SNVSCH2 September   2024 LM65645-Q1

ADVANCE INFORMATION  

  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 System 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 Mode Selection
        1. 7.3.3.1 MODE/SYNC Pin Uses for Synchronization
        2. 7.3.3.2 Clock Locking
      4. 7.3.4 Adjustable Switching Frequency
      5. 7.3.5 Dual Random Spread Spectrum (DRSS)
      6. 7.3.6 Internal LDO, VCC UVLO, and BIAS Input
      7. 7.3.7 Bootstrap Voltage (BST Pin)
      8. 7.3.8 Soft Start and Recovery From Dropout
      9. 7.3.9 Safety Features
        1. 7.3.9.1 Power-Good Monitor
        2. 7.3.9.2 Overcurrent and Short-Circuit Protection
        3. 7.3.9.3 Hiccup
        4. 7.3.9.4 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 Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Custom Design With WEBENCH® Tools
        2. 8.2.2.2 Choosing the Switching Frequency
        3. 8.2.2.3 FB for Adjustable or Fixed Output Voltage Mode
        4. 8.2.2.4 Inductor Selection
        5. 8.2.2.5 Output Capacitor Selection
        6. 8.2.2.6 Input Capacitor Selection
        7. 8.2.2.7 CBOOT
        8. 8.2.2.8 External UVLO
        9. 8.2.2.9 Maximum Ambient Temperature
    3. 8.3 Best Design Practices
    4. 8.4 Power Supply Recommendations
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
        1. 8.5.1.1 Ground and Thermal Considerations
      2. 8.5.2 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)
  • RZT|20
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.2 Typical Application

Figure 8-1 and Figure 8-2 show typical application circuits for the LM656x5-Q1, when using the adjustable output mode or the fixed output mode, respectively. This device is designed to function over a wide range of external components and system parameters. However, the internal compensation is designed for a certain range of external inductance and output capacitance. As a quick-start guide, Table 8-1 through Table 8-5 provide typical component values for a range of application parameters. The component values in these table represent stable designs and are not necessarily optimized. Note that the designs in these tables are based on a typical input voltage of 12V; or 36V for the 24V outputs.

LM65645-Q1 Example Application Circuit for Adjustable Output Voltage Mode With LM656x5 Figure 8-1 Example Application Circuit for Adjustable Output Voltage Mode With LM656x5
LM65645-Q1 Example Application Circuit for Fixed Output Voltage Mode With LM656x5 Figure 8-2 Example Application Circuit for Fixed Output Voltage Mode With LM656x5
Table 8-1 Typical External Components for Fixed Output Voltage Mode
Output Voltage Frequency FB LM6x625 LM6x635 LM6x645
L COUT L COUT L COUT(1)
3.3V 400kHz GND 8.2μH 75μF 6.8μH 94μF 5.6μH 110μF
3.3V 2200kHz GND 1.5μH 20μF 1.5μH 25μF 1.0μH 30μF
5V 400kHz VCC 10μH 50μF 8.2μH 55μF 8.2μH 70μF
5V 2200kHz VCC 2.2μH 15μF 1.5μH 20μF 1.5μH 25μF
(1) Please note all COUT values are the de-rated output capacitor values in the tables.
Table 8-2 Typical External Components for LM6x625 in Adjustable Output Voltage Mode
Output Voltage Frequency L COUT(1) RFBT RFBB CFF
3.3V 400kHz 8.2μH 75μF 100kΩ 31.6kΩ 20pF
5V 400kHz 10μH 50μF 100kΩ 19.1kΩ 20pF
24V 400kHz 47μH 15μF 205kΩ 7.15kΩ
3.3V 2200kHz 1.5μH 25μF 100kΩ 31.6kΩ 5pF
5V 2200kHz 1.5μH 15μF 100kΩ 19.1kΩ 5pF
24V 2200kHz 8.2μH 10μF 205kΩ 7.15kΩ
Table 8-3 Typical External Components for LM6x635 in Adjustable Output Voltage Mode
Output Voltage Frequency L COUT (1) RFBT RFBB CFF
3.3V 400kHz 6.8μH 70μF 100kΩ 31.6kΩ 10pF
5V 400kHz 10μH 60μF 100kΩ 19.1kΩ 15pF
24V 400kHz 47μH 25μF 205kΩ 7.15kΩ 10pF
3.3V 2200kHz 1.2μH 30μF 100kΩ 31.6kΩ 5pF
5V 2200kHz 1.5μH 20μF 100kΩ 19.1kΩ 5pF
24V 2200kHz 5.6μH 10μF 205kΩ 7.15kΩ 5pF
Table 8-4 Typical External Components for LM6x645 in Adjustable Output Voltage Mode
Output Voltage Frequency L COUT(1) RFBT RFBB CFF
3.3V 400kHz 5.6μH 80μF 100kΩ 31.6kΩ 15pF
5V 400kHz 8.2μH 70μF 100kΩ 19.1kΩ 15pF
24V 400kHz 22μH 30μF 205kΩ 7.15kΩ 10pF
3.3V 2200kHz 1.2μH 40μF 100kΩ 31.6kΩ 5pF
5V 2200kHz 1.2μH 30μF 100kΩ 19.1kΩ 5pF
24V 2200kHz 5.6μH 10μF 205kΩ 7.15kΩ 5pF
Table 8-5 Typical External Components for Various Adjustable Output Voltage Applications
Output Voltage Output Current Frequency L COUT (1) RFBT RFBB CFF
3.3V 3.5A 1100kHz 3.3μH 45μF N/A N/A N/A
1V 4.5A 500kHz 2.2μH 550μF 100kΩ 402kΩ 25pF
12V 3.5A 1100kHz 6.8μH 15μF 100kΩ 7.15kΩ 10pF
16V 3.5A 1600kHz 5.6μH 10μF 100kΩ 5.23kΩ 5pF