LMS1487E
Low Power RS-485 / RS-422 Differential Bus Transceiver
General Description
The LMS1487E is a low power differential bus/line trans-
ceiver designed for high speed bidirectional data communi-
cation on multipoint bus transmission lines. It is designed for
balanced transmission lines. It meets ANSI Standards TIA/
EIA RS422-B, TIA/EIA RS485-A and ITU recommendation
and V.11 and X.27. The driver outputs and receiver inputs
have
15kV ESD protection. The LMS1487E combines a
TRI-STATE
TM
differential line driver and differential input re-
ceiver, both of which operate from a single 5.0V power
supply. The driver and receiver have an active high and
active low, respectively, that can be externally connected to
function as a direction control. The driver outputs and re-
ceiver inputs are internally connected to form a differential
input/output (I/O) bus port that is designed to offer minimum
loading to bus whenever the driver is disabled or when V
CC
= 0V. These ports feature wide positive and negative com-
mon mode voltage ranges, making the device suitable for
multipoint
applications
in
noisy
environments.
The
LMS1487E is available in 8-Pin SOIC and 8-pin DIP pack-
ages. It is a drop-in replacement to Maxim's MAX1487E.
Features
n
Meet ANSI standard RS-485 and RS-422
n
Data rate 2.5 Mbps
n
Single supply voltage operation, 5V
n
Wide input and output voltage range
n
Thermal shutdown protection
n
Short circuit protection
n
Low quiescent current 660A (max)
n
Allows up to 128 transceivers on the bus
n
Open circuit fail-safe for receiver
n
Extended operating temperature range -40C to 85C
n
Drop-in replacement to MAX1487E
n
Available in 8-pin SOIC and 8-pin DIP packages
Applications
n
Low power RS-485 systems
n
Network hubs, bridges, and routers
n
Point of sales equipment (ATM, barcode scanners,...)
n
Local area networks (LAN)
n
Integrated service digital network (ISDN)
n
Industrial programmable logic controllers
n
High speed parallel and serial applications
n
Multipoint applications with noisy environment
Typical Application
20085601
A typical multipoint application is shown in the above figure. Terminating resistor, RT are typically required but only located at the two ends of the cable.
Pull-up and pull-down resistors maybe required at the end of the bus to provide fail-safe biasing. The biasing resistors provide a bias to the cable when all
drivers are in TRI-STATE, See National Application Note, AN-847 for further information.
November 2003
LMS1487E
Low
Power
RS-485
/
RS-422
Differential
Bus
T
ransceiver
2003 National Semiconductor Corporation
DS200856
www.national.com
Connection Diagram
8-Pin SOIC / DIP
20085602
Top View
Truth Table
DRIVER SECTION
RE
*
DE
DI
A
B
X
H
H
H
L
X
H
L
L
H
X
L
X
Z
Z
RECEIVER SECTION
RE
*
DE
A-B
RO
L
L
+0.2V
H
L
L
-0.2V
L
H
X
X
Z
L
L
OPEN
*
H
Note: * = Non Terminated, Open Input only
X = Irrelevant
Z = TRI-STATE
H = High level
L = Low level
LMS1487E
www.national.com
2
Pin Descriptions
Pin # I/O
Name
Function
1
O
RO
Receiver Output: If A
>
B by 200 mV, RO will be high; If A
<
B by 200 mV, RO will be low. RO
will be high also if the inputs (A and B) are open (non-terminated).
2
I
RE
*
Receiver Output Enable: RO is enabled when RE
*
is low; RO is in TRI-STATEwhen RE
*
is high
3
I
DE
Driver Output Enable: The driver outputs (A and B) are enabled when DE is high; they are in
TRI-STATETRI-STATE
when DE is low. Pins A and B also function as the receiver input pins
(see below)
4
I
DI
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
5
NA
GND
Ground
6
I/O
A
Non-inverting Driver Output and Receiver Input pin. Driver output levels conform to RS-485
signaling levels
7
I/O
B
Inverting Driver Output and Receiver Input pin. Driver Output levels conform to RS-485 signaling
levels
8
NA
V
CC
Power Supply: 4.75V
V
CC
5.25V
Ordering Information
Package
Part Number
Package Marking
Transport Media
NSC Drawing
8-Pin SOIC
LMS1487ECM
LMS1487ECM
95 Units/Rail
M08A
LMS1487ECMX
2.5k Units Tape and Reel
LMS1487EIM
LMS1487EIM
95 Units/Rail
LMS1487EIMX
2.5k Units Tape and Reel
8-Pin DIP
LMS1487ECNA
LMS1487ECNA
40 Units/Rail
N08E
LMS1487EINA
LMS1487EINA
40 Units/Rail
LMS1487E
www.national.com
3
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage, V
CC
(Note 2)
6V
Input Voltage, V
IN
(DI, DE, or RE)
-0.3V to V
CC
+ 0.3V
Voltage Range at Bus Terminals (AB)
-7V to 12V
Receiver Output
-0.3V to V
CC
+ 0.3V
Package Thermal Impedance,
JA
SOIC
125 C/W
DIP
92 C/W
Junction Temperature (Note 3)
150C
Operating Free-Air Temperature
Range, T
A
Commercial
0C to 70C
Industrial
-40C to 85C
Storage Temperature Range
-65C to 150C
Soldering Information
Infrared or Convection (20 sec.)
