10

LTC1346A

LTC485

7V TO – 7V

GND POTENTIAL DIFFERENCE

5V

100

Ω

100

Ω

AA

B

B

GND

LTC1346A • F09

LTC1346A

5V

GND

TTL

IN

TTL

OUT

–5V

–+

Figure 9. RS422/RS485 Receiver Interface

LTC1346 • F10

RECEIVER

OUTPUT

5V/DIV

A

B

–10V

–5V

0V

0V

5V

RECEIVER

INPUT

5V/DIV

RECEIVER

OUTPUT

5V/DIV

15V

5V

0V

LTC1346 • F11

10V

5V

0V

A

B

RECEIVER

INPUT

5V/DIV

Figure 10. – 7V Common Mode

Figure 11. 12V Common Mode

Multiprotocol Application

The LTC1346A can be used in multiprotocol applications

where V.35, RS232 and RS422 (used in RS530, RS449

among others) signals may appear at the same port. The

LTC1346A switched current source driver is not compat-

ible with RS232 or RS422. However, the outputs when

disabled can share lines with RS232 drivers with a shut-

down feature such as the LT1030 and RS422 drivers with

a disable feature such as the LTC486/LTC487 (Figure 12a).

The LTC1346A driver will not be damaged or load the

shared lines when disabled. The LTC1346A receiver can

receive V.35, RS232 and RS422 signals as shown in Figure

12b. The LTC1346A receiver is directly compatible with

V.35 and RS422. For RS232 signal, the noninverting input

of the receiver should be grounded. Because the line

termination for each of the protocols is different, some

form of termination switching should be included, either

the connector (as shown in Figures 12a and 12b) or on the

PCB.