HC4GX15 Datasheet, PDF (330/668 Pages) Altera Corporation – HardCopy IV Device Handbook

1–66
Chapter 1: HardCopy IV GX Transceiver Architecture
Receiver Channel Datapath
Figure 1–53 shows the LVDS transmitter to HardCopy IV GX receiver (PCML)
coupled link.
Figure 1–53. LVDS Transmitter to HardCopy IV GX Receiver (PCML)
LVDS
Transmitter
Physical Medium
Physical Medium
HardCopy IV GX
Receiver
50- Ω
RX Termination
50- Ω
RX Termination
R_s (1)
RX
V_CM ^{1.1 V}
Note to Figure 1–53:
(1) R_S is the parasitic resistance present in the on-chip RX termination and biasing circuitry.
Table 1–16 shows the allowed transmitter and receiver settings in a LVDS transmitter
to HardCopy IV GX receiver DC-coupled link.
Table 1–16. Settings for a LVDS transmitter to HardCopy IV GX Receiver DC-Coupled Link (Note 1)
Receiver (HardCopy IV GX) Settings
RX VCM
Differential Termination
R_S
1.1 V
100-Ω
(2)
Notes to Table 1–16:
(1) When DC-coupling an LVDS transmitter to the HardCopy IV GX receiver, use RX Vcm = 1.1 V and series resistance
value RS to verify compliance with the LVDS specification.
(2) Pending characterization.
Programmable Equalization and DC Gain
The transfer function of the physical medium can be represented as a low-pass filter in
the frequency domain. Frequency components below –3 dB frequency pass through
with minimal loss. Frequency components greater than –3 dB frequency are
attenuated as a function of frequency due to skin-effect and dielectric losses. This
variation in frequency response yields data-dependent jitter and other ISI effects,
which can cause incorrect sampling of the input data.
Each HardCopy IV GX receiver buffer has independently programmable equalization
circuitry that boosts the high-frequency gain of the incoming signal, thereby
compensating for the low-pass filter effects of the physical medium. The amount of
high-frequency gain required depends on the loss characteristics of the physical
medium. The HardCopy IV GX equalization circuitry supports 16 equalization
settings that provide up to 16 dB of high-frequency boost. You can select the
appropriate equalization setting in the ALTGX MegaWizard Plug-In Manager.
HardCopy IV Device Handbook Volume 3
© June 2009 Altera Corporation