Datasheet

Detailed Description
The MAX3802 has four independent adaptive equalizers
(receivers) and four independent drivers. Disconnecting
the power pins of unused equalizers and drivers lowers
the power consumption of the MAX3802. Equalizer and
driver descriptions apply to the four identical sections.
Cable Driver
The cable driver accepts differential or single-ended CML
input data at rates up to 3.2Gbps. The maximum CML
output of the driver can be adjusted over a typical range
of 445mV to 825mV by changing the value of the R
MOD_
resistor between 10kΩ and 20kΩ (resistor connected
between RMOD_ pin and ground).
Adaptive Cable Equalizer
The adaptive cable equalizer is capable of equalizing
differential or single-ended CML input data at rates up
to 3.2Gbps. It automatically adjusts to attenuation levels
of 30dB at 1.6GHz (due to skin-effect losses in copper
cable). The equalizer consists of a CML input buffer, a
flat-response amplifier, a skin-effect compensation ampli-
fier, a current-steering network, a dual power-detector
feedback loop, an output limiting amplifier, and a CML
output buffer (Figure 1).
General Theory of Operation
The shape of the power spectrum of a random bit stream
can be described by the square of the wellknown sinc
function, where sinc(f) = sin(πf)/(πf) for f ≠ 0. For sufficient-
ly long bit patterns (nonrandom bit stream), sinc
2
(f) is a
good approximation. From the shape of the sinc
2
(f) func-
tion, the ratio of the power densities at any two frequen-
cies can be estimated. The MAX3802 adaptive equalizer
employs this principle by incorporating a feedback loop
that continuously monitors the power at high- and low-
Figure 1. MAX3802 Functional Diagram
VARIABLE
ATTENUATOR
VARIABLE
ATTENUATOR
CURRENT-STEERING NETWORK
∑
FLAT
RESPONSE
AMP
CML
CML
CML CML
SKIN-
EFFECT
COMP
AMP
|H(f)|
POWER
DETECTOR
EIN_
DOUT_
2
2
LOS_
CABLE
DRIVER
|H(f)|
f
RMOD_
R
MOD_
2
DIN_
2
EOUT_
LIMITING
AMP
600MHz
PWR DETECTOR
200MHz
PWR DETECTOR
LOOP
FILTER
MAX3802
√
MAX3802 3.2Gbps Quad Adaptive Cable Equalizer
with Cable Driver
www.maximintegrated.com
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