SNVS690I January   2011  – August 2021 LMZ14201H


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  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. 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. 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. Design Steps for the LMZ14201H Application
          1. Enable Divider, RENT and RENB Selection
          2. Output Voltage Selection
          3. Soft-Start Capacitor, CSS, Selection
          4. Output Capacitor, CO, Selection
            1. Capacitance
            2. ESR
          5. Input Capacitor, CIN, Selection
          6. ON-Time, RON, Resistor Selection
            1. Discontinuous Conduction and Continuous Conduction Mode Selection
      3. 8.2.3 Application Curve
  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
Enable Divider, RENT and RENB Selection

The enable input provides a precise 1.18-V reference threshold to allow direct logic drive or connection to a voltage divider from a higher enable voltage such as VIN. The enable input also incorporates 90 mV (typical) of hysteresis resulting in a falling threshold of 1.09 V. The maximum recommended voltage into the EN pin is 6.5 V. For applications where the midpoint of the enable divider exceeds 6.5 V, a small Zener diode can be added to limit this voltage.

The function of the RENT and RENB divider shown in the Section 7.2 is to allow the designer to choose an input voltage below which the circuit will be disabled. This implements the feature of programmable undervoltage lockout. This is often used in battery-powered systems to prevent deep discharge of the system battery. It is also useful in system designs for sequencing of output rails or to prevent early turnon of the supply as the main input voltage rail rises at power up. Applying the enable divider to the main input rail is often done in the case of higher input voltage systems such as 24-V AC/DC systems where a lower boundary of operation should be established. In the case of sequencing supplies, the divider is connected to a rail that becomes active earlier in the power-up cycle than the LMZ14201H output rail. The two resistors should be chosen based on the following ratio:

Equation 1. RENT / RENB = (VIN-ENABLE/ 1.18 V) – 1

The EN pin is internally pulled up to VIN and can be left floating for always-on operation. However, it is good practice to use the enable divider and turn on the regulator when VIN is close to reaching its nominal value. This will ensure smooth start-up and will prevent overloading the input supply.