When implementing systems using gigabit
serial data transmissions in cables or in
backplane transmission lines, you're very
limited in the lengths you can achieve
because of the severe attenuation and distortion.
An established way to compensate
is to use equalization at the receiver.
The equalizer anticipates the distortion and
adds corrective measures that enable you to
implement higher-speed interfaces over
longer signal paths. Now, you can buy such
equalizers for some standard serial interfaces
that run as fast as 10 Gbits/s. For example,
National Semiconductor's DS64EV400 programmable
quad equalizer compensates for
medium losses and reduces deterministic jitter
for four data channels.
Part of National's PowerWise product portfolio,
the chip consumes 94 mW per channel.
With these equalizers, you can boost
signal strength as much as 20 dB on up to
10 m of CAT5 cable or up to 40 in. of FR-4
pc-board backplane up to 6.4 Gbits/s and
up to 30 in. for FR-4 at rates to 10 Gbits/s.
Equalizer output has a low 0.175 UI (unit
interval) of residual jitter.
The DS64EV400 is designed for use with
FPGAs and ASICs in building systems using
any of the high-speed buses like Fibre Channel
and Ethernet/XAUI. Each equalizer channel
has eight equalization levels that all can
be set simultaneously by three control pins
or individually programmed through a serial
management bus (SMB) link.
The chip permits both ac and dc coupling
to the data paths and can accommodate
long run-length data patterns like PRBS-31
or balanced codes like 8B/10B. The
DS64EV400 also uses differential currentmode
logic (CML) I/O and is protected
against electrostatic discharge (ESD).
The DS64EV400 is made with a proprietary
silicon-germanium (SiGe) biCMOS process
and comes in a 7- by 7-mm, 48-pin leadless
leadframe package (LLP). Supply voltage
may be 2.5 or 3.3 V. The DS32EV400 is
available for data rates up to 3.2 Gbits/s.
Pricing is $16 for the DS64EV400 and $13
for the DS32EV400 in 1000-unit lots.
National Semiconductor
www.national.com
