7

LTC1344

Figure 6. Typical V.11 Interface

Z

Z

Z

S1

ON

S2

OFF

124

Ω

LTC1344

V.11

RECEIVER

A

B

C

1344 F07

51.5

Ω

51.5

Ω

–3V

3V

10V

–10V

– 3.25mA

3.25mA

Figure 7. V.11 Interface Using the LTC1344

V.28 (RS232) Termination

A typical V.28 unbalanced interface is shown in Figure 8.

A V.28 single-ended generator output A with ground C is

connected to a single-ended receiver with inputs A

nected to A, ground C

ground to C. The V.28 standard requires a 5k terminating

resistor to ground which is included in almost all compli-

ant receivers as shown in Figure 9. Because the termina-

tion is included in the receiver, both switches S1 and S2 in

the LTC1344 are turned off.

A

CABLE

TERMINATION

LOAD

GENERATOR

BALANCED

INTERCONNECTING

CABLE

RECEIVER

A

'

CC

'

1344 F08

Figure 8. Typical V.28 Interface

S1

OFF

S2

OFF

124

Ω

LTC1344

V.28

RECEIVER

A

B

C

1344 F09

51.5

Ω

51.5

Ω

5k

Figure 9. V.28 Interface Using the LTC1344

V.35 Termination

A typical V.35 balanced interface is shown in Figure 10. A

V.35 differential generator with outputs A and B with

ground C is connected to a differential receiver with

ground C

V.35 interface requires a T-network termination at the

receiver end and the generator end. In V.35 mode both

switches S1 and S2 in the LTC1344 are turned on as

shown in Figure 11.

The differential impedance measured at the connector

must be 100

Ω ±10Ω and the impedance between shorted

terminals A

Ω ±15Ω. The

input impedance of the V.35 receiver is connected in

parallel with the T-network inside the LTC1344, which can

cause the overall impedance to fail the specification on the

A

CABLE

TERMINATION

LOAD

GENERATOR

BALANCED

INTERCONNECTING

CABLE

RECEIVER

A

'

BB

'

C

'

C

100

Ω

MIN

1344 F06