MAX9675EVKIT+ Maxim Integrated Products, MAX9675EVKIT+ Datasheet - Page 23

• Manufacturer Part Number: MAX9675EVKIT+
• Description: KIT EVAL FOR MAX9675
• Manufacturer: Maxim Integrated Products

Specifications of MAX9675EVKIT+

• Main Purpose: Interface, Crosspoint Switch/Multiplexer
• Embedded: No
• Utilized Ic / Part: MAX9675
• Primary Attributes: 16 x 16 Video Crosspoint Switch
• Secondary Attributes: Graphical User Interface, USB Interface
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX9675 output buffers can be programmed to
either A
typically used when driving a short-length (less than
3cm), high-impedance “local” PCB trace. To drive a
cable or a 75Ω transmission line trace, program the
gain of the output buffer to +2V/V and place a 75Ω
resistor in series with the output. The series termination
resistor and the 75Ω load impedance act as a voltage-
divider that divides the video signal in half. Set the gain
to +2V/V to transmit a standard 1V video signal down a
cable. The series 75Ω resistor is called the back-match,
reverse termination, or series termination. This 75Ω
resistor reduces reflections, and provides isolation,
increasing the output-capacitive-driving capability.
The MAX9675’s unique digital interface simplifies pro-
gramming multiple MAX9675 devices in an array.
Multiple devices are connected with DOUT of the first
device connecting to DIN of the second device, and so
on (Figure 9). Two distinct programming modes, indi-
vidual output address mode (MODE = 0) and complete
matrix mode (MODE = 1), are selected by toggling a
single MODE control pin high or low. Both modes oper-
ate with the same physical board layout. This allows ini-
tial programming of the IC by daisy-chaining and
sending one long data word while still being able to
address immediately and update individual locations in
the matrix.
In Individual Output Address Mode, the devices are
connected in a serial bus configuration, with the data
routing gate (Figure 3) connecting DIN to DOUT, mak-
ing each device a virtual node on the serial bus. A sin-
gle 16-bit control word is sent to all devices
simultaneously. Only the device with the corresponding
chip address responds to the programming word, and
updates its output. In this mode, the chip address is set
through hardware pin strapping of A3–A0. The host
then communicates with the device by sending a 16-bit
word consisting of 2 don’t care MSB bits, 4 chip
address bits, and 10 bits of data to make the word
Driving a PCB Interconnect or a Cable
V
= +1V/V or +2V/V. The +1V/V configuration is
Individual Output Address Mode (Mode 0)
______________________________________________________________________________________
(A
Matrix Programming
V
= +1V/V or +2V/V)
110MHz, 16 x 16 Video Crosspoint
Switch with Programmable Gain
exactly 2 bytes in length. The 10 data bits are broken
down into 4 bits to select the output to be programmed;
1 bit to set the output enable; 1 bit to set gain; and 4
bits to select the input to be connected to that output.
In this method, the matrix is programmed one output at
a time.
In Complete Matrix Mode, the devices are connected in
a daisy-chain fashion where n x 96 bits are sent to pro-
gram the entire matrix, and where n = the number of
MAX9675 devices connected in series. This long data
word is structured such that the first bit is the LSB of
the last device in the chain and the last data bit is the
MSB of the first device in the chain. The total length of
the data word is equal to the number of crosspoint
devices to be programmed in series times 96 bits per
crosspoint device. This programming method is most
often used at startup to initially configure the switching
matrix.
Figure 8. Optimal Isolation Resistor vs. Capacitive Load
30
25
20
15
10
5
0
0
OPTIMAL ISOLATION RESISTANCE
100
vs. CAPACITIVE LOAD
CAPACITIVE LOAD (pF)
Complete Matrix Mode (Mode 1)
200
300
400
500
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