Datasheet
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MAX9257A/MAX9258A
Fully Programmable Serializer/Deserializer
with UART/I
2
C Control Channel
Cables and Connectors
Interconnect for LVDS typically has a differential imped-
ance of 100I. Use cables and connectors that have
matched differential impedance to minimize impedance
discontinuities. Twisted-pair and shielded twisted-pair
cables offer superior signal quality compared to ribbon
cable and tend to generate less EMI due to magnetic
field canceling effects. Balanced cables pick up noise
as common mode that is rejected by the LVDS receiver.
Choosing I2C Pullup Resistors
I
2
C requires pullup resistors to provide a logic-high level
to data and clock lines. There are tradeoffs between
power dissipation and speed, and a compromise must
be made in choosing pullup resistor values. Every device
connected to the bus introduces some capacitance even
when device is not in operation. I
2
C specifies 300ns
rise times to go from low to high (30% to 70%) for fast
mode, which is defined for a date rate up to 400kbps
(see I
2
C specifications for details). To meet the rise time
require ment, choose the pullup resistors so the rise time
t
R
= 0.85R
PULLUP
x C
BUS
< 300ns. If the transition time
becomes too slow, the setup and hold times may not be
met and waveforms will not be recognized.
MAX9257A Register Table
ADDRESS BITS DEFAULT NAME DESCRIPTION
0
7:6 10 PRATE
Pixel clock frequency range
00 = 5MHz to 10MHz
01 = 10MHz to 20MHz
10 = 20MHz to 40MHz (default)
11 = 40MHz to 70MHz
5:4 11 SRATE
Serial-data rate range
00 = 60Mbps to 100Mbps
01 = 100Mbps to 200Mbps
10 = 200Mbps to 400Mbps
11 = 400Mbps to 840Mbps (default)
3 0 PAREN Parity enable 0 = disabled (default), 1 = enabled
2:0 101 PWIDTH
Parallel data width
(includes HSYNC and VSYNC, excludes DCB, INV, and parity bits)
000 = 10 100 = 18
001 = 12 101 = 18 (default)
010 = 14 110 = 18
011 = 16 111 = 18
1
7:5 000 SPREAD
Spread-spectrum setting
For PRATE ranges 00, 01: all spread options possible
For PRATE ranges 10, 11: maximum spread is 2%
000 = Off (default) 100 = Off
001 = 1.5% 101 = 3%
010 = 1.75% 110 = 3.5%
011 = 2% 111 = 4%
4:0 11111 Reserved (set to 11111)