ADM1487 AD [Analog Devices], ADM1487 Datasheet - Page 8

• Manufacturer Part Number: ADM1487
• Description: Ultra-Low Power RS-485/RS-422 Transceiver with Low EMI and +/-10kV ESD Protection
• Manufacturer: AD [Analog Devices]

ADM1487
CMOS outout stages, which include parasitic diodes from
their driver outputs to each supply rail and can latch up
when these diodes conduct.
The ADM1487 output includes Schottky diodes in series
with the positive supply to the drain of the P-channel output
device and in series with the drain of the N-channel output
device. These diodes prevent the P-channel's parasitic diode
from conducting when the output voltage exceeds V
prevent the N-channel's parasitic diode from conducting
when the output voltage falls below ground.
SLEW RATE CONTROL
The driver output stage of the ADM1487 has a controlled
slew rate to minmize signal reflections on incorrectly termi-
nated lines and to reduce electromagnetic interference (EMI).
0.21 0 (5. 33 )
0. 16 0 (4.06 )
0. 11 5 (2.93 )
8-Pin Plastic Dual-In-Line Package (N-8)
0. 02 2 (0.5 58 )
0. 01 4 (0.3 56 )
M A X
Figure 9. ADM1487 Driver Output Stage
8
0. 43 0 (10 . 92 )
0. 34 8 (8.84 )
1 4
P IN 1
0.1 0 0
(2 .54 )
B S C
RECEIVER
RECEIVER
V
ENABLE
ENABLE
C C
OUTPUT
DRIVER
0.07 0 (1. 77 )
0.04 5 (1. 15 )
IN (DI)
DATA
5
(RO)
(
(DE)
P A RA S IT IC
0. 28 0 (7.11 )
0. 24 0 (6.10 )
P A RA S ITIC
D IO D E D
0. 06 0 (1. 52 )
0. 01 5 (0. 38 )
DIO DE D
RE V E RS E -BIA S E D
W H E N O UT P UT
PRELIMINARY TECHNICAL DATA
S CH O T T KY
0.1 3 0
(3 .30 )
M IN
> V
S E A TI N G
P L A N E
P
P
1
2
3
4
CC
R E V ER S E -B IAS E D
Figure 10. Typical Half-Duplex RS-485/RS-422 Network
+V
W HE N O U TP U T
ADM1487
D
S C HO TT K Y
< G N D - V
0. 32 5 (8. 25 )
0. 30 0 (7. 62 )
D
R
0. 01 5 (0. 3 81 )
0. 00 8 (0. 2 04 )
D
8
7
6
5
Dimensions shown in inches and (mm).
0. 19 5 (4. 95 )
0. 11 5 (2. 93 )
A
OUTLINE DIMENSIONS
B
R
T
CC
100n
CABLE TERMINATED
and
ADDITIONAL
B
ADM1487s
AT ENDS
+5V
(V
)
A
– 8 –
CC
B
CURRENT LIMIT AND THERMAL SHUTDOWN
The ADM1487 incorporates two protection mechanisms to
guard the drivers against short-circuits, bus contention or
other fault conditions. The first is a current-limited output
stage that protects the driver against short-circuits over the
entire common-mode voltage range by limiting the output
current to about 70mA. Under extreme fault condtions
where the current limit is not effective, a thermal shutdown
circuit puts the driver outputs into a high-impedance state if
the die temperature exceeds 150°C, and does not turn them
back on until the temperature has fallen to 130°C.
ENHANCED ESD PROTECTION
All Analog Devices parts incorporate protection against
electrostatic discharge (ESD) to protect the devices dur-
ing handling, assembly and normal operation. In addition,
the ADM1487 has enhanced ESD protection up to ±10kV
on the A and B I/O pins to protect against severe opera-
tional conditions such as line transients, connection and
disconnection.
APPLICATION INFORMATION
Figure 10 shows a typical application of the ADM1487.
This is a half-duplex RS-485/RS-422 network. Up to 254
additional ADM1487s can be connected along the cable
(termination resistors are only required at each end).
A
0. 00 9 8 (0 .25 )
0. 00 4 0 (0 .10 )
+5V (V
100n
0. 24 4 0 (6 . 20 )
0. 22 8 4 (5 . 80 )
S E A TI N G
CC
PL A N E
R
)
T
5
6
7
8
0. 0 5 00
(1 . 27 )
0. 19 6 8 (5 . 00 )
0. 18 9 0 (4 . 80 )
8 5
1
B S C
ADM1487
8-Pin SO Package (R-8)
P I N 1
R
D
0. 01 9 2 (0 . 49 )
0. 01 3 8 (0 . 35 )
0. 10 2 (2.59 )
0. 09 4 (2.39 )
4
0. 15 7 4 (4 . 00 )
0. 14 9 7 (3 . 80 )
4
3
2
1
0. 00 9 8 (0 .25 )
0. 00 7 5 (0 .19 )
DE
RO
DI
8
0
0. 01 9 6 (0 .50 )
0. 00 9 9 (0 .25 )
0. 05 0 0 (1 .27 )
0. 01 6 0 (0 .41 )
Rev. PrC
x 4 5