a EIA RS-485 Transceiver 5 V Low Power ADM1485

1 REV. aADM14855 V Low PowerEIA RS-485 TransceiverOne Technology Way, Box 9106, Norwood, MA 02062-9106, : 781/329-4700 : analog Devices, Inc. All rights furnished by analog Devices is believed to be accurate andreliable. However, no responsibility is assumed by analog Devices for itsuse, nor for any infringements of patents or other rights of third parties thatmay result from its use. No license is granted by implication or otherwiseunder any patent or patent rights of analog Devices. Trademarks andregistered trademarks are the property of their respective BLOCK DIAGRAM8-LeadADM1485 RDROREDIVCCBAGNDDEFEATURESM eets EIA RS-485 Standard30 Mbps Data RateSingle 5 V Supply 7 V to +12 V Bus Common-Mode RangeHigh Speed, Low Power BiCMOST hermal Shutdown ProtectionShort-Circuit ProtectionDriver Propagation Delay: 10 nsReceiver Propagation Delay.

2 15 nsHigh-Z Outputs with Power OffSuperior Upgrade for LTC1485 APPLICATIONSLow Power RS-485 SystemsDTE-DCE InterfacePacket SwitchingLocal Area NetworksData ConcentrationData MultiplexersIntegrated Services Digital Network (ISDN)GENERAL DESCRIPTIONThe ADM1485 is a differential line Transceiver suitable for highspeed bidirectional data communication on multipoint bus trans-mission lines. It is designed for balanced data transmission andcomplies with both RS-485 and RS-422 EIA Standards. The partcontains a differential line driver and a differential line the driver and the receiver may be enabled disabled, the outputs are ADM1485 operates from a single 5 V Power supply.

3 Excessivepower dissipation caused by bus contention or by output shortingis prevented by a thermal shutdown circuit. This feature forcesthe driver output into a high impedance state if, during fault condi-tions, a significant temperature increase is detected in the internaldriver to 32 transceivers may be connected simultaneously on a bus,but only one driver should be enabled at any time. It is important,therefore, that the remaining disabled drivers do not load the ensure this, the ADM1485 driver features high outputimpedance when disabled and also when powered minimizes the loading effect when the Transceiver is not beingused.

4 The high impedance driver output is maintained over theentire common-mode voltage range from 7 V to +12 receiver contains a fail-safe feature that results in a logichigh output state if the inputs are unconnected (floating).The ADM1485 is fabricated on BiCMOS, an advanced mixedtechnology process combining low Power CMOS with fastswitching bipolar technology. All inputs and outputs containprotection against ESD; all driver outputs feature high sourceand sink current capability. An epitaxial layer is used to guardagainst part is fully specified over the commercial and industrialtemperature range and is available in PDIP, SOIC, and smallMSOP 'The ADM1485 features extremely fast switching speeds.

5 Minimal driver propagation delays permit transmission at typical data rates of 30 Mbps while low skew minimizes EMI interference. REV. 2 ADM1485 SPECIFICATIONS(VCC = 5 V 5%. All specifications TMIN to TMAX, unless otherwise noted.)ParameterMin TypMaxUnit Test Conditions/CommentsDRIVERD ifferential Output Voltage, = , Test Circuit = 5 V, R = 50 (RS-422), Test Circuit = 27 ( RS-485 ), Test Circuit = 7 V to +12 V, Test Circuit 2 |VOD| for Complementary Output = 27 or 50 , Test Circuit 1 Common-Mode Output Voltage VOC3VR = 27 or 50 , Test Circuit 1 |VOD| for Complementary Output = 27 or 50 Output Short-Circuit Current (VOUT = High)35250mA 7 V VO +12 VOutput Short-Circuit Current (VOUT = Low)

