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NM485DC

P1-P3P4-P6
NM485DC Series
Isolated Dual EIA-485 Driver and Receiver
KII_NM485DC.A07 Page 1 of 6
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ELECTRICAL CHARACTERISTICS
Parameter Test conditions Min. Typ. Max. Units
Supply voltage, VCC 4.75 5.0 5.25 V
High level input voltage, V
IH
DX ENABLE and D inputs
2.8 V
Low level input voltage, V
IL 0.8 V
Common mode output voltage, VOC
Driver
-7.0 12 V
High level output current IOH -60 mA
Low level output current, I
OL 60 mA
Common mode input voltage, V
IC
Receiver
±12 V
Differential input voltage, VID ±12 V
High level output current, I
OH -5.0 mA
Low level output current, I
OL 25 mA
EACH RECEIVER ELECTRICAL CHARACTERISTICS
Parameter Test conditions Min. Typ. Max. Units
High threshold differential input, VTH VO=2.7V, IO=-0.4mA 0.2 V
Low threshold differential input, V
TL VO=0.5V, IO=16mA -0.2 V
Input hysteresis, ∆V
T 50 mV
High level output voltage, V
OH VID=200mV, IOH=-5.0mA 2.7 V
Low level output voltage, V
OL VID=200mV, IOL=25mA 0.8 V
Line input current, I
I
Other input at 0V, VI=12V 1.0 mA
Other input at 0V, V
I=-12V -0.8 mA
Short circuit output current, I
OS -15 mA
Input resistance, R
I 12 KΩ
RECEIVER SWITCHING CHARACTERISTICS
Parameter Test conditions Min. Typ. Max. Units
Propagation delay time L to H, TPLH VID=-1.5V to 1.5V, CL=15pF 70 155 ns
Propagation delay time H to L, T
PHL 72 135 ns
RECEIVER FUNCTION TABLE
Differential inputs A-B RXOUT
VID≥0.2V High level
-0.2V<V
ID<+0.2V Undefined
V
ID≤-0.2V Low level
ISOLATION CHARACTERISTICS
Parameter Conditions Min. Typ. Max. Units
Isolation test voltage Flash tested for 1 second 1000 Vrms
ABSOLUTE MAXIMUM RATINGS
Supply voltage VCC with respect to pin 11 7V
Input voltage D
X ENABLE and D inputs 7V
Input voltage range, receiver A or B inputs -25V to +25V
Receiver differential input voltage range -25V to +25V
Output voltage range, driver -10V to +15V
Power dissipation 2000mW
Isolation capacitance 40pF
Isolation voltage (flash tested for 1 second) 1000Vrms
Data transmission rate 1.25Mbps
Lead temperature 1.5mm from case for 10 seconds 300ºC
All data taken at TA=25°C, VCC=5V.
FEATURES
RoHS compliant
Single 5V supply
Thermal shutdown protection
EIA-485 and CCITT V.28 compatible
Dual differential driver and receiver
Driver tri-state outputs active high enable
Low Profile 24 pin DIL package style
1kVrms Isolation
DESCRIPTION
The NM485DC is an electrically isolated dual
differential driver and receiver designed for bal-
anced mulipoint bus transmission at rates up to
1.25Mbits per second. The device provides two
receive channels and two driver channels. The
two driver channels have an active high enable.
No external components are needed and a single
5V input supply powers all functions either side of
the isolation boundary. The driver outputs provide
limiting for positive and negative currents and
thermal shutdown protection from line fault condi-
tions on the transmission bus line. The receiver
outputs will always be high if the receiver inputs
are open. The isolation voltage between input and
output is 1000Vrms, the devices are supplied in a
low profile 24 pin DIL plastic package.
NM485DC Series
Isolated Dual EIA-485 Driver and Receiver
KII_NM485DC.A07 Page 2 of 6
www.murata-ps.com/support
EACH DRIVER ELECTRICAL CHARACTERISTICS
Parameter Test conditions Min. Typ. Max.
Units
High level output voltage, VOH IOH=-33mA 3.7
V
Low level output voltage, V
OL IOH=33mA 1.1 V
Differential output voltage, V
OD1 IO=0 1.5 6.0 V
Differential output voltage, V
OD2
RL=100 2.0 V
RL=54 1.5 5.0 V
Change in magnitude of differential output voltage, ∆V
OD
RL=54 or 100
±0.2 V
Common mode output voltage, ∆VOC -1.0 3.0 V
Change in magnitude of common mode output voltage, ∆V
OC ±0.2 V
Output current power off, I
O VCC=0, VO=-7.0V to 12V ±100 µA
High level input current, I
IH VIH=4.0V 2.0 20 µA
Low level input current, I
IL VIL=0.8V -15 mA
Short circuit output current, I
OS
VO=-7.0V
1
-250 mA
V
O=12V
1
250 mA
DRIVER SWITCHING CHARACTERISTICS
Parameter Test conditions Min. Typ. Max. Units
Differential output delay time, TDD RL=54, CL=50pF 20 25 ns
Output disable time from high level, T
PHZ RL=110, CL=50pF 90 120 ns
Output disable time from low level, T
PLZ RL=110, CL=50pF 30 45 ns
Propagation delay time L to H, T
PLH
RL=27, CL=50pF
70 145 ns
Propagation delay time H to L, T
PHL 70 145 ns
Differential output transition time, T
TD RL=54, CL=50pF 150 300 ns
Output enable time to high level, T
PZH RL=110, CL=50pF 80 120 ns
Output enable time to low level, T
PZL RL=110, CL=50pF 40 60 ns
DRIVER FUNCTION TABLE
DXIN DX ENABLE DXY Output DXZ Output
High level High level High level Low level
Low level High level Low level High level
Irrelevant Low level High impedance High impedance
TEMPERATURE CHARACTERISTICS
Parameter Min. Typ. Max. Units
