lated differential driver and receiver designed for
bi-directional data communication or multipoint
bus transmission at rates up to 2.5Mbits per
second. The device combines a tri-state dif-
ferential line driver and a differential input line
receiver. The driver and receiver have active high
and active low enables, respectively, which can
be connected together to function as direction
control. The receiver features a high output state
when the inputs are left open. Thermal shutdown
protection forces the driver into a high imped-
ance state, under line fault conditions. No external
components are needed as a single 5V supply
powers all functions either side of the isolation
boundary. The device is supplied in a low profile
24 pin plastic package.
Parameter
Propagation delay time L to H, T
PLH
Propagation delay time H to L, T
PHL
Output disable time from high level
Output disable time from low level
Output enable time to high level
Output enable time to low level
Test conditions
V
ID
=-1.5V to 1.5V, C
L
=15pF
C
L
=15pF
C
L
=15pF
C
L
=15pF
C
L
=15pF
Min.
Typ.
150
130
90
90
130
80
Max.
180
150
150
150
150
150
Units
ns
ns
ns
ns
ns
ns
RECEIVER FUNCTION TABLE
Differential inputs A-B
V
ID
≥0.2V
-0.2V<V
ID
<+0.2V
V
ID
≤-0.2V
Irrelevant
R ENABLE
Low level
Low level
Low level
High level
R
OUT
High level
Undefined
Low level
High level
ISOLATION CHARACTERISTICS
Parameter
Isolation test voltage
Isolation capacitance
Conditions
Flash tested for 1 second
Min.
1000
Typ.
40
Max.
Units
Vrms
pF
ABSOLUTE MAXIMUM RATINGS
Supply voltage V
CC
with respect to pin 11
Input voltage D ENABLE, R ENABLE and D
IN
Receiver differential input voltage range
Output voltage range, driver
Power dissipation
Data transmission rate
Lead temperature 1.5mm from case for 10 seconds
All data taken at T
A
=25°C, V
CC
=5V.
7V
7V
-14V to +14V
-14V to +14V
1000mW
2.5Mbps
300ºC
For full details go to
www.murata-ps.com/rohs
www.murata-ps.com/support
KDC_NM485SLC.A05
Page 1 of 5
NM485SLC
Low Power Isolated EIA-485 Driver and Receiver
DRIVER ELECTRICAL CHARACTERISTICS
Parameter
High level output voltage, V
OH
Low level output voltage, V
OL
Differential output voltage, V
OD1
Differential output voltage, V
OD2
Change in magnitude of differential output voltage, ΔV
OD
Common mode output voltage, ΔV
OC
Change in magnitude of common mode output voltage, ΔV
OC
Output current power off, I
O
High level input current, I
IH
Low level input current, I
IL
Short circuit output current, I
OS
Test conditions
I
OH
=-25mA
I
OH
=25mA
I
O
=0
R
L
=100Ω
R
L
=54Ω
R
L
=54Ω or 100Ω
V
CC
=0, V
O
=-7.0V to 12V
V
IH
=4.0V
V
IL
=0.8V
V
O
=-7.0V
1
V
O
=12V
1
Min.
Typ.
3.7
1.1
Max.
Units
V
V
V
V
V
V
V
V
μA
μA
mA
mA
mA
1.5
2.0
1.5
-1.0
6.0
5.0
±0.2
3.0
±0.2
±100
20
-15
-250
250
2.0
-8.0
DRIVER SWITCHING CHARACTERISTICS
Parameter
Differential output delay time, T
DD
Output disable time from high level, T
PHZ
Output disable time from low level, T
PLZ
Propagation delay time L to H, T
PLH
Propagation delay time H to L, T
PHL
Differential output transition time, T
TD
Output enable time to high level, T
PZH
Output enable time to low level, T
PZL
Test conditions
R
L
=54Ω, C
L
=50pF
R
L
=110Ω, C
L
=50pF
R
L
=110Ω, C
L
=50pF
R
L
=27Ω, C
L
=50pF
R
L
=54Ω, C
L
=50pF
R
L
=110Ω, C
L
=50pF
R
L
=110Ω, C
L
=50pF
Min.
Typ.
20
70
60
80
80
150
80
80
Max.
25
120
120
150
150
300
120
120
Units
ns
ns
ns
ns
ns
ns
ns
ns
DRIVER FUNCTION TABLE
D
IN
High level
Low level
Irrelevant
D ENABLE
High level
High level
Low level
D
Y
Output
High level
Low level
High impedance
D
Z
Output
Low level
High level
High impedance
TEMPERATURE CHARACTERISTICS
Parameter
Operating free-air temperature range
Storage temperature range
Min.
0
-40
Typ.
Max.
70
125
Units
ºC
ºC
RoHS COMPLIANCE INFORMATION
This series is compatible with RoHS soldering systems with a peak wave solder temperature of 300ºC
for 10 seconds. The pin termination finish on this product series is Matte Tin over Nickel Preplate. The
series is backward compatible with Sn/Pb soldering systems.
