Full-Carry Look-Ahead Across the Four
Bits

Systems Achieve Partial Look-Ahead
Performance with the Economy of Ripple
Carry

Supply Voltage and Ground on Corner
Pins to Simplify P-C Board Layout

description
The *283 and 'LS283 adders are electrically and
functionally identical to the ‘B3A and 'LSB3A.
respectively; only the arrangement of the terminals
has been changed. The ‘S283 high performance
Versions are also functionally identical.
These improved full adders perform the addition of
two 4-bit binary words. The sum (Z) outputs are
provided for each bit and the resultant carry (C4) is
obtained from the fourth bit. These adders feature
full internal look-ahead across all four bits generating
the carry term in ten nanoseconds, typically, for the
283 and ‘LS283, and 7.5 nanoseconds for the ‘S283.
This capability provides the system designer with
partial look-ahead performance at the economy and
reduced package count of a ripple-carry
implementation.
The adder logic, including the carry, is implemented
in its true form. End around carry can be accomplish-
ed without the need for logic or level inversion.
Series 54, Series 54LS, and Series 54S circuits are
characterized for operation over the full temperature
range of 55°C to 125°C. Series 74, Series 74LS, and
Series 74S circuits are characterized for 0°C 10 70°C
operation.