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

8.4.1 Up and Down Translation

Up Translation: When the signal is driven from A to B and the An port is HIGH, the switch will be OFF and the Bn port will then be driven to a voltage higher than Vref_A by the pullup resistor that is connected to the pull-up supply voltage. This functionality allows seamless translation between the higher and lower voltages selected by the user, without the need for directional control. Pull-up resistors are always required on the high side, and pull-ups are only required on the low side if the output of the low side device is open drain or its input has a leakage greater than 1 µA.

GUID-20221115-SS0I-P1QP-HKJG-HT3PRK4DW8TF-low.svgFigure 8-3 Up Translation Example Schematic with Push-Pull and Open Drain Configuration

Up translation with the LSF requires attention to two important factors: maximum data rate and sink current. Maximum data rate is directly related to the rising edge of the output signal. Sink current depends on supply values and the chosen pull-up resistor values. Equation 1 shows the maximum data rate formula, and Equation 2 presents the maximum sink current formula, both of which are estimations. A low RC value is needed to reach high speeds, which also require strong drivers. For estimated data rate and sink current calculations based on circuit component, see the Up Translation with the LSF Family video.

Equation 1. 13 × 2RB1CB1 = 16RB1CB1 (bitssecond)
Equation 2. IOL ≅ VCCARA1+ VCCBRB1 (A)

Down Translation: When the signal is being driven HIGH from the Bn port to An port, the switch will be OFF, clamping the voltage on the An port to the voltage set by Vref_A. A pull-up resistor can be added on either side of the device. There are special circumstances that allow the removal of one or both of the pull-up resistors. If the signal is always going to be down translated from a push-pull transmitter, then the resistor on the B-side can be removed. If the leakage current into the receiver on the A-side is less than 1 µA, then the resistor on the A-side can also be removed. This arrangement, with no external pull-up resistors, can be used when down translating from a push-pull output to a low-leakage input. For an open drain transmitter, the pull-up resistor on the B-side is necessary because an open drain output cannot drive high by itself. Table 9-2 lists a summary of device operation. For additional details on the functional operation of the LSF family of devices, see the Up Translation with the LSF Family and Down Translation with the LSF Family videos.