JAJSRI9A October   2023  – March 2024 LM51772

ADVANCE INFORMATION  

  1.   1
  2. 1 特長
  3. 2 アプリケーション
  4. 3 概要
  5. 4 概要 (続き)
  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  Programmable Conduction Mode PCM
      4. 8.3.4  Reference System
        1. 8.3.4.1 VIO LDO and nRST-PIN
      5. 8.3.5  Supply Voltage Selection – VMAX Switch and Selection Logic
      6. 8.3.6  Enable and Undervoltage Lockout
        1. 8.3.6.1 UVLO
        2. 8.3.6.2 VDET Comparator
      7. 8.3.7  Internal VCC Regulator
        1. 8.3.7.1 VCC1 Regulator
        2. 8.3.7.2 VCC2 Regulator
      8. 8.3.8  Error Amplifier and Control
        1. 8.3.8.1 Output Voltage Regulation
        2. 8.3.8.2 Internal Output Voltage Regulation
        3. 8.3.8.3 Dynamic Voltage Scaling
      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  Over Current Protection
        3. 8.3.22.3  Output Over Voltage Protection 1 (OVP1)
        4. 8.3.22.4  Output Over Voltage Protection 2 (OVP2)
        5. 8.3.22.5  Input Voltage Protection (IVP)
        6. 8.3.22.6  Input Voltage Regulation (IVR)
        7. 8.3.22.7  Power Good
        8. 8.3.22.8  Boot-Strap Under Voltage Protection
        9. 8.3.22.9  Boot-strap Over Voltage Clamp
        10. 8.3.22.10 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 LM51772 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 MOSFETs QH1 and QL1
        11. 10.2.2.11 MOSFETs QH2 and QL2
        12. 10.2.2.12 Loop Compensation
        13. 10.2.2.13 External Component Selection
      3. 10.2.3 Application Curves
    3. 10.3 Power Supply Recommendations
    4. 10.4 Layout
      1. 10.4.1 Layout Guidelines
        1. 10.4.1.1 Power Stage Layout
        2. 10.4.1.2 Gate Driver Layout
        3. 10.4.1.3 Controller Layout
      2. 10.4.2 Layout Example
  12. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 ドキュメントの更新通知を受け取る方法
    3. 11.3 サポート・リソース
    4. 11.4 Trademarks
    5. 11.5 静電気放電に関する注意事項
    6. 11.6 用語集
  13. 12Revision History
  14. 13Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

8.3.18 Gate Driver

The LM51772 features four internal logic-level nMOS gate drivers. The drivers maintain the high frequency switching of both half bridges needed for a buck-boost operation. If the device is in boost or buck mode, the other half bridge high-side switch needs to be permanent on. The internal gate drivers support this by sharing the current from the other half bridge, which is switching. Therefore, a minimum of quiescent current can be provided as no additional char pump is needed. Due to the high drive current, the LM51772 can support a wide range of external power FETs as well as a parallel operation of them.

The LO and HO outputs are protected with a shoot-through protection, which allows both outputs are not turned on at the same time. If the PWM modulation logic of the buck-boost turns the LOx pin off, the HOx pin is not turned on until the following are true:

  1. A minimum internal transition time (tt(dead)) is reached.
  2. The voltage on the LOx pin drops below the detection threshold VTH(GATEOUT).
This behavior is maintained and vice versa if the HOx pin turns off first.

The high-side supply voltage for the gate driver are monitored by an additional bootstrap UVLO comparator. This comparator monitors the differential voltage between SWx and HBx. If the voltage drops below the threshold the buck-boost converter operation turns off. The device restarts automatically once the positive going threshold is reached with the soft-start scheme.

Additionally, the LM51772 monitors the upper voltage between SWx and HBx. If this voltage exceeds the threshold voltage of the clamping circuit, the LM51772 activates a internal current source to pull the voltage down.

The minimum observed internal transition (dead) -time can be selected by the registers SEL_SCALE_DT, SEL_MIN_DEADTIME_GDR. The SEL_SCALE_DT can also be selected via the CFG-PIN in case the I2C interface is not used in the application. Additionally there is a optional frequency dependency of the transition (dead) -time between high and low side. This addresses the usual differences of the silicon MOSFET Qg in high power applications with low switching frequencies and lower power application with higher switching frequencies. The frequency dependency can be enabled/disable be the register EN_CONST_TDEAD


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Figure 8-24 Functional Block Diagram Gate Driver