Two-Channel, Triple/Quad

RGB Video Switches and Buffers

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11

When LE is connected to ground, the E

—

N

–

register is

transparent and independent of C

—

S

–

activity. This allows

all MAX463–MAX466 devices to be simultaneously shut

down, regardless of the C

—

S

–

input state. Simply connect

LE to ground and connect all E

—

N

–

inputs together (Figure

5a). For the MAX464 and MAX466, LE must be hard-

wired to either V+ or ground (rather than driving LE with

a gate) to prevent crosstalk from the digital inputs to

IN0A.

Another option for output disable is to connect LE to V+,

parallel the outputs of several MAX463-MAX466s, and use

E

—

N

–

to individually disable all devices but the one in use

(Figure 5b).

When the outputs are disabled, the off isolation from

the analog inputs to the amplifier outputs is typically

wave and a 150

Ω load impedance. Figure 6 shows the

test circuits used to measure isolation and crosstalk.

Table 1a. Amplifier and Channel Selection

with LE = V+

Table 1b. Amplifier and Channel Selection

with LE = GND

Disables amplifiers. Outputs high-Z.

A0 register = channel B

1

1

0

Disables amplifiers. Outputs high-Z.

X

1

1

Enables amplifier outputs, latches A0

register, programs outputs to output A

or B, according to the setting of A0 at

C

—

S

–

's last edge.

X

0

1

Disables amplifiers. Outputs high-Z.

A0 register = channel A

0

1

0

Enables amplifier outputs.

Selects channel B.

1

0

0

Enables amplifier outputs.

Selects channel A.

0

0

0

FUNCTION

A0

E

—

N

–

C

—

S

–

Latches all input registers.

Changes nothing.

Enables amplifier outputs.

Selects channel B.

Enables amplifier outputs.

Selects channel A.

X

X

1

Disables amplifiers. Outputs high-Z.

X

1

0

1

0

0

0

0

0

FUNCTION

A0

E

—

N

–

C

—

S

–

MAX463–

MAX466

MAX463–

MAX466

MAX463–

MAX466

MAX463–

MAX466

SHUTDOWN

LE

LE

EN

EN

CS

EN

+5V

+5V

AO

LE

EN

CS

AO

LE

(a)

(b)

Figure 5. (a) Simultaneous Shutdown of all MAX463–MAX466, (b) Enable (

–

E

—

N

–

) Register Latched by

–

C

—

S

–

NOTE: ISOLATION RESISTORS,

IF REQUIRED, NOT SHOWN.