SN74LS251 8-Line To 1-Line Data Selectors/Multiplexers With 3-State Outputs |

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8-Line To 1-Line Data Selectors/Multiplexers With 3-State Outputs

8-Line To 1-Line Data Selectors/Multiplexers With 3-State Outputs - SN74LS251


These monolithic data selectors/multiplexers contain full on-chip binary decoding to select one-of-eight data sources and feature a strobe-controlled three-state output. The strobe must be at a low logic level to enable these devices. The three-state outputs permit a number of outputs to be connected to a common bus. When the strobe input is high, both outputs are in a high-impedance state in which both the upper and lower transistors of each totem-pole output are off, and the output neither drives nor loads the bus significantly. When the strobe is low, the outputs are activated and operate as standard TTL totem-pole outputs.

To minimize the possibility that two outputs will attempt to take a common bus to opposite logic levels, the output control circuitry is designed so that the average output disable time is shorter than the average output enable time. The SN54251 and SN74251 have output clamp diodes to attenuate reflections on the bus line.



  • Three-State Versions of '151, 'LS151, 'S151
  • Three State Outputs Interface Directly with System Bus
  • Perform Parallel-to-Serial Conversion
  • Permit Multiplexing from N-Lines to One Line
  • Complementary Outputs Provide True and Inverted Data
  • Fully Compatible with Most TTL Circuits



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Part number Order Function Technology Family VCC (Min) (V) VCC (Max) (V) Channels (#) Voltage (Nom) (V) F @ nom voltage (Max) (MHz) ICC @ nom voltage (Max) (mA) tpd @ nom Voltage (Max) (ns) Configuration Type IOL (Max) (mA) IOH (Max) (mA) Rating Operating temperature range (C) Package Group Package size: mm2:W x L (PKG) Bits (#) Digital input leakage (Max) (uA) ESD CDM (kV) ESD HBM (kV)
SN74LS251 Order now Encoder
LS     4.75     5.25     1     5     35     12     45     8:1     3-State Output     8     -2.6     Catalog     0 to 70     PDIP | 16
SOIC | 16
SO | 16    
16PDIP: 181 mm2: 9.4 x 19.3 (PDIP | 16)
16SO: 80 mm2: 7.8 x 10.2 (SO | 16)
16SOIC: 59 mm2: 6 x 9.9 (SOIC | 16)    
8     5     0.75     2    
SN54LS251 Samples not available Encoder/Multiplexer     LS     4.5     5.5     1     5     35     12     45     8:1     3-State Output     8/-2.6       Military     -55 to 125     CDIP | 16
CFP | 16
LCCC | 20    
16CDIP: 135 mm2: 6.92 x 19.56 (CDIP | 16)
16CFP: 69 mm2: 6.73 x 10.3 (CFP | 16)
20LCCC: 79 mm2: 8.89 x 8.89 (LCCC | 20)    
8     5     0.75     2