NM485SLC
Low Power Isolated EIA-485 Driver and Receiver
KDC_NM485SLC.A03 Page 1 of 5
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FEATURES
RoHS compliant
Site compatible with NM485D
Single 5V supply
Thermal shutdown protection
EIA-485 and CCITT V.10 & V.11 compatible
Differential driver and receiver
Driver tri-state outputs active high enable
Low Profile 24 pin DIL package style
1kVrms Isolation
Thermal shutdown protection
DESCRIPTION
The NM485SLC is a low power electrically iso-
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.
ELECTRICAL CHARACTERISTICS
Parameter Test conditions Min. Typ. Max. Units
Supply voltage, VCC 4.75 5.0 5.25 V
Isolated reference voltage, VREF 5.0
+VREF Current RL=54 25 mA
High level input voltage, VIH D ENABLE, R ENABLE and DIN
2.8 V
Low level input voltage, VIL 0.8 V
Common mode output voltage, VOC
Driver
-7.0 12 V
High level output current IOH -60 mA
Low level output current, IOL 60 mA
Common mode input voltage, VIC
Receiver
±12 V
Differential input voltage, VID ±12 V
High level output current, IOH -5.0 mA
Low level output current, IOL 25 mA
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, VTL VO=0.5V, IO=16mA -0.2 V
Input hysteresis, ∆VT70 mV
High level output voltage, VOH VID=200mV, IOH=-5.0mA 2.7 V
Low level output voltage, VOL VID=-200mV, IOL=25mA 0.8 V
Line input current, II
Other input at 0V, VI=12V 1.0 mA
Other input at 0V, VI=-7.0V -0.8
Short circuit output current, IOS 85 mA
Input resistance, RI12 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 150 180 ns
Propagation delay time H to L, TPHL 130 150 ns
Output disable time from high level CL=15pF 90 150 ns
Output disable time from low level CL=15pF 90 150 ns
Output enable time to high level CL=15pF 130 150 ns
Output enable time to low level CL=15pF 80 150 ns
RECEIVER FUNCTION TABLE
Differential inputs A-B R ENABLE ROUT
VID≥0.2V Low level High level
-0.2V<VID<+0.2V Low level Undefined
VID≤-0.2V Low level Low level
Irrelevant High level High level
ISOLATION CHARACTERISTICS
Parameter Conditions Min. Typ. Max. Units
Isolation test voltage Flash tested for 1 second 1000 Vrms
Isolation capacitance 40 pF
ABSOLUTE MAXIMUM RATINGS
Supply voltage VCC with respect to pin 11 7V
Input voltage D ENABLE, R ENABLE and DIN 7V
Receiver differential input voltage range -14V to +14V
Output voltage range, driver -14V to +14V
Power dissipation 1000mW
Data transmission rate 2.5Mbps
Lead temperature 1.5mm from case for 10 seconds 300ºC
All data taken at TA=25°C, VCC=5V.
NM485SLC
Low Power Isolated EIA-485 Driver and Receiver
KDC_NM485SLC.A03 Page 2 of 5
www.murata-ps.com/support
DRIVER ELECTRICAL CHARACTERISTICS
Parameter Test conditions Min. Typ. Max. Units
High level output voltage, VOH IOH=-25mA 3.7 V
Low level output voltage, VOL IOH=25mA 1.1 V
Differential output voltage, VOD1 IO=0 1.5 6.0 V
Differential output voltage, VOD2
RL=100 2.0 V
RL=54 1.5 5.0 V
Change in magnitude of differential output voltage, ∆VOD
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, ∆VOC ±0.2 V
Output current power off, IOVCC=0, VO=-7.0V to 12V ±100 µA
High level input current, IIH VIH=4.0V 2.0 20 µA
Low level input current, IIL VIL=0.8V -8.0 -15 mA
Short circuit output current, IOS
VO=-7.0V1-250 mA
VO=12V1250 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, TPHZ RL=110, CL=50pF 70 120 ns
Output disable time from low level, TPLZ RL=110, CL=50pF 60 120 ns
Propagation delay time L to H, TPLH RL=27, CL=50pF 80 150 ns
Propagation delay time H to L, TPHL 80 150 ns
Differential output transition time, TTD RL=54, CL=50pF 150 300 ns
Output enable time to high level, TPZH RL=110, CL=50pF 80 120 ns
Output enable time to low level, TPZL RL=110, CL=50pF 80 120 ns
DRIVER FUNCTION TABLE
DIN D ENABLE DY Output DZ 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 070ºC
Storage temperature range -40 125 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.
NM485SLC
Low Power Isolated EIA-485 Driver and Receiver
KDC_NM485SLC.A03 Page 3 of 5
www.murata-ps.com/support
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 120, 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 RB receive to the inverting DZ drive and the non-inverting RA receive to the non-inverting
DY 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
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NM485SLC
Low Power Isolated EIA-485 Driver and Receiver
KDC_NM485SLC.A03 Page 4 of 5
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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.
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.
Figure 3
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NM485SLC
Low Power Isolated EIA-485 Driver and Receiver
KDC_NM485SLC.A03 Page 5 of 5
www.murata-ps.com/support
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
notice. © 2012 Murata Power Solutions, Inc.
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/
PACKAGE SPECIFICATIONS
MECHANICAL DIMENSIONS
PIN CONNECTIONS RECOMMENDED FOOTPRINT
Pin Function Description
1R
OUT Receiver number output TTL logic
2 R ENABLE Receiver ENABLE (low)
3V
CC +5V supply
4 NC No Internal Connection
5 D ENABLE Driver ENABLE (High)
6D
IN Driver input TTL logic
7-10 NC No Internal Connection
11 GND Ground
12-13 NC No Internal Connection
14 VREF Isolated +5V output
15 NC No Internal Connection
16 ISO GND Isolated ground TUBE OUTLINE DIMENSIONS
17-18 NC No Internal Connection
19 DZDriver differential inverting output
20 DYDriver differential non-inverting output
21-22 NC No Internal Connection
23 RAReceiver differential non-inverting input
24 RBReceiver differential inverting input
1.28 (32.60) MAX
0.58
(14.72)
0.3 (7.60)
MAX
0.1 (2.54)
0.6673
(16.95) MAX
0.012 (0.30)
0.008 (0.20)
0.16
(4.10)
0.02 (0.002)
0.50 (0.005)
1.1 (27.94)
NM485SLC
XYYWW
Weight: 5.0g
All pins on a 0.1 (2.54) pitch.
All dimensions are in inches ±0.01 (mm ±0.25).
All dimensions are in inches ±0.01 (mm ±0.25) Tube Quantity : 15
All dimensions are in inches ±0.01 (mm ±0.25)
