Pin Descriptions

Pin

#

I/O

Name

Function

1

O

RO

be high also if the inputs (A and B) are open (non-terminated).

2

I

RE (Note 1)

Receiver Output Enable: RO is enabled when RE (Note 1) is low; RO is in TRI-STATE when RE

(Note 1) is high.

3

I

DE

Driver Output Enable: The driver outputs (A and B) are enabled when DE is high; they are in

TRI-STATE when DE is low. Pins A and B also function as the receiver input pins (see below).

4

I

DI

Driver Input: A low on DI forces A low and B high while a high on DI forces A high and B low when

the driver is enabled.

5

NA

GND

Ground

6

I/O

A

Non-inverting Driver Output and Receiver Input pin. Driver output levels conform to RS-485 signaling

levels.

7

I/O

B

Inverting Driver Output and Receiver Input pin. Driver output levels conform to RS-485 signaling

levels.

8NA

V

CC

Power Supply: 4.75V

≤ V

Applications Information

The DS1487 is a low power transceiver designed for use in

RS-485 multipoint applications. The DS1487 can transmit

data up to 2.0 Mbps based on a ratio of driver transition time

to the unit interval (bit time) of 10%. This maximum data rate

may be further limited by the interconnecting media. The

common mode range of −7V to +12V. This allows up to 128

DS1487 also guarantees the driver’s output differential volt-

age into a worst case load that models standard termination

loads and 32 unit loads (=128 DS1487’s) referenced to the

maximum common mode voltage extremes. With a minimum

of 1.5V swing into this load, a 1.3V differential noise margin

is supported along with the standard common mode rejec-

tion range of the receivers.

DS012920-13

*Note: Non Terminated, Open Input only

FIGURE 12.

DS012920-14

*Note: Non Terminated, Open Input only

FIGURE 13.

www.national.com

5