M21234 Datasheet, PDF (18/20 Pages) M/A-COM Technology Solutions, Inc. – Adaptive Coaxial Cable Equalizer

Functional Description
Figure 3-2. Single-ended Typical Input Matching/termination Network
8.2 nH
BNC
1 uF
75Ω
75Ω
1 uF
37.5Ω
M21234
SDI
SDI
3.4.3
High-Speed Output
The high-speed differential outputs after equalization are made available on the SDO/SDO pins. The M21234
operates from 1.8V to 3.3V supplies. Outmode0 and Outmode1 control what standard of output is used. See
below:
OUTMODE[1:0]
00:
01:
10:
11:
Output Mode
CML, 750 mVpp (default)
CML, 500 mVpp
LVDS, common mode = 1.2V, 700 mVpp
LVPECL, common mode = Vdd - 1.3V, 1600 mVpp differential (3.3V supply only)
3.4.4
Adaptive Equalization Selection
In typical operation, the adaptive equalization is enabled with EQ_BYP = Low; however, with EQ_BYP = High, the
adaptive equalization and DC restore circuit is bypassed and the input is fed directly to the output.
3.4.5
Cable Length Indicator
When the adaptive equalization is enabled (EQ_BYP = Low), an analog voltage inversely proportional to the cable
length is made available on CLEN and defined by the equation V_CLEN = (V_DD - 0.9V) – (slope x Cable length).
The transfer function of M21234 is designed for all bit rates. The slope is 0.0021 with Belden 8281 and 0.0015 with
Belden 1694A. The dynamic range of CLEN will exceed older legacy devices. When the adaptive equalization is
disabled (EQ_BYP = High), the voltage falls to its highest value (it indicates 0m cable length). During an LOS (Loss
of input Signal) event, the voltage falls to its lowest value.
21234-DSH-001-B
Mindspeed Technologies^®
19
Mindspeed Proprietary and Confidential