® 16k CXP
51
UM 16k CXP – Indice E - 06/13
e2v semiconductors SAS 2013
9
APPENDIX C: Data Cables
•
CXP cables and the separate lanes of a CXP-multi-cable shall be coaxial with a characteristic impedance
of 75Ω ± 4 Ω. When a series connection of CXP-cables is considered, all of the BNC connectors used
have to be of the 75Ω type, including any inline couplers.
•
A CXP cable and the separate lanes of a CXP-multi-cable shall have a return loss better than or equal to :
•
Frequency Range
•
Return Loss
•
0-500MHz
•
-20dB
•
500MHz – 3.2GHz
•
-15dB
•
The maximum length of a CoaXPress cable is the lowest figure from three different requirements:
power supply voltage drop, high speed link requirements and low speed link requirements.
o
Power Supply Voltage Drop : A CXP cable and the separate lanes of a CXP multi-cable shall
each have a total DC roundtrip resistance of less than 4.98Ω for each of the coax cables.
o
High Speed Link Requirement : A CXP cable and the separate lanes of a CXP-multi-cable that
are specified for a given bit rate shall have an attenuation that is less or equal to the
following attenuation at its corresponding frequency (example with Belden 1694A Cable) :
Bit Rate
(Gbps)
Maximum Attenuation
(dB)
@ Frequency
(GHz)
Belden 1694A
(m)
1.250
-21.2
0.625
130
2.500
-26
1.25
110
3.125
-26.8
1.5625
100
5.000
-20.9
2.5
60
6.250
-15.8
3.125
40
o
Low Speed Link Requirement : A CXP cable and the separate lanes of a CXP-multi-cable shall
have a signal attenuation at 30 MHz of less than, or equal to, -4.74dB.
•
Cable Current Capacity : A CXP cable and the separate lanes of a CXP-multi-cable shall each be
designed to carry 1A in normal operation.
•
A CXP-cable and the separate lanes of a CXP-multi-cable shall have attenuation versus frequency
characteristic exhibiting cable-like behaviour over the frequency ranges as indicated in the table
below. A series connection of cables shall also fulfil this requirement as if it is one cable including all
of its connectors and inline couplers.
Cable Rating
(Gbps)
Frequency Range
From
To
1.250
1
0.625
2.500
1
1.25
3.125
1
1.5625
5.000
1
2.5
6.250
-15.8
3.125