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Allegro MicroSystems A3940KLPTR
- Part No.:
- A3940KLPTR
- Manufacturer:
- Allegro MicroSystems
- Category:
- Motor Drivers, Controllers
- Package:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
A3940KLPTR.pdf
- Description:
- IC MOTOR DRIVER 7V-40V 28TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,730
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Product details
Overview
A3940KLPTR from Allegro MicroSystems is a full-bridge power MOSFET controller designed for automotive high-power motor drive systems. It delivers four high-current gate drive outputs, supports 100% duty cycle operation via integrated charge pump, and provides programmable dead-time adjustment (0.3–345 µs), VBB operating range of 7–40 V, and thermal shutdown at 172°C. It is used in electric power steering (EPS) and HVAC blower control.
For engineers reviewing the A3940KLPTR datasheet, A3940KLPTR pinout, A3940KLPTR application, or A3940KLPTR equivalent, key selection considerations include bootstrap/charge-pump gate drive architecture, motor lead short-to-battery/short-to-ground fault detection with VDSTH threshold programming, adjustable dead time via IDEAD/LONG pins, and -40°C to +150°C junction temperature rating.
Technical Context
The A3940KLPTR implements a dual-channel, n-channel MOSFET full-bridge driver with independent high-side (GHA/GHB) and low-side (GLA/GLB) gate drivers. Its internal 13.3 V LDO (VREG13) powers low-side drivers and charges bootstrap capacitors, while the charge pump (VCP = VBB + 9.5–11.8 V) enables DC operation of high-side n-FETs without external high-voltage supplies.
Fault management includes latched short-to-ground/short-to-battery detection (using VDSTH-programmable thresholds), non-latched VBB undervoltage (5.25 V trip) and overvoltage (user-adjustable from 19.6 V to 36.4 V via OVSET), and thermal shutdown at 172°C with 12°C hysteresis. All faults force coast mode (GHx = GLx = 0) except sleep mode, which places outputs in high-impedance state.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VBB Range | 7 V to 40 V - supports wide automotive battery voltage range including cold-crank (7 V) and load-dump (40 V) conditions. |
| VREG13 Output | 12.6–14.0 V @ 15 mA - powers low-side gate drivers and charges bootstrap capacitors; dropout ≤0.7 V ensures stability under load. |
| VCP Output | VBB + 9.5–11.8 V - charge pump enables 100% duty cycle high-side n-FET drive without external boost supply. |
| Dead Time | 0.3–345 µs - programmable via RDEAD (12.1 kΩ–499 kΩ) and LONG pin to prevent shoot-through across phase legs. |
| TJ Max | +172°C - thermal shutdown threshold with 12°C hysteresis ensures robust operation in under-hood environments. |
| Fault Detection | VSTG/VSTB thresholds set by VDSTH (0.3–3.0 V); fault noise filter = 1.7 µs - rejects PWM switching transients during motor commutation. |
| Logic Interface | 5 V-tolerant inputs (PHASE, ENABLE, MODE, SR, RESET, LONG); internal 50 kΩ pull-downs - simplifies microcontroller interface without external biasing. |
Pinout & Package
Package: 28-pin TSSOP with exposed thermal pad (LP package). Thermal pad must be soldered to PCB ground plane for thermal performance and EMI reduction.
