SN74ALS638A Octal Bus Transceivers |

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Octal Bus Transceivers

Octal Bus Transceivers - SN74ALS638A


These octal bus transceivers are designed for asynchronous two-way communication between open-collector and 3-state buses. The devices transmit data from the A bus (open-collector) to the B bus (3 state) or from the B bus to the A bus, depending on the logic level at the direction-control (DIR) input. The output-enable () input can be used to disable the device so the buses are isolated.

The -1 version of SN74ALS638A is identical to the standard version, except that the recommended maximum IOL is increased to 48 mA.

The SN74ALS638A, SN74ALS639A, SN74AS638A, and SN74AS639 are characterized for operation from 0°C to 70°C.




  • Bidirectional Bus Transceivers in High-Density 20-Pin Packages
  • Choice of True or Inverting Logic
  • A-Bus Outputs Are Open Collector; B-Bus Outputs Are 3 State
  • Package Options Include Plastic Small-Outline (DW) Packages and Standard Plastic (N) 300-mil DIPs



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Part number Order Technology Family VCC (Min) (V) VCC (Max) (V) Bits (#) Voltage (Nom) (V) F @ nom voltage (Max) (MHz) ICC @ nom voltage (Max) (mA) tpd @ nom Voltage (Max) (ns) IOL (Max) (mA) IOH (Max) (mA) Rating Operating temperature range (C)
SN74ALS638A Order now ALS     4.5     5.5     8     5     75     41     30     24     -15     Catalog     0 to 70