SNVS629F May   2011  – December 2019 LM5050-1 , LM5050-1-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Full Application
      2.      Typical Redundant Supply Configuration
  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: LM5050-1
    3. 6.3 ESD Ratings: LM5050-1-Q1
    4. 6.4 Recommended Operating Conditions
    5. 6.5 Thermal Information
    6. 6.6 Electrical 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 IN, GATE, and OUT Pins
      2. 7.3.2 VS Pin
      3. 7.3.3 OFF Pin
    4. 7.4 Device Functional Modes
      1. 7.4.1 ON/OFF Control Mode
      2. 7.4.2 External Power Supply Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 MOSFET Selection
      2. 8.1.2 Short Circuit Failure of an Input Supply
    2. 8.2 Typical Applications
      1. 8.2.1 Typical Application With Input and Output Transient Protection
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Power Supply Components (R1 C1,) Selection
          2. 8.2.1.2.2 MOSFET (Q1) Selection
          3. 8.2.1.2.3 D1 and D2 Selection for Inductive Kick-Back Protection
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Using a Separate VS Supply for Low Vin Operation
      3. 8.2.3 ORing of Two Power Sources
      4. 8.2.4 Reverse Input Voltage Protection With IQ Reduction
      5. 8.2.5 Basic Application With Input Transient Protection
      6. 8.2.6 48-V Application With Reverse Input Voltage (VIN = –48 V) Protection
        1. 8.2.6.1 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Related Links
    3. 11.3 Community 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

7.3.1 IN, GATE, and OUT Pins

When power is initially applied, the load current will flow from source to drain through the body diode of the MOSFET. Once the voltage across the body diode exceeds VSD(REG) then the LM5050-1 begins charging the MOSFET gate through a 32 µA (typical) charge pump current source . In forward operation, the gate of the MOSFET is charged until it reaches the clamping voltage of the 12-V GATE to IN pin Zener diode internal to the LM5050-1.

The LM5050-1 is designed to regulate the MOSFET gate-to-source voltage. If the MOSFET current decreases to the point that the voltage across the MOSFET falls below the VSD(REG) voltage regulation point of 22 mV (typical), the GATE pin voltage will be decreased until the voltage across the MOSFET is regulated at 22 mV. If the source-to-drain voltage is greater than the VSD(REG) voltage, the gate-to-source voltage will increase and eventually reach the 12-V GATE to IN pin Zener clamp level.

If the MOSFET current reverses, possibly due to failure of the input supply, such that the voltage across the LM5050-1 IN and OUT pins is more negative than the VSD(REV) voltage of -28 mV (typical), the LM5050-1 will quickly discharge the MOSFET gate through a strong GATE to IN pin discharge transistor.

If the input supply fails abruptly, as would occur if the supply was shorted directly to ground, a reverse current will temporarily flow through the MOSFET until the gate can be fully discharged. This reverse current is sourced from the load capacitance and from the parallel connected supplies. The LM5050-1 responds to a voltage reversal condition typically within 25 ns. The actual time required to turn off the MOSFET will depend on the charge held by the gate capacitance of the MOSFET being used. A MOSFET with 47 nF of effective gate capacitance can be turned off in typically 180 ns. This fast turnoff time minimizes voltage disturbances at the output, as well as the current transients from the redundant supplies.