SBVS066S December   2005  – November 2024 TPS74401

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 Enable, Shutdown
      2. 6.3.2 Power-Good (VQFN Package Only)
      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
    5. 6.5 Programming
      1. 6.5.1 Programmable Soft-Start
      2. 6.5.2 Sequencing Requirements
  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
    2. 7.2 Typical Applications
      1. 7.2.1 Setting the TPS74401
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
        3. 7.2.1.3 Application Curves
      2. 7.2.2 Using an Auxiliary Bias Rail
      3. 7.2.3 Without an Auxiliary Bias
    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 Documentation Support
      1. 8.1.1 Related Documentation
      2. 8.1.2 Device Nomenclature
    2. 8.2 Device Support
      1. 8.2.1 Development Support
        1. 8.2.1.1 Evaluation Modules
        2. 8.2.1.2 Spice Models
    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 TPS74401 offers industry-leading dropout performance, making the device excellent for high-current, low VIN and low VOUT applications. The extremely low dropout of the TPS74401 also allows the device to be used in place of a dc/dc converter and also achieve good efficiencies. Equation 3 provides a quick estimate of the efficiencies.

Equation 3. Efficiency≈VOUT×IOUTVIN×IIN+IQ≈VOUTVIN at IOUT>>IQ

This efficiency allows users to redesign the power architecture to achieve a small, simple, and low-cost option.

There are two different specifications for dropout voltage with the TPS74401. The first specification (see Figure 7-12) is referred to as VIN Dropout and is for users who wish to apply an external bias voltage to achieve low dropout. This specification assumes that VBIAS is at least 1.62V above VOUT; for example, when VBIAS is powered by a 3.3V rail with 5% tolerance and with VOUT = 1.5V. If VBIAS is higher than (3.3V × 0.95) or VOUT is less than 1.5V, VIN dropout is less than specified.

The second specification (see Figure 7-13) is referred to as VBIAS Dropout and is for users who wish to have VBIAS < VIN + 1.62V. 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 and therefore must be greater than VOUT + VDO (VBIAS). Because of this usage, IN and BIAS tied together easily consume excessive power. Pay attention and do not exceed the power rating of the IC package.