| 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; eliminates PCB trace IR drop error. |
| 2 LSS | Low-side source return | Reference node for low-side short-to-battery detection and GLx driver return; connects to common source of low-side FETs. |
| 3 GLB | Low-side gate drive B | Sinks up to 800 mA (25°C) to turn on low-side n-FET in Phase B leg; rise/fall times <90 ns/70 ns into 3300 pF. |
| 4 SB | Motor phase B terminal | Connects directly to motor winding B; serves as negative supply for CB bootstrap capacitor and short-to-battery sense reference. |
| 5 GHB | High-side gate drive B | Sources up to 700 mA (25°C) to drive high-side n-FET in Phase B; requires external series resistor for slew rate control. |
| 6 CB | Bootstrap capacitor B | Charged to VREG13 – 1.5 V when SB is low; floats with SB to provide >VBB gate voltage for high-side n-FET turn-on. |
| 7 VIN | VREG13 input | Accepts VCP (charge pump) or direct VBB ≥11 V; enables flexible power architecture with or without charge pump. |
| 8 VREG13 | 13.3 V regulated output | Powers GLx drivers and charges CA/CB; short-circuit current limit = 60 mA prevents regulator latch-up during fault. |
| 9 CA | Bootstrap capacitor A | Same function as CB but for Phase A leg; decoupling critical for stable high-side gate drive during PWM transitions. |
| 10 GHA | High-side gate drive A | Phase A high-side driver; identical specs to GHB; paired with GLA for full-bridge control of motor winding A–B. |
| 11 SA | Motor phase A terminal | Connects directly to motor winding A; negative supply for CA and short-to-battery sense reference for Phase A. |
| 12 GLA | Low-side gate drive A | Phase A low-side driver; sinks up to 800 mA; complements GHA to form half-bridge leg for bidirectional current control. |
| 13 VBB | Battery supply input | Main power input (7–40 V); feeds VREG5, VREG13 (via VIN), and charge pump; fault asserted if outside UV/OV window. |
| 14 CP2 | Charge pump positive | Connects to positive side of charge pump capacitor; required only when using internal charge pump for VCP generation. |
| 15 VCP | Charge pump output | Regulated output (VBB + 9.5–11.8 V); powers VIN and enables 100% duty cycle operation; ripple ≤500 mV ensures gate drive stability. |
| 16 CP1 | Charge pump negative | Connects to negative side of charge pump capacitor; left open if charge pump disabled (VCP tied to VBB). |
| 17 GND | Ground reference | Common return for logic, regulators, and gate drivers; exposed thermal pad is electrically isolated from GND per datasheet. |
| 18 FAULT | Open-drain fault indicator | Asserts high on any fault (short, UV/OV, thermal); pulls low internally during fault; requires external pull-up to VREG5 or MCU. |
| 19 OVSET | VBB overvoltage threshold | Analog input (0–0.9 V) setting VBB(OV) from 19.6 V to 36.4 V; current draw ≤1.4 µA enables high-impedance resistor divider. |
| 20 VREG5 | 5 V regulated output | Powers internal logic, thermal sensor, and external VDSTH/OVSET dividers; 4.5–5.5 V tolerance ensures reliable digital operation. |
| 21 MODE | Decay mode select | Logic 0 = fast decay (both FETs off), Logic 1 = slow decay (high-side off only); internal 50 kΩ pull-down defaults to slow decay. |
| 22 SR | Synchronous rectification | Logic 1 enables low-side FET conduction during off-time to reduce power loss; improves efficiency in PWM motor control. |
| 23 ENABLE | Driver enable | Logic 1 enables PHASE-controlled operation; logic 0 disables all gate outputs (coast); internal 50 kΩ pull-down ensures safe power-up. |
| 24 PHASE | Direction control | Logic 1 = forward (SA→SB), Logic 0 = reverse (SB→SA); determines which high/low pair (GHA+GLB or GHB+GLA) is active. |
| 25 RESET | Reset/sleep control | Logic 0 clears latched faults and forces coast → sleep mode (Z-state outputs); logic 1 wakes device after VCP pump-up (~3.5 ms @7 V). |
| 26 LONG | Dead-time scaling | Logic 0 = short dead time (0.3–11 µs), Logic 1 = long dead time (8.3–345 µs); scales RDEAD-based timing by factor of 32. |
| 27 IDEAD | Dead-time current set | Analog input (2 V reference) sourcing current to ground via RDEAD; sets base dead time before LONG scaling; 4–167 µA range. |
| 28 VDSTH | Drain-source threshold | Analog input (0.3–3.0 V) setting short-to-ground/short-to-battery detection thresholds; current ≤1.0 µA allows precision divider design. |
Key Features
| Feature | Design Value |
|---|---|