Operating free-air temperature range 060ºC
Storage temperature range -40 125 ºC
1. Duration of short circuit should not exceed 1 second.
NM485DC Series
Isolated Dual EIA-485 Driver and Receiver
KII_NM485DC.A07 Page 3 of 6
www.murata-ps.com/support
APPLICATION NOTES
The EIA-485 standard is an upgrade version of the EIA RS-422 standard. The use of balanced data transmission lines in distributing data to several systems components
and peripherals over relatively long lines, requires the use of multiple driver/receiver combinations on a single twisted pair line. This is referred to as a party-line (see
figure 1).
The NM485DC is an isolated interface device providing EIA-485 compatibility. A single supply provides all necessary power for the device, either side of the isolation bound-
ary. The isolation feature allows the logic and differential grounds to be isolated from each other, eliminating ground loop current and inherently long noise paths.
The maximum number of drivers and receivers that may be placed on a single communication bus depends upon their loading characteristics, relative to the definition of
a Unit Load (U.L.), transmission speed does not affect the unit load capability. As the NM485DC complies with the EIA-485 standard a maximum of 32 unit loads per line is
recommended. A unit load usually consists of a driver-receiver pair, but not the line termination resistors.
With only a 5V supply connected, the NM485DC receiver and differential outputs give levels greater than +2.7V and ±1.5V respectively. This known output state may be
used as a reference for use in environments with considerable levels of noise. An unused driver should be disabled by grounding it’s enable pin to reduce power dissipation.
Figure 2 illustrates the way one receiver and one driver of the NM485DC may be connected to implement an isolated EIA-485 interface with a typical UART and processor
bus. Figure 3 demonstrates how the NM485DC may be used as a transceiver. This is possible by using the driver enable to determine the data direction. For example, the
device could receive when the driver enable is low and transmit when it is high.
Precise circuitry will depend on the application and in particular the use of the control lines shown will need to be altered to suit the situation. For instance the maximum
sychronous baud rate of the 8251A is 64kbps, whereas the NM485DC had a maximum baud rate of 1.25Mbps.
Implementing an isolated LONWORKS
(
™
)
network using the
NM485DC
The Echleon LONWORKS (Local Operating Network) network
is designed to be used in industrial applications in which other
eletrical equipment is operated. Often the LON
(R)
will be the
method of controlling machinery or sensing machine activity.
The environment is therefore likely to be electrically noisy and
to reduce the possibility of data corruption, an isolated network
communications system is a preferred method of data transfer.
The EIA-485 standard provides a method of achieving multi-
point (multi-drop) data transmission over balanced twisted
pair transmission lines. The standard is a differential scheme
offering a large degree of common mode immunity compared
to single ended schemes. The isolated differential method offers
the highest common mode and line noise immunity for wire
based systems.
The NM485DC is a fully isolated EIA-485 standard dual driver
and receiver, which requires only a single 5V supply. The
device offers full data direction programming and can hence be
configured as a transceiver. The NM485DC can be operated at
transmitting or receiving data rates of up to 1.25Mbps, hence
is fully compatible with the LONTALK
(
™
)
transmission rate
standards.
Configuring the NM485D as a transceiver
The NM485D is configured as a transceiver simply by con-
necting the inverting R1
B receive to the inverting D1Z drive and
the non-inverting R1
A receive to the non-inverting D1Y drive,
similarly R2
B to D2Z and R2A to D2Y for the second transceiver
(see figure 3), in this way the NM485D is configured as a dual
transceiver. The data direction is determined by the driver en-
able pins (D
X ENABLE), the transceiver acting as a transmitter
when the enable pin is high and a receiver when the enable pin
is low.
If only a single transceiver is required it is recommended that
the second transceiver driver is disabled, this reduces the power
consumption to around 0.6W. The second driver is disabled by
taking the driver enable pin low, this should be via a pull-down
resistor (recommend value is 1K).
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Figure 2
Figure 3
P1-P3P4-P6

NM485DC

Mfr. #:
Buy NM485DC
Manufacturer:
Murata Power Solutions
Description:
RS-485 Interface IC 24pin DIL 5V supply Driver and Receiver
Lifecycle:
New from this manufacturer.
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