SBVS082K June   2007  – June 2024 TPS74901

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: IOUT = 50mA
    7. 5.7 Typical Characteristics: IOUT = 1 A
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagrams
    3. 6.3 Feature Description
      1. 6.3.1 Enable and Shutdown
      2. 6.3.2 Power-Good
      3. 6.3.3 Internal Current Limit
      4. 6.3.4 Thermal Protection
    4. 6.4 Device Functional Modes
      1. 6.4.1 Normal Operation
      2. 6.4.2 Dropout Operation
      3. 6.4.3 Disabled
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Input, Output, and BIAS Capacitor Requirements
      2. 7.1.2 Transient Response
      3. 7.1.3 Dropout Voltage
      4. 7.1.4 Output Noise
      5. 7.1.5 Programmable Soft-Start
      6. 7.1.6 Sequencing Requirements
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
      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 Power Dissipation
        2. 7.4.1.2 Thermal Considerations
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Device Nomenclature
      2. 8.1.2 Development Support
        1. 8.1.2.1 Evaluation Modules
        2. 8.1.2.2 Spice Models
    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

7.1.3 Dropout Voltage

The TPS74901 offers very low dropout performance, making the device designed for high-current low VIN and low VOUT applications. The low dropout of the TPS74901 allows the device to be used in place of a DC/DC converter and still achieve good efficiencies. This capability provides designers with the power architecture for applications to achieve the smallest, simplest, and lowest-cost solution.

There are two different specifications for dropout voltage with the TPS74901. The first specification (see Figure 7-1) is referred to as VIN dropout and is used when an external bias voltage is applied to achieve low dropout. This specification assumes that VBIAS is at least 3.25V above VOUT, which is the case for VBIAS when powered by a 5V rail with 5% tolerance and with VOUT = 1.5V (3.25V is a test condition of this device and can be adjusted by referring to Figure 5-11). If VBIAS is higher than VOUT + 3.25V, VIN dropout is less than specified.

TPS74901 Typical Application of the TPS74901 Using an Auxiliary Bias RailFigure 7-1 Typical Application of the TPS74901 Using an Auxiliary Bias Rail

The second specification (shown in Figure 7-2) is referred to as VBIAS dropout and is applied to applications where IN and BIAS are tied together. This option allows the device to be used in applications where an auxiliary bias voltage is not available or low dropout is not required. Dropout is limited by BIAS in these applications because VBIAS provides the gate drive to the pass transistor; therefore, VBIAS must be 1.75V above VOUT. Because of this usage, IN and BIAS tied together easily consume a huge amount of power. Pay attention not to exceed the power rating of the device package.

TPS74901 Typical Application of the TPS74901 Without an Auxiliary BiasFigure 7-2 Typical Application of the TPS74901 Without an Auxiliary Bias