| Charge-pump boosted gate drive | Enables 100% duty cycle operation of high-side n-channel MOSFETs without external high-voltage supply; VCP = VBB + 9.5–11.8 V. |
| Programmable dead-time control | Adjustable from 0.3 µs to 345 µs via RDEAD and LONG pin, preventing shoot-through during PWM/phase transitions in high-power bridges. |
| Motor lead fault diagnostics | Detects short-to-battery and short-to-ground on both phases using VDSTH-programmable thresholds and Kelvin VDRAIN sensing for accuracy. |
| Integrated dual LDOs | VREG13 (13.3 V/15 mA) powers gate drivers and bootstrap caps; VREG5 (5 V/4 mA) supplies logic and external divider networks - no external regulators needed. |
| Automotive-grade thermal protection | Thermal shutdown at TJ = 172°C with 12°C hysteresis ensures reliability in under-hood applications; operates from -40°C to +150°C junction. |
Applications
| Electric Power Steering (EPS) | HVAC Blower Motor Control |
|---|---|
|
Use Scenario: Bidirectional 12 V/24 V brushed or brushless DC motor control in vehicle steering assist systems requiring high torque at low speed and fail-safe fault response. IC Role / Device Role / Timing Role: Full-bridge gate driver controlling external n-channel MOSFET H-bridge; manages PWM commutation, synchronous rectification, and real-time motor lead fault detection. Use Value: Integrated VDSTH/VDRAIN monitoring detects open-circuit or short-circuit motor faults within 1.7 µs, enabling ISO 26262-compliant functional safety responses. |
Use Scenario: Variable-speed fan control in automotive climate systems, operating across battery voltage transients (7–40 V) and ambient temperatures (-40°C to +125°C). IC Role / Device Role / Timing Role: High-current gate driver enabling efficient PWM-based speed regulation; charge pump ensures stable high-side drive during cold-crank (7 V VBB). Use Value: Programmable dead time (0.3–345 µs) accommodates diverse MOSFET switching speeds, reducing EMI and preventing shoot-through in noisy automotive electrical environments. |
| Seat-Motor Actuation | Engine Cooling Fan Control |
|
Use Scenario: Precision position control of multi-directional seat adjustment motors, requiring smooth bidirectional motion, stall detection, and thermal derating. IC Role / Device Role / Timing Role: Full-bridge controller managing direction (PHASE), decay mode (MODE), and braking (ENABLE); FAULT output signals overcurrent or thermal events to MCU. Use Value: VREG13 undervoltage lockout (8.25 V) and VBB UV/OV protection prevent erratic behavior during battery fluctuations, ensuring consistent actuator positioning. |
Use Scenario: High-power radiator fan drive in diesel and heavy-duty vehicles, subject to extreme thermal stress and load-dump transients up to 40 V. IC Role / Device Role / Timing Role: Robust gate driver with 172°C thermal shutdown and Kelvin VDRAIN sensing; supports discrete MOSFETs rated >100 A continuous. Use Value: Exposed thermal pad (LP package) enables direct PCB copper pour attachment, achieving ≤30°C/W junction-to-board thermal resistance for sustained high-power operation. |
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 successor with enhanced ESD rating (±8 kV HBM), updated thermal shutdown (165°C), and improved VBB OV hysteresis (3.1 V vs. 2.1–4.1 V). | Designed for new designs requiring extended lifecycle support; maintains identical pinout, register map, and fault reporting behavior. | Select A3941KLPTR-T for new designs - it replaces A3940KLPTR with no layout or firmware changes required. |
| MPQ6532-AEC1 | Monolithic 3-phase BLDC gate driver (not full-bridge); integrates 3x half-bridges, 5 V/3.3 V LDOs, and SPI fault reporting - no external bootstrap/charge-pump components. | Targets sensored/sensorless BLDC motors; lacks VDSTH-programmable short detection and Kelvin VDRAIN; not suitable for brushed DC or discrete full-bridge topologies. | Choose MPQ6532-AEC1 only for 3-phase BLDC applications where integration reduces BOM count; not a functional substitute for A3940KLPTR's discrete full-bridge control. |
Compared with A3940KLPTR, A3941KLPTR-T offers extended production availability and minor electrical refinements while preserving full hardware compatibility; MPQ6532-AEC1 provides higher integration for BLDC but abandons the discrete full-bridge flexibility and programmable fault thresholds essential for brushed motor safety-critical systems.
