SNVS697E January   2011  – December 2016 SM72485

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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 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 Control Circuit Overview
      2. 7.3.2 Current Limit
      3. 7.3.3 N-Channel Buck Switch and Driver
      4. 7.3.4 Thermal Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Start-Up Regulator (VCC)
      2. 7.4.2 Regulation Comparator
      3. 7.4.3 Overvoltage Comparator
      4. 7.4.4 ON-Time Generator and Shutdown
  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 Selection 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. 8.2.2.1.10 C4
          11. 8.2.2.1.11 C5
        2. 8.2.2.2 Low Output Ripple Configurations
          1. 8.2.2.2.1 Reduced Ripple Configuration
          2. 8.2.2.2.2 Minimum Ripple Configuration
          3. 8.2.2.2.3 Alternate Minimum Ripple Configuration
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

1 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)

2 Applications

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

3 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 NUMBER PACKAGE BODY SIZE (NOM)
SM72485 VSSOP (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