SBVA100 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. 2System Architecture Design – How Many Parallel LDO's are Required?
    1. 2.1 Noise
    2. 2.2 PSRR
    3. 2.3 Specifications That Limit the Maximum LDO Current
      1. 2.3.1 Dropout (or Available Headroom Voltage)
      2. 2.3.2 Temperature
    4. 2.4 Load Current (ILOAD) and Load Voltage (VLOAD)
  5. 3System VLOAD and Current Sharing Simulation of Parallel LDOs using Ballast Resistors
  6. 4Examples
    1. 4.1 TPS7A94
    2. 4.2 TPS7A47xx
    3. 4.3 TPS7A57
  7. 5References

2 System Architecture Design – How Many Parallel LDO's are Required?

The following definitions are used in this white paper:

    ILOAD System Load Current
    n Number of parallel LDOs
    VIN Input Voltage
    VOUT Output Voltage
    Headroom Voltage VIN - VOUT
    VDROP Dropout Voltage = Minimum headroom voltage required to regulate VOUT
    ILDO_MAX_DROPOUT_LIM The limited current each LDO can provide from the available headroom voltage
    ILDO_MAX_TEMP_LIM The limited current each LDO can provide before exceeding the specified TJ limit
    ILDO_MAX The maximum rated current of the LDO
    ILDO_PSRR The maximum output current for a single LDO that meets the specified PSRR specification, as shown in the PSRR measurements