LMK00306_16 Datasheet, PDF (18/39 Pages) Texas Instruments – 3-GHz 6-Output Ultra-Low Additive Jitter Differential Clock Buffer/Level Translator

LMK00306
SNAS578D – FEBRUARY 2012 – REVISED MARCH 2016
7 Parameter Measurement Information
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7.1 Differential Voltage Measurement Terminology
The differential voltage of a differential signal can be described by two different definitions causing confusion
when reading datasheets or communicating with other engineers. This section will address the measurement and
description of a differential signal so that the reader will be 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 V_ID or V_OD 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 V_SS and is a calculated
parameter. Nowhere in the IC does this signal exist with respect to ground, it only exists in reference to its
differential pair. V_SS can be measured directly by oscilloscopes with floating references, otherwise this value can
be calculated as twice the value of V_OD as described in the first description.
Figure 23 illustrates the two different definitions side-by-side for inputs and Figure 24 illustrates the two different
definitions side-by-side for outputs. The V_ID (or V_OD) definition show the DC levels, V_IH and V_OL (or V_OH and V_OL),
that the non-inverting and inverting signals toggle between with respect to ground. V_SS 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.
V_ID and V_OD are often defined as volts (V) and V_SS is often defined as volts peak-to-peak (V_PP).
V_IH
V_CM
V_IL
GND
V_ID Definition
Non-Inverting Clock
V_ID
Inverting Clock
V_ID = | V_IH ± V_IL |
V_SS Definition for Input
V_SS
V_SS = 2·V_ID
Figure 23. Two Different Definitions for Differential Input Signals
V_OH
V_OS
V_OL
GND
V_OD Definition
Non-Inverting Clock
V_OD
Inverting Clock
V_OD = | V_OH - V_OL |
V_SS Definition for Output
V_SS
V_SS = 2·V_OD
Figure 24. Two Different Definitions for Differential Output Signals
Refer to Application Note AN-912 (literature number SNLA036), Common Data Transmission Parameters and
their Definitions, for more information.
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