TABLE 1. Device Pin Descriptions

Pin

No.

Name

Description

1

RO

Receiver Output: When RE (Receiver Enable) is LOW, the receiver is enabled (ON), if DO/RI

≥ DO

(Note 1)/RI (Note 1) by 200 mV, RO will be HIGH. If DO/RI

≤ DO (Note 1)/RI (Note 1) by 200 mV,

RO will be LOW. Additionally RO will be HIGH for OPEN (Non-terminated) Inputs.

2RE

(Note 1)

Receiver Output Enable: When RE (Note 1) is LOW the receiver output is enabled. When RE (Note

1) is HIGH, the receiver output is in TRI-STATE (OFF). When RE (Note 1) is HIGH and DE is LOW,

the device will enter a low-current sleep mode after 600 ns.

3

DE

Driver Output Enable: When DE is HIGH, the driver outputs are enabled. When DE is LOW, the

driver outputs are in TRI-STATE (OFF). When RE (Note 1) is HIGH and DE is LOW, the device will

enter a low-current sleep mode after 600 ns.

4

DI

Driver Input: When DE (Driver Enable) is HIGH, the driver is enabled, if DI is LOW, then DO/RI will

be LOW and DO (Note 1)/RI (Note 1) will be HIGH. If DI is HIGH, then DO/RI is HIGH and DO

(Note 1)/RI (Note 1) is LOW.

5

GND

Ground Connection.

6

DO/RI

Driver Output/Receiver Input, 485 Bus Pin.

7DO

(Note 1)

/RI

(Note 1)

Driver Output/Receiver Input, 485 Bus Pin.

8V

CC

Positive Power Supply Connection: Recommended operating range for V

Unit Load

A unit load for an RS-485 receiver is defined by the input cur-

rent versus the input voltage curve. The gray shaded region

is the defined operating range from −7V to +12V. The top

border extending from −3V at 0 mA to +12V at +1 mA is de-

fined as one unit load. Likewise, the bottom border extending

from +5V at 0 mA to −7V at −0.8 mA is also defined as one

unit load (see

Figure 15 ). An RS-485 driver is capable of

driving up to 32 unit loads. This allows up to 32 nodes on a

single bus. Although sufficient for many applications, it is

sometimes desirable to have even more nodes.

available. These devices will allow up to 64 nodes or 128

nodes guaranteed over temperature depending upon which

perature.

Figure 15 are scaled. Both 0 mA reference points at +5V and

−3V stay the same. The other reference points are +12V at

+0.5 mA for the top border and −7V at −0.4 mA for the bot-

tom border (see

top and bottom borders shown in

Figure 15 are scaled also.

Again, both 0 mA reference points at +5V and −3V stay the

same. The other reference points are +12V at +0.25 mA for

the top border and −7V at −0.2 mA for the bottom border

(see

Figure 15 ).

creased number of nodes on one bus. In a single master

DS012919-15

*Note: Non Terminated, Open Input only

FIGURE 14. Entering Sleep Mode Conditions (modes and exit parameters shown)

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