SLVSFD0 September   2019 LM74202-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
      2.      ISO16750-2 Load Dump Pulse 5b Performance at 12 V
  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
    3. 6.3      Recommended Operating Conditions
    4. Table 1. Thermal Information
    5. 6.4      Electrical Characteristics
    6. 6.5      Timing Requirements
    7. 6.6      Typical Characteristics
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Undervoltage Lockout (UVLO)
      2. 8.3.2 Overvoltage Protection (OVP)
      3. 8.3.3 Reverse Battery Protection
      4. 8.3.4 Hot Plug-In and In-Rush Current Control
      5. 8.3.5 Overload and Short Circuit Protection
        1. 8.3.5.1 Overload Protection
          1. 8.3.5.1.1 Active Current Limiting
          2. 8.3.5.1.2 Electronic Circuit Breaker with Overload Timeout, MODE = OPEN
        2. 8.3.5.2 Short Circuit Protection
          1. 8.3.5.2.1 Start-Up With Short-Circuit On Output
        3. 8.3.5.3 FAULT Response
          1. 8.3.5.3.1 Look Ahead Overload Current Fault Indicator
        4. 8.3.5.4 Current Monitoring
        5. 8.3.5.5 IN, OUT, RTN and GND Pins
        6. 8.3.5.6 Thermal Shutdown
        7. 8.3.5.7 Low Current Shutdown Control (SHDN)
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Step by Step Design Procedure
        2. 9.2.2.2 Setting Undervoltage Lockout and Overvoltage Set Point for Operating Voltage Range
        3. 9.2.2.3 Programming the Current-Limit Threshold—R(ILIM) Selection
        4. 9.2.2.4 Programming Current Monitoring Resistor—RIMON
        5. 9.2.2.5 Limiting the Inrush Current
          1. 9.2.2.5.1 Selection of Input TVS for Transient Protection
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
    1. 10.1 Transient Protection
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.3.5.1.1 Active Current Limiting

When the active current limiting mode is selected, during overload events, the device continuously regulates the load current to the overcurrent limit I(OL) programmed by the R(ILIM) resistor as shown in Equation 4.

Equation 4. LM74202-Q1 equ_04_SLVSDG2.gif

where

  • I(OL) is the overload current limit in Ampere
  • R(ILIM) is the current limit resistor in kΩ

During an overload condition, the internal current-limit amplifier regulates the output current to I(LIM). The FLT signal assert after a delay of tPGOODF. The output voltage droops during the current regulation, resulting in increased power dissipation in the device. If the device junction temperature reaches the thermal shutdown threshold (T(TSD)), the internal FET is turn off. The device configured in latch-off mode stays latched off until it is reset by either of the following conditions:

  • Cycling V(IN) below V(PORF)
  • Toggling SHDN

When the device is configured in auto-retry mode, it commences an auto-retry cycle tCBretry(dly) ms after TJ < [T(TSD) – 10°C]. The FLT signal remains asserted until the fault condition is removed and the device resumes normal operation. Figure 29 and Figure 30 illustrates the behavior of the system during current limiting with auto-retry functionality.

LM74202-Q1 scope_shot_01_slvsdg2.png
Load transition from 22 Ω to 12 Ω MODE pin connected to RTN
RILIM = 8 kΩ
Figure 29. Auto-Retry MODE Fault Behavior
LM74202-Q1 scope_shot_02_slvsdg2.png
RILIM = 5.36 kΩ
Figure 30. Response During Coming Out of Overload Fault