SLVS350J October   2002  – May 2019 TPS795

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      TPS79530 Ripple Rejection vs Frequency
      2.      TPS79530 vs Frequency
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagrams
    3. 7.3 Feature Description
      1. 7.3.1 Shutdown
      2. 7.3.2 Start-Up
      3. 7.3.3 Undervoltage Lockout (UVLO)
      4. 7.3.4 Regulator Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Normal Operation
      2. 7.4.2 Dropout Operation
      3. 7.4.3 Disabled
  8. 8 Application and Implementation
    1. 8.1 Application Information
    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 Requirements
        2. 8.2.2.2 Output Noise
        3. 8.2.2.3 Dropout Voltage
        4. 8.2.2.4 Programming the TPS79501 Adjustable LDO Regulator
      3. 8.2.3 Application Curves
    3. 8.3 What to Do and What Not to Do
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Board Layout Recommendation to Improve PSRR and Noise Performance
      2. 10.1.2 Regulator Mounting
      3. 10.1.3 Thermal Considerations
      4. 10.1.4 Estimating Junction Temperature
    2. 10.2 Layout Examples
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 Evaluation Modules
        2. 11.1.1.2 Spice Models
      2. 11.1.2 Device Nomenclature
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.2.4 Programming the TPS79501 Adjustable LDO Regulator

The output voltage of the TPS79501 adjustable regulator is programmed using an external resistor divider as shown in Figure 26.

TPS795 ai_adj_ldo_lvs350.gifFigure 26. Typical Application, Adjustable Output

The output voltage is calculated using Equation 1.

Equation 1. TPS795 q_vout_lvs350.gif

where

  • VREF = 1.2246 V typical (the internal reference voltage)

Resistors R1 and R2 should be chosen for approximately 40-µA divider current. Lower value resistors can be used for improved noise performance, but the device wastes more power. Higher values should be avoided, as leakage current at FB increases the output voltage error.

The recommended design procedure is to choose R2 = 30.1 kΩ to set the divider current at 40 µA, C1 = 15 pF for stability, and then calculate R1 using Equation 2.

Equation 2. TPS795 q_r1_lvs350.gif

To improve the stability of the adjustable version, TI suggests placing a small compensation capacitor between OUT and FB.

The approximate value of this capacitor can be calculated using Equation 3.

Equation 3. TPS795 q_c1_lvs350.gif

The suggested value of this capacitor for several resistor ratios is shown in the table within Figure 26. If this capacitor is not used (such as in a unity-gain configuration), then the minimum recommended output capacitor is 2.2 µF instead of 1 µF.