6 35250mA 7 V VO +12 VCMOS Input Logic Threshold Low, Input Logic Threshold High, Input Current (DE, DI) ARECEIVERD ifferential Input Threshold Voltage, VTH + 7 V VCM +12 VInput Voltage Hysteresis, VTH70mVVCM = 0 VInput Resistance12k 7 V VCM +12 VInput Current (A, B)1mAVIN = +12 V = 7 VCMOS Input Logic Threshold Low, Input Logic Threshold High, Enable Input Current (RE) 1 ACMOS Output Voltage Low, = + mACMOS Output Voltage High, = mAShort-Circuit Output Current785mAVOUT = GND or VCCT hree-State Output Leakage Current V VOUT VPOWER SUPPLY CURRENTICC (Outputs Enabled) Inputs = GND or VCCICC (Outputs Disabled)

7 Inputs = GND or VCCS pecifications subject to change without SPECIFICATIONSP arameterMin TypMaxUnit Test Conditions/CommentsDRIVERP ropagation Delay Input to Output tPLH, tPHL21015 nsRLDIFF = 54 , CL1 = CL2 = 100 pF, Test Circuit 3 Driver O/P to O/P tSKEW15 nsRLDIFF = 54 , CL1 = CL2 = 100 pF, Test Circuit 3 Driver Rise/Fall Time tR, tF815 nsRLDIFF = 54 , CL1 = CL2 = 100 pF, Test Circuit 3 Driver Enable to Output Valid1025nsRL = 110 , CL = 50 pF, Test Circuit 4 Driver Disable Timing1025nsRL = 110 , CL = 50 pF, Test Circuit 4 Matched Enable Switching02nsRL = 110 , CL = 50 pF, Test Circuit 4*|tAZH tBZL|, |tBZH tAZL|Matched Disable Switching02nsRL = 110 , CL = 50 pF, Test Circuit 4*|tAHZ tBLZ|, |tBHZ tALZ|RECEIVERP ropagation Delay Input to Output tPLH, tPHL81530 nsCL = 15 pF, Test Circuit 5 Skew |tPLH tPHL|5nsCL = 15 pF, Test Circuit 5 Receiver Enable tEN1520 nsCL = 15 pF, RL = 1 k , Test Circuit 6 Receiver Disable tEN2520 nsCL = 15 pF, RL = 1 k.

8 Test Circuit 6Tx Pulse Width Distortion1nsRx Pulse Width Distortion1ns*Guaranteed by subject to change without notice.(VCC = 5 V 5%. All specifications TMIN to TMAX, unless otherwise noted.)'REV. ADM1485 3 ABSOLUTE MAXIMUM RATINGS*(TA = 25 C, unless otherwise noted.)VCC .. V to +7 VInputsDriver Input (DI) .. V to VCC + VControl Inputs (DE, RE) .. V to VCC + VReceiver Inputs (A, B) .. 9 V to +14 VOutputsDriver Outputs (A, B) .. 9 V to +14 VReceiver Output .. V to VCC + VPower Dissipation 8-Lead MSOP.

9 900 mW JA, Thermal Impedance .. 206 C/WPower Dissipation 8-Lead PDIP .. 500 mW JA, Thermal Impedance .. 130 C/WPower Dissipation 8-Lead SOIC .. 450 mW JA, Thermal Impedance .. 170 C/WOperating Temperature RangeCommercial (J Version) .. 0 C to 70 CIndustrial (A Version) .. 40 C to +85 CStorage Temperature Range .. 65 C to +150 CLead Temperature (Soldering, 10 sec) .. 300 CVapor Phase (60 sec) .. 215 CInfrared (15 sec) .. 220 C*Stresses above those listed under Absolute Maximum Ratings may cause perma-nent damage to the device.

10 This is a stress rating only; functional operation of thedevice at these or any other conditions above those listed in the operationalsections of this specification is not implied. Exposure to absolute maximum ratingsfor extended periods of time may affect device FUNCTION DESCRIPTIONSPin Mnemonic Output. When enabled if A > Bby 200 mV, then RO = High. If A < B by200 mV, then RO = Output Enable. A low levelenables the receiver output, RO. A highlevel places it in a high impedance Output Enable. A high level enablesthe driver differential outputs, A and B.