SBVS438A April   2024  – May 2025 TPS7B92

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Wide Supply Range
      2. 6.3.2 Low Quiescent Current
      3. 6.3.3 Dropout Voltage (VDO)
      4. 6.3.4 Current Limit
      5. 6.3.5 Leakage Null Control Circuit
    4. 6.4 Device Functional Modes
      1. 6.4.1 Normal Operation
      2. 6.4.2 Dropout Operation
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 External Capacitor Requirements
        2. 7.2.2.2 Input and Output Capacitor Requirements
        3. 7.2.2.3 Reverse Current
        4. 7.2.2.4 Power Dissipation (PD)
        5. 7.2.2.5 Estimating Junction Temperature
      3. 7.2.3 Application Curves
    3. 7.3 Best Design Practices
    4. 7.4 Power Supply Recommendations
    5. 7.5 Layout
      1. 7.5.1 Layout Guidelines
        1. 7.5.1.1 Power Dissipation
      2. 7.5.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Development Support
        1. 8.1.1.1 Evaluation Module
        2. 8.1.1.2 Spice Models
      2. 8.1.2 Device Nomenclature
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

6.3.3 Dropout Voltage (VDO)

Dropout voltage (VDO) is defined as VIN – VOUT at the rated output current (IRATED), where the pass transistor is fully on. VIN – VOUT is input voltage minus the output voltage. IRATED is the maximum IOUT listed in the Recommended Operating Conditions table. In dropout operation, the pass transistor is in the ohmic or triode region of operation, and acts as a switch. Dropout voltage indirectly specifies a minimum input voltage greater than the nominal programmed output voltage where the output voltage is expected to stay in regulation. If the input voltage falls to less than the value required to maintain output regulation, then the output voltage falls as well.

For a CMOS regulator, the dropout voltage is determined by the drain-source, on-state resistance (RDS(ON)) of the pass transistor. Therefore, if the linear regulator operates at less than the rated current, the dropout voltage for that current scales accordingly. Equation 1 calculates the RDS(ON) of the device.

Equation 1. R D S ( O N )   =   V D O I R A T E D