SBVA093 December   2022 LP2992 , TPS786 , TPS7A30 , TPS7A3001-EP , TPS7A33 , TPS7A39 , TPS7A4501-SP , TPS7A47 , TPS7A47-Q1 , TPS7A4701-EP , TPS7A49 , TPS7A52 , TPS7A52-Q1 , TPS7A53 , TPS7A53-Q1 , TPS7A53A-Q1 , TPS7A53B , TPS7A54 , TPS7A54-Q1 , TPS7A57 , TPS7A7100 , TPS7A7200 , TPS7A7300 , TPS7A80 , TPS7A8300 , TPS7A83A , TPS7A84 , TPS7A84A , TPS7A85 , TPS7A85A , TPS7A87 , TPS7A89 , TPS7A90 , TPS7A91 , TPS7A92 , TPS7A94 , TPS7A96 , TPS7B7702-Q1 , TPS7H1111-SEP , TPS7H1111-SP , TPS7H1210-SEP

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
  4. 2Comprehensive Review of Error in LDO's
    1. 2.1 Commentary on Real World Error Voltage (VE) in Single LDO's
      1. 2.1.1 VREF Pin
      2. 2.1.2 VFB Pin
  5. 3Current Sharing and Load Voltage Analysis for n Parallel LDO's
    1. 3.1 Commentary on Parallel LDO's in Real World Applications
  6. 4Ballast Resistor Design and Analysis
    1. 4.1 Selecting the Ballast Resistor Value
    2. 4.2 PCB Ballast Resistor Design vs. Discrete Ballast Resistance
  7. 5Impacts and Opportunities of PCB Parasitic Impedance
  8. 6Design Examples
    1. 6.1 TPS7A57
    2. 6.2 TPS7A47xx
  9. 7Conclusion
  10. 8References

Abstract

In this paper we provide a comprehensive analysis and new mathematical foundation to design any number of parallel LDO's using ballast resistors. Using this foundation, we show how to optimize the parallel LDO performance by including the parasitic PCB impedance in the ballast resistance analysis. This enables lower values of discrete ballast resistance and maximum performance in the design.