field-proven fault diagnostics and design reuse.
Availability
A3940KLWTR is available at Aetrix Electronics and suitable for electric power steering, HVAC blower motor control, and engine cooling fan applications requiring stable component supply despite end-of-life status.
Supply support for A3940KLWTR 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 semiconductor company specializing in magnetic sensing, power ICs, and motor control solutions for automotive and industrial markets.
The A3940 product line was developed specifically for high-reliability automotive motor control, emphasizing robust fault diagnostics, wide temperature operation, and seamless integration with n-channel power MOSFET bridges.
FAQ
What is the recommended replacement for A3940KLWTR in new designs?
The A3941KLPTR-T is the manufacturer-recommended substitution for A3940KLWTR in new designs. It maintains pin compatibility while offering extended VBB rating (45 V), tighter thermal shutdown accuracy (±5°C), and faster fault response. A3940KLWTR remains viable for existing production builds with verified qualification data, but A3941KLPTR-T should be selected for all new automotive motor control projects requiring updated specifications and long-term supply assurance.
Does A3940KLWTR support 100% duty cycle operation with n-channel MOSFETs?
Yes, A3940KLWTR supports true 100% duty cycle operation using its integrated charge pump, which generates VCP = VBB + 10.7 V typical. This boosted voltage ensures sufficient gate-to-source potential for high-side n-MOSFETs even when VBATT is at minimum (7 V). The charge pump eliminates reliance on bootstrap capacitor recharge cycles, enabling continuous conduction without shoot-through risk.
How is short-to-ground fault detection implemented in A3940KLWTR?
A3940KLWTR implements short-to-ground detection using Kelvin-connected VDRAIN and configurable VDSTH input. When a high-side MOSFET is commanded on, the voltage between VDRAIN and the corresponding motor phase (e.g., SA or SB) is compared to VDSTH. If exceeded, FAULT asserts. VDSTH threshold is adjustable from 0.3 V to 3.0 V, allowing precise tuning for different MOSFET RDS(on) and cable resistance.
What is the purpose of the LONG and IDEAD pins on A3940KLWTR?
The LONG and IDEAD pins jointly configure dead time between complementary high-side and low-side gate drive transitions. IDEAD sets current (4–167 µA) via external resistor to ground, determining base dead time; LONG selects scaling factor-logic 0 applies 1×, logic 1 applies 32×-yielding total dead time from 0.3 µs to 345 µs. This prevents shoot-through across diverse MOSFET gate charge characteristics.
Can A3940KLWTR operate without the charge pump circuit?
Yes, A3940KLWTR can operate without the charge pump. Disconnect CP1 and CP2, connect VCP to VBB, and tie VIN to VBB (≥11 V) to power VREG13 directly. In this configuration, high-side drive relies solely on bootstrap capacitors, limiting duty cycle to <100%. The charge pump is optional but required for continuous DC operation and optimal efficiency in high-duty-cycle applications like EPS hold torque.
A3940KLWTR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 28-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tape & Reel (TR)
- 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
A3940KLWTR FAQ
1.How can I place an order for A3940KLWTR through Aetrix?
Please submit a Request for Quotation (RFQ) for A3940KLWTR 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 A3940KLWTR reliable?
The price and inventory of A3940KLWTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3940KLWTR is usually 5 days.
3.What payment methods are accepted for A3940KLWTR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3940KLWTR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3940KLWTR?
A3940KLWTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3940KLWTR 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 A3940KLWTR?
For technical support, including A3940KLWTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3940KLWTR requirements.
6.How does Aetrix verify that A3940KLWTR is sourced from the original manufacturer or authorized distributors?
All A3940KLWTR 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 A3940KLWTR meets industry standards.
7.What is the process for return or replacement of A3940KLWTR?
All A3940KLWTR units undergo pre-shipment inspection (PSI). If there is an issue with A3940KLWTR, 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 A3940KLWTR part is unused and in its original packaging.
Return procedure for A3940KLWTR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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