Engineering Information
EqcoLogic NV
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EQCO875SC.3/ EQC850SC.3
Single Coax Transceiver for Fast Ethernet
1.1
Features
1.2
Combined transmitter and receiver with an integrated equalizer to form a full-duplex
bidirectional connection over a single 75Ω coax cable (EQCO875SC.3) or 50Ω coax cable
(EQCO850SC.3)
Compatible with FX version of Fast Ethernet
Low Power - 205mW from single 3.3V supply
Integrated termination resistors for low external discrete count
Fully supports PoE based Power distribution over the coax, on top of the data signals
16-pin, 0.65mm pin pitch, 4mm QFN package
Pb-free and RoHS compliant
Applications
This solution is useful and economical for many markets and applications, including the following:
Camera networks - Home Security, Surveillance, industrial/inspection, medical cameras
Home Networking over coax infrastructure
When Cat5 or Cat6 cabling is not available and existing 75Ω coax is not used for analogue
TV signals.
TV, STB, PVR connections including inter-room links
1.3
Typical Cable Lengths
Version
EQCO875SC.3
EQCO875SC range using
RG11
225m
Table 1: Typical Device Performance
RG6 ( 5mm)
150m
DS-EQCO875SC.3 (Ethernet)-2v0-2011-10-25
Page 1 of 11
©2014 Eqcologic NV
Engineering Information
EqcoLogic NV
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2
2.1
Functional Description
Overview
The EQCO875SC.3 single coax transceiver is designed to simultaneously transmit and receive
signals on a single 75Ω coax cable for fast ethernet. A sister product, the EQCO850SC.3 can
achieve similar performance when used in 50Ω coaxial systems
The EQCO875SC.3 is ideally suited for Fast Ethernet connections over 75Ω coax cable at 125Mbps
1
data rate. The EQCO875SC.3 connects seamlessly to any FX
2
-compliant physical layer controller
(PHY). For correct operation the signals are expected to be 4B/5B encoded, DC balanced and to
have a bit rate of 125 Mbps.
This EQCO875SC.3 is useful and economical for connecting remote PoE enabled Fast Ethernet IP
cameras and other Ethernet over Coax applications.
Figure 1 (below) illustrates a typical Ethernet Coaxial connection:
Up to 225m
IEEE 802.3
FX
Compliant
PHY
IEEE 802.3
FX
Compliant
PHY
EQCO875SC
75Ω Coax
(including inline
connectors as reqd)
EQCO875SC
Figure 1: Coaxial Ethernet PMD connection
Figure 2 (below) shows a simplified block diagram of the EQCO875SC.3 when in Fast Ethernet mode:
EQCO875SC.3
SDIp
SDIn
Input
Pre-Driver
Active Signal
Splitter/Combiner
SDIO
REF
Transmit
wake-up
Detection
Equalizer
Core
SDOp
SDOn
RX Output
Driver
Figure 2: EQCO875SC.3 block diagram showing electrical connections
1
2
Wire rate after 4B/5B coding
FX is the terminology used in 802.3 to denote Fibre Optic transmission
DS-EQCO875SC.3 (Ethernet)-2v0-2011-10-25
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©2014 Eqcologic NV
Engineering Information
2.2
Package and Pinout
CCUT
16
DVCC
15
OPT0
14
DGND
13
EqcoLogic NV
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AVCC
1
12
SDOp
SDIO
2
11
SDOn
REF
3
ECQO875SC.3
GND TAB
10
SDIp
AGND
4
9
SDIn
5
OPT1
6
CLK
7
DAT
8
NC
Figure 3: EQCO875SC.3 Pin Layout (viewed from top)
2.3
(TAB)
15
13
1
Pin Descriptions
Pin Name
GND
DVCC
DGND
AVCC
Pin Number
Signal Type
Power
Power
Power
Power
Description
Connect to ground of power supply
Digital VCC
Connect to +3.3V power supply
Digital GND
Connect to ground of power supply
Analog VCC
Connect to +3.3V power supply via Ferrite Bead (RF Choke) and
capacitor to cable outer screen
Analog GND
Connect to cable outer screen
Serial Input Output
Connect to centre conductor of 75Ω coax cable
.
Reference
Connect through 75Ω resistor (or impedance matched to cable) to
cable outer screen
Do not connect
Serial Input Positive/Negative
Differential serial input. Connect to the Ethernet PHY FX out pins.