Availability
A3940KLPTR is available at Aetrix Electronics and suitable for electric power steering (EPS), HVAC blower control, and seat-motor actuation requiring stable component supply despite its discontinued status for new designs.
Supply support for A3940KLPTR 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 high-performance magnetic sensing and power IC solutions for automotive and industrial markets.
The A3940 product line was developed specifically for automotive high-power brushed DC motor control, emphasizing robust fault diagnostics, wide input voltage operation, and thermal resilience in under-hood environments.
FAQ
Is A3940KLPTR still in production?
No, A3940KLPTR is a discontinued product. Allegro MicroSystems ceased production as of December 5, 2016. It is not recommended for new design applications, and samples are no longer available. Aetrix Electronics provides legacy supply support for existing production programs with traceable, verified inventory.
What is the recommended replacement for A3940KLPTR?
The officially recommended substitution is A3941KLPTR-T, a pin-compatible upgrade with enhanced ESD performance, refined thermal shutdown behavior, and continued production support. A3941KLPTR-T requires no PCB or firmware changes and maintains identical functional operation for full-bridge brushed DC motor control.
Does A3940KLPTR support 100% duty cycle operation?
Yes, A3940KLPTR supports true 100% duty cycle operation via its integrated charge pump, which generates VCP = VBB + 9.5–11.8 V to sustain high-side n-channel MOSFET gate drive even at minimum VBB = 7 V. This eliminates need for external high-voltage supplies in automotive cold-crank conditions.
How does the VDSTH pin configure short-circuit detection?
The VDSTH pin accepts a DC voltage (0.3–3.0 V) that sets both short-to-ground and short-to-battery detection thresholds. For example, at VDSTH = 1.0 V, short-to-ground triggers at 0.82–1.13 V and short-to-battery at 0.76–1.30 V. This analog programming enables precise fault sensitivity tuning without changing external components.
What package type does A3940KLPTR use?
A3940KLPTR uses the 28-pin TSSOP package with exposed thermal pad (LP package). The thermal pad is electrically isolated from GND per the datasheet and must be soldered to a dedicated PCB copper pour for optimal thermal dissipation and EMI suppression in high-power motor drive layouts.
A3940KLPTR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- 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-TSSOP-EP
A3940KLPTR FAQ
1.How can I place an order for A3940KLPTR through Aetrix?
Please submit a Request for Quotation (RFQ) for A3940KLPTR 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 A3940KLPTR reliable?
The price and inventory of A3940KLPTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A3940KLPTR is usually 5 days.
3.What payment methods are accepted for A3940KLPTR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A3940KLPTR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A3940KLPTR?
A3940KLPTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A3940KLPTR 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 A3940KLPTR?
For technical support, including A3940KLPTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A3940KLPTR requirements.
6.How does Aetrix verify that A3940KLPTR is sourced from the original manufacturer or authorized distributors?
All A3940KLPTR 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 A3940KLPTR meets industry standards.
7.What is the process for return or replacement of A3940KLPTR?
All A3940KLPTR units undergo pre-shipment inspection (PSI). If there is an issue with A3940KLPTR, 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 A3940KLPTR part is unused and in its original packaging.
Return procedure for A3940KLPTR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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