235C
Lead Temperature Range
+260C
ESD Rating (Human Body Model)(Note 4)
Bus Pins
15kV
Other Pins
2kV
ESD Rating (Machine Model)
All Pins
200V
Operating Ratings
Min Nom Max
Supply Voltage, V
CC
4.75
5.0
5.25
V
Voltage at any Bus Terminal
(Separately or Common Mode)
-7
12
V
High-Level Input Voltage, V
IH
(Note 5)
2
V
Low-Level Input Voltage, V
IL
(Note 5)
0.8
V
Differential Input Voltage, V
ID
(Note 6)
12
V
Electrical Characteristics
Over recommended ranges of supply voltage and operating free-air temperature (unless otherwise noted)
Symbol
Parameter
Conditions
Min
Typ
Max
Units
Driver Section
|V
OD1
|
Differential Output Voltage
R =
(Figure 1)
5.25
V
|V
OD2
|
Differential Output Voltage
R = 50
(Figure 1) , RS-422
2.0
V
R = 27
(Figure 1) , RS-485
1.5
5.0
V
OD
Change in Magnitude of
Driver Differential Output
Voltage for Complementary
Output States
R = 27
or 50 (Figure 1) , (Note 7)
0.2
V
V
OC
Common Mode Output
Voltage
R = 27
or 50 (Figure 1)
3.0
V
V
OC
Change in Magnitude of
Driver Common-Mode Output
Voltage for Complementary
Output States
R = 27
or 50 (Figure 1), (Note 7)
0.2
V
V
IH
CMOS Input Logic Threshold
High
DE, DI, RE
2.0
V
V
IL
CMOS Input Logic Threshold
Low
DE, DI, RE
0.8
V
I
IN1
Logic Input Current
DE, DI, RE
2
A
Receiver Section
I
IN2
Input Current (A, B)
DE = 0V, V
CC
= 0V or 5.25V
V
IN
= 12V
0.25
mA
V
IN
= - 7V
-0.2
V
TH
Differential Input Threshold
Voltage
-7V
V
CM
+ 12V
-0.2
+0.2
V
V
TH
Input Hysteresis
(V
TH+-
V
TH-
)
V
CM
= 0
95
mV
V
OH
CMOS High-level Output
Voltage
I
OH
= 4 mA, V
ID
= -200 mV
3.5
V
LMS1487E
www.national.com
4
Electrical Characteristics
(Continued)
Over recommended ranges of supply voltage and operating free-air temperature (unless otherwise noted)
Symbol
Parameter
Conditions
Min
Typ
Max
Units
V
OL
CMOS Low-level Output
Voltage
I
OL
= -4 mA, V
ID
= 200 mV
0.4
V
I
OZR
Tristate Output Leakage
Current
0.4V
V
O
+ 2.4V
1
A
R
IN
Input Resistance
- 7V
V
CM
+12V
48
k
Power Supply Current
I
CC
Supply Current
DE = V
CC,
RE = GND or V
CC
400
660
A
DE = 0V, RE = GND or V
CC
360
560
I
OSD1
Driver Short-circuit Output
Current
V
O
= high, -7V
V
CM
+12V
250
mA
I
OSD2
Driver Short-circuit Output
Current
V
O
= low, - 7V
V
CM
+12V
250
mA
I
OSR
Receiver Short-circuit Output
Current
0 V
V
O
V
CC
95
mA
Switching Characteristics
Driver
T
PLH
,
T
PHL
Propagation Delay Input to
Output
R
L
= 54
, C
L
= 100 pF
10
40
80
ns
T
SKEW
Driver Output Skew
R
L
= 54
, C
L
= 100 pF
5
10
ns
T
R
,
T
F
Driver Rise and Fall Time
R
L
= 54
, C
L
= 100 pF
3
10
40
ns
T
ZH
,
T
ZL
Driver Enable to Ouput Valid
Time
C
L
= 100 pF
25
70
ns
T
HZ
,
T
LZ
Driver Output Disable Time
C
L
= 15 pF
35
70
ns
Receiver
T
PLH
,
T
PHL
Propagation Delay Input to
Output
R
L
= 54
, C
L
= 100 pF
20
90
200
ns
T
SKEW
Receiver Output Skew
R
L
= 54
, C
L
= 100 pF
5
ns
T
ZH
,
T
ZL
Receiver Enable Time
C
L
= 15 pF
20
50
ns
T
HZ
,
T
LZ
Receiver Disable Time
C
L
= 15 pF
20
50
ns
F
MAX
Maximum Data Rate
2.5
Mbps
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics.
Note 2: All voltage values, except differential I/O bus voltage, are with respect to the network ground terminal.
Note 3: The maximum power dissipation is a function of T
J(MAX)
,
JA
, and T
A
. The maximum allowable power dissipation at any ambient temperature, T
A
, is
P
D
= (T
J(MAX)
- T
A
)/
JA
. All numbers apply for packages soldered directly into a PC board.
Note 4: ESD rating based upon human body model, 100 pF discharged through 1.5 k
.
Note 5: Voltage limits apply to DI, DE, RE pins.
Note 6: Differential input/output bus voltage is measured at the non-inverting terminal A with respect to the inverting terminal B.
Note 7: |
V
OD
| and |
V
OC
| are changes in magnitude of V
OD
and V
OC
, respectively when the input changes from high to low levels.
Note 8: Peak current
LMS1487E
www.national.com
5
PDF 
ZIP