Serial Output Positive/Negative
Differential serial output. Connect to the Ethernet PHY FX in pins.
Connect Opt0 to DGND and Opt1 to DVCC to enable Fast Ethernet
mode
Used for Production test, Connect to DGND.
Cable Cut Detection
Table 2: Device Pin List
4
2
3
AGND
SDIO
REF
Power
Bidirectional
Bidirectional
8
10, 9
12, 11
14,5
6,7
16
NC
SDIp/SDIn
SDOp/
SDOn
OPT0, OPT1
CLK,
DAT
CCUT
Output
Input
Output
Input
Input
Analog
DS-EQCO875SC.3 (Ethernet)-2v0-2011-10-25
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©2014 Eqcologic NV
Engineering Information
2.3.1
SDIp/SDIn
EqcoLogic NV
Open your Eyes™
SDIp/SDIn together form a differential input pair. The serial data received on these pins will be
transmitted on SDIO. The Input Pre-Driver automatically corrects for variations in signal levels
and different edge slew rates at these inputs before they go into the Active Splitter/Combiner for
transmission over the coax.
Both SDIp and SDIn inputs are differentially terminated by 110 Ω on chip. The center of the 110 Ω
is connected to DGND with a 10 kΩ resistor for DC biasing. The inputs also have protection diodes
to ground for ESD purposes. These inputs
should always be capacitively coupled
to the FX output
of the Ethernet PHY. A Transmit Wake-up detection circuit puts both the Input Pre-Driver and the
Active Signal Splitter/Combiner into a low power mode when no signal is detected on the
SDIp/SDIn signal pair.
2.3.2
SDIO/REF
The signal on the SDIO pin is the sum of the incoming signal (i.e. the signal transmitted by the
EQCO875SC on the far end side of the coax) and the outgoing signal (i.e. the signal created based
on SDIp/SDIn). The far end signal is extracted by subtraction of the near end signal and it is this
voltage that the equalizer analyses and adaptively equalizes for level and frequency response
based on the knowledge that the originating signal is 4B/5B encoded before transmission.
The REF signal carries a precise anti-phase current to the transmit current on SDIO. REF must be
connected directly to AGND
at the connector
(see Figure 8) via a resistor precisely matched to the
impedance of the coaxial cable used.
2.3.3
SDOp/SDOn
SDOp/SDOn together form a differential pair outputting the reconstructed far end transmit signal.
The common mode output voltage of these signals is 1.2V and they have an internal differential
source matching of 100Ω according to LVDS standards, allowing AC or DC coupling to Ethernet
PHYs.
2.3.4
CCUT
Pin 16 of the EQCO875SC is an optional signal for cable cut detection. If used, it can detect when
there is a cut in the cable and it shuts down the internal receiver to stop reflections from being
interpreted as data. This feature is not compatible with sending power over the cable as this
might expose pin 16 to voltages higher than this input can tolerate. To use this feature connect
this signal to inner of the coax connector via a 3kΩ resistor. If used, the connection between the
3kΩ resistor and the 75Ω transmission line between SDIO and the inner contact of the coax
connector should be kept as short as possible, to avoid stub effects in the transmission line.
2.3.5
2.3.6
OPT0, OPT1
Connect Opt0 to DGND, and Opt1 to DVCC to enable Fast Ethernet mode.
CLK, DAT Pins
These pins are normally used to access an internal register during production test. Connect them
to DGND for normal operation.
They must not be left floating.
DS-EQCO875SC.3 (Ethernet)-2v0-2011-10-25
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©2014 Eqcologic NV
Engineering Information
2.4
2.4.1
EqcoLogic NV
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Circuit Operation
Pre-driver
The Pre-driver removes any dependency on Ethernet PHY for the amplitude and rise time of the
outgoing signal on SDIO.
2.4.2
Active signal splitter/combiner
The active splitter/combiner [3] 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.
2.4.3
Equalizer Core
Figure 4: Principle of Equalizer Operation
The EQCO875SC has an embedded 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 4. 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; one at each end of the coax. The EQCO875SC can be used
with any FAST ETHERNET compliant Fibre 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.
DS-EQCO875SC.3 (Ethernet)-2v0-2011-10-25
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©2014 Eqcologic NV
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