SNOSDF6 October   2023 LM74930-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  6. 5 Pin Configuration and Functions
  7. 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 Switching Characteristics
    7. 6.7 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Charge Pump
      2. 7.3.2  Dual Gate Control (DGATE, HGATE)
        1. 7.3.2.1 Load Disconnect Switch Control (HGATE, OUT)
        2. 7.3.2.2 Reverse Battery Protection (A, C, DGATE)
      3. 7.3.3  Overcurrent Protection (CS+, CS-, ILIM, IMON, TMR)
      4. 7.3.4  Overcurrent Protection with Circuit Breaker (ILIM, TMR)
      5. 7.3.5  Overcurrent Protection With Latch-Off
      6. 7.3.6  Short-Circuit Protection (ISCP)
        1. 7.3.6.1 Device Wake-Up With Output Short-Circuit Condition
      7. 7.3.7  Analog Current Monitor Output (IMON)
      8. 7.3.8  Overvoltage and Undervoltage Protection (OV, UVLO, OVCLAMP)
      9. 7.3.9  Disabling Reverse Current Blocking Functionality (MODE)
      10. 7.3.10 Device Functional Modes
        1. 7.3.10.1 Low Quiescent Current Shutdown Mode (EN)
  9. 8 Applications and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application: 200-V Unsuppressed Load Dump Protection Application
      1. 8.2.1 Design Requirements for 200-V Unsuppressed Load Dump Protection
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  VS Capacitance, Resistor R1 and Zener Clamp (DZ)
        2. 8.2.2.2  Charge Pump Capacitance VCAP
        3. 8.2.2.3  Input and Output Capacitance
        4. 8.2.2.4  Overvoltage and Undervoltage Protection Component Selection
        5. 8.2.2.5  Selection of Scaling Resistor (RSET) and Short-Circuit Protection Setting Resistor (RSCP)
        6. 8.2.2.6  Overcurrent Limit (ILIM), Circuit Breaker Timer (TMR), and Current Monitoring Output (IMON) Selection
        7. 8.2.2.7  Selection of Current Sense Resistor, RSNS
        8. 8.2.2.8  Hold-Up Capacitance
        9. 8.2.2.9  MOSFET Q1 Selection
        10. 8.2.2.10 MOSFET Q2 Selection
        11. 8.2.2.11 Input TVS Selection
      3. 8.2.3 Application Curves
    3. 8.3 Best Design Practices
    4. 8.4 Power Supply Recommendations
      1. 8.4.1 Transient Protection
      2. 8.4.2 TVS Selection for 12-V Battery Systems
      3. 8.4.3 TVS Selection for 24-V Battery Systems
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
      2. 8.5.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.8 Overvoltage and Undervoltage Protection (OV, UVLO, OVCLAMP)

Connect a resistor ladder as shown in Figure 7-9 for overvoltage and undervoltage threshold programming.

GUID-20231012-SS0I-H3K4-DW6K-KLM8BCCC0LDX-low.svgFigure 7-9 Programming Overvoltage Threshold and Battery Sensing

A disconnect switch is integrated between A and SW pin to monitor common source node voltage as well. This switch is turned OFF when EN pin is pulled low.

LM74930-Q1 also supports overvoltage clamp operation with circuit breaker (Timer)functionality. To enable device operation in overvoltage clamp with circuit breaker functionality, connect OVCLAMP pin to OV pin as shown in #IMAGE_XGF_ZPC_DZB. In case of overvoltage event, device clamps output voltage to threshold set by the external resistor divider R3, R4. The TMR pin source current during overvoltage clamp with circuit breaker functionality is 5.5-μA typical. The circuit breaker time after which load disconnect switch is turned off can be calculated using Equation 8.

Equation 8. TOVC=1.2×CTMR2.8 μA

The rest of the device functionality in terms of auto-retry and latch off behavior of HGATE drive is same as described in overcurrent with circuit breaker section.

GUID-20231012-SS0I-XT8V-JX6V-X5DFP2LNML6Z-low.svgFigure 7-10 LM74930-Q1 Overvoltage Clamp With Circuit Breaker Functionality
The falling threshold of OVCLAMP comparator is kept lower than OV comparator to ensure no false timer reset when system is recovering from overvoltage event. As device does hysteretic output on/off control during overvoltage clamp operation it is recommonded to keep the minimum output voltage level during overvoltage clamp operation above OVCLAMP falling threshold. Equation 9 shows the minimum output capacitor required to ensure no false timer resets during overvoltage clamp operation for given load current.
Equation 9. COUT>VT×CGATE_EFF×ILOAD×R4 IHGATE_DRV×R3+R4×VOVF-VOVCLAMPF

where

  • VT is the MOSFET VGS threshold voltage
  • IHGATE_DRV is HGATE drive strength = 55 μA (typical)

  • CGATE_EFF is effective gate capacitance as seen by HGATE pin (CGS + CdVdT)

  • VOVF and VOVCLAMPF is a falling threshold of OV and OVCLAMP comparators respectively