74HC182 Datasheet, PDF (2/9 Pages) NXP Semiconductors – Look-ahead carry generator

Philips Semiconductors
Look-ahead carry generator
Product specification
74HC/HCT182
FEATURES
• Provides carry look-ahead across a group of four ALU’s
• Multi-level look-ahead for high-speed arithmetic
operation over long word length
• Output capability: standard
• I_CC category: MSI
GENERAL DESCRIPTION
The 74HC/HCT182 are high-speed Si-gate CMOS devices
and are pin compatible with low power Schottky TTL
(LSTTL). They are specified in compliance with JEDEC
standard no. 7A.
The 74HC/HCT182 carry look-ahead generators accept
up to four pairs of active LOW carry propagate (P₀, P₁, P₂,
P₃) and carry generate (G₀, G₁, G₂, G₃) signals and an
active HIGH carry input (C_n). The devices provide
anticipated active HIGH carries (C_n+x, C_n+y, C_n+z) across
four groups of binary adders.
The “182” also has active LOW carry propagate (P) and
carry generate (G) outputs which may be used for further
levels of look-ahead.
The logic equations provided at the outputs are:
C_n+x = G₀ + P₀C_n
C_n+y = G₁ + P₁G₀ + P₁P₀C_n
C_n+z = G₂ + P₂G₁ + P₂P₁G₀ + P₂P₁P₀C_n
G = G₃ + P₃G₂ + P₃P₂G₁ + P₃P₂P₁G_O
P = P₃P₂P₁P₀
The “182” can also be used with binary ALU’s in an active
LOW or active HIGH input operand mode. The
connections to and from the ALU to the carry look-ahead
generator are identical in both cases.
QUICK REFERENCE DATA
GND = 0 V; T_amb = 25 °C; t_r = t_f = 6 ns
SYMBOL PARAMETER
CONDITIONS
t_PHL/ t_PLH
C_I
C_PD
propagation delay
P_n to P
C_n to any output
P_n or G_n to any output
input capacitance
power dissipation capacitance per
package
C_L = 15 pF; V_CC = 5 V
notes 1 and 2
Notes
1. C_PD is used to determine the dynamic power dissipation (P_D in µW):
P_D = C_PD × V_CC2 × f_i + ∑ (C_L × V_CC2 × f_o) where:
f_i = input frequency in MHz
f_o = output frequency in MHz
∑ (C_L × V_CC2 × f_o) = sum of outputs
C_L = output load capacitance in pF
V_CC = supply voltage in V
2. For HC the condition is V_I = GND to V_CC
For HCT the condition is V_I = GND to V_CC − 1.5 V
TYPICAL
HC
HCT
UNIT
11
14
ns
17
21
ns
14
17
ns
3.5
3.5
pF
50
50
pF
ORDERING INFORMATION
See “74HC/HCT/HCU/HCMOS Logic Package Information”.
December 1990
2