SBVS392A june   2022  – august 2023 TPS7B4255-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  6. 5 Pin Configuration and Functions
  7. 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
    6. 6.6 Timing Characteristics
    7. 6.7 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Tracker Output Voltage (VOUT)
        1. 7.3.1.1 Output Voltage Equal to the Reference Voltage
        2. 7.3.1.2 Output Voltage Less Than the Reference Voltage
      2. 7.3.2 Reverse Current Protection
      3. 7.3.3 Undervoltage Lockout
      4. 7.3.4 Thermal Protection
      5. 7.3.5 Current Limit
      6. 7.3.6 Output Short to Battery
      7. 7.3.7 Tracking Regulator With an Enable Circuit
    4. 7.4 Device Functional Modes
      1. 7.4.1 Normal Operation
      2. 7.4.2 Dropout Operation
      3. 7.4.3 Operation With VIN < 3 V
      4. 7.4.4 Disable With ADJ/EN Control
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Dropout Voltage
      2. 8.1.2 Reverse Current
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Input and Output Capacitor Selection
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
        1. 8.4.1.1 Package Mounting
        2. 8.4.1.2 Board Layout Recommendations to Improve PSRR and Noise Performance
        3. 8.4.1.3 Power Dissipation and Thermal Considerations
        4. 8.4.1.4 Thermal Performance Versus Copper Area
      2. 8.4.2 Layout Examples
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Device Nomenclature
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Mechanical, Packaging, and Orderable Information
    1. 10.1 Mechanical Data

Package Options

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

8.1.1 Dropout Voltage

Dropout voltage (VDO) is defined as the input voltage minus the output voltage (VIN – VOUT) when the pass transistor is fully on. This condition arises when the input voltage falls to the point where the error amplifier must drive the gate of the pass transistor to the rail and has no remaining headroom for the control loop to operate. The pass transistor is in the ohmic or triode region of operation, and acts as a switch. The dropout voltage directly specifies a minimum input voltage greater than the nominal programmed output voltage at which the output voltage is expected to stay in regulation. If the input voltage falls to less than the nominal output regulation, then the output voltage follows, minus the dropout voltage (VDO).

In dropout mode, the output is no longer regulated, and transient performance is severely degraded. The device loses PSRR, and load transients can cause large output voltage deviation.

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 output current (IRATED, see the Recommended Operating Conditions table), the dropout voltage for that current scales accordingly. The following equation calculates the RDS(ON) of the device.

Equation 3. R DS(ON) = V DO I RATED