SBVS446A August   2023  – January 2024 TPS7A53B

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 Voltage Regulation Features
        1. 6.3.1.1 DC Regulation
        2. 6.3.1.2 AC and Transient Response
      2. 6.3.2 System Start-Up Features
        1. 6.3.2.1 Programmable Soft-Start (NR/SS Pin)
        2. 6.3.2.2 Internal Sequencing
          1. 6.3.2.2.1 Enable (EN)
          2. 6.3.2.2.2 Undervoltage Lockout (UVLO) Control
          3. 6.3.2.2.3 Active Discharge
        3. 6.3.2.3 Power-Good Output (PG)
      3. 6.3.3 Internal Protection Features
        1. 6.3.3.1 Foldback Current Limit (ICL)
        2. 6.3.3.2 Thermal Protection (Tsd)
    4. 6.4 Device Functional Modes
      1. 6.4.1 Regulation
      2. 6.4.2 Disabled
      3. 6.4.3 Current Limit Operation
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1  Recommended Capacitor Types
        1. 7.1.1.1 Input and Output Capacitor Requirements (CIN and COUT)
        2. 7.1.1.2 Noise-Reduction and Soft-Start Capacitor (CNR/SS)
        3. 7.1.1.3 Feed-Forward Capacitor (CFF)
      2. 7.1.2  Soft-Start and Inrush Current
      3. 7.1.3  Optimizing Noise and PSRR
      4. 7.1.4  Charge Pump Noise
      5. 7.1.5  Current Sharing
      6. 7.1.6  Adjustable Operation
      7. 7.1.7  Power-Good Operation
      8. 7.1.8  Undervoltage Lockout (UVLO) Operation
      9. 7.1.9  Dropout Voltage (VDO)
      10. 7.1.10 Device Behavior During Transition From Dropout Into Regulation
      11. 7.1.11 Load Transient Response
      12. 7.1.12 Reverse Current Protection Considerations
      13. 7.1.13 Power Dissipation (PD)
      14. 7.1.14 Estimating Junction Temperature
      15. 7.1.15 TPS7A53EVM Thermal Analysis
    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 Board Layout
      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

Package Options

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

7.1.1.2 Noise-Reduction and Soft-Start Capacitor (CNR/SS)

The TPS7A53B features a programmable, monotonic, voltage-controlled soft-start that is set with an external capacitor (CNR/SS). Use an external CNR/SS to minimize inrush current into the output capacitors. This soft-start feature eliminates power-up initialization problems when powering field-programmable gate arrays (FPGAs), digital signal processors (DSPs), or other processors. The controlled voltage ramp of the output also reduces peak inrush current during start-up, minimizing start-up transients to the input power bus.

To achieve a monotonic start-up, the TPS7A53B error amplifier tracks the voltage ramp of the external soft-start capacitor until the voltage approaches the internal reference. The soft-start ramp time depends on the soft-start charging current (INR/SS), the soft-start capacitance (CNR/SS), and the internal reference (VNR/SS). Use Equation 1 to calculate the soft-start ramp time:

Equation 1. tSS = (VNR/SS × CNR/SS) / INR/SS

INR/SS is provided in the Electrical Characteristics table and has a typical value of 6.2μA.

The noise-reduction capacitor, in conjunction with the noise-reduction resistor, forms a low-pass filter (LPF) that filters out noise from the reference before being gained up with the error amplifier, thereby reducing the device noise floor. The LPF is a single-pole filter and Equation 2 calculates the cutoff frequency. The typical value of RNR is 250kΩ. Increasing the CNR/SS capacitor has a greater affect because the output voltage increases when the noise from the reference is gained up even more at higher output voltages. For low-noise applications, use a 10nF to 1µF CNR/SS.

Equation 2. fcutoff = 1 / (2 × π × RNR × CNR/SS)