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| NM485DC Isolated Dual EIA-485 Driver and Receiver ELECTRICAL CHARACTERISTICS Parameter Supply voltage, VCC High level input voltage, VIH Low level input voltage, VIL Common mode output voltage, VOC High level output current IOH Low level output current, IOL Common mode input voltage, VIC Differential input voltage, VID High level output current, IOH Low level output current, IOL Test conditions DX ENABLE and D inputs Min. 4.75 2.8 -7.0 Typ. 5.0 Max. 5.25 0.8 12 -60 60 12 12 -5.0 25 Units V V V V mA mA V V mA mA Driver Receiver 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 EACH RECEIVER ELECTRICAL CHARACTERISTICS Parameter High threshold differential input, VTH Low threshold differential input, VTL Input hysteresis, VT High level output voltage, VOH Low level output voltage, VOL Line input current, II Short circuit output current, IOS Input resistance, RI Test conditions VO=2.7V, IO=-0.4mA VO=0.5V, IO=16mA VID=200mV, IOH=-5.0mA VID=200mV, IOL=25mA Other input at 0V, VI=12V Other input at 0V, VI=-12V Min. -0.2 Typ. Max. 0.2 Units V V mV V V mA mA mA K 50 2.7 0.8 1.0 -0.8 -15 12 DESCRIPTION The NM485DC is an electrically isolated dual differential driver and receiver designed for balanced 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 conditions 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. RECEIVER SWITCHING CHARACTERISTICS Parameter Propagation delay time L to H, TPLH Propagation delay time H to L, TPHL Test conditions VID=-1.5V to 1.5V, CL=15pF Min. Typ. 70 72 Max. 155 135 Units ns ns RECEIVER FUNCTION TABLE Differential inputs A-B VID0.2V -0.2V High level Undefined Low level ISOLATION CHARACTERISTICS Parameter Isolation test voltage Conditions Flash tested for 1 second Min. 1000 Typ. Max. Units Vrms ABSOLUTE MAXIMUM RATINGS Supply voltage VCC with respect to pin 11 Input voltage DX ENABLE and D inputs Input voltage range, receiver A or B inputs Receiver differential input voltage range Output voltage range, driver Power dissipation Isolation capacitance Isolation voltage (flash tested for 1 second) Data transmission rate Lead temperature 1.5mm from case for 10 seconds All data taken at TA=25C, VCC=5V. 7V 7V -25V to +25V -25V to +25V -10V to +15V 2000mW 40pF 1000Vrms 1.25Mbps 300C For full details go to www.murata-ps.com/rohs www.murata-ps.com Technical enquiries - email: mk@murata-ps.com, tel: +44 (0)1908 615232 KII_NM485DC.A02 Page 1 of 7 NM485DC Isolated Dual EIA-485 Driver and Receiver EACH DRIVER ELECTRICAL CHARACTERISTICS Parameter High level output voltage, VOH Low level output voltage, VOL Differential output voltage, VOD1 Differential output voltage, VOD2 Change in magnitude of differential output voltage, VOD Common mode output voltage, VOC Change in magnitude of common mode output voltage, VOC Output current power off, IO High level input current, IIH Low level input current, IIL Short circuit output current, IOS Test conditions IOH=-33mA IOH=33mA IO=0 RL=100 RL=54 RL=54 or 100 VCC=0, VO=-7.0V to 12V VIH=4.0V VIL=0.8V VO=-7.0V1 VO=12V1 Min. Typ. 3.7 1.1 Max. Units V V V V V V V V A A 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 DRIVER SWITCHING CHARACTERISTICS Parameter Differential output delay time, TDD Output disable time from high level, TPHZ Output disable time from low level, TPLZ Propagation delay time L to H, TPLH Propagation delay time H to L, TPHL Differential output transition time, TTD Output enable time to high level, TPZH Output enable time to low level, TPZL Test conditions RL=54, CL=50pF RL=110, CL=50pF RL=110, CL=50pF RL=27, CL=50pF RL=54, CL=50pF RL=110, CL=50pF RL=110, CL=50pF Min. Typ. 20 90 30 70 70 150 80 40 Max. 25 120 45 145 145 300 120 60 Units ns ns ns ns ns ns ns ns DRIVER FUNCTION TABLE DXIN High level Low level Irrelevant DX ENABLE High level High level Low level DXY Output High level Low level High impedance DXZ Output Low level High level High impedance TEMPERATURE CHARACTERISTICS Parameter Operating free-air temperature range Storage temperature range 1. Duration of short circuit should not exceed 1 second. Min. 0 -40 Typ. Max. 60 125 Units C C www.murata-ps.com Technical enquiries - email: mk@murata-ps.com, tel: +44 (0)1908 615232 KII_NM485DC.A02 Page 2 of 7 NM485DC Isolated Dual EIA-485 Driver and Receiver 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 boundary. 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 (TM) 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 multipoint (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 (TM) transmission rate standards. Figure 1 Figure 2 Configuring the NM485D as a transceiver The NM485D is configured as a transceiver simply by connecting the inverting R1B receive to the inverting D1Z drive and the non-inverting R1A receive to the non-inverting D1Y drive, similarly R2B 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 enable pins (DX 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). Figure 3 www.murata-ps.com Technical enquiries - email: mk@murata-ps.com, tel: +44 (0)1908 615232 KII_NM485DC.A02 Page 3 of 7 NM485DC Isolated Dual 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 configuration is therefore 32 nodes at 1.25Mbps. The NM485D isolated serial interface devices 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 simple and straight forward (see figure 5). 