2000 Fairchild Semiconductor Corporation
DS006474
www.fairchildsemi.com
August 1986
Revised March 2000
DM74S182 Look-
Ahead C
a
rry Generat
or
DM74S182
Look-Ahead Carry Generator
General Description
These circuits are high-speed, look-ahead carry genera-
tors, capable of anticipating a carry across four binary
adders or groups of adders. They are cascadable to per-
form full look-ahead across n-bit adders. Carry, generate-
carry, and propagate-carry functions are provided as
shown in the pin designation table.
When used in conjunction with the 181 arithmetic logic unit,
these generators provide high-speed carry look-ahead
capability for any word length. Each DM74S182 generates
the look-ahead (anticipated carry) across a group of four
ALU's and, in addition, other carry look-ahead circuits may
be employed to anticipate carry across sections of four
look-ahead packages up to n-bits. The method of cascad-
ing circuits to perform multi-level look-ahead is illustrated
under typical application data.
Carry input and output of the ALU's are in their true form,
and the carry propagate (P) and carry generate (G) are in
negated form; therefore, the carry functions (inputs, out-
puts, generate, and propagate) of the look-ahead genera-
tors are implemented in the compatible forms for direct
connection to the ALU. Reinterpretations of carry functions,
as explained on the 181 data sheet are also applicable to
and compatible with the look-ahead generator. Positive
logic equations for the DM74S182 are:
C
n
+
x
=
G0
+
P0 C
n
C
n
+
y
=
G1
+
P1 G0
+
P1 P0 C
n
C
n
+
z
=
G2
+
P2 G1
+
P2 P1 G0
+
P2 P1 P0 C
n
G
=
G3 (P3
+
G2) (P3
+
P2
+
G1)
(P3
+
P2
+
P1
+
G0)
P
=
P3 P2 P1 P0
Features
s
Typical propagation delay time 7 ns
s
Typical power dissipation 260 mW
Ordering Code:
Connection Diagram
Pin Designations
Order Number
Package Number
Package Description
DM74S182N
N16E
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Designation
Pin Nos.
Function
G0, G1, G2, G3
3, 1, 14, 5
Active LOW
Carry Generate Inputs
P0, P1, P2, P3
4, 2, 15, 6
Active LOW
Carry Propagate Inputs
C
n
13
Carry Input
C
n
+
x
, C
n
+
y
,
12, 11, 9
Carry Outputs
C
n
+
z
G
10
Active LOW
Carry Generate Output
P
7
Active LOW
Carry Propagate Output
V
CC
16
Supply Voltage
GND
8
Ground
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2
D
M
74S182
Logic Diagram
V
CC
=
PIN 16
GND
=
PIN 8
Typical Application
64-Bit ALU, Full-Carry Look Ahead in Three Levels
A and B inputs, and F outputs of 181 are not shown.
3
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DM74S182
Absolute Maximum Ratings
(Note 1)
Note 1: 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 tables are not guaranteed at the absolute maximum ratings.
The "Recommended Operating Conditions" table will define the conditions
for actual device operation.
Recommended Operating Conditions
Electrical Characteristics
over recommended operating free air temperature (unless otherwise noted)
Note 2: All typicals are at V
CC
=
5V, T
A
=
25
C.
Note 3: Not more than one output should be shorted at a time, and the duration should not exceed one second.
Note 4: I
CCH
is measured with all outputs OPEN, inputs P3 and G3 at 4.5V, and all other inputs grounded.
Note 5: I
CCL
is measured with all outputs OPEN, inputs G0, G1, and G2 at 4.5V, and all other inputs grounded.
Supply Voltage
7V
Input Voltage
5.5V
Operating Free Air Temperature Range
0
C to
+
70
C
Storage Temperature Range
-
65
C to
+
150
C
Symbol
Parameter
Min
Nom
Max
Units
V
CC
Supply Voltage
4.75
5
5.25
V
V
IH
HIGH Level Input Voltage
2
V
V
IL
LOW Level Input Voltage
0.8
V
I
OH
HIGH Level Output Current
-
1
mA
I
OL
LOW Level Output Current
20
mA
T
A
Free Air Operating Temperature
0
70
C
Symbol
Parameter
Conditions
Min
Typ
Max
Units
(Note 2)
V
I
Input Clamp Voltage
V
CC
=
Min, I
I
=
-
18 mA
-
1.2
V
V
OH
HIGH Level
V
CC
=
Min, I
OH
=
Max
2.7
3.4
V
Output Voltage
V
IL
=
Max, V
IH
=
Min
V
OL
LOW Level
V
CC
=
Min, I
OL
=
Max
0.5
V
Output Voltage
V
IH
=
Min, V
IL
=
Max
I
I
Input Current @ Max Input Voltage V
CC
=
Max, V
I
=
5.5V
1
mA
I
IH
HIGH Level
V
CC
=
Max
P0, P1 or G3
200
A
Input Current
V
I
=
2.7V
P3
100
P2
150
C
n
50
G0, G2
350
G1
400
I
IL
LOW Level
V
CC
=
Max
P0, P1 or G3
-
8
mA
Input Current
V
I
=
0.5V
P3
-
4
P2
-
6
C
n
-
2
G0, G2
-
14
G1
-
16
I
OS
Short Circuit Output Current
V
CC
=
Max (Note 3)
-
40
-
100
mA
I
CCH
Supply Current with Outputs HIGH V
CC
=
Max (Note 4)
39
55
mA
I
CCL
Supply Currents with Outputs LOW V
CC
=
Max (Note 5)
69
109
mA
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4
D
M
74S182
Switching Characteristics
at V
CC
=
5V and T
A
=
25
C
R
L
=
280
Symbol
Parameter
From (Input)
C
L
=
15 pF
C
L
=
50 pF
Units
To (Output)
Min
Max
Min
Min
t
PLH
Propagation Delay Time
GN or PN to C
n
+
x, y, z
7
10
ns
LOW-to-HIGH Level Output
t
PHL
Propagation Delay Time
GN or PN to C
n
+
x, y, z
7
11
ns
HIGH-to-LOW Level Output
t
PLH
Propagation Delay Time
GN or PN to G
7.5
11
ns
LOW-to-HIGH Level Output
t
PHL
Propagation Delay Time
GN or PN to G
10.5
14
ns
HIGH-to-LOW Level Output
t
PLH
Propagation Delay Time
PN to P
6.5
10
ns
LOW-to-HIGH Level Output
t
PHL
Propagation Delay Time
PN to P
10
14
ns
HIGH-to-LOW Level Output
t
PLH
Propagation Delay Time
C
n
to to C
n
+
x, y, z
10
13
ns
LOW-to-HIGH Level Output
t
PHL
Propagation Delay Time
C
n
to to C
n
+
x, y, z
10.5
14
ns
HIGH-to-LOW Level Output
5
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DM74S182 Look-
Ahead C
a
rry Generat
or
Physical Dimensions
inches (millimeters) unless otherwise noted
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Package Number N16E
Fairchild does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and
Fairchild reserves the right at any time without notice to change said circuitry and specifications.
LIFE SUPPORT POLICY
FAIRCHILD'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD
SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the
body, or (b) support or sustain life, and (c) whose failure
to perform when properly used in accordance with
instructions for use provided in the labeling, can be rea-
sonably expected to result in a significant injury to the
user.
2. A critical component in any component of a life support
device or system whose failure to perform can be rea-
sonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness.
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