TIDUF09 December   2022

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
    3. 2.3 Theory of Operation
    4. 2.4 Highlighted Products
      1. 2.4.1 TPS7A57 Low Dropout (LDO) Regulator
      2. 2.4.2 LMG1020 Low Side Driver
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Test Setup
      1. 3.2.1 Optional Load Transient Circuit Operation
    3. 3.3 Test Results
      1. 3.3.1 Current Sharing
      2. 3.3.2 VLOAD vs ILOAD
      3. 3.3.3 Load Transient Response
      4. 3.3.4 Current Limit
      5. 3.3.5 Startup
      6. 3.3.6 Noise
      7. 3.3.7 PSRR
      8. 3.3.8 Thermal
      9. 3.3.9 Thermal Limit Protection
  9. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
    2. 4.2 Tools
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks
  10. 5About the Author

1 System Description

Low-noise low-dropout regulators (LDO) are required in many applications to ensure that power supply noise does not couple into the signal chain. The requirements for current continue to increase as new high-speed analog-to-digital converters (ADCs), digital-to-analog converters (DACs), and clocking circuitry increase data speed and bandwidth. Transient performance must also improve to meet modern FPGA regulation band requirements. Using a single LDO for the supply is not always possible due to device availability and power dissipation limitations. The TIDA-050061 reference design solves this issue by using multiple LDOs configured to share current in parallel. The current sharing is achieved by using low-value ballast resistors, which can be designed as a discrete resistor or a copper trace on the printed-circuit board (PCB). The topology presented in this reference design can be expanded to include more LDOs if needed, there is no limit to the number of LDOs that can be placed in parallel.

This circuit uses the high-current LDO, TPS7A57, which is a 5-A device. The reference design is populated with three TPS7A57 devices and can provide up to 13.5 A of current using the 2.5 m-ohm ballast resistors. Low inductive current loops and a high speed load transient circuit are included to assist customer evaluation of the reference design.