LT6553

6

6553i

TYPICAL APPLICATIO

RGB Buffer Demo Board

The DC714 Demo Board illustrates optimal routing, by-

passing and termination using the LT6553 as an RGB

video buffer. The schematic is shown in Figure 1. All inputs

and outputs are routed to have a characteristic impedance

of 75

Ω and 75Ω shunt and series terminations are con-

nected as close to the part as possible. For ideal operation,

a 75

Ω shunt termination should be connected at the

output. The LT6553’s gain of 2 will compensate for the

resulting divider between the series and shunt termination

resistors.

A fourth signal trace is provided at the bottom of the

board with dimensions identical to the combined input

and output of the other channels. This trace can be used

for calibrating out the effects of electrical delay and

impedance mismatching and is not necessary in an end-

user application. Several jumpers and additional connec-

tors are also included to allow for testing of the enable

feature and single supply operation.

RGB Video Selector/Cable Driver

A video multiplexer can be implemented using the EN pins

of parallel LT6553s as shown in Figure 2. In this applica-

tion, all outputs are connected together and one LT6553 is

switched on while the other is switched off. A fast inverter

is used to ensure that only one set of R, G and B channels

is buffered at any time. As shown, the outputs are con-

nected before the 75

Ω series termination resistors in

order to reduce any DC attenuation that may result from

the non-infinite output impedance of the disabled LT6553.

Figure 1. DC714 Demo Board Schematic

J4

BANANA JACK

10

11

12

13

14

15

16

R6

75

Ω

R5

75

Ω

R4

75

Ω

R1

75

Ω

R2

75

Ω

R3

75

Ω

Z = 75

Z = 75

Z = 75

Z = 75

C1

4700pF

9

INB

AGND

ING

AGND

INR

DGND

EN

8

7

6

5

4

3

2

1

OUTB

OUTG

OUTR

U1

LT6553CGN

6553 F01

C2

470pF

C3

4700pF

C4

10

µF, 16V

1210

J2

BANANA JACK

J9

5

1

OUTR

4

3

2

C5

470pF

DUAL

SINGLE

C6

1000pF

C7

470pF

C8

4700pF

C9

10

µF, 16V

1210

J10

5

J12

BNC

NOTE 5

BNC x3

5

1

CAL

4

3

2

1

OUTG

4

3

2

J11

5

1

OUTB

4

3

2

J8

BNC

5

1

J3

BANANA JACK

E3

AGND

E1

EN

E2

DGND

CAL

AGND

4

3

2

13

2

JP3

SUPPLY

ENABLE

EXT

3

1 2

JP1

CONTROL

J5

5

1

INR

4

3

2

J6

5

BNC

× 3

1

ING

4

3

2

J7

5

1

Z = 75

Z = 75

Z = 75

INB

4

3

2

AGND

FLOAT

3

1 2

JP2

DGND

J1

50

Ω BNC

EN

5432

1