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

8.3.8.2 Internal Output Voltage Regulation

To maintain fixed voltage and interface programmable voltage the device contains an internal voltage divider. In this case the FB is not applicable for sensing the output voltage for the loop regulation. Instead the VOUT-pin is used to sense the output voltage on the power stage.

The device detects via the FB-pin if it shall operate with an external or internal voltage divider. If the voltage on the FB-pin is higher than VT+(SEL,iFB), before the soft-start is initiated, if the part should operate with a internal or external feedback. The selection of internal and external FB cannot be done dynamically and the pin information gets latched until the next EN or V(POR) power cycle.

The resolution of the programming can be changed with the SEL_DIV20 bit.

If the V_OUT register read back is used the low voltage clamping will be done with whatever SEL_DIV20 value is programmed at this time. If SEL_DIV20 is updated after VOUT_A, the clamping might not be correct anymore. To guarantee correct clamping its recommended to (re-)write VOUT_A after changing SEL_DIV20 bit.

Below an overview of the possible Vo setting according the VOUT_A and SEL_DIV20

Table 8-2 SEL_DIV 20 = 0b0:
ParameterValue
Output voltage min. 3.3V
Output voltage max.24V
Output voltage programming step size typ.10mV

You can use the following equation to calculate the nominal output voltage:

Equation 1. V ( O , N O M ) = V O U T _ T A R G E T 1 _ M S B 3 : 0 V O U T _ T A R G E T 1 _ L S B 7 : 0   ∙   10   m V
Table 8-3 SEL_DIV 20 = 0b1:
ParameterValue
Output voltage min. 3.3V
Output voltage max48V
Output voltage programming step size typ.20mV

Table 9-18

The read-out register value of the 'VOUT_A' control register is clamped for the lower and for the upper limit of the register range.

  • The reg. readout value is clamped to the lowest clamp voltage ( e.g. 3.3V if SEL_FB_DIV20 = 0b1) if a register value below the value of clamp voltage ( e.g. 3.3V) has been written in before.
  • The reg. readout value is clamped to the highest clamp voltage ( e.g. 48V if SEL_FB_DIV20 = 0b1) if a register value above the highest value of clamp voltage ( e.g. 48V) has been written in before.

You can use the following equation to calculate the nominal output voltage:

Equation 2. V ( O , N O M ) = V O U T _ T A R G E T 1 _ M S B 3 : 0 V O U T _ T A R G E T 1 _ L S B 7 : 0   ∙   20   m V
GUID-20221007-SS0I-NJ8C-HVR0-H45V14FPKNDN-low.svg Figure 8-15 EA Functions Block Diagram