SNVSBW0B October   2022  – August 2024 LM64440-Q1 , LM64460-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
    1. 5.1 Wettable Flanks
    2. 5.2 Pinout Design for Clearance and FMEA
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Characteristics
    7. 6.7 Systems Characteristics
    8. 6.8 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Input Voltage Range (VIN1, VIN2)
      2. 7.3.2  Output Voltage Setpoint (FB)
      3. 7.3.3  Precision Enable and Input Voltage UVLO (EN)
      4. 7.3.4  MODE/SYNC Operation
        1. 7.3.4.1 Level-Dependent MODE/SYNC Control
        2. 7.3.4.2 Pulse-Dependent MODE/SYNC Control
      5. 7.3.5  Clock Locking
      6. 7.3.6  Power-Good Monitor (PGOOD)
      7. 7.3.7  Bias Supply Regulator (VCC, BIAS)
      8. 7.3.8  Bootstrap Voltage and UVLO (CBOOT)
      9. 7.3.9  Spread Spectrum
      10. 7.3.10 Soft Start and Recovery From Dropout
      11. 7.3.11 Overcurrent and Short-Circuit Protection
      12. 7.3.12 Thermal Shutdown
      13. 7.3.13 Input Supply Current
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Standby Mode
      3. 7.4.3 Active Mode
        1. 7.4.3.1 CCM Mode
        2. 7.4.3.2 AUTO Mode – Light-Load Operation
          1. 7.4.3.2.1 Diode Emulation
          2. 7.4.3.2.2 Frequency Foldback
        3. 7.4.3.3 FPWM Mode – Light-Load Operation
        4. 7.4.3.4 Minimum On-Time (High Input Voltage) Operation
        5. 7.4.3.5 Dropout
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Design 1 – Automotive Synchronous 6A Buck Regulator at 2.1MHz
        1. 8.2.1.1 Design Requirements
      2. 8.2.2 Design 2 – Automotive Synchronous 4A Buck Regulator at 2.1MHz
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1  Custom Design With WEBENCH® Tools
          2. 8.2.2.2.2  Setting the Output Voltage
          3. 8.2.2.2.3  Choosing the Switching Frequency
          4. 8.2.2.2.4  Inductor Selection
          5. 8.2.2.2.5  Output Capacitor Selection
          6. 8.2.2.2.6  Input Capacitor Selection
          7. 8.2.2.2.7  Bootstrap Capacitor
          8. 8.2.2.2.8  VCC Capacitor
          9. 8.2.2.2.9  BIAS Power Connection
          10. 8.2.2.2.10 Feedforward Network
          11. 8.2.2.2.11 Input Voltage UVLO
        3. 8.2.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
        1. 8.4.1.1 Thermal Design and Layout
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Third-Party Products Disclaimer
      2. 9.1.2 Development Support
        1. 9.1.2.1 Custom Design With WEBENCH® Tools
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information
    1. 11.1 Tape and Reel Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.1 Overview

The LM644x0-Q1 is an easy-to-use, synchronous, buck DC/DC converter designed for a wide variety of automotive applications where strict reliability and low EMI are of paramount importance. The devices operates over an input voltage range of 3.95V to 36V, with operation down to 3V after start-up and transients as high as 42V. The LM64460-Q1 delivers up to 6A DC while the LM64440-Q1 delivers 4A DC load current with high conversion efficiency and ultra-low input quiescent current in a very small design size.

The LM644x0-Q1 operates at a default switching frequency of 2.1MHz but can be synchronized across a frequency range of 200kHz to 2.2MHz. The converter includes specific features for optimal EMI performance in noise-sensitive automotive applications, such as:

  • An optimized package and pinout design enables a shielded switch-node layout that mitigates radiated EMI.
  • Parallel input paths with a symmetrical capacitor layout minimize parasitic inductance, switch-voltage ringing, and radiated field coupling.
  • Pseudo-random spread spectrum (PRSS) modulation reduces peak emissions.
  • Frequency synchronization and pin-selectable FPWM mode enable constant switching frequency across the full load current range.
  • Integrated high-side and low-side power MOSFETs with enhanced gate-drive control enable low-noise PWM switching.

Together, these features significantly reduce EMI filtering requirements, thus eliminating shielding and other expensive EMI mitigation measures, while helping to meet the CISPR 25 Class 5 automotive EMI standard for conducted and radiated emissions.

The enhanced HotRod QFN package of the LM644x0-Q1 has a carefully designed wettable-flank pinout arrangement that provides additional clearance spacing between adjacent VIN, SW, or PGND power pins to improve reliability and pin FMEA. The converter also incorporates other features for comprehensive system requirements, including:

  • A precision enable input with hysteresis for programmable line undervoltage lockout (UVLO)
  • Cycle-by-cycle peak and valley current limits for excellent inductor sizing
  • An open-drain power-good monitor for power-rail sequencing and fault reporting
  • Internally fixed output voltage soft start
  • Monotonic start-up into prebiased loads
  • Thermal shutdown with automatic recovery

The LM644x0-Q1 is qualified to AEC-Q100 grade 1 and has electrical characteristics specified up to a maximum junction temperature of 150°C. The following help provide an excellent point-of-load regulator design for automotive applications requiring enhanced reliability and durability:

  • Wide input voltage range
  • Low quiescent current consumption
  • Optimized thermal design and high-temperature operation
  • Improved pin FMEA
  • Small design size