SNVSBW0C October   2022  – October 2025 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

7.3.4.2 Pulse-Dependent MODE/SYNC Control

Most systems that require more than a single mode of operation from the LM644x0-Q1 are controlled by digital circuitry such as a microprocessor. These systems can generate dynamic signals easily but have difficulty generating multi-level signals. Pulse-dependent MODE/SYNC control is useful with these systems.

To initiate pulse-dependent MODE/SYNC control, a valid synchronization signal must be applied. Upon completion of the fourth pulse in a valid synchronization pulse train, MODE/SYNC operates in pulse-dependent MODE/SYNC control mode, shown in Figure 7-3 and Figure 7-4. The only way to return to Level-dependent MODE/SYNC control is to restart the LM644x0-Q1.

LM64440-Q1 LM64460-Q1 Transition from FPWM Mode to Pulse-Dependent ControlFigure 7-3 Transition from FPWM Mode to Pulse-Dependent Control
LM64440-Q1 LM64460-Q1 Transition from AUTO Mode to Pulse-Dependent ControlFigure 7-4 Transition from AUTO Mode to Pulse-Dependent Control

After Pulse-dependent MODE/SYNC control has been initiated, Table 7-2 shows a summary of the pulse-dependent mode selection settings.

Table 7-2 Pulse-Dependent Mode Selection Settings
MODE/SYNCMODE
VMODE/SYNC > VMODE_HFPWM mode with spread spectrum
VMODE/SYNC < VMODE_LAUTO mode with spread spectrum
Synchronization clockSYNC mode without spread spectrum
VMODE/SYNC > VMODE_H and Double Pulse (Figure 7-6)FPWM mode without spread spectrum
VMODE/SYNC < VMODE_L and Double Pulse (Figure 7-7)AUTO mode without spread spectrum

Figure 7-5 shows the transition between AUTO mode and FPWM mode while in Pulse-dependent MODE/SYNC control. The LM644x0-Q1 transitions to a new mode of operation after tMODE has expired.

LM64440-Q1 LM64460-Q1 Transition from AUTO Mode and FPWM ModeFigure 7-5 Transition from AUTO Mode and FPWM Mode

Two positive-going pulses can be used to turn off spread spectrum in AUTO and FPWM modes. The two positive pulses must be consistent with the characteristics of a valid sync signal. Figure 7-6 through Figure 7-9 show the only waveforms that result in spread spectrum being turned off. Refer to the Electrical Characteristics for more information about the timing specifications.

LM64440-Q1 LM64460-Q1 Spread Spectrum Disabled in FPWM ModeFigure 7-6 Spread Spectrum Disabled in FPWM Mode
LM64440-Q1 LM64460-Q1 Spread Spectrum Disabled in AUTO ModeFigure 7-7 Spread Spectrum Disabled in AUTO Mode
LM64440-Q1 LM64460-Q1 Spread Spectrum Disabled in Transition from FPWM Mode to AUTO ModeFigure 7-8 Spread Spectrum Disabled in Transition from FPWM Mode to AUTO Mode
LM64440-Q1 LM64460-Q1 Spread Spectrum Disabled in Transition from AUTO Mode to FPWM ModeFigure 7-9 Spread Spectrum Disabled in Transition from AUTO Mode to FPWM Mode

To enter SYNC mode, the valid synchronization signal must be present for 2048 cycles.

If the MODE/SYNC voltage becomes constant longer than tMODE, the LM644x0-Q1 enters either AUTO mode or FPWM mode. At this time, spread spectrum is turned on and MODE/SYNC operates in pulse-dependent mode.

LM64440-Q1 LM64460-Q1 Transition from SYNC Mode to AUTO ModeFigure 7-10 Transition from SYNC Mode to AUTO Mode
LM64440-Q1 LM64460-Q1 Transition from SYNC Mode to FPWM ModeFigure 7-11 Transition from SYNC Mode to FPWM Mode