SNVSCF0 October   2024 LM65680-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
  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  Single-Output Dual-Phase Operation
      5. 7.3.5  Mode Selection
        1. 7.3.5.1 MODE/SYNC Pin Uses for Synchronization
        2. 7.3.5.2 Clock Locking
      6. 7.3.6  Adjustable Switching Frequency
      7. 7.3.7  Dual Random Spread Spectrum (DRSS)
      8. 7.3.8  Internal LDO, VCC UVLO, and BIAS Input
      9. 7.3.9  Bootstrap Voltage (BST Pin)
      10. 7.3.10 Soft Start and Recovery From Dropout
      11. 7.3.11 Safety Features
        1. 7.3.11.1 Power-Good Monitor
        2. 7.3.11.2 Overcurrent and Short-Circuit Protection
        3. 7.3.11.3 Hiccup
        4. 7.3.11.4 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
      1. 8.1.1 Power Train Components
        1. 8.1.1.1 Buck Inductor
        2. 8.1.1.2 Output Capacitors
        3. 8.1.1.3 Input Capacitors
        4. 8.1.1.4 EMI Filter
      2. 8.1.2 Error Amplifier and Compensation
      3. 8.1.3 Maximum Ambient Temperature
        1. 8.1.3.1 Derating Curves
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Inductor Selection
        2. 8.2.2.2 Output Capacitors
        3. 8.2.2.3 Feed-forward Capacitor (CFF)
        4. 8.2.2.4 Input Capacitor Selection
        5. 8.2.2.5 Choosing the Switching Frequency
        6. 8.2.2.6 Setting the Output Voltage
        7. 8.2.2.7 Compensation Components
        8. 8.2.2.8 CBST
        9. 8.2.2.9 External UVLO
      3. 8.2.3 Application Curves
    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 Development Support
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
        1. 9.2.1.1 PCB Layout Resources
        2. 9.2.1.2 Thermal Design Resources
    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

8.2.1 Design Requirements

The following example provides a detailed design procedure based on the specifications found in Table 8-5.

Table 8-5 Detailed Design Parameters
DESIGN PARAMETER VALUE
Input voltage range (steady-state) 8V to 65V
Min transient input voltage (cold crank) 4.5V
Max transient input voltage (load dump) 70V
Output voltage 5V
Output current 0A to 8A
Switching frequency 400kHz
Output voltage regulation ±1%
Active current, no load 15µA
Shutdown current 1.3µA
Soft-start time 5.3ms

The switching frequency is set at 400kHz by resistor RRT. In terms of control loop performance, the target loop crossover frequency is 50kHz with a phase margin greater than 50°.

The selected buck regulator powertrain components are cited in Table 8-6, and many of the components are available from multiple vendors. This design uses a low-DCR, metal-powder composite inductor, and ceramic output capacitor implementation.

Table 8-6 List of Materials for Application Circuit
REFERENCE DESIGNATOR QTY SPECIFICATION MANUFACTURER PART NUMBER
CIN 4 CAP, CERM, 4.7μF, 100V, +/- 10%, X7S, 1210, AEC-Q200 Murata GCM32DC72A475KE02L
TDK CGA6M3X7S2A475K200
CO 2 47μF ±10% 10VDC, X7S, 1210 Embossed T/R, AEC-Q200 Murata GCM32EC71A476KE02K
47µF, 10V, X7S, 1210, ceramic, AEC-Q200 TDK CGA6P1X7S1A476M250AC
LO 1 3.3µH, 5.9mΩ, 10.1A, 6.71 × 6.51 × 6.1mm, AEC-Q200 Coilcraft XGL6060-332MEC
3.3µH, 15.7mΩ, 17.7A, 6.95 × 6.6 × 4.3mm, AEC-Q200 Cyntec VCUW064E-3R3MS5
3.3µH, 10.8mΩ, 15A, 6.45 × 6.65 × 5.8mm, AEC-Q200 Würth Electronik 74439346033
U1 1 LM656x0-Q1 70V buck converter, AEC-Q100 Texas Instruments LM65680RZYRQ1