SNVSCQ8B November   2025  – July 2026 LM654A5-Q1 , LM654B0-Q1

PRODMIX  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  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 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Descriptions
      1. 7.3.1  Output Voltage Selection
      2. 7.3.2  EN Pin and Use as VIN UVLO
      3. 7.3.3  Device Configuration
      4. 7.3.4  Mode Selection
        1. 7.3.4.1 MODE/SYNC Pin Uses for Synchronization
        2. 7.3.4.2 Clock Locking
      5. 7.3.5  Adjustable Switching Frequency and Phase Shift
      6. 7.3.6  Dual Random Spread Spectrum (DRSS)
      7. 7.3.7  Internal LDO, VCC UVLO, and BIAS Input
      8. 7.3.8  Bootstrap Voltage (BST Pin)
      9. 7.3.9  Soft Start and Recovery From Dropout
      10. 7.3.10 Safety Features
        1. 7.3.10.1 Power-Good Monitor
        2. 7.3.10.2 Overcurrent and Short-Circuit Protection
        3. 7.3.10.3 Hiccup
        4. 7.3.10.4 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Active Mode
        1. 7.4.2.1 Peak Current Mode Operation
        2. 7.4.2.2 Auto Mode Operation
          1. 7.4.2.2.1 Diode Emulation
        3. 7.4.2.3 FPWM Mode Operation
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Example Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Choosing the Switching Frequency
        2. 8.2.2.2 Inductor Selection
        3. 8.2.2.3 Output Capacitors
        4. 8.2.2.4 Input Capacitor Selection
        5. 8.2.2.5 Setting the Output Voltage
        6. 8.2.2.6 Compensation Components
        7. 8.2.2.7 Feed-forward Capacitor (CFF)
        8. 8.2.2.8 Maximum Ambient Temperature
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      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. 9.2 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
7.4.2.2.1 Diode Emulation

Diode emulation prevents reverse current through the inductor, which requires a lower frequency needed to regulate given a fixed peak inductor current. Diode emulation also limits ripple current as frequency is reduced. Frequency reduces when the peak inductor current goes below IPEAK-MIN. With a fixed peak current, as output current is reduced to zero, frequency must be reduced to near zero to maintain regulation.

LM654A5-Q1 LM654B0-Q1 PFM Operation
In auto mode, the low-side device is turned off after inductor current is near zero. As a result, after output current is less than half of inductor ripple in CCM, the device operates in DCM. This is equivalent to saying that diode emulation is active.
Figure 7-11 PFM Operation

The LM654xx-Q1 has a minimum peak inductor current setting in auto mode. That being said, when current is reduced to a low value with fixed input voltage, on-time is constant. Regulation is then achieved by adjusting frequency. This mode of operation is called PFM mode regulation.