SNVS847F June   2012  – November 2017 LM34926

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 Ratings
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Switching Characteristics
    7. 6.7 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 Overview
      2. 7.3.2  VCC Regulator
      3. 7.3.3  Regulation Comparator
      4. 7.3.4  Overvoltage Comparator
      5. 7.3.5  On-Time Generator
      6. 7.3.6  Current Limit
      7. 7.3.7  N-Channel Buck Switch and Driver
      8. 7.3.8  Synchronous Rectifier
      9. 7.3.9  Undervoltage Detector
      10. 7.3.10 Thermal Protection
      11. 7.3.11 Ripple Configuration
      12. 7.3.12 Soft Start
    4. 7.4 Device Functional Modes
  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  Transformer Turns Ratio
        3. 8.2.2.3  Total IOUT
        4. 8.2.2.4  RFB1, RFB2
        5. 8.2.2.5  Frequency Selection
        6. 8.2.2.6  Transformer Selection
        7. 8.2.2.7  Primary Output Capacitor
        8. 8.2.2.8  Secondary Output Capacitor
        9. 8.2.2.9  Type III Feedback Ripple Circuit
        10. 8.2.2.10 Secondary Diode
        11. 8.2.2.11 VCC and Bootstrap Capacitor
        12. 8.2.2.12 Input Capacitor
        13. 8.2.2.13 UVLO Resistors
        14. 8.2.2.14 VCC Diode
      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 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 Custom Design With WEBENCH® Tools
    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

  • Wide 7.5-V to 100-V Input Range
  • Integrated 300-mA High-Side
    and Low-Side Switches
  • No Schottky Required
  • Constant On-Time Control
  • No Loop Compensation Required
  • Ultra-Fast Transient Response
  • Nearly Constant Operating Frequency
  • Intelligent Peak Current Limit
  • Adjustable Output Voltage From 1.225 V
  • Precision 2% Feedback Reference
  • Frequency Adjustable to 1 MHz
  • Adjustable Undervoltage Lockout (UVLO)
  • Remote Shutdown
  • Thermal Shutdown
  • Packages:
    • WSON-8
    • SO PowerPAD™-8 Packages
  • Create a Custom Design Using the LM34926 With the WEBENCH® Power Designer

2 Applications

  • Isolated Telecom Bias Supply
  • Isolated Automotive and Industrial Electronics

3 Description

The LM34926 regulator features all of the functions needed to implement a low-cost, efficient, isolated bias regulator. This high-voltage regulator contains two 100-V N-channel MOSFET switches — a high-side buck switch and a low-side synchronous switch. The constant on-time (COT) control scheme employed in the LM34926 requires no loop compensation and provides excellent transient response. The regulator operates with an on-time control that is inversely proportional to the input voltage. This feature allows the operating frequency to remain relatively constant. An intelligent peak current limit is implemented with integrated sense circuit. Other features include a programmable input undervoltage comparator to inhibit operation during low-voltage conditions. Protection features include thermal shutdown and VCC Undervoltage Lockout (UVLO). The LM34926 device is offered in WSON-8 and SO PowerPAD-8 plastic packages.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
LM34926 HSOP (8) 4.89 mm × 3.90 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

LM34926 Typ App Schem.gif