SNVS874E August   2012  – September 2021 LMZ20501

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 System Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Nano Scale Package
      2. 7.3.2 Internal Synchronous Rectifier
      3. 7.3.3 Current Limit Protection
      4. 7.3.4 Start-Up
      5. 7.3.5 Dropout Behavior
      6. 7.3.6 Power Good Flag Function
      7. 7.3.7 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 PWM Operation
      2. 7.4.2 PFM Operation
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Detailed Design Procedure
        1. 8.2.1.1 Custom Design With WEBENCH® Tools
        2. 8.2.1.2 Setting The Output Voltage
        3. 8.2.1.3 Output and Feedforward Capacitors
        4. 8.2.1.4 Input Capacitors
        5. 8.2.1.5 Maximum Ambient Temperature
        6. 8.2.1.6 Options
      2. 8.2.2 Application Curves
    3. 8.3 Do's and Don'ts
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
      1. 10.2.1 Soldering Information
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
        1. 11.1.2.1 Custom Design With WEBENCH® Tools
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
    1. 12.1 Tape and Reel Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • SIL|8
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.3 Current Limit Protection

The LMZ20501 incorporates cycle-by-cycle peak current limit on both the high- and low-side MOSFETs. This feature limits the output current in case the output is overloaded. During the overload, the peak inductor current is limited to that value found in Section 6.5 under the heading of "ILIM".

In addition to current limit, a short circuit protection mode is also implemented. When the feedback voltage is brought down to less than 300 mV, but greater than 150 mV, by a short circuit, the synchronous rectifier is turned off. This provides more voltage across the inductor to help maintain the required volt-second balance. If a "harder" short brings the feedback voltage to below 150 mV, the current limit and switching frequency are both reduced to approximately one half of the nominal values. In addition, when the current limit is tripped, the device stops switching for approximately 85 µs. At the end of the time-out, switching resumes and the cycle repeats until the short is removed.

The effect of both overload and short circuit protection can be seen in Figure 7-3. This graph demonstrates that the device will supply slightly more than 1 A to the load when in overload and much less current during fold-back mode. This is typical behavior for any regulator with this type of current limit protection.

GUID-26E07432-1198-488E-982E-9F1CADC3FE4C-low.pngFigure 7-3 Typical Current Limit Profile VIN = 5 V, VOUT = 3.3 V