Main MenuBackSearchfairchildsemi.com© 1999 Fairchild Semiconductor Corporation DS006417 www.fairchildsemi.comJune 1989Revised November 1999DM74LS257B 3-STATE Quad 2-Data Selectors/MultiplexersDM74LS257B3-STATE Quad 2-Data Selectors/MultiplexersGeneral DescriptionThese Schottky-clamped high-performance multiplexersfeature 3-STATE outputs that can interface directly withdata lines of bus-organized systems. With all but one of thecommon outputs disabled (at a high impedance state), thelow impedance of the single enabled output will drive thebus line to a HIGH or LOW logic level. To minimize the pos-sibility that two outputs will attempt to take a common busto opposite logic levels, the output enable circuitry isdesigned such that the output disable times are shorterthan the output enable times.This 3-STATE output feature means that n-bit (paralleled)data selectors with up to 258 sources can be implementedfor data buses. It also permits the use of standard TTL reg-isters for data retention throughout the system.Features■ 3-STATE versions LS157 and LS158 with same pinouts■ Schottky-clamped for significant improvement in A-Cperformance■ Provides bus interface from multiple sources in high-performance systems■ Average propagation delay from data input 12 ns■ Typical power dissipation: 50 mW Ordering Code: Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.Connection DiagramFunction TableH = HIGH Level X = Don’t CareL = LOW Level Z = High Impedance (off)Logic DiagramOrder Number Package Number Package DescriptionDM74LS257BM M16A 16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 NarrowDM74LS257BN N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 WideInputs Output YOutputSelect A B LS257ControlHXXXZLLLXLLLHXHLHXLLLHXHHwww.fairchildsemi.com 2DM74LS257BAbsolute Maximum Ratings(Note 1)Note 1: The “Absolute Maximum Ratings” are those values beyond whichthe safety of the device cannot be guaranteed. the device should not beoperated at these limits. The parametric values defined in the ElectricalCharacteristics tables are not guaranteed at the absolute maximum ratings.The Recommended Operating Conditions table will define the conditionsfor actual device operation.Recommended Operating ConditionsDC Electrical CharacteristicsNote 2: All typicals are at VCC = 5V, TA = 25°C.Note 3: Not more than one output should be shorted at a time, and the duration should not exceed one second.Note 4: ICC is measured with all outputs open and all possible inputs grounded, while achieving the stated output conditions.Supply Voltage 7VInput Voltage 7VOperating Free Air Temperature Range 0°C to +70°CStorage Temperature Range −65°C to +150°CSymbol Parameter Min Nom Max UnitsVCCSupply Voltage 4.75 5 5.25 VVIHHIGH Level Input Voltage 2 VVILLOW Level Input Voltage 0.8 VIOHHIGH Level Output Current −2.6 mAIOLLOW Level Output Current 24 mATAFree Air Operating Temperature 0 70 °CSymbol Parameter Conditions MinTypMax Units(Note 2)VIInput Clamp Voltage VCC = Min, II = −18 mA −1.5 VVOHHIGH Level Output Voltage VIL = Max, VIH = Min 2.4 3.1 VVOLLOW Level Output VIL = Max, VIH = Min 0.35 0.5VVoltage IOL = 12 mA, VCC = Min 0.25 0.4IIInput Current @ Max VCC = Max, Select 0.2mAInput Voltage VI = 7V Other 0.1IIHHIGH Level Input VCC = Max, Select 40µACurrent VI = 2.7V Other 20IILLOW Level Input VCC = Max, Select −0.8mACurrent VI = 0.4V Other −0.4IOZHOFF-State Output Current with VCC = Max, VO = 2.7V20 µAHIGH Level Output Voltage Applied VIH = Min, VIL = MaxIOZLOFF-State Output Current with VCC = Max, VO = 0.4V−20 µALOW Level Output Voltage Applied VIH = Min, VIL = MaxIOSShort Circuit Output Current VCC = Max (Note 3) −20 −100 mAICCHSupply Current with Outputs HIGH VCC = Max (Note 4) 5.9 10 mAICCLSupply Current with Outputs LOW VCC = Max (Note 4) 9.2 16 mAICCZSupply Current with Outputs Disabled VCC = Max (Note 4) 12 19 mA3 www.fairchildsemi.comDM74LS257BSwitching Characteristics VCC = 5V and TA = 25°CNote 5: CL = 5 pFSymbol ParameterRL = 667ΩUnitsFrom (Input)CL = 45 pF CL = 150 pFTo (Output) Min Max Min MaxtPLHPropagation Delay TimeData to Output 18 27 nsLOW-to-HIGH Level OutputtPHLPropagation Delay TimeData to Output 18 27 nsHIGH-to-LOW Level OutputtPLHPropagation Delay TimeSelect to Output 28 35 nsLOW-to-HIGH Level OutputtPHLPropagation Delay TimeSelect to Output 35 42 nsHIGH-to-LOW Level OutputtPZHOutput Enable TimeOutput Control to Y 15 27 nsto HIGH Level OutputtPZLOutput Enable TimeOutput Control to Y 28 38 nsto LOW Level OutputtPHZOutput Disable Time fromOutput Control to Y 28 nsHIGH Level Output (Note 5)tPLZOutput Disable Time fromOutput Control to Y 25 nsLOW Level Output (Note 5)www.fairchildsemi.com 4DM74LS257BPhysical Dimensions inches (millimeters) unless otherwise noted16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 NarrowPackage Number M16APhysical Dimensions inches (millimeters) unless otherwise noted (Continued)5 www.fairchildsemi.comDM74LS257B 3-STATE Quad 2-Data Selectors/MultiplexersPhysical Dimensions inches (millimeters) unless otherwise noted (Continued)16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 WidePackage Number N16EFairchild does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied andFairchild reserves the right at any time without notice to change said circuitry and specifications.LIFE SUPPORT POLICYFAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORTDEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILDSEMICONDUCTOR CORPORATION. As used herein:1. Life support devices or systems are devices or systemswhich, (a) are intended for surgical implant into thebody, or (b) support or sustain life, and (c) whose failureto perform when properly used in accordance withinstructions for use provided in the labeling, can be rea-sonably expected to result in a significant injury to theuser.2. A critical component in any component of a life supportdevice or system whose failure to perform can be rea-sonably expected to cause the failure of the life supportdevice or system, or to affect its safety or