SNAS660D June   2015  – May 2021 LM53600-Q1 , LM53601-Q1


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Device Comparison
  6. Pin Configuration and Functions
  7. Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 System Characteristics
    7. 7.7 Timing Requirements
    8. 7.8 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Control Scheme
      2. 8.3.2 Soft-Start Function
      3. 8.3.3 Current Limit
      4. 8.3.4 Hiccup Mode
      5. 8.3.5 RESET Function
      6. 8.3.6 Forced PWM Operation
      7. 8.3.7 Auto Mode Operation and IQ_VIN
      8. 8.3.8 SYNC Operation
      9. 8.3.9 Spread Spectrum
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown
      2. 8.4.2 FPWM Operation
      3. 8.4.3 Auto Mode Operation
  9. Applications and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Off-Battery 5-V, 1-A Output Automotive Converter with Spread Spectrum
        1. Design Requirements
        2. Detailed Design Procedure
          1. Inductor Selection
          2. Output Capacitor Selection
          3. Input Capacitor Selection
          4. FB Voltage Divider for Adjustable Versions
          5. RPU - RESET Pull Up Resistor
        3. Application Curves
      2. 9.2.2 Off-Battery 3.3 V, 1 A Output Automotive Converter with Spread Spectrum
        1. Design Requirements
        2. Design Procedure
        3. Application Curves
    3. 9.3 Do's and Don't's
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Ground and Thermal Plane Considerations
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

Ground and Thermal Plane Considerations

As mentioned above, it is recommended to use one of the middle layers as a solid ground plane. A ground plane provides shielding for sensitive circuits and traces. It also provides a quiet reference potential for the control circuitry. The AGND and PGND pins should be connected to the ground plane using vias right next to the bypass capacitors. PGND pins are connected to the source of the internal low side MOSFET switch. They should be connected directly to the grounds of the input and output capacitors. The PGND net contains noise at the switching frequency and may bounce due to load variations. The PGND trace, as well as PVIN and SW traces, should be constrained to one side of the ground plane. The other side of the ground plane contains much less noise and should be used for sensitive routes.

It is recommended to provide adequate device heat sinking by utilizing the exposed pad (EP) of the IC as the primary thermal path. Use a minimum 4 by 4 array of 10 mil thermal vias to connect the EP to the system ground plane for heat sinking. The vias should be evenly distributed under the exposed pad. Use as much copper as possible for system ground plane on the top and bottom layers for the best heat dissipation. It is recommended to use a four-layer board with the copper thickness, starting from the top, as: 2 oz / 1 oz / 1 oz / 2 oz. A four-layer board with enough copper thickness and proper layout provides low current conduction impedance, proper shielding and lower thermal resistance.

Table 11-2 Resources for Thermal PCB Design
AN-2020 Thermal Design By Insight, Not HindsightSNVA419
AN-1520 A Guide to Board Layout for Best Thermal Resistance for Exposed Pad PackagesSNVA183
SPRA953B Semiconductor and IC Package Thermal MetricsSPRA953
SNVA719 Thermal Design made Simple with LM43603 and LM43602SNVA719
SLMA002 PowerPAD™ Thermally Enhanced PackageSLMA002
SLMA004 PowerPAD Made EasySLMA004
SBVA025 Using New Thermal MetricsSBVA025