SNAS512K September   2011  – October 2025 LMK00301

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  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 Typical Characteristics
  8. 7 Parameter Measurement Information
    1. 7.1 Differential Voltage Measurement Terminology
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 VCC and VCCO Power Supplies
    4. 8.4 Device Functional Modes
      1. 8.4.1 Clock Inputs
      2. 8.4.2 Clock Outputs
        1. 8.4.2.1 Reference Output
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
        1. 9.2.1.1 Driving the Clock Inputs
        2. 9.2.1.2 Crystal Interface
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Termination and Use of Clock Drivers
          1. 9.2.2.1.1 Termination for DC Coupled Differential Operation
          2. 9.2.2.1.2 Termination for AC Coupled Differential Operation
          3. 9.2.2.1.3 Termination for Single-Ended Operation
      3. 9.2.3 Application Curves
    3. 9.3 Power Supply Recommendations
      1. 9.3.1 Power Supply Sequencing
      2. 9.3.2 Current Consumption and Power Dissipation Calculations
        1. 9.3.2.1 Power Dissipation Example #1: Separate VCC and VCCO Supplies with Unused Outputs
        2. 9.3.2.2 Power Dissipation Example #2: Worst-Case Dissipation
      3. 9.3.3 Power Supply Bypassing
        1. 9.3.3.1 Power Supply Ripple Rejection
      4. 9.3.4 Thermal Management
    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 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

7.1 Differential Voltage Measurement Terminology

The differential voltage of a differential signal can be described by two different definitions causing confusion when reading data sheets or communicating with other engineers. This section addresses the measurement and description of a differential signal so that the reader is able to understand and discern between the two different definitions when used.

The first definition used to describe a differential signal is the absolute value of the voltage potential between the inverting and non-inverting signal. The symbol for this first measurement is typically VID or VOD depending on if an input or output voltage is being described.

The second definition used to describe a differential signal is to measure the potential of the non-inverting signal with respect to the inverting signal. The symbol for this second measurement is VSS and is a calculated parameter. Nowhere in the IC does this signal exist with respect to ground, this signal only exists in reference to the differential pair. VSS can be measured directly by oscilloscopes with floating references, otherwise this value can be calculated as twice the value of VOD as described in the first description.

Figure 7-1 illustrates the two different definitions side-by-side for inputs and Figure 7-2 illustrates the two different definitions side-by-side for outputs. The VID (or VOD) definition show the DC levels, VIH and VOL (or VOH and VOL), that the non-inverting and inverting signals toggle between with respect to ground. VSS input and output definitions show that if the inverting signal is considered the voltage potential reference, the non-inverting signal voltage potential is now increasing and decreasing above and below the non-inverting reference. Thus the peak-to-peak voltage of the differential signal can be measured.

VID and VOD are often defined as volts (V) and VSS is often defined as volts peak-to-peak (VPP).

LMK00301 Two Different Definitions for Differential Input SignalsFigure 7-1 Two Different Definitions for Differential Input Signals
LMK00301 Two Different Definitions for Differential Output SignalsFigure 7-2 Two Different Definitions for Differential Output Signals

See also the AN-912 Common Data Transmission Parameters and their Definitions application note.