For further information, please visit www.murata-ps.com/rohs
1. Duration of short circuit should not exceed 1 second.
www.murata-ps.com/support
KDC_NM485SLC.A05
Page 2 of 5
NM485SLC
Low Power Isolated EIA-485 Driver and Receiver
APPLICATION NOTES
The increased use of balanced data transmission lines, (distributing data to several system components and peripherals over relatively long lines) has brought about the need for
multiple driver/receiver combinations on a single twisted pair line. This resulted in an upgraded version of EIA RS-422, named EIA-485. EIA-485 takes into account EIA RS-422
requirements for balanced line data transmission, and allows for multiple drivers and receivers.
The NM485SLC is a low power isolated differential interface providing EIA-485 compatibility. The use of a differential communications interface such as the NM485SLC allows
data transmission at high rates and over long distances to be accomplished. This is because effects of external noise sources and cross talk are much less pronounced on
the data signal. Any external noise source coupling onto the differential lines will appear as an extra common mode voltage which the receiver is insensitive to. The difference
between the signal levels on the two lines will therefore remain the same. Similarly a change in the local ground potential at one end of the line will appear as just another change
in the common mode voltage level of the signals. Twisted pair cable is commonly used for differential communications since its twisted nature tends to cause cancellation of the
magnetic fields generated by the current flowing through each wire, thus reducing the effective inductance of the pair.
Computer and industrial serial interfacing are areas where noise can seriously affect the integrity of data transfer, and a proven route to improve noise performance for any
interface system is galvanic isolation. Galvanic isolation removes the ground loop currents from data lines and hence the impressed noise voltage which affects the signal is also
eliminated. The isolation feature of the NM485SLC also means that common mode noise effects are removed and many forms of radiated noise are reduced to negligible limits.
The NM485SLC has driver thermal shutdown protection which protects the device from line fault conditions. If the outputs of the driver are accidently shorted to a power supply
or low impedance source, up to 250mA can flow through the part. The thermal shutdown circuit disables the driver output when the internal temperature of the I.C. reaches 150ºC
and turns it back on when the temperature cools to 130ºC. If two or more NM485SLCs are used and drivers are shorted directly, the driver outputs can not supply enough current
to activate the thermal shutdown. Thus the internal shutdown circuit will not prevent contention faults when two drivers are active on the same bus at the same time.
Figure 1 demonstrates how the differential lines of the NM485SLC can be connected to form a transceiver. Data direction is controlled by the driver enable and receiver enable
pins. This means the device can receive when the receiver enable is low and transmit when the driver enable is high. As the driver is active high, to reduce the power dissipation
even further, it is advisable to disable the driver when not transmitting data.
Some data encoding schemes require the output of the receiver to maintain a known state, usually a logic 1, when the data transmission is complete and all drivers are forced
into three-state, high impedance.
The NM485SLC receiver has a fail safe feature which guarantees the output to be in a logic 1 state when the receiver inputs are left floating (open circuit). However, when the
cable is terminated with 120Ω, the differential inputs to the receiver are shorted together, not left floating. Since the receiver has about 70mV hysteresis, the output will maintain
the last bit received.
Implementing an isolated LONWORKS
(
™
)
network using the NM485SLC
The Echleon LONWORKS (Local Operating Network) network is designed to be used in industrial applications in which other electrical 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 NM485SLC is a fully isolated EIA-485 standard 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 NM485SLC can be operated at transmitting or receiving data rates of up to 2.5Mbps, hence is fully compatible with the
LONTALK
(
™
)
transmission rate standards.
Configuring the NM485SLC as a transceiver
The NM485SLC is configured as a transceiver simply by connecting the inverting R
B
receive to the inverting D
Z
drive and the non-inverting R
A
receive to the non-inverting
D
Y
drive. The data direction is determined by the driver enable pins (D ENABLE and R ENABLE), the transceiver acting as a transmitter when the enable pin is high and a
receiver when the enable pin is low.
Figure 1
www.murata-ps.com/support
KDC_NM485SLC.A05
Page 3 of 5
NM485SLC
Low Power Isolated EIA-485 Driver and Receiver
APPLICATION NOTES (continued)
System Performance
The EIA-485 standard allows a maximum of 32 unit loads to be connected to the network, this is less than the LONWORKS standard of 64 nodes. A unit load is any single
driver, receiver or transceiver in the EIA-485 standard, or any single node under the LONWORKS scheme. Similarly the EIA-485 standard specifies a maximum data rate
standard of 10Mbps, whereas the maximum LONWORKS data rate standard is 1.25Mbps. The resultant maximum system performance for the LONWORKS EIA-485 con-
figuration is therefore 32 nodes at 1.25Mbps. The NM485SLC isolated serial interface device supports this configuration, as well as any lower specified system.
The EIA-485 standard defines the maximum line length as a function of data rate (in Mbps). This implies that the user must choose between the line length of the network
and its maximum data transmission rate.
