Specifications

Gigabit Multimedia Serial Link Deserializer
with LVDS System Interface
MAX9268
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Line Equalizer
The MAX9268 includes an adjustable line equalizer to
further compensate cable attenuation at high frequencies.
The cable equalizer has 12 selectable levels of compensa-
tion, from 2.1dB to 13dB (Table 6). The EQS input selects
the default equalization level at power-up. The state of EQS
is latched upon power-up or when resuming from power-
down mode. To select other equalization levels, set the
corresponding register bits in the MAX9268 (0x05 D[3:0]).
Use equalization in the MAX9268, together with preempha-
sis in the GMSL serializer, to create the most reliable link
for a given cable.
Spread Spectrum
To reduce the EMI generated by the transitions on the serial
link and outputs of the MAX9268, both the GMSL serial-
izer and MAX9268 support spread spectrum. Turning on
spread spectrum on the GMSL serializer spreads the serial
data and the MAX9268 outputs. Do not enable spread for
both the GMSL serializer and the MAX9268. The two select-
able spread-spectrum rates at the MAX9268 outputs are
Q2% and Q4% (Table 7).
Set the MAX9268 SSEN input high to select 2% spread
at power-up, and SSEN input low to select no spread at
power-up. The state of SSEN is latched upon power-up or
when resuming from power-down mode.
Turning on spread spectrum on the GMSL serializer or the
MAX9268 does not affect the audio data stream. Changes
in the GMSL serializer spread settings only affect the
MAX9268 MCLK output if it is derived from TXCLKOUT_
(MCLKSRC = 0).
The MAX9268 includes a sawtooth divider to control the
spread-modulation rate. Autodetection or manual program-
ming of the TXCLKOUT_ operation range guarantees a
spread-spectrum modulation frequency within 20kHz to
40kHz. Additionally, manual configuration of the sawtooth
divider (SDIV, 0x03 D[4:0]) allows the user to set a modula-
tion frequency according to the TXCLKOUT_ frequency.
Always keep the modulation frequency between 20kHz to
40kHz to ensure proper operation.
Manual Programming of the
Spread-Spectrum Divider
The modulation rate for the MAX9268 relates to the
TXCLKOUT_ frequency as follows:
( )
TXCLKOUT_
M
f
f 1 DRS
MOD SDIV
= +
×
where:
f
M
= Modulation frequency
DRS = DRS input value (0 or 1)
f
TXCLKOUT_
= LVDS clock frequency
MOD = Modulation coefficient given in Table 8
SDIV = 5-bit SDIV setting, manually programmed by the FC
To program the SDIV setting, first look up the modulation
coefficient according to the spread-spectrum settings.
Table 6. Cable Equalizer Boost Levels
Table 7. LVDS and Control Output Spread
Rates
Table 8. Modulation Coefficients and
Maximum SDIV Settings
BOOST SETTING
(0x05 D[3:0])
TYPICAL BOOST GAIN (dB)
0000 2.1
0001 2.8
0010 3.4
0011 4.2
0100
5.2
Power-up default
(EQS = high)
0101 6.2
0110 7
0111 8.2
1000 9.4
1001
10.7
Power-up default
(EQS = low)
1010 11.7
1011 13
SS SPREAD (%)
00
No spread spectrum.
Power-up default when SSEN = low.
01
Q2% spread spectrum.
Power-up default when SSEN = high.
10 No spread spectrum
11
Q4% spread spectrum
SPREAD-
SPECTRUM
SETTING (%)
MODULATION
COEFFICIENT
(dec)
SDIV UPPER
LIMIT (dec)
4 208 15
2 208 30