SNVS116E May   1998  – December 2014 LM3420

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 LM3420 Electrical Characteristics
    6. 6.6 LM3420A Electrical Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Parameter Measurement Information
    1. 7.1 Test Circuits
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Compensation
      2. 8.3.2 VREG External Voltage Trim
    4. 8.4 Device Functional Modes
      1. 8.4.1 Operation as Control Section
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application: Constant Current/Constant Voltage Li-Ion Battery Charger
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Compensation Capacitor
      3. 9.2.3 Application Curve
      4. 9.2.4 Other Application Circuits
        1. 9.2.4.1 Low Dropout Constant Current/Constant Voltage 2-Cell Charger
        2. 9.2.4.2 High-Efficiency Switching Regulator Constant Current/Constant Voltage 2-Cell Charger
        3. 9.2.4.3 Low Dropout Constant Current/Constant Voltage Li-Ion Battery Charger
        4. 9.2.4.4 High-Efficiency Switching Charger With High Side Current Sensing
        5. 9.2.4.5 Fast-Pulsed Constant Current 2-Cell Charger
        6. 9.2.4.6 MOSFET Low Dropout Charger
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Trademarks
    2. 12.2 Electrostatic Discharge Caution
    3. 12.3 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

1 Features

  • Input Voltage Range: up to 20 V
  • Voltage Options for Charging 1, 2, 3, or 4 Cells
  • Output Current up to 15 mA
  • Precision (0.5%) End-of-Charge Control
    • LM3420 ±1%
    • LM3420A ±0.5%
  • Drive Capability for External Power Stage
  • Temperature Drift Curvature Correction for Voltage Stability
  • Low Quiescent Current, 85 μA (Typ.)
  • Tiny SOT-23-5 package

2 Applications

  • Lithium-Ion Battery Charging
  • Suitable for Linear and Switching Regulator Charger Designs

3 Description

The LM3420 series of controllers are monolithic integrated circuits designed for charging and end-of-charge control for lithium-ion rechargeable batteries. The LM3420 is available in an 8.4-V version for one through four cell charger applications.

Included in a very small package is an (internally compensated) op amp, a bandgap reference, an NPN output transistor, and voltage setting resistors. The amplifier's inverting input is externally accessible for loop frequency compensation. The output is an open-emitter NPN transistor capable of driving up to 15 mA of output current into external circuitry.

A trimmed precision bandgap reference utilizes temperature drift curvature correction for excellent voltage stability over the operating temperature range. The LM3420 series allows for precision end-of-charge voltage threshold for lithium-ion rechargeable batteries. The premium grade LM3420A is available with an initial voltage threshold tolerance of ±0.5%, while the standard grade LM3420 has an initial voltage threshold tolerance of ±1%.

The LM3420 is available in a sub-miniature 5-lead surface mount package thus allowing very compact designs.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
LM3420 SOT-23 (5) 2.90 mm x 1.60 mm
  1. For all available packages, see the orderable addendum at the end of the datasheet.

Simplified Schematic

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