Teledyne LeCroy QPHY-DDR4 - Manual (Page 17)

QPHY-DDR4 Software Option
QPHY-DDR4 Measurement Preparation
Deskewing the Probes
For DDR measurements it is crucial to make sure the probes are properly deskewed before running
QPHY-DDR4 to ensure proper signal timing. Ideally, when deskewing the same settings should be used
as when QualiPHY is acquiring the signals for analysis. This will ensure that the channels are deskewed
using the same setup as when running conformance tests. Deskew values are saved and stored by
QPHY at the beginning of each run.
Required Equipment
• PCF200 (included with D1330-PS)
• Square-Pin (SP) tip (included with D1330-PS)
• 50
Ω terminator
Note: Alternatively an LPA-K-A adapter and a SMA cable could be used
Methodology
Before beginning the procedure the oscilloscope should be warmed for at least 20 minutes.
1.) Connect the PCF200 to the oscilloscope’s fast edge output. The PCF200 fixture has two different
signal paths that can be used, depending on the type of probe tip being used for the
measurement. The upper signal path is for deskewing Solder-In (SI), Quick-Connect (QC) and
Adjustable Tip (AT) probe tips and the lower circuit is for Square-Pin (SP) probe tips. Depending
upon which probe tip is being used the appropriate signal path should be connected to the fast
edge output. For ease of connectivity it is recommended that SP tip is used. As long as the same
tip is used to deskew each probe it does not matter which style of probe tip is used.
2.) Probes are connected electrically in a single-ended arrangement using their designated area on
the fixture. The positive side of the probe must be connected to the signal trace (in between the
two white strips), while the negative side is connected to the ground plane (outside of the white
strips). The positive polarity is indicated on the tip of the probe by a plus sign. In order to minimize
reflections a 50
Ω terminator shall be applied to the end of the signal path in use. If a 50 Ω
terminator is not available a SMA cable can be used to terminate the PCF200 to one of the
oscilloscope’s outputs.
3.) Set the oscilloscope trigger source to “fast edge”, set the trigger type to “edge”, set the trigger
level to 50%, and set the oscilloscope timebase delay to zero. It is recommended that the
oscilloscope be bandwidth limited to the same setting which QualiPHY uses. For DDR4 the
bandwidth limit is set to 13 GHz.
924291 Rev A 17