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Device Configuration
4.2.6
Input/Output Selection
The LMH0318 has 2:1 Mux on the Input and 1:2 Fan out on the output. Different input and output
configuration can be selected. The following settings allow these different configurations:
RAW
FF
04
07
//Select Channel Registers
RAW
31
00
03
//Set to 00: Enable IN0 to OUT0 and OUT1
//
RAW
FF
04
07
//Select Channel Registers
RAW
31
01
03
//Set to 01: Enable IN0 to OUT0 (OUT1 is powered down)
//
RAW
FF
04
07
//Select Channel Registers
RAW
31
02
03
//Set to 10: Enable IN1 to OUT1 (OUT0 is powered down)
//
RAW
FF
04
07
//Select Channel Registers
RAW
31
03
03
//Set to 11: Enable IN1 to OUT0 and OUT1
4.2.7
CTLE Test Mode
The LMH0318 Continuous Time Linear Equalizer compensates for the high frequency loss caused by the
transmission media. Deterministic jitter due to the ISI (Inter Symbol Interference) caused by the media can
be equalized by the LMH0318 CTLE.
In the default mode, the CTLE boost is determined by register 0x03. The default value of 0x80'h equalizes
10-15 inches PCB FR4 trace loss. The user may change register 0x03 to enable different boost settings
for different media loss characteristics .
shows recommended CTLE boost settings vs different
media trace length.
Table 4. CTLE Boost Setting vs Media Trace Length
FR4 TRACE
SDD21 (dB)
WRITE
BOOST SETTING
BOOST SETTING
LENGTH
REGISTER
@ 6 GHz
VALUE
@ 3 GHz (dB)
@ 6 GHz (dB)
(Inches)
1
-1.5
0x03
0x00
4.9
5.8
5
-7.5
0x03
0x00
4.9
5.8
10
-10.5
0x03
0x10
7.7
10.2
15
-15.5
0x03
0x50
10.9
15.3
20
-19.5
0x03
0x50
10.9
15.3
25
-24.5
0x03
0x60
13.2
17
30
-27.5
0x03
0x94
16.2
21.8
10
LMH0318 Programming Guide
SNLU183 – September 2015
Copyright © 2015, Texas Instruments Incorporated