SNAA377 December   2025 LMK05318 , LMK05318B , LMK5B12204 , LMK5B12212 , LMK5B33216 , LMK5B33414 , LMK5C22212A , LMK5C23208A , LMK5C33216 , LMK5C33216A , LMK5C33414A

 

  1.   1
  2.   Trademarks
  3.   Abstract
  4. 1Introduction
  5. 2General Termination Guidelines
    1. 2.1 Identify the Driver and Receiver Requirements
    2. 2.2 Determine the Coupling Type
      1. 2.2.1 DC-Coupled Signal
      2. 2.2.2 AC-Coupled Signal
  6. 3Differential
    1. 3.1 Setting the Common-Mode Voltage (Thevenin Termination)
    2. 3.2 LVPECL
      1. 3.2.1 DC-Coupled LVPECL
      2. 3.2.2 AC-Coupled LVPECL
    3. 3.3 LVDS
      1. 3.3.1 DC-Coupled LVDS
      2. 3.3.2 AC-Coupled LVDS
    4. 3.4 HSDS
      1. 3.4.1 DC-Coupled HSDS
      2. 3.4.2 AC-Coupled HSDS
    5. 3.5 HCSL
      1. 3.5.1 DC-Coupled HCSL
      2. 3.5.2 AC-Coupled HCSL
    6. 3.6 LP-HCSL
      1. 3.6.1 DC-Coupled LP-HCSL
      2. 3.6.2 AC-Coupled LP-HCSL
  7. 4Single-Ended
    1. 4.1 LVCMOS
      1. 4.1.1 DC-Coupled LVCMOS (Series Termination)
      2. 4.1.2 AC-Coupled LVCMOS (Series Termination)
    2. 4.2 Differential P or N
      1. 4.2.1 DC-Coupled Differential P or N
  8. 5Summary
  9. 6References

2.1 Identify the Driver and Receiver Requirements

The first step is to gather the details listed in Table 2-1 for both the clock driver and the receiver. Each signal type has a voltage swing, common-mode voltage (for differential), and trace impedance requirement. Each signal type can vary across product family and vendor. Therefore, read the Electrical Characteristics table for every clock driver and receiver data sheet prior to starting the design.

Table 2-1 Termination Requirements for Single-Ended and Differential Signals
PARAMETER PURPOSE OF KNOWING EXAMPLES(1)
Signal type To know what termination to use for the driver and receiver
  • LVPECL
  • LVDS
  • HCSL
  • LVCMOS
Voltage swing To meet receiver requirements
  • VID
  • VOD
  • VPP
Common-mode voltage
(differential signals only)		 To meet receiver requirements(2)
  • VCM
  • VICM (input VCM)
  • VOCM (output VCM)
Impedance To maintain signal integrity and minimize reflections, overshoot, undershoot, and ringing
  • ZO = 50Ω, single-ended
  • ZO = 100Ω, differential
(1) Common examples used to define and refer to the parameter in the industry.
(2) Receivers must be presented with a signal that is biased to the specified DC bias level (common-mode voltage) for proper operation. Some receivers have a self-biasing input feature that enables automatic biasing. See the device data sheet to confirm the requirements.