MAX9268 Maxim, MAX9268 Datasheet - Page 23

• Manufacturer Part Number: MAX9268
• Description: The MAX9268 deserializer utilizes Maxim's gigabit multimedia serial link (GMSL) technology
• Manufacturer: Maxim

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.
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
Table 6. Cable Equalizer Boost Levels
BOOST SETTING
(0x05 D[3:0])
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
Gigabit Multimedia Serial Link Deserializer
______________________________________________________________________________________
TYPICAL BOOST GAIN (dB)
Power-up default
Power-up default
Spread Spectrum
(EQS = high)
(EQS = low)
Line Equalizer
10.7
11.7
2.1
2.8
3.4
4.2
5.2
6.2
8.2
9.4
13
7
with LVDS System Interface
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.
The modulation rate for the MAX9268 relates to the
TXCLKOUT_ frequency as follows:
where:
To program the SDIV setting, first look up the modulation
coefficient according to the spread-spectrum settings.
Table 7. LVDS and Control Output Spread
Rates
Table 8. Modulation Coefficients and
Maximum SDIV Settings
f
DRS = DRS input value (0 or 1)
f
MOD = Modulation coefficient given in Table 8
SDIV = 5-bit SDIV setting, manually programmed by the FC
M
TXCLKOUT_
SETTING (%)
SPECTRUM
SS
00
01
10
11
SPREAD-
= Modulation frequency
4
2
No spread spectrum.
Power-up default when SSEN = low.
Q2% spread spectrum.
Power-up default when SSEN = high.
No spread spectrum
Q4% spread spectrum
= LVDS clock frequency
f
M
=
(
1 DRS
+
Manual Programming of the
MODULATION
COEFFICIENT
Spread-Spectrum Divider
(dec)
)
208
208
SPREAD (%)
f
MOD SDIV
TXCLKOUT_
×
SDIV UPPER
LIMIT (dec)
15
30
23