SN75LBC784

QUADRUPLE RS-423-B DRIVER/RECEIVER

SLLS187A – NOVEMBER 1994 – REVISED AUGUST 1995

1

POST OFFICE BOX 655303

Resistor

1.5

µs and Receiver Transition Times of

20 ns Typ

Withstand

±25 V

MIL-STD-833C Method 3015

description

The SN75LBC784 performs as four independent

RS-423-B driver/receiver pairs designed to

interface data terminal equipment (DTE) with data

circuit-terminating equipment (DCE) at rates up to

120 kbps and distances to 1.2 km. The

SN75LBC784 provides an upgrade to the RS-232

serial interface and can be backward compatible

with existing serial ports while offering the higher

performance required by new faster peripherals,

such as v.34 (v.fast) modems. The RS-232

standard, and subsequent revisions, only support

data rates up to 20 kbps over about 15 meters of

cable. For RS-423-B the data rate is increased to

120 kbps and transmission distance to 1.2 km by

reducing the maximum output signal swing,

increasing the driver output current, and reducing

the receiver input voltage thresholds.

The receivers consist of differential comparators with hysteresis and resistive attenuation on the inputs. The

resistive attenuation improves the input common mode range and also provides additional protection from ESD

and over-voltage stress. The differential and common mode input impedances are sufficiently high to meet

RS-423-B. When a differential voltage input of 500 mV is applied across the entire common mode range ( see

Figure 5), the receiver characteristics and bias voltage allow the receiver to remain in its intended binary state.

The drivers meet all RS-423-B specifications with built-in current limits and thermal-overload protection.

Slew-rate controlling circuitry is included in the design, which is adjusted to suit the application by means of an

5 V externally, the transistion time defaults to approximately 1.5 ms. The BIAS input, when shorted to 5 V

externally, provides the internal node voltages. The receiver is compatible to RS-232 with the use of external

input resistors to meet the RS-232 input resistance specification of 3 k

Ω to 7 kΩ.

The SN75LBC784 is characterized for operation over the temperature range of 0

°C to 70°C.

LinBiCMOS is a trademark of Texas Instruments Incorporated.

Copyright

© 1995, Texas Instruments Incorporated

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

28

27

26

25

24

23

22

21

20

19

18

17

16

15

3A

3Z

BIAS

4A

4Z

BIAS

GND

4B

4Y

3B

3Y

3C

4C

BIAS

2Z

2A

BIAS

1Z

1A

1Y

1B

2Y

2B

2C

1C

DW PACKAGE

(TOP VIEW)

INPUTS

OUTPUTS

L

H

L

H

FUNCTION TABLE

AB

L

L

H

H

H

H

L

L

H

H

L

L

ZY

H

L

H

L

H = high level,

L = low level,

X = irrelevant,

Z = high impedance (off)

? = indeterminate

L

H

L

H

L

L

H

H

L

L

H

H

?

?

?

?

H

L

H

L

C

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.