SNVSB87 November   2018 LM3880-Q1


  1. Features
  2. Applications
  3. Description
    1.     Device Images
      1.      Simple Power Supply Sequencing
  4. Revision History
  5. Pin Configuration and Functions
    1.     Pin Functions
  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
      1. 6.5.1 Timing Requirements
    6. 6.6 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Enable Pin Operation
      2. 7.3.2 Incomplete Sequence Operation
    4. 7.4 Device Functional Modes
      1. 7.4.1 Power Up With EN Pin
      2. 7.4.2 Power Down With EN Pin
  8. Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Open Drain Flags Pullup
      2. 8.1.2 Enable the Device
    2. 8.2 Typical Application
      1. 8.2.1 Simple Sequencing of Three Power Supplies
        1. Design Requirements
        2. Detailed Design Procedure
        3. Application Curves
      2. 8.2.2 Sequencing Using Independent Flag Supply
    3. 8.3 Do's and Don'ts
  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. 11.1.2 Device Nomenclature
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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


The LM3880-Q1 simple power supply sequencer provides a simple solution for sequencing multiple rails in a controlled manner. Six independent timers are integrated to control the timing sequence (power up and power down) of three open-drain output flags. These flags permit connection to either a shutdown or enable pin of linear regulators and switchers to control the operation of the power supplies. This allows design of a complete power system without concern for large inrush currents or latch-up conditions that can occur.

The timing sequence of the device is controlled entirely by the enable (EN) pin. Upon power up, all the flags are held low until this precision enable is pulled high. When the EN pin is asserted, the power-up sequence starts. An internal counter delays the first flag (FLAG1) from rising until a fixed time period has expired. When the first flag is released, another timer will begin to delay the release of the second flag (FLAG2). This process repeats until all three flags have sequentially been released.

The power-down sequence is the same as power-up sequence, but in reverse. When the EN pin is deasserted a timer will begin that delays the third flag (FLAG3) from pulling low. The second and first flag will then follow in a sequential manner after their appropriate delays. The three timers that are used to control the power-down scheme can also be individually programmed and are completely independent of the power-up timers.