DS64EV400 Datasheet, PDF (14/18 Pages) National Semiconductor (TI) – Programmable Quad Equalizer

DS64EV400 Applications
Information
FIGURE 9. Automatic Enable Configuration
30032007
UNUSED EQUALIZER CHANNELS
It is recommended to put all unused channels into standby
mode.
GENERAL RECOMMENDATIONS
The DS64EV400 is a high performance circuit capable of de-
livering excellent performance. Careful attention must be paid
to the details associated with high-speed design as well as
providing a clean power supply. Refer to the LVDS Owner's
Manual for more detailed information on high speed design
tips to address signal integrity design issues.
PCB LAYOUT CONSIDERATIONS FOR DIFFERENTIAL
PAIRS
The CML inputs and outputs must have a controlled differen-
tial impedance of 100Ω. It is preferable to route CML lines
exclusively on one layer of the board, particularly for the input
traces. The use of vias should be avoided if possible. If vias
must be used, they should be used sparingly and must be
placed symmetrically for each side of a given differential pair.
Route the CML signals away from other signals and noise
sources on the printed circuit board. See AN-1187 for addi-
tional information on LLP packages.
POWER SUPPLY BYPASSING
Two approaches are recommended to ensure that the
DS64EV400 is provided with an adequate power supply.
First, the supply (V_DD) and ground (GND) pins should be con-
nected to power planes routed on adjacent layers of the
printed circuit board. The layer thickness of the dielectric
should be minimized so that the V_DD and GND planes create
a low inductance supply with distributed capacitance. Sec-
ond, careful attention to supply bypassing through the proper
use of bypass capacitors is required. A 0.01μF bypass ca-
pacitor should be connected to each V_DD pin such that the
capacitor is placed as close as possible to the DS64EV400.
Smaller body size capacitors can help facilitate proper com-
ponent placement. Additionally, three capacitors with capac-
itance in the range of 2.2 μF to 10 μF should be incorporated
in the power supply bypassing design as well. These capac-
itors can be either tantalum or an ultra-low ESR ceramic and
should be placed as close as possible to the DS64EV400.
DC COUPLING
The DS64EV400 supports both AC coupling with external ac
coupling capacitor, and DC coupling to its upstream driver, or
downstream receiver. With DC coupling, users must ensure
the input signal common mode is within the range of the elec-
trical specification V_ICMDC and the device output is terminated
with 50 Ω to V_DD.
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