DS36C278TM/NOPB National Semiconductor, DS36C278TM/NOPB Datasheet - Page 7

• Manufacturer Part Number: DS36C278TM/NOPB
• Description: IC TRANSCEIVER EIA LP 8-SOIC
• Manufacturer: National Semiconductor
• Type: Transceiverr

Specifications of DS36C278TM/NOPB

• Number Of Drivers/receivers: 1/1
• Protocol: RS485
• Voltage - Supply: 4.75 V ~ 5.25 V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Number Of Receivers: 1
• Number Of Transmitters: 1
• Number Of Transceivers: 1
• Data Transmission Topology: Multipoint
• Receiver Signal Type: Differential
• Transmitter Signal Type: Differential
• Single Supply Voltage (typ): 5V
• Single Supply Voltage (min): 4.75V
• Single Supply Voltage (max): 5.25V
• Dual Supply Voltage (typ): Not RequiredV
• Dual Supply Voltage (min): Not RequiredV
• Dual Supply Voltage (max): Not RequiredV
• Supply Current: 0.5mA
• Power Supply Requirement: Single
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 8
• Package Type: SOIC N
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: *DS36C278TM; *DS36C278TM/NOPB; DS36C278TM

Typical Application Information
Unit Load
A unit load for an RS-485 receiver is defined by the input
current 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
defined as one unit load. Likewise, the bottom border ex-
tending from +5V at 0 mA to −7V at −0.8 mA is also defined
as one unit load (see Figure 18 ). 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 applica-
tions, it is sometimes desirable to have even more nodes.
For example, an aircraft that has 32 rows with 4 seats per
row would benefit from having 128 nodes on one bus. This
would allow signals to be transferred to and from each
individual seat to 1 main station. Usually there is one or two
less seats in the last row of the aircraft near the restrooms
and food storage area. This frees the node for the main
station.
The DS36C278, the DS36C279, and the DS36C280 all have
devices will allow up to 64 nodes or 128 nodes guaranteed
over temperature depending upon which option is selected.
The
the
1
⁄
No.
Pin
2
1
2
3
4
5
6
7
8
unit load and
1
1
⁄
4
⁄
2
UL is available in commercial temperature.
UL option is available in industrial temperature and
DO*/RI*
DO/RI
Name
GND
V
RE*
RO
DE
DI
CC
1
⁄
4
unit load (UL) options available. These
Receiver Output: When RE (Receiver Enable) is LOW, the receiver is enabled (ON), if DO/RI ≥ DO*/RI*
by 200 mV, RO will be HIGH. If DO/RI ≤ DO*/RI* by 200 mV, RO will be LOW. Additionally RO will be
HIGH for OPEN (Non-terminated) Inputs.
Receiver Output Enable: When RE* is LOW the receiver output is enabled. When RE* is HIGH, the
receiver output is in TRI-STATE (OFF).
Driver Output Enable: When DE is HIGH, the driver outputs are enabled. When DE is LOW, the driver
outputs are in TRI-STATE (OFF).
Driver Input: When DE (Driver Enable) is HIGH, the driver is enabled, if DI is LOW, then DO/RI will be
LOW and DO*/RI* will be HIGH. If DI is HIGH, then DO/RI is HIGH and DO*/RI* is LOW.
Ground Connection.
Driver Output/Receiver Input, 485 Bus Pin.
Driver Output/Receiver Input, 485 Bus Pin.
Positive Power Supply Connection: Recommended operating range for V
FIGURE 17. Typical RS-485 Bus Interface
TABLE 1. Device Pin Descriptions
7
First, for a
Figure 18 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
bottom border (see Figure 18 ). Second, for a
the top and bottom borders shown in Figure 18 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 18 ).
The advantage of the
increased number of nodes on one bus. In a single master
multi-slave type of application where the number of slaves
exceeds 32, the DS36C278/279/280 may save in the cost of
extra devices like repeaters, extra media like cable, and/or
extra components like resistors.
The DS36C279 and DS36C280 have an additional feature
which offers more advantages. The DS36C279 has an au-
tomatic sleep mode function for power conscious applica-
tions. The DS36C280 has a slew rate control for EMI con-
scious applications. Refer to the sleep mode and slew rate
control portion of the application information section in the
corresponding datasheet for more information on these
features.
Description
1
⁄
2
UL device the top and bottom borders shown in
1
⁄
2
UL and
CC
is +4.75V to +5.25V.
1
⁄
4
UL devices is the
1
⁄
4
01204017
www.national.com
UL device