SNVS416C November   2005  – February 2016 LM27951

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 Charge Pump
      2. 7.3.2 Soft Start
      3. 7.3.3 Thermal Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Enable and PWM Pins
      2. 7.4.2 Adjusting LED Brightness (PWM Control)
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Maximum Output Current, Maximum LED Voltage, Minimum Input Voltage
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Setting LED Currents
        2. 8.2.2.2 Capacitor Selection
        3. 8.2.2.3 Parallel Dx Outputs for Increased Current Drive
        4. 8.2.2.4 Power Efficiency
        5. 8.2.2.5 Power Dissipation
      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 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    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

  • Input Voltage Range: 2.8 V to 5.5 V
  • Drives up to Four LEDs With up to 30 mA each
  • Regulated Current Sources with 0.2% (Typical) Matching
  • 3/2×, 1× Gain Transition Based on LED Vƒ
  • Peak Efficiency Over 85%
  • PWM Brightness Control
  • Very Small Solution Size - No Inductor
  • Fixed 750-kHz Switching Frequency
  • < 1-µA Shutdown Current

2 Applications

  • White LED Display Backlights
  • White LED Keypad Backlights
  • General Purpose LED Lighting

3 Description

The LM27951 is a switched capacitor white-LED driver capable of driving up to four LEDs with 30 mA through each LED. Its four tightly regulated current sources ensure excellent LED current and brightness matching. LED drive current is programmed by an external sense resistor. The LM27951 operates over an input voltage range from 2.8 V to 5.5 V and requires only four low-cost ceramic capacitors.

The LM27951 provides excellent efficiency without the use of an inductor by operating the charge pump in a gain of 3/2, or in a gain of 1. Maximum efficiency is achieved over the input voltage range by actively selecting the proper gain based on the LED forward voltage requirements.

The LM27951 uses constant frequency pre-regulation to minimize conducted noise on the input. It has a fixed 750-kHz switching frequency optimized for portable applications. The LM27951 consumes less than 1 µA of supply current when shut down.

The LM27951 is available in a 14-pin no-pullback WSON package.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
LM27951 WSON (14) 4.00 mm × 3.00 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.

Simplified Schematic

LM27951 simp_schem_snvs416.gif