Teledyne LeCroy QPHY-SAS2 - Manual (Page 32)

32
917718 Rev A
In the Measure section:

CM Offset (P1) is the common mode offset. This is measured by taking the mean of the common mode
trace. This is the measured value of Tx – Common Mode Offset (5.3.2). This test is informational only.

CM RMS (P2) is the common mode RMS voltage. This is measured by taking the RMS of the common mode
trace. This is the measured value for Tx – CM RMS voltage (5.3.2). This value must be less than 30mV
in order to pass this test.
Tx 5.3.4 and 5.3.5 Vpp, VMA, EQ (D30.3)
The purpose of these tests is to verify that the peak-to-peak voltage, the voltage modulation amplitude and the
amount of equalization are within the specification limits. After the completion of the Vpp, VMA and EQ tests the
oscilloscope is in the following configuration:
Figure 25 - Oscilloscope Configuration after the Vpp, VMA and EQ tests
Shown on this screen:

F2 is Eye Diagram created from the input signal using a 2 pole PLL with a natural frequency of 3.9MHz and
a damping factor of .800. This is shown for information only.

F4 is a histogram of the input waveform.

F5 is this histogram converted to a waveform (this is required to perform certain measurements on the
histogram).

F6 is the differential input waveform. This is calculated by subtracting the negative input from the positive
input.