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. If protection from voltage transients is required, then a bi-directional TransZorb from each line side to ground should be connected (see figure 6). A TransZorb with a breakdown voltage higher than the common-mode voltage required should be used. However the added parasitic capacitance will load down the bus, and should therefore be taken into consideration. Figure 4 Figure 5 Figure 6 www.murata-ps.com Technical enquiries - email: mk@murata-ps.com, tel: +44 (0)1908 615232 KII_NM485DC.A02 Page 4 of 7 NM485DC Isolated Dual EIA-485 Driver and Receiver APPLICATION NOTES (continued) NM485D receiver output status The receiver output will be high (>2.7V) when the differential input lines are left open (open circuit). However, when a line termination resistor is attached, the inputs are effectively shorted together, not left floating. Since the receiver has typically 70mV of hysteresis, the output will remain in its last active state, high or low. To force the receiver output to a known state, the configuration shown in figure 7 should be used. It should be noted that this arrangement will use typically 100mW of power, for each receiver connected in this manner. The termination resistors are used to generate a DC bias, which forces the receiver into a high state, when no signal is applied. This arrangement will still allow the output to switch due to a change at the input, whilst maintaining line termination characteristics. 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 NM485DC 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 NM485DC 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 NM485DC 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. RoHS COMPLIANCE INFORMATION This series is compatible with RoHS soldering systems with a peak wave solder temperature of 300C 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 www.murata-ps.com Technical enquiries - email: mk@murata-ps.com, tel: +44 (0)1908 615232 KII_NM485DC.A02 Page 5 of 7 NM485DC Isolated Dual EIA-485 Driver and Receiver PACKAGE SPECIFICATIONS MECHANICAL DIMENSIONS 1.28 (32.60) MAX 0.58 (14.72) NM485DC 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: 5.9g All pins on a 0.1 (2.54) pitch. All dimensions are in inches (mm) 0.01 (0.25). PIN CONNECTIONS Pin 1 2 3 4 5 6 7 8 9 10 11 12-15 16 17 18 19 20 21 22 23 24 Function R1OUT NC VCC R2OUT D1 ENABLE D1IN NC D2 ENABLE D2IN NC GND NC ISO GND D2Y D2Z D1Z D1Y R2B R2A R1A R1B Description Receiver number 1 output TTL logic No internal connection +5V supply Receiver number 2 output TTL logic Driver no.1 ENABLE Driver no.1 input TTL logic No Internal Connection Driver number 2 ENABLE Driver number 2 input TTL logic No Internal Connection Ground No Internal Connection Isolated ground Driver number 2 differential non-inverting output Driver number 2 differential output Driver number 1 differential inverting output Driver number 1 differential non-inverting output Receiver number 2 differential inverting input Receiver number 2 differential non-inverting input Receiver number 1 differential non-inverting input Receiver number 1 differential inverting input RECOMMENDED FOOTPRINT All dimensions are in inches (mm) 0.01 (0.25) TUBE OUTLINE DIMENSIONS All dimensions are in inches (mm) 0.01 (0.25) Tube Quantity : 15 www.murata-ps.com Technical enquiries - email: mk@murata-ps.com, tel: +44 (0)1908 615232 KII_NM485DC.A02 Page 6 of 7 NM485DC Isolated Dual EIA-485 Driver and Receiver USA: UK: France: Japan: Tucson (Az), Tel: (800) 547 2537, email: sales@murata-ps.com Milton Keynes, Tel: +44 (0)1908 615232, email: mk@murata-ps.com Montigny Le Bretonneux, Tel: +33 (0)1 34 60 01 01, email: france@murata-ps.com Tokyo, Tel: 3-3779-1031, email: sales_tokyo@murata-ps.com Osaka, Tel: 6-6354-2025, email: sales_osaka@murata-ps.com Website: www.murata-ps.jp Shanghai, Tel: +86 215 027 3678, email: shanghai@murata-ps.com Guangzhou, Tel: +86 208 221 8066, email: guangzhou@murata-ps.com Canada: Toronto, Tel: (866) 740 1232, email: toronto@murata-ps.com Murata Power Solutions, Inc. 11 Cabot Boulevard, Mansfield, MA 02048-1151 U.S.A. Tel: (508) 339-3000 (800) 233-2765 Fax: (508) 339-6356 www.murata-ps.com email: sales@murata-ps.com ISO 9001 REGISTERED 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. (c) 2008 Murata Power Solutions, Inc. Germany: Munchen, Tel: +49 (0)89-544334-0, email: munich@murata-ps.com China: www.murata-ps.com Technical enquiries - email: mk@murata-ps.com, tel: +44 (0)1908 615232 KII_NM485DC.A02 Page 7 of 7 |
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