74F182 Carry Lookahead Generator
April 1988
Revised July 1999
74F182
Carry Lookahead Generator
General Description
The 74F182 is a high-speed carry lookahead generator. It
is generally used with the 74F181 or 74F381 4-bit arith-
metic logic units to provide high-speed lookahead over
word lengths of more than four bits.
Features
s
Provides lookahead carries across a group of four ALUs
s
Multi-level lookahead high-speed arithmetic operation
over long word lengths
Ordering Code:
Order Number
74F182SJ
74F182PC
Package Number
M16D
N16E
Package Description
16-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.
Logic Symbols
Connection Diagram
© 1999 Fairchild Semiconductor Corporation
DS009492
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74F182
Unit Loading/Fan Out
Pin Names
C
n
G
0
, G
2
G
1
G
3
P
0
, P
1
P
2
P
3
C
n+x
−
C
n+z
G
P
Carry Input
Carry Generate Inputs (Active LOW)
Carry Generate Input (Active LOW)
Carry Generate Input (Active LOW)
Carry Propagate Inputs (Active LOW)
Carry Propagate Input (Active LOW)
Carry Propagate Input (Active LOW)
Carry Outputs
Carry Generate Output (Active LOW)
Carry Propagate Output (Active LOW)
Description
U.L.
HIGH/LOW
1.0/2.0
1.0/14.0
1.0/16.0
1.0/8.0
1.0/8.0
1.0/6.0
1.0/4.0
50/33.3
50/33.3
50/33.3
Input I
IH
/I
IL
Output I
OH
/I
OL
20
µA/−1.2
mA
20
µA/−8.4
mA
20
µA/−9.6
mA
20
µA/−4.8
mA
20
µA/−4.8
mA
20
µA/−3.6
mA
20
µA/−2.4
mA
−1
mA/20 mA
−1
mA/20 mA
−1
mA/20 mA
Functional Description
The 74F182 carry lookahead generator accepts up to four
pairs of Active LOW Carry Propagate (P
0
–P
3
) and Carry
Generate (G
0
–G
3
) signals and an Active HIGH Carry input
(C
n
) and provides anticipated Active HIGH carries (C
n
+
x
,
C
n+y
, C
n+z
) across four groups of binary adders. The
74F182 also has Active LOW Carry Propagate (P) and
Carry Generate (G) outputs which may be used for further
levels of lookahead. The logic equations provided at the
outputs are:
C
n+x
=
G
0
+
P
0
C
n
C
n+y
=
G
1
+
P
1
G
0
+
P
1
P
0
C
n
C
n+z
=
G
2
+
P
2
G
1
+
P
2
P
1
G
0
+
P
2
P
1
P
0
C
n
G
=
G
3
+
P
3
G
2
+
P
3
P
2
G
1
+
P
3
P
2
P
1
G
0
P
=
P
2
P
2
P
1
P
0
Also, the 74F182 can be used with binary ALUs in an
active LOW or active HIGH input operand mode. The con-
nections (Figure 1) to and from the ALU to the carry looka-
head generator are identical in both cases. Carries are
rippled between lookahead blocks. The critical speed path
follows the circled numbers. There are several possible
arrangements for the carry interconnects, but all achieve
about the same speed. A 28-bit ALU is formed by dropping
the last 74F181 or 74F381.
