Homedatasheet54LS257A

54LS257A Datasheet

Multiplexers->Bipolar->LS Family
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Description

Features, Applications

These Schottky-clamped high-performance multiplexers feature TRI-STATE outputs that can interface directly with data lines of bus-organized systems With all but one of the common outputs disabled (at a high impedance state) the low impedance of the single enabled output will drive the bus line to a high or low logic level To minimize the possibility that two outputs will attempt to take a common bus to opposite logic levels the output enable circuitry is designed such that the output disable times are shorter than the output enable times This TRI-STATE output feature means that n-bit (paralleled) data selectors with to 258 sources can be implemented for data buses It also permits the use of standard TTL registers for data retention throughout the system

Features

TRI-STATE versions LS157 and LS158 with same pinouts Schottky-clamped for significant improvement in A-C performance Provides bus interface from multiple sources in highperformance systems Average propagation delay from data input 12 ns Typical power dissipation 35 mW Alternate military aerospace devices (54LS257A 54LS258A) are available Contact a National Semiconductor Sales Office Distributor for specifications

H e High Level L e Low Level X e Don't Care Z e High Impedance (off)

TRI-STATE is a registered trademark of National Semiconductor Corporation C1995 National Semiconductor Corporation 6417 RRD-B30M105 Printed S A

If Military Aerospace specified devices are required please contact the National Semiconductor Sales Office Distributors for availability and specifications Supply Voltage Input Voltage 7V Note The ``Absolute Maximum Ratings'' are those values beyond which the safety of the device cannot be guaranteed The device should not be operated at these limits The parametric values defined in the ``Electrical Characteristics'' table are not guaranteed at the absolute maximum ratings The ``Recommended Operating Conditions'' table will define the conditions for actual device operation

Operating Free Air Temperature Range C DM54LS and 70 C Storage Temperature Range

Symbol VCC VIH VIL IOH IOL TA Parameter Min Supply Voltage High Level Input Voltage Low Level Input Voltage High Level Output Current Low Level Output Current Free Air Operating Temperature

over recommended operating free air temperature range (unless otherwise noted) Symbol VI VOH VOL Parameter Input Clamp Voltage High Level Output Voltage Low Level Output Voltage Conditions VCC e Min b18 mA VCC e Min IOH e Max VIL e Max VIH e Min VCC e Min IOL e Max VIL e Max VIH e Min IOL 12 mA VCC e Min II IIH IIL IOZH Input Current Input Voltage Max VCC e Max e 7V VCC e Max 2 7V VCC e Max 0 4V VCC e Max 2 7V VIH e Min VIL e Max VCC e Max 0 4V VIH e Min VIL e Max VCC e Max (Note 2) VCC e Max (Note 3) VCC e Max (Note 3) VCC e Max (Note DM54 DM74

DM54 DM74 Select Other Select Other Select Other

High Level Input Current Low Level Input Current Off-State Output Current with High Level Output Voltage Applied Off-State Output Current with Low Level Output Voltage Applied Short Circuit Output Current Supply Current with Outputs High Supply Current with Outputs Low Supply Current with Outputs Disabled

Note 1 All typicals are at VCC 25 C Note 2 Not more than one output should be shorted at a time and the duration should not exceed one second Note 3 ICC is measured with all outputs open and all possible inputs grounded while achieving the stated output conditions

at VCC e 5V and 25 C (See Section 1 for Test Waveforms and Output Load) From (Input) To (Output) 45 pF Min tPLH tPHL tPLH tPHL tPZH tPZL tPHZ tPLZ Propagation Delay Time Low to High Level Output Propagation Delay Time High to Low Level Output Propagation Delay Time Low to High Level Output Propagation Delay Time High to Low Level Output Enable Time to High Level Output Enable Time to Low Level Output Disable Time from High Level Output (Note 1) Output Disable Time from Low Level Output (Note 1) Data to Output Data to Output Select to Output Select to Output Control to Y Output Control to Y Output Control to Y Output Control to Y Max 150 pF Min Max ns Units

over recommended operating free air temperature range (unless otherwise noted) Symbol VI VOH Parameter Input Clamp Voltage High Level Output Voltage Low Level Output Voltage Conditions VCC e Min b18 mA VCC e Min IOH e Max VIL e Max VIH e Min VCC e Min IOL e Max VIL e Max VIH e Min IOL 12 mA VCC e Min II Input Current Input Voltage Max VCC e Max e 7V VCC e Max DM54 DM74 Select Other Select Other mA V Min Typ (Note 1) Max


Features

Parameters

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Manufacturer information

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