SNVS697E January 2011  – December 2016 SM72485

PRODUCTION DATA. 

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1Absolute Maximum Ratings
    2. 6.2ESD Ratings
    3. 6.3Recommended Operating Conditions
    4. 6.4Thermal Information
    5. 6.5Electrical Characteristics
    6. 6.6Typical Characteristics
  7. Detailed Description
    1. 7.1Overview
    2. 7.2Functional Block Diagram
    3. 7.3Feature Description
      1. 7.3.1Control Circuit Overview
      2. 7.3.2Current Limit
      3. 7.3.3N-Channel Buck Switch and Driver
      4. 7.3.4Thermal Protection
    4. 7.4Device Functional Modes
      1. 7.4.1Start-Up Regulator (VCC)
      2. 7.4.2Regulation Comparator
      3. 7.4.3Overvoltage Comparator
      4. 7.4.4ON-Time Generator and Shutdown
  8. Application and Implementation
    1. 8.1Application Information
    2. 8.2Typical Application
      1. 8.2.1Design Requirements
      2. 8.2.2Detailed Design Procedure
        1. 8.2.2.1Selection of External Components
          1. 8.2.2.1.1 RFB1 and RFB2
          2. 8.2.2.1.2 Fs and RT
          3. 8.2.2.1.3 L1
          4. 8.2.2.1.4 C3
          5. 8.2.2.1.5 C2 and R3
          6. 8.2.2.1.6 ESR and R3
          7. 8.2.2.1.7 RCL
          8. 8.2.2.1.8 D1
          9. 8.2.2.1.9 C1
          10. 8.2.2.1.10C4
          11. 8.2.2.1.11C5
        2. 8.2.2.2Low Output Ripple Configurations
          1. 8.2.2.2.1Reduced Ripple Configuration
          2. 8.2.2.2.2Minimum Ripple Configuration
          3. 8.2.2.2.3Alternate Minimum Ripple Configuration
      3. 8.2.3Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1Layout Guidelines
    2. 10.2Layout Example
  11. 11Device and Documentation Support
    1. 11.1Documentation Support
      1. 11.1.1Related Documentation
    2. 11.2Receiving Notification of Documentation Updates
    3. 11.3Community Resources
    4. 11.4Trademarks
    5. 11.5Electrostatic Discharge Caution
    6. 11.6Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Features

  • Operating Input Voltage: 6 V to 95 V
  • Integrated 100-V, N-Channel Buck Switch
  • Internal Start-Up Regulator
  • No Loop Compensation Required
  • Ultra-Fast Transient Response
  • On-time Varies Inversely With Input Voltage
  • Operating Frequency Remains Constant With Varying Line Voltage and Load Current
  • Adjustable Output Voltage From 2.5 V
  • Highly Efficient Operation
  • Precision Internal Reference
  • Low Bias Current
  • Intelligent Current Limit
  • Thermal Shutdown
  • Package
    • VSSOP (3 mm × 3 mm)
    • WSON (4 mm × 4 mm)

Applications

  • PV Panel Smart Junction Boxes
  • Nonisolated Telecommunication Buck Regulator
  • Secondary High Voltage Post Regulator
  • 42-V Automotive Systems

Description

The SM72485 step-down switching regulator features all of the functions required to implement a low cost, efficient, Buck bias regulator. This high voltage regulator contains an 100-V N-channel buck switch. The device is easy to implement and is provided in the VSSOP and the thermally enhanced WSON package. The regulator is based on a control scheme using an on-time inversely proportional to VIN. This feature allows the operating frequency to remain relatively constant. The control scheme requires no loop compensation. An intelligent current limit is implemented with forced off-time, which is inversely proportional to VOUT. This scheme ensures short circuit control while providing minimum foldback. Other features include: Thermal shutdown, VCC undervoltage lockout, gate drive undervoltage lockout, maximum duty cycle limiter, and a precharge switch.

Device Information(1)

PART NUMBERPACKAGEBODY SIZE (NOM)
SM72485VSSOP (8)3.00 mm × 3.00 mm
WSON (8)4.00 mm × 4.00 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.

Typical Application, Basic Step-Down Regulator

SM72485 30142301.gif