MAX4549 Maxim, MAX4549 Datasheet - Page 12

• Manufacturer Part Number: MAX4549
• Description: The MAX4548/MAX4549 serial-interface, programmable, triple 3x2 audio/video crosspoint switches are ideal for multimedia applications
• Manufacturer: Maxim

Serially Controlled, Triple 3x2 Audio/Video
Crosspoint Switches
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.
12
Figure 4. 2-Wire Serial-Interface Timing Diagram (“WriteWord’’)
Table 1. Command-Byte Format
Figure 3. 2-Wire Serial-Interface Timing Diagram (“WriteByte’’)
______________________________________________________________________________________
BIT
C7
C6
C5
C4
C3
C2
C1
C0
SDA
SCL
SCL
SDA
SRT
Clickless Mode
Bias
COM2C
COM1C
COM2B
COM1B
COM2A
COM1A
A7
SRT
A7
REGISTER
A0
ACK
C7
A0
ACK
C7
C0
ACK
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.
Table 2. COM Data-Byte Format
(C0, C1, C2, C3, C4, C5 = “1”)
BIT
D15
D7
D6
D5
D4
D3
D2
D1
D0
C0
ACK
Don’t care
Don’t care
Don’t care
Don’t care
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.
D7
D8
Applications Information
ACK
DESCRIPTION
D7
D0
ACK
D0
STOP
ACK
STOP
POWER-UP
DEFAULT
STATE
—
—
—
—
1
0
0
0