SDLS967H may   2016  – july 2023 LSF0108-Q1

PRODMIX  

  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 (Q1)
    5. 6.5 Electrical Characteristics - RKS Package
    6. 6.6 Electrical Characteristics - PW Package
    7. 6.7 Switching Characteristics (Translating Down)
    8. 6.8 Switching Characteristics (Translating Up)
    9. 6.9 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 Wettable Flanks
    4. 8.4 Device Functional Modes
      1. 8.4.1 Up and Down Translation
  10. 9 Applications and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 I2C PMBus, SMBus, GPIO
        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 LSF0108-Q1 Bandwidth
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Mixed-Mode Voltage Translation
        1. 9.2.2.1 Single Supply Translation
        2. 9.2.2.2 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 Receiving Notification of Documentation Updates
    2. 10.2 Support Resources
    3. 10.3 Trademarks
    4. 10.4 Electrostatic Discharge Caution
    5. 10.5 Glossary
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

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

9.2.2.1 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-20230424-SS0I-1ZNC-XMWR-VSCZHPVVV995-low.svg Figure 9-7 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 6. 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.