The isolated interface has been used in previous configurations (e.g. NM232D) to increase the available line length as isolated data lines are much less susceptible to
ground currents and variations in local supplies. The feature of isolation in a LON environment is intended to be used primarily to improve noise susceptibility, therefore,
unless the line length improvements can be reliably demonstrated by the user, the EIA-485 recommendations on maximum cable length are assumed to apply.
The complete hardware implementation for the LONWORKS EIA-485 network is relatively straight forward (see figure 2). There is a minimum of components required,
only 1 interface part and one resistor, and the complete LONTALK transmission protocols are supported. The isolation barrier of 1000Vrms offers improved noise immunity
compared to a non-isolated system and eliminates node-to-node supply voltage mismatch and possible ground current loops.
Figure 2
Figure 3
TECHNICAL NOTES
ISOLATION VOLTAGE
‘Hi Pot Test’, ‘Flash Tested’, ‘Withstand Voltage’, ‘Proof Voltage’, ‘Dielectric Withstand Voltage’ & ‘Isolation Test Voltage’ are all terms that relate to the same thing, a test voltage,
applied for a specified time, across a component designed to provide electrical isolation, to verify the integrity of that isolation.
Murata Power Solutions NM485SLC series of DC/DC converters are all 100% production tested at their stated isolation voltage. This is 1000Vrms for 1 second.
A question commonly asked is, “What is the continuous voltage that can be applied across the part in normal operation?”
For a part holding no specific agency approvals, such as the NM485SLC series, both input and output should normally be maintained within SELV limits i.e. less than 42.4V peak,
or 60VDC. The isolation test voltage represents a measure of immunity to transient voltages and the part should never be used as an element of a safety isolation system. The part
could be expected to function correctly with several hundred volts offset applied continuously across the isolation barrier; but then the circuitry on both sides of the barrier must
be regarded as operating at an unsafe voltage and further isolation/insulation systems must form a barrier between these circuits and any user-accessible circuitry according to
safety standard requirements.
REPEATED HIGH-VOLTAGE ISOLATION TESTING
It is well known that repeated high-voltage isolation testing of a barrier component can actually degrade isolation capability, to a lesser or greater degree depending on materials,
construction and environment. The NM485SLC series has toroidal isolation transformers, with no additional insulation between primary and secondary windings of enameled wire.
While parts can be expected to withstand several times the stated test voltage, the isolation capability does depend on the wire insulation. Any material, including this enamel
(typically polyurethane) is susceptible to eventual chemical degradation when subject to very high applied voltages thus implying that the number of tests should be strictly limited.
We therefore strongly advise against repeated high voltage isolation testing, but if it is absolutely required, that the voltage be reduced by 20% from specified test voltage. This
consideration equally applies to agency recognized parts rated for better than functional isolation where the wire enamel insulation is always supplemented by a further insulation
system of physical spacing or barriers.
www.murata-ps.com/support
KDC_NM485SLC.A05
Page 4 of 5
NM485SLC
Low Power Isolated EIA-485 Driver and Receiver
PACKAGE SPECIFICATIONS
MECHANICAL DIMENSIONS
1.28 (32.60) MAX
NM485SLC
0.58
(14.72)
XYYWW
0.3 (7.60)
MAX
0.1 (2.54)
0.02 (0.002)
0.50 (0.005)
1.1 (27.94)
0.16
(4.10)
0.012 (0.30)
0.008 (0.20)
0.6673
(16.95) MAX
Weight: 5.0g
All pins on a 0.1 (2.54) pitch.
All dimensions are in inches ±0.01 (mm ±0.25).
PIN CONNECTIONS
Pin
1
2
3
4
5
6
7-10
11
12-13
14
15
16
17-18
19
20
21-22
23
24
Function
R
OUT
R ENABLE
V
CC
NC
D ENABLE
D
IN
NC
GND
NC
V
REF
NC
ISO GND
NC
D
Z
D
Y
NC
R
A
R
B
Description
Receiver number output TTL logic
Receiver ENABLE (low)
+5V supply
No Internal Connection
Driver ENABLE (High)
Driver input TTL logic
No Internal Connection
Ground
No Internal Connection
Isolated +5V output
No Internal Connection
Isolated ground
No Internal Connection
Driver differential inverting output
Driver differential non-inverting output
No Internal Connection
Receiver differential non-inverting input
Receiver differential inverting input
RECOMMENDED FOOTPRINT
All dimensions are in inches ±0.01 (mm ±0.25)
TUBE OUTLINE DIMENSIONS
All dimensions are in inches ±0.01 (mm ±0.25)
Tube Quantity : 15
Murata Power Solutions, Inc.
11 Cabot Boulevard, Mansfield, MA 02048-1151 U.S.A.
ISO 9001 and 14001 REGISTERED
This product is subject to the following
operating requirements
and the
Life and Safety Critical Application Sales Policy:
Refer to:
http://www.murata-ps.com/requirements/
Murata Power Solutions, Inc. makes no representation that the use of its products in the circuits described herein, or the use of other
technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein do not imply
the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifications are subject to change without
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