Audio off-isolation is -85dB at 20kHz, crosstalk is
-85dB at 20kHz, and video off-isolation is -62dB at
10MHz. The SA, SB, and SC (shunt) inputs further
improve off-isolation, allowing for the addition of exter-
nal shunt capacitors to connect the outputs to AC
grounds. When using the bias resistors, MID_ inputs
improve crosstalk by providing an AC ground at the
common bias points. Resistance from the bias points to
the inputs allows AC signals to pass through the device
and improve crosstalk performance (refer to the
Functional Diagram
). These devices feature a clickless
operation mode for noiseless audio switching. Use the
serial interface to select the clickless or standard-
switching mode for each individual output.
Applications Information
The MAX4548/MAX4549 are divided into five functional
blocks: the control-logic block, three switch-matrix
blocks, and the bias-resistor block (see
Functional
Diagram
). The control-logic block accepts commands
through the serial interface and uses those commands
to control the four remaining blocks.
MAX4548/MAX4549
Serially Controlled, Triple 3x2 Audio/Video
Crosspoint Switches
12 ______________________________________________________________________________________
COM2BC3
COM1BC2
COM2AC1
COM1AC0
COM1CC4
COM2CC5
BIT
BiasC6
Clickless ModeC7
REGISTER
Table 1. Command-Byte Format
Controls the switch connected to S_;
1 = close switch, 0 = open switch.
Controls the switch connected to NO3_;
1 = close switch, 0 = open switch.
Controls the switch connected to NO2_;
1 = close switch, 0 = open switch.
Controls the switch connected to NO1_;
1 = close switch, 0 = open switch.
Don’t care
Don’t care
DESCRIPTION
Don’t care
Don’t care
1D3
0D2
0D1
0D0
—D4
—D5
BIT
—D6
—D7
POWER-UP
DEFAULT
STATE
Table 2. COM Data-Byte Format
(C0, C1, C2, C3, C4, C5 = “1”)