*ALUs may be either 74F181 or 74F381
FIGURE 1. 32-Bit ALU with Rippled Carry between 16-Bit Lookahead ALUs
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2
74F182
Truth Table
Inputs
C
n
X
L
X
H
X
X
L
X
X
H
X
X
X
L
X
X
X
H
G
0
H
H
L
X
X
H
H
X
L
X
X
X
H
H
X
X
L
X
X
X
X
H
X
X
X
L
H
X
X
X
L
H
=
HIGH Voltage Level
L
=
LOW Voltage Level
X
=
Immaterial
Outputs
G
2
P
2
G
3
P
3
C
n+x
C
n+y
C
n+z
L
L
H
H
G
P
P
0
H
X
X
L
X
H
X
X
X
L
X
X
H
X
X
X
X
L
G
1
P
1
H
H
H
L
X
X
X
H
H
H
X
L
X
X
X
X
H
H
X
X
L
X
H
X
X
X
L
L
X
H
X
X
X
X
L
L
X
X
H
X
X
X
X
L
X
H
X
X
L
H
H
H
H
L
X
X
X
X
H
H
H
X
L
X
X
H
X
X
X
X
L
L
L
X
H
X
X
X
X
L
L
X
X
H
X
L
H
H
H
H
L
X
X
X
H
X
X
X
X
L
L
L
X
X
X
H
L
L
L
L
H
H
H
L
L
L
L
H
H
H
H
H
H
H
H
L
L
L
L
H
H
H
H
L
3
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74F182
Logic Diagram
Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.
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4
74F182
Absolute Maximum Ratings
(Note 1)
Storage Temperature
Ambient Temperature under Bias
Junction Temperature under Bias
V
CC
Pin Potential to Ground Pin
Input Voltage (Note 2)
Input Current (Note 2)
Voltage Applied to Output
in HIGH State (with V
CC
=
0V)
Standard Output
3-STATE Output
Current Applied to Output
in LOW State (Max)
ESD Last Passing Voltage (Min)
twice the rated I
OL
(mA)
4000V
−0.5V
to V
CC
−0.5V
to
+5.5V
−65°C
to
+150°C
−55°C
to
+125°C
−55°C
to
+150°C
−0.5V
to
+7.0V
−0.5V
to
+7.0V
−30
mA to
+5.0
mA
Recommended Operating
Conditions
Free Air Ambient Temperature
Supply Voltage
0°C to
+70°C
+4.5V
to
+5.5V
Note 1:
Absolute maximum ratings are values beyond which the device
may be damaged or have its useful life impaired. Functional operation
under these conditions is not implied.
Note 2:
Either voltage limit or current limit is sufficient to protect inputs.
DC Electrical Characteristics
Symbol
V
IH
V
IL
V
CD
V
OH
V
OL
I
IH
I
BVI
I
CEX
V
ID
I
OD
I
IL
Parameter
Input HIGH Voltage
Input LOW Voltage
Input Clamp Diode Voltage
Output HIGH
Voltage
Output LOW
Voltage
Input HIGH
Current
Input HIGH Current
Breakdown Test
Output HIGH
Leakage Current
Input Leakage
Test
Output Leakage
Circuit Current
Input LOW
Current
4.75
3.75
−1.2
−2.4
−3.6
−4.8
−8.4
−9.6
I
OS
I
CCH
I
CCL
Output Short-Circuit Current
Power Supply Current
Power Supply Current
−60
18.4
23.5
−150
28.0
36.0
mA
mA
mA
Max
Max
Max
mA
Max
10% V
CC
5% V
CC
10% V
CC
2.5
2.7
0.5
5.0
7.0
50
Min
2.0
0.8
−1.2
Typ
Max
Units
V
V
V
V
V
µA
µA
µA
V
µA
Min
Min
Min
Max
Max
Max
0.0
0.0
V
CC
Conditions
Recognized as a HIGH Signal
Recognized as a LOW Signal
I
IN
= −18
mA
I
OH
= −1
mA
I
OH
= −1
mA
I
OL
=
20 mA
V
IN
=
2.7V
V
IN
=
7.0V
V
OUT
=
V
CC
I
ID
=
1.9
µA
All Other Pins Grounded
V
IOD
=
150 mV
All Other Pins Grounded
V
IN
=
0.5V (C
n
)
V
IN
=
0.5V (P
3
)
V
IN
=
0.5V (P
2
)
V
IN
=
0.5V (G
3
, P
0
, P
1
)
V
IN
=
0.5V (G
0
, G
2
)
V
IN
=
0.5V (G
1
)
V
OUT
=
0V
V
O
=
HIGH
V
O
=
LOW
5
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