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
8.2.2.2.5 Output Capacitor Selection

The value of the output capacitor and the ESR determine the output voltage ripple and load transient performance. The output capacitor is usually determined by load transient and stability requirements rather than the output voltage ripple. For LM64440-Q1, use Table 8-7 and for LM64460-Q1, use Table 8-8 to select the output capacitance and CFF feedforward capacitance values for a few common applications. Use a 1kΩ RFF in series with CFF to further improve noise performance.

Table 8-7 Recommended Output Capacitors and CFF Values for LM64440-Q1
CONFIGURATION 3.3V OUTPUT 5V OUTPUT
COUT CFF COUT CFF
2.1MHz – Ceramic 3 × 22µF, 16V ceramic 10pF 2 × 47µF, 10V ceramic 10pF
2.1MHz – Alternative 2 × 22µF, 16V ceramic +
47µF, 10mΩ electrolytic		 – 2 × 47µF, 10V ceramic +
47µF, 10mΩ electrolytic		 –
400kHz – Ceramic 4 × 22µF, 16V ceramic 33pF 2 × 47µF, 10V ceramic 22pF
400kHz – Alternative 1 × 22µF, 16V ceramic +
100µF, 10mΩ electrolytic		 15pF 1 × 47µF, 10V ceramic +
47µF, 10mΩ electrolytic		 10pF
Table 8-8 Recommended Output Capacitors and CFF Values for LM64460-Q1
CONFIGURATION 3.3V OUTPUT 5V OUTPUT
COUT CFF COUT CFF
2.1MHz – Ceramic 4 × 22µF, 16V ceramic 10pF 2 × 47µF, 10V ceramic 10pF
2.1MHz – Alternative 2 × 22µF, 16V ceramic +
100µF, 10mΩ electrolytic		 – 2 × 47µF, 10V ceramic +
100µF, 10mΩ electrolytic		 –
400kHz – Ceramic 5 × 22µF, 16V ceramic 15pF 3 × 47µF, 10V ceramic 15pF
400kHz – Alternative 2 × 22µF, 16V ceramic +
100µF, 10mΩ electrolytic		 – 1 × 47µF, 10V ceramic +
100µF, 10mΩ electrolytic		 –
Note:

Most ceramic capacitors deliver less capacitance than the rating of the capacitor indicates. Be sure to check selected capacitors for initial accuracy, temperature derating, and particularly voltage derating. Table 8-7 and Table 8-8 assumes typical derating for X7R-dielectric capacitors. If lower voltage or lower temperature-rated capacitors are used, more capacitance than listed can be required.

More conveniently, Equation 10 calculates the required effective ceramic capacitance for a given application:

Equation 10. LM64440-Q1 LM64460-Q1

where FC is the target loop crossover frequency in units of kHz, which can be set at 10% to 15% of switching frequency and up to a maximum of 100kHz.

This example requires improved transient performance, resulting in two 47µF, 10V, X7R ceramics as the output capacitance and 10pF for CFF. An alternative configuration is to use a low-ESR electrolytic capacitor in parallel with a reduced ceramic capacitance.