DS36C280TM National Semiconductor, DS36C280TM Datasheet - Page 7

• Manufacturer Part Number: DS36C280TM
• Description: BUS TRANSCEIVER RS485, SMD, 36C280
• Manufacturer: National Semiconductor

Specifications of DS36C280TM

• Supply Voltage Range: 4.75V To 5.25V
• Digital Ic Case Style: SOIC
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +85°C
• Svhc: No SVHC (15-Dec-2010)
• Operating Temperature Max: 85°C
• Operating: RoHS Compliant
• Base Number: 36
• Ic Generic Number: 36C280
• Rohs Compliant: Yes

Typical Application Information
Unit Load
A unit load for a 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 ). A RS-485 driver is capable
of driving up to 32 unit loads. This allows upto 32 nodes on
a single bus. Although sufficient for many applications, it is
sometime desirable to have even more nodes. For example
an aircraft that has 32 rows with 4 seats per row could
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 upto 64 nodes or 128 nodes guaranteed
over temperature depending upon which option is selected.
The
the
First, for a
Figure 18 are scaled. Both 0 mA reference points at +5V and
Pin
1
⁄
#
1
2
3
4
5
6
7
8
2
unit load and
1
1
⁄
4
⁄
2
UL is available in commercial temperature.
UL option is available in industrial temperature and
RO
SR
DE/RE*
DI
GND
DO/RI
DO*/RI*
V
Name
CC
1
⁄
2
UL device the top and bottom borders shown in
1
⁄
4
Receiver Output: When DE/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.
Slew Rate Control: A resistor connected to Ground controls the Driver Output rising and falling edge rates.
Combined Driver and Receiver Output Enable: When signal is LOW the receiver output is enabled and the
driver outputs are in TRI-STATE (OFF). When signaI is HlGH, the receiver output is in TRI-STATE (OFF)
and the driver outputs are enabled.
Driver Input: When DE/RE* is HlGH, 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
unit load (UL) options available. These
FIGURE 17. Typical Pin Connection
TABLE 1. Device Pin Descriptions
7
−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 were 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 addition feature which
offer more advantages. The DS36C279 has an automatic
sleep mode function for power conscious applications. The
DS36C280 has a slew rate control for EMI conscious appli-
cations. Refer to the sleep mode and slew rate control
portion of the application information section in the corre-
sponding datasheet for more information on these features.
Description
01205217
1
⁄
2
CC
UL and
is +4.75V to +5.25V.
1
⁄
4
UL devices is the
1
⁄
4
www.national.com
UL device