Programmable Pre-Emphasis; Programmable Differential Output Voltage - Altera Cyclone V Device Handbook

5-32

Programmable Pre-Emphasis

Programmable Pre-Emphasis
The V setting and the output impedance of the driver set the output current limit of a high-speed
OD
transmission signal. At a high frequency, the slew rate may not be fast enough to reach the full V
before the next edge, producing pattern-dependent jitter. With pre-emphasis, the output current is boosted
momentarily during switching to increase the output slew rate.
Pre-emphasis increases the amplitude of the high-frequency component of the output signal, and thus helps
to compensate for the frequency-dependent attenuation along the transmission line. The overshoot introduced
by the extra current happens only during a change of state switching to increase the output slew rate and
does not ring, unlike the overshoot caused by signal reflection. The amount of pre-emphasis required depends
on the attenuation of the high-frequency component along the transmission line.
Figure 5-11: Programmable Pre-Emphasis
This figure shows the LVDS output with pre-emphasis.
Table 5-26: Quartus II Software Assignment Editor—Programmable Pre-Emphasis
This table lists the assignment name for programmable pre-emphasis and its possible values in the Quartus II software
Assignment Editor.
To
Assignment name
Allowed values
Related Information
Programmable IOE Features in Cyclone V Devices

Programmable Differential Output Voltage

The programmable V
and power consumption. A higher V
V swing reduces power consumption. You can statically adjust the V
OD
changing the V
Altera Corporation
Voltage boost
from pre-emphasis
OUT
OUT
Field
settings allow you to adjust the output eye opening to optimize the trace length
OD
OD
settings in the Quartus II software Assignment Editor.
OD
V
P
V
OD
V
P
Differential output
voltage (peak–peak)
Assignment (Default setting in bold)
tx_out
Programmable Pre-emphasis
0 (disabled) and 1 (enabled)
on page 5-29
swing improves voltage margins at the receiver end, and a smaller
of the differential signal by
OD
I/O Features in Cyclone V Devices
Send Feedback
CV-52005
2014.01.10
level
OD