SNVSCD4 September   2024 LM70660 , LM706A0

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1  Input Voltage Range (VIN)
      2. 6.3.2  High-Voltage Bias Supply Regulator (VCC, BIAS, VDDA)
      3. 6.3.3  Enable (EN)
      4. 6.3.4  Power-Good Monitor (PG)
      5. 6.3.5  Switching Frequency (RT)
      6. 6.3.6  Dual Random Spread Spectrum (DRSS)
      7. 6.3.7  Soft Start
      8. 6.3.8  Output Voltage Setpoint (FB)
      9. 6.3.9  Minimum Controllable On-Time
      10. 6.3.10 Error Amplifier and PWM Comparator (FB, EXTCOMP)
      11. 6.3.11 Slope Compensation
      12. 6.3.12 Shunt Current Sensing
      13. 6.3.13 Hiccup Mode Current Limiting
      14. 6.3.14 Device Configuration (CONFIG)
      15. 6.3.15 Single-Output Dual-Phase Operation
      16. 6.3.16 Pulse Frequency Modulation (PFM) / Synchronization
      17. 6.3.17 Thermal Shutdown (TSD)
    4. 6.4 Device Functional Modes
      1. 6.4.1 Shutdown Mode
      2. 6.4.2 Standby Mode
      3. 6.4.3 Active Mode
      4. 6.4.4 Sleep Mode
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Power Train Components
        1. 7.1.1.1 Buck Inductor
        2. 7.1.1.2 Output Capacitors
        3. 7.1.1.3 Input Capacitors
        4. 7.1.1.4 EMI Filter
      2. 7.1.2 Error Amplifier and Compensation
      3. 7.1.3 Maximum Ambient Temperature
        1. 7.1.3.1 Derating Curves
    2. 7.2 Typical Applications
      1. 7.2.1 Design 1 – High Efficiency, Wide Input, 400kHz Synchronous Buck Regulator
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
          1. 7.2.1.2.1 Custom Design With WEBENCH® Tools
          2. 7.2.1.2.2 Custom Design With Excel Quickstart Tool
          3. 7.2.1.2.3 Buck Inductor
          4. 7.2.1.2.4 Current-Sense Resistance
          5. 7.2.1.2.5 Output Capacitors
          6. 7.2.1.2.6 Input Capacitors
          7. 7.2.1.2.7 Frequency Set Resistor
          8. 7.2.1.2.8 Feedback Resistors
          9. 7.2.1.2.9 Compensation Components
        3. 7.2.1.3 Application Curves
      2. 7.2.2 Design 2 – High Efficiency 24V to 3.3V 400kHz Synchronous Buck Regulator
        1. 7.2.2.1 Design Requirements
        2. 7.2.2.2 Detailed Design Procedure
        3. 7.2.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
        1. 7.4.1.1 Thermal Design and Layout
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Development Support
        1. 8.1.1.1 Custom Design With WEBENCH® Tools
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
        1. 8.2.1.1 PCB Layout Resources
        2. 8.2.1.2 Thermal Design Resources
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information
    1. 10.1 Tape and Reel Information

Package Options

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

7.2.2.1 Design Requirements

Table 7-3 shows the intended input, output, and performance parameters for this automotive design example.

Table 7-3 Design Parameters
DESIGN PARAMETER VALUE
Input voltage range (steady-state) 12V to 42V
Min transient input voltage (cold crank) 5V
Max transient input voltage (load dump) 65V
Output voltage 3.3V
Output current 10A
Switching frequency 400kHz
Output voltage regulation ±1%
Active current, no load 12µA
Shutdown current 2.2µA
Soft-start time 3ms

The switching frequency is set at 400kHz by resistor RRT The selected buck regulator powertrain components are cited in Table 7-4 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 7-4 List of Materials for Application Circuit 2
REFERENCE DESIGNATOR QTY SPECIFICATION MANUFACTURER PART NUMBER
CIN 4 4.7μF, 100V, X7S, 1210, ceramic Murata GCM32DC72A475KE02L
TDK CGA6M3X7S2A475K200
CO 4 47µF, 10V, X7R, 1210, ceramic, AEC-Q200 Murata GRM32ER71A476KE15L
47µF, 10V, X7S, 1210, ceramic, AEC-Q200 TDK CNA6P1X7S1A476M250AE
LO 1 2.2µH, 3.8mΩ, 21.5A, 11.3 × 10 × 6mm, AEC-Q200 Coilcraft XGL1060-222MEC
2.2μH, 3.8mΩ, 26A, 11.2 × 10.3 × 6.5mm, AEC-Q200 Cyntec VCHA106E-2R2MS6
2.2μH, 4.1mΩ, 21.4A, 11.2 × 10.3 × 5.4mm, AEC-Q200 Cyntec VCHA105D-2R2MS6
RS 1 Shunt, 4mΩ, 0508, 1W, AEC-Q200 Susumu KRL2012E-M-R004-F-T5
U1 1 LM706A0 65V, 10A synchronous DC/DC buck converter Texas Instruments LM706A0RRXR