DS1487N NSC [National Semiconductor], DS1487N Datasheet - Page 5

• Manufacturer Part Number: DS1487N
• Description: Low Power RS-485 1⁄4 Unit Load Multipoint Transceiver
• Manufacturer: NSC [National Semiconductor]

Pin
#
1
2
3
4
5
6
7
8
Parameter Measurement Information
*Note: Non Terminated, Open Input only
*Note: Non Terminated, Open Input only
Pin Descriptions
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
DS1487 provides a
common mode range of −7V to +12V. This allows up to 128
transceivers (
I/O
NA
I/O
I/O
NA
O
I
I
I
RE (Note 1)
Name
1
GND
V
⁄
RO
4
DE
DI
A
B
CC
unit load) to be connected to the bus. The
1
⁄
4
unit load to the RS-485 bus across the
Receiver Output: If A
be high also if the inputs (A and B) are open (non-terminated).
Receiver Output Enable: RO is enabled when RE (Note 1) is low; RO is in TRI-STATE when RE
(Note 1) is high.
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).
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.
Ground
Non-inverting Driver Output and Receiver Input pin. Driver output levels conform to RS-485 signaling
levels.
Inverting Driver Output and Receiver Input pin. Driver output levels conform to RS-485 signaling
levels.
Power Supply: 4.75V
>
V
B by 200 mV, RO will be high; If A
CC
5.25V
FIGURE 12.
FIGURE 13.
(Continued)
5
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.
Function
<
B by 200 mV, RO will be low. RO will
DS012920-14
DS012920-13
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