SNVS690I January   2011  – August 2021 LMZ14201H

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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
      1. 7.1.1 COT Control Circuit Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Output Overvoltage Comparator
      2. 7.3.2 Current Limit
      3. 7.3.3 Thermal Protection
      4. 7.3.4 Zero Coil Current Detection
      5. 7.3.5 Prebiased Start-Up
    4. 7.4 Device Functional Modes
      1. 7.4.1 Discontinuous Conduction and Continuous Conduction Modes
  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 Design Steps for the LMZ14201H Application
          1. 8.2.2.1.1 Enable Divider, RENT and RENB Selection
          2. 8.2.2.1.2 Output Voltage Selection
          3. 8.2.2.1.3 Soft-Start Capacitor, CSS, Selection
          4. 8.2.2.1.4 Output Capacitor, CO, Selection
            1. 8.2.2.1.4.1 Capacitance
            2. 8.2.2.1.4.2 ESR
          5. 8.2.2.1.5 Input Capacitor, CIN, Selection
          6. 8.2.2.1.6 ON-Time, RON, Resistor Selection
            1. 8.2.2.1.6.1 Discontinuous Conduction and Continuous Conduction Mode Selection
      3. 8.2.3 Application Curve
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Power Module SMT Guidelines
    2. 10.2 Layout Example
      1. 10.2.1 Power Dissipation and Board Thermal Requirements
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information
8.2.2.1.5 Input Capacitor, CIN, Selection

The LMZ14201H module contains an internal 0.47 µF input ceramic capacitor. Additional input capacitance is required external to the module to handle the input ripple current of the application. This input capacitance should be as close as possible to the module. Input capacitor selection is generally directed to satisfy the input ripple current requirements rather than by capacitance value.

Worst-case input ripple current rating is dictated by Equation 10:

Equation 10. I(CIN(RMS)) ≊ 1 / 2 × IO × √ (D / 1-D)

where

  • D ≊ VO / VIN

(As a point of reference, the worst-case ripple current will occur when the module is presented with full load current and when VIN = 2 × VO).

Recommended minimum input capacitance is 10-uF X7R ceramic with a voltage rating at least 25% higher than the maximum applied input voltage for the application. TI also recommends to pay attention to the voltage and temperature deratings of the capacitor selected. Also note ripple current rating of ceramic capacitors may be missing from the capacitor data sheet and you may have to contact the capacitor manufacturer for this rating.

If the system design requires a certain maximum value of input ripple voltage ΔVIN to be maintained then Equation 11 may be used.

Equation 11. CIN ≥ IO × D × (1–D) / fSW-CCM × ΔVIN

If ΔVIN is 1% of VIN for a 24-V input to 12-V output application this equals 240 mV and fSW = 400 kHz.

CIN≥ 1 A × 12 V/24 V × (1– 12 V/24 V) / (400000 × 0.240 V)

CIN≥ 2.6 μF

Additional bulk capacitance with higher ESR may be required to damp any resonant effects of the input capacitance and parasitic inductance of the incoming supply lines.