78P2351-DB/CMI Maxim Integrated Products, 78P2351-DB/CMI Datasheet - Page 8

• Manufacturer Part Number: 78P2351-DB/CMI
• Description: BOARD DEMO 78P2351 COAX CABLE
• Manufacturer: Maxim Integrated Products

Specifications of 78P2351-DB/CMI

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Design Guidelines for TERIDIAN 78P235x LIUs
RETURN LOSS MATCHING CIRCUIT
Meeting the 15dB return loss requirements at the CMI-coded coax ports often requires a significant amount of
engineering hours due to the unique impedance characteristics of each system design, particularly at frequencies
above 200MHz. Return loss is a parameter that can only be measured at the system level. Evaluating any
individual component’s return loss won’t be efficient and will provide misleading results.
For challenging environments where the coax connector, transformer, and LIU are not located near each other or
even on the same card, a flexible termination scheme is required to meet the return loss performance for both
transmit and receive paths. The diagram in Figure 8 below shows a suggested circuit to optimize the impedance
on the transmission lines by adding discrete component footprints right near the transformers in the differential
paths. The capacitance (C) and inductance (L) values are unique for each design and will generally be in the
range of a few nH or pF.
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BNC
BNC
Figure 8. (Optional) Discrete components to improve the return loss
BAV99
BAV99
BAV99
BAV99
 2008 Teridian Semiconductor Corp.
Transformer Dual CT
T1
0.1uF
VCC
C
R
R
C
R
C
R
75
L
75
L
L
L
C
75
75
To LIU
75
75
75
Rev 2.1