SLUSD87A March   2018  – January 2024

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 Fixed Frequency PWM Control
      2. 6.3.2 Bootstrap Voltage (CB)
      3. 6.3.3 Setting the Output Voltage
      4. 6.3.4 Enable ( SHDN ) and VIN Undervoltage Lockout
      5. 6.3.5 Current Limit
      6. 6.3.6 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Continuous Conduction Mode
      2. 6.4.2 Eco-mode
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
        1. 7.2.1.1 Step-By-Step Design Procedure
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Custom Design With WEBENCH® Tools
        2. 7.2.2.2 Output Inductor Selection
        3. 7.2.2.3 Output Capacitor Selection
        4. 7.2.2.4 Schottky Diode Selection
        5. 7.2.2.5 Input Capacitor Selection
        6. 7.2.2.6 Bootstrap Capacitor Selection
      3. 7.2.3 Application Performance Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Development Support
        1. 8.1.1.1 Custom Design With WEBENCH® Tools
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.2.2.5 Input Capacitor Selection

A low ESR ceramic capacitor is needed between the VIN pin and ground pin. This capacitor prevents large voltage transients from appearing at the input. Use a 1-µF to 10-µF value with X5R or X7R dielectric. Depending on construction, a ceramic capacitor value can decrease up to 50% of the nominal value when rated voltage is applied. Consult with the capacitor manufactures data sheet for information on capacitor derating over voltage and temperature. The capacitor must also have a ripple current rating greater than the maximum input current ripple of the LMR14010A. The input ripple current can be calculated using below Equations.

For this example design, one 2.2-µF, 50-V capacitor is selected. The input capacitance value determines the input ripple voltage of the regulator. The input voltage ripple can be calculated using Equation 10. Using the design example values, IOUTMAX = 1 A, CIN = 2.2 µF, ƒSW = 700 kHz, yields an input voltage ripple of 162 mV and an rms input ripple current of 0.5 A.

Equation 9. GUID-04E95605-29CE-486A-A164-4D152FF58889-low.gif
Equation 10. GUID-C413B072-3EDA-401C-82AB-247F7F81C21F-low.gif