ZHCSI50B may   2018  – may 2023 LSF0102-Q1

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  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 (Translating Down): VCCB = 3.3 V
    7. 6.7  Switching Characteristics (Translating Down): VCCB = 2.5 V
    8. 6.8  Switching Characteristics Translating Up): VCCB = 3.3 V
    9. 6.9  Switching Characteristics (Translating Up): VCCB = 2.5 V
    10. 6.10 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 Auto Bidirectional Voltage Translation
      2. 8.3.2 Output Enable
      3. 8.3.3 Device Functional Modes
        1. 8.3.3.1 Up and Down Translation
          1. 8.3.3.1.1 Up Translation
          2. 8.3.3.1.2 Down Translation
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Bidirectional Translation
        1. 9.2.1.1 Design Requirements
          1. 9.2.1.1.1 Enable, Disable, and Reference Voltage Guidelines
          2. 9.2.1.1.2 Bias Circuitry
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Bidirectional Translation
          2. 9.2.1.2.2 Pull-Up Resistor Sizing
          3. 9.2.1.2.3 Application Curve
          4. 9.2.1.2.4 Mixed-Mode Voltage Translation
          5. 9.2.1.2.5 Single Supply Translation
          6. 9.2.1.2.6 Voltage Translation for Vref_B < Vref_A + 0.8 V
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 接收文档更新通知
    3. 10.3 支持资源
    4. 10.4 Trademarks
    5. 10.5 静电放电警告
    6. 10.6 术语表
  12. 11Mechanical, Packaging, and Orderable Information

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9.2.1.2.5 Single Supply Translation

Sometimes, an external device will have an unknown voltage that could be above or below the desired translation voltage, preventing a normal connection of the LSF. Resistors are added on the A side in place of the second supply in this case – this is an example of when LSF single supply operation is utilized, shown in Figure 9-5. In the following figure, a single 3.3 V supply is used to translate between a 3.3 V device and a device that can change between 1.8 V and 5.0 V. R1 and R2 are added in place of the second supply. Note that due to some current coming out of the Vref_A pin, this cannot be treated as a simple voltage divider.

GUID-20230510-SS0I-KJR4-MCBC-B7LCLRRWXK6T-low.svg Figure 9-5 Single Supply Translation with 3.3 V Supply

The steps to select the resistor values for R1 and R2 are as follows:

  1. Select a value for R1. Typically, 1 MΩ is used to reduce current consumption.
  2. Plug in values for your system into the following equation. Note that Vref_A is the lowest voltage in the system. VCCB is the primary supply and R1 is the selected value from step 1.

Equation 4. R2 = 200 (103) × R1 × VREFA(200 (103) + R1)(VCCB - VREFA) - 0.85 × R1 

The single supply used must be at least 0.8 V larger than the lowest desired translation voltage. The voltage at Vref_A must be selected as the lowest voltage to be used in the system. The LSF evaluation module (LSF-EVM) contains unpopulated pads to place R1 and R2 for single supply operation testing. For an example single supply translation schematic and details, see the Single Supply Translation with the LSF Family video.