National Semiconductor LMS1487 Technical data
LMS1487
5V Low Power RS-485 / RS-422 Differential Bus
Transceiver
LMS1487 5V Low Power RS-485 / RS-422 Differential Bus Transceiver
April 2003
General Description
The LMS1487 is a low power differential bus/line transceiver
designed for high speed bidirectional data communication 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 LMS1487 combines a TRI-STATE
differential line driver and differential input receiver, 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 and receiver differential inputs
are internally connected to form differential input/output (I/O)
bus ports that are designed to offer minimum loading to bus
whenever the driver is disabled or when V
ports feature wide positive and negative common mode
voltage ranges, making the device suitable for multipoint
applications in noisy environments. The LMS1487 is available in a 8-Pin SOIC and 8-pin DIP packages. It is a drop-in
socket replacement to Maxim’s MAX1487
= 0V. These
CC
Typical Application
Features
n Meet ANSI standard RS-485-A and RS-422-B
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 320µA
n Allows up to 128 transceivers on the bus
n Open circuit fail-safe for receiver
n Extended operating temperature range −40˚C to 85˚C
n Drop-in replacement to MAX1487
n Available in 8-pin SOIC and 8-pin DIP package
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
A Typical multipoint application is shown in the above figure. Terminating resistors, 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.
© 2003 National Semiconductor Corporation DS200530 www.national.com
20053001
Connection Diagram
LMS1487
Truth Table
DRIVER SECTION
RECEIVER SECTION
8-Pin SOIC / DIP
Top View
RE
XHHHL
XHL LH
XLXZZ
RE
LL ≥ +0.2V H
LL ≤ −0.2V L
HX X Z
L L OPEN
DE DI A B
DE A-B RO
20053002
*
H
Note:*= Non Terminated, Open Input only
X = Irrelevant
Z = TRI-STATE
H = High level
L = Low level
Pin Descriptions
Pin#I/O Name Function
1 O RO Receiver Output: If A
will be high also if the inputs (A and B) are open (non-terminated
2I RE
3 I DE Driver Output Enable: The driver outputs (A and B) are enabled when DE is high; they are in
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
5 N/A GND Ground
6 I/O A Non-inverting Driver Output and Receiver Input pin. Driver Output levels conform to RS-485
7 I/O B Inverting Driver Output and Receiver Input pin. Driver Output levels conform to RS-485 signaling
8 N/A V
CC
Receiver Output Enable: RO is enabled when RE is low; RO is in TRI-STATE when RE is high
TRI-STATE when DE is low. Pins A and B also function as the receiver input pins (see below)
when the driver is enabled
signaling levels
levels
Power Supply: 4.75V ≤ VCC≤ 5.25V
>
B by 200 mV, RO will be high; If A<B by 200mV, RO will be low. RO
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Ordering Information
Package Part Number Package Marking Transport Media NSC Drawing
8-Pin SOIC
8-Pin DIP
LMS1487CM
LMS1487CMX 2.5k Units Tape and Reel
LMS1487IM
LMS1487IMX 2.5k Units Tape and Reel
LMS1487CNA LMS1487CNA 40 Units/Rail
LMS1487INA LMS1487INA 40 Units/Rail
LMS1487CM
LMS1487IM
95 Units/Rail
95 Units/Rail
LMS1487
M08A
N08E
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Absolute Maximum Ratings (Note 1)
ESD Rating (Note 4) 7kV
If Military/Aerospace specified devices are required,
LMS1487
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage, V
Input Voltage, V
(Note 2) 7V
CC
(DI, DE, or RE) −0.3V to VCC+ 0.3V
IN
Voltage Range at Any Bus Terminal
(AB) −7V to 12V
Receiver Outputs −0.3V to V
Package Thermal Impedance, θ
JA
CC
+ 0.3V
SOIC 125˚C/W
DIP 88˚C/W
Junction Temperature (Note 3) 150˚C
Operating Free-Air Temperature
Range, T
A
Commercial 0˚C to 70˚C
Industrial −40˚C to 85˚C
Storage Temperature Range −65˚C to 150˚C
Soldering Information
Infrared or Convection (20 sec.) 235˚C
Lead Temperature 260˚C
Operating Ratings
Supply Voltage, V
Voltage at any Bus Terminal
(Separately or Common Mode)
V
or V
IN
IC
High-Level Input Voltage, V
(Note 5)
Low-Level Input Voltage, V
(Note 5)
Differential Input Voltage, V
(Note 6)
High-Level Output
Driver, I
Receiver, I
Low-Level Output
Driver, I
Receiver, I
CC
OH
OH
OL
OL
Min Nom Max
4.75 5.0 5.25 V
−7 12 V
IH
IL
ID
2V
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
| Differential Output Voltage R =∞(Figure 1) 5.25 V
OD1
|V
| Differential Output Voltage R = 50Ω (Figure 1) ,RS-422 2.0 V
OD2
R=27Ω (Figure 1) ,RS-485 1.5 5.0
∆V
OD
V
OC
∆V
OC
V
IH
V
IL
I
IN1
Receiver Section
I
IN2
V
TH
Change in Magnitude of
R=27Ω or 50Ω (Figure 1) , (Note 7) 0.2 V
Driver Differential Output
Voltage for Complementary
Output States
Common-Mode Output
R=27Ω or 50Ω (Figure 1) 3.0
Voltage
Change in Magnitude of
R=27Ω or 50Ω (Figure 1), (Note 7) 0.2 V
Driver Common-Mode Output
Voltage for Complementary
Output States
CMOS Inout Logic Threshold
DE, DI, RE 2.0 V
High
CMOS Input Logic Threshold
DE, DI, RE 0.8
Low
Logic Input Current DE, DI, RE
Input Current (A, B) DE = 0V, VCC= 0V or 5.25V
= 12V
V
IN
V
= − 7V −0.2
IN
Differential Input Threshold
−7V ≤ VCM≤ + 12V −0.2 +0.2
Voltage
±
2µA
0.25 mA
0.8 V
±
12 V
−150 mA
−42 mA
80 mA
26 mA
V
V
V
∆V
TH
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Input Hysteresis Voltage
(V
TH+−VTH−
)
V
= 0 95 mV
CM
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