SLVSJL6 June   2026 LM851772-Q1

ADVANCE INFORMATION  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Handling Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Requirements
    7. 6.7 Typical Characteristics
  8. 7 Parameter Measurement Information
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Buck-Boost Control Scheme
        1. 8.3.1.1 Buck Mode
        2. 8.3.1.2 Boost Mode
        3. 8.3.1.3 Buck-Boost Mode
      2. 8.3.2  Power Save Mode
      3. 8.3.3  Reference System
        1. 8.3.3.1 Power On Reset and nRST-PIN
      4. 8.3.4  Internal VCC Regulators
        1. 8.3.4.1 VCC1 Regulator
        2. 8.3.4.2 VCC2 Regulator
      5. 8.3.5  Enable and Undervoltage Lockout
        1. 8.3.5.1 UVLO
      6. 8.3.6  Error Amplifier and Control
        1. 8.3.6.1 Output Voltage Regulation
        2. 8.3.6.2 Output Voltage Feedback
        3. 8.3.6.3 Voltage Regulation Loop
        4. 8.3.6.4 Dynamic Voltage Scaling
      7. 8.3.7  Output Voltage Discharge
      8. 8.3.8  Peak Current Sensor
      9. 8.3.9  Short Circuit - Hiccup Protection
      10. 8.3.10 Current Monitor/Limiter
        1. 8.3.10.1 Overview
        2. 8.3.10.2 Output Current Limitation
        3. 8.3.10.3 Output Current Monitor
      11. 8.3.11 Oscillator Frequency Selection
      12. 8.3.12 Frequency Synchronization
      13. 8.3.13 Output Voltage Tracking
        1. 8.3.13.1 Analog Voltage Tracking
        2. 8.3.13.2 Digital Voltage Tracking
      14. 8.3.14 Slope Compensation
      15. 8.3.15 Configurable Soft Start
      16. 8.3.16 Drive Pin
      17. 8.3.17 Dual Random Spread Spectrum – DRSS
      18. 8.3.18 Gate Driver
      19. 8.3.19 Cable Drop Compensation (CDC)
      20. 8.3.20 CFG-Pin and R2D Interface
      21. 8.3.21 Advanced Monitoring Features
        1. 8.3.21.1  Overview
        2. 8.3.21.2  BUSY
        3. 8.3.21.3  OFF
        4. 8.3.21.4  VOUT
        5. 8.3.21.5  IOUT
        6. 8.3.21.6  INPUT
        7. 8.3.21.7  TEMPERATURE
        8. 8.3.21.8  CML
        9. 8.3.21.9  OTHER
        10. 8.3.21.10 ILIM_OP
        11. 8.3.21.11 nFLT/nINT Pin Output
        12. 8.3.21.12 Status Byte
      22. 8.3.22 Protection Features
        1. 8.3.22.1 Thermal Shutdown (TSD)
        2. 8.3.22.2 Overcurrent Protection
        3. 8.3.22.3 Output Overvoltage Protection 1 (OVP1)
        4. 8.3.22.4 Output Overvoltage Protection 2 (OVP2)
        5. 8.3.22.5 Input Voltage Protection (IVP)
        6. 8.3.22.6 Power Good
        7. 8.3.22.7 Boot-Strap Undervoltage Protection
        8. 8.3.22.8 Boot-strap Overvoltage Clamp
        9. 8.3.22.9 CRC - CHECK
    4. 8.4 Device Functional Modes
      1. 8.4.1 Overview
      2. 8.4.2 Logic State Description
    5. 8.5 Programming
      1. 8.5.1 I2C Bus Operation
      2. 8.5.2 Clock Stretching
      3. 8.5.3 Data Transfer Formats
      4. 8.5.4 Single READ From a Defined Register Address
      5. 8.5.5 Sequential READ Starting from a Defined Register Address
      6. 8.5.6 Single WRITE to a Defined Register Address
      7. 8.5.7 Sequential WRITE Starting at a Defined Register Address
  10. 9 LM851772-Q1 Registers
  11. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1  Custom Design with WEBENCH Tools
        2. 10.2.2.2  Frequency
        3. 10.2.2.3  Feedback Divider
        4. 10.2.2.4  Inductor and Current Sense Resistor Selection
        5. 10.2.2.5  Output Capacitor
        6. 10.2.2.6  Input Capacitor
        7. 10.2.2.7  Slope Compensation
        8. 10.2.2.8  UVLO Divider
        9. 10.2.2.9  Soft-Start Capacitor
        10. 10.2.2.10 nRST and EN/UVLO Pull-up Resistor Selection
        11. 10.2.2.11 MOSFETs QH1 and QL1
        12. 10.2.2.12 MOSFETs QH2 and QL2
        13. 10.2.2.13 Loop Compensation
        14. 10.2.2.14 External Component Selection
      3. 10.2.3 Application Curves
    3. 10.3 USB-PD Source with Power Path
    4. 10.4 Parallel (Multiphase) Operation
    5. 10.5 Wireless Charging Supply
    6. 10.6 Power Supply Recommendations
    7. 10.7 Layout
      1. 10.7.1 Layout Guidelines
        1. 10.7.1.1 Power Stage Layout
        2. 10.7.1.2 Gate Driver Layout
        3. 10.7.1.3 Controller Layout
      2. 10.7.2 Layout Example
  12. 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
  13. 12Revision History
  14. 13Mechanical, Packaging, and Orderable Information
    1. 13.1 Tape and Reel Information
    2.     132

8.3.3.1 Power On Reset and nRST-PIN

The power on reset system (POR) supplies the input pin buffers and comparators. Once the voltage on the VIN-pin or BIAS-pin is above the positive going POR threshold VT+(POR) and the nRST-PIN is higher than VT+(nRST) the internal logic of the device is active and proceeds to the standby mode. The I2C interface is active and the converter operations follows the initial settings until updated configurations are sent with the programming interface.

When the nRST-pin is below the standby threshold VT-(nRST), the device is held in a low power shutdown mode to maintain a minimum input quiescent current on the device supply rails.