SBVS476A May   2025  – July 2025 TPS7B4258-Q1

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 Tracker Output Voltage (VOUT)
        1. 6.3.1.1 Output Voltage Equal to Reference Voltage
        2. 6.3.1.2 Output Voltage Less Than the Reference Voltage
        3. 6.3.1.3 Output Voltage Larger Than the Reference Voltage
      2. 6.3.2 Reverse Current Protection
      3. 6.3.3 Undervoltage Lockout
      4. 6.3.4 Thermal Protection
      5. 6.3.5 Current Limit
      6. 6.3.6 Output Short to Battery
      7. 6.3.7 Tracking Regulator With an Enable Circuit
    4. 6.4 Device Functional Modes
      1. 6.4.1 Normal Operation
      2. 6.4.2 Dropout Operation
      3. 6.4.3 Operation With VIN < 3.3V
      4. 6.4.4 Disable With ADJ/EN Control
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Dropout Voltage
      2. 7.1.2 Reverse Current
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Input and Output Capacitor Selection
        2. 7.2.2.2 Feedback Resistor Selection
        3. 7.2.2.3 Feedforward Capacitor
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
        1. 7.4.1.1 Package Mounting
        2. 7.4.1.2 Board Layout Recommendations to Improve PSRR and Noise Performance
        3. 7.4.1.3 Power Dissipation and Thermal Considerations
        4. 7.4.1.4 Thermal Performance Versus Copper Area
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 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

7.1.1 Dropout Voltage

Dropout voltage (VDO) is defined as VIN – VOUT when the pass transistor is fully on. VIN is the input voltage and VOUT is the output voltage. This condition arises when the input voltage falls to a point where the error amplifier drives the gate of the pass transistor to the rail. During this condition, there is no remaining headroom for the control loop to operate. At this operating point, the pass transistor is driven fully on. Dropout voltage directly specifies the minimum VIN − VOUT differential the device requires to maintain a regulated output voltage. 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 voltage is no longer regulated, and transient performance is severely degraded. The device loses PSRR, and load transients potentially 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), the dropout voltage for that current scales accordingly. IRATED is specified in the Recommended Operating Conditions table. The following equation calculates the RDS(ON) of the device.

Equation 4. TPS7B4258-Q1