SNVSAH5A September   2017  – May 2020 LM73605 , LM73606

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
      2.      Efficiency versus Load Current VOUT = 5 V, fSW = 500 kHz, Auto Mode
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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 Timing Characteristics
    7. 6.7 Switching Characteristics
    8. 6.8 System Characteristics
    9. 6.9 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Synchronous Step-Down Regulator
      2. 7.3.2  Auto Mode and FPWM Mode
      3. 7.3.3  Fixed-Frequency Peak Current-Mode Control
      4. 7.3.4  Adjustable Output Voltage
      5. 7.3.5  Enable and UVLO
      6. 7.3.6  Internal LDO, VCC_UVLO, and BIAS Input
      7. 7.3.7  Soft Start and Voltage Tracking
      8. 7.3.8  Adjustable Switching Frequency
      9. 7.3.9  Frequency Synchronization and Mode Setting
      10. 7.3.10 Internal Compensation and CFF
      11. 7.3.11 Bootstrap Capacitor and VBOOT-UVLO
      12. 7.3.12 Power-Good and Overvoltage Protection
      13. 7.3.13 Overcurrent and Short-Circuit Protection
      14. 7.3.14 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Standby Mode
      3. 7.4.3 Active Mode
        1. 7.4.3.1 CCM Mode
        2. 7.4.3.2 DCM Mode
        3. 7.4.3.3 PFM Mode
        4. 7.4.3.4 Fault Protection Mode
  8. 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  Output Voltage Setpoint
        3. 8.2.2.3  Switching Frequency
        4. 8.2.2.4  Input Capacitors
        5. 8.2.2.5  Inductor Selection
        6. 8.2.2.6  Output Capacitor Selection
        7. 8.2.2.7  Feedforward Capacitor
        8. 8.2.2.8  Bootstrap Capacitors
        9. 8.2.2.9  VCC Capacitor
        10. 8.2.2.10 BIAS
        11. 8.2.2.11 Soft Start
        12. 8.2.2.12 Undervoltage Lockout Setpoint
        13. 8.2.2.13 PGOOD
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Layout For EMI Reduction
      2. 10.1.2 Ground Plane
      3. 10.1.3 Optimize Thermal Performance
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
        1. 11.1.2.1 Custom Design With WEBENCH® Tools
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Related Links
    4. 11.4 Receiving Notification of Documentation Updates
    5. 11.5 Support Resources
    6. 11.6 Trademarks
    7. 11.7 Electrostatic Discharge Caution
    8. 11.8 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2 Typical Application

The LM73605 and LM73606requires only a few external components to perform high-efficiency power conversion, as shown in Figure 25.

LM73605 LM73606 LM73605-simplified-schematic-snvsah5.gifFigure 25. LM73605 and LM73606 Basic Schematic

The LM73605 and LM73606 also integrate many practical features to meet a wide range of system design requirements and optimization, such as UVLO, programmable soft-start time, start-up tracking, programmable switching frequency, clock synchronization, and a power-good flag. Note that for ease of use, the feature pins do not require an additional component when not in use. They can be either left floating or shorted to ground. Please refer to the Pin Configuration and Functions for details.

A comprehensive schematic with all features utilized is shown in Figure 26.

LM73605 LM73606 LM73605-comprehenisve-schematic-snvsah5.gifFigure 26. LM73605 and LM73606 Comprehensive Schematic with All Features Utilized

The external components must fulfill not only the needs of the power conversion, but also the stability criteria of the control loop. The LM73605 and LM73606are optimized to work with a range of external components. For quick component selection, Table 3 can be used.

Table 3. Typical Component Selection

fSW (kHz) VOUT (V) L (µH) COUT (µF)(1) RFBT (kΩ) RFBB (kΩ) RT (kΩ)
350 1 2.2 500 100 OPEN 115
500 1 1.5 400 100 OPEN 78.7 or open
1000 1 0.68 200 100 OPEN 39.2
2200 1 0.47 100 100 OPEN 17.4
350 3.3 4.7 200 100 43.5 115
500 3.3 3.3 150 100 43.5 78.7 or open
1000 3.3 1.8 88 100 43.5 39.2
2200 3.3 1.2 44 100 43.5 17.4
350 5 6.8 120 100 25 115
500 5 4.7 88 100 25 78.7 or open
1000 5 3.3 66 100 25 39.2
2200 5 2.2 44 100 25 17.4
350 12 15 66 100 9.1 115
500 12 10 44 100 9.1 78.7 or open
1000 12 6.8 22 100 9.1 39.2
350 24 22 40 100 4.3 115
500 24 15 30 100 4.3 78.7 or open
(1) All the COUT values are after derating. Add more when using ceramics.