EQCO875SC.3 Datasheet, PDF (6/20 Pages) Microchip Technology – EQCO875SC.3/EQCO850SC.3 Single-Coax Transceiver for Fast Ethernet

EQCO875SC.3/EQCO850SC.3
2.0 CIRCUIT OPERATION
2.1 Pre-Driver
The pre-driver removes any dependency on Ethernet
PHY for the amplitude and rise time of the outgoing
signal on SDIO.
2.2 Active Signal Splitter/Combiner
The Active Splitter/Combiner controls the amplitude
and rise time of the outgoing coax signal and transmits
it via a precise 75Ω output termination resistor. The
output resistor, when balanced with the coax
characteristic impedance, also forms part of a hybrid
splitter circuit which subtracts the TX output from the
signal on the SDIO output to give yield the far-end TX
signal. The return-loss of the coax termination is a key
factor in the performance of the line hybrid.
2.3 Equalizer Core
The EQCO875SC-HS has an embedded high-speed
equalizer in the receive path with unique characteristics:
• Auto-adaptive
The equalizer controls a multiple-pole analog filter
which compensates for attenuation of the cable, as
illustrated in Figure 2-1. The filter frequency response
needed to restore the signal is automatically determined
by the device using a time-continuous feedback loop
that measures the frequency components in the signal.
Upon the detection of a valid signal, the control loop
converges within a few microseconds.
• Variable gain
EQCO875SCs are used in pairs, with one at each end of
the coax cable. The EQCO875SC can be used with any
Fast Ethernet compliant fiber optic PHY; any differences
in transmit amplitude are removed by the input pre-driver.
The receiver equalizer has variable gain to compensate
for attenuation through the coax cable.
FIGURE 2-1:
PRINCIPLE OF EQUALIZER OPERATION
DS60001314A-page 6
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