LMH0394_15 Datasheet, PDF (18/35 Pages) Texas Instruments – 3G HD/SD SDI Low Power Extended Reach Adaptive Cable Equalizer

LMH0394
SNLS312M – AUGUST 2010 – REVISED JULY 2015
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Programming (continued)
Bit 7 of SPI register 02h is used for the launch amplitude setting. At the default setting of “0b”, the LMH0394
operates normally and expects a launch amplitude of 800 mV_P-P. Bit 7 may be set to “1b” to optimize the
LMH0394 for input signals with 6 dB of attenuation (400 mV_P-P).
7.5.1.11 Cable Length Indicator (CLI)
The cable length indicator (CLI) provides an indication of the length of the cable attached to input. CLI is
accessible through bits [7:0] of SPI register 06h. The 8-bit setting ranges in decimal value from 0 to 247
(“00000000” to “11110111” binary), corresponding to 0 to 400 m of Belden 1694A cable. For 3G and HD input,
CLI is 1.25 m per step. For SD input, CLI is 1.25 m per step, less 20 m, from 0 to 191 decimal, and 3.5 m per
step from 192 to 247 decimal.
To calculate the Belden 1694A cable length (in meters) from the CLI decimal value for 3G or HD input:
(1)
To calculate the Belden 1694A cable length (in meters) from the CLI decimal value for SD input:
(2)
Figure 15 shows typical CLI values vs. Belden 1694A cable length. CLI is valid for Belden 1694A cable lengths of
0-200 m at 2.97 Gbps, 0-220 m at 1.485 Gbps, and 0-400 m at 270 Mbps. Note: Given the continuous adaptive
nature of the equalizer, the CLI values may vary constantly within several steps.
250
225
200
175
150
SD
125
100
75
50
3G/HD
25
0
0 50 100 150 200 250 300 350 400
BELDEN 1694A CABLE LENGTH (m)
Figure 15. CLI vs. Belden 1694A Cable Length
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