SN54ALS520, SN74ALS518, SN74ALS520, SN74ALS521
8-BIT IDENTITY COMPARATORS

SDAS224B – JUNE 1982 – REVISED NOVEMBER 1995
Copyright  1995, Texas Instruments Incorporated
1POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
• Compare Two 8-Bit Words
• Choice of Totem-Pole or Open-Collector
Outputs
• SN74ALS518 and ′ALS520 Have 20-kΩ
Pullup Resistors on Q Inputs
• Package Options Include Plastic
Small-Outline (DW) Packages, Ceramic
Chip Carriers (FK), and Standard Plastic (N)
and Ceramic (J) 300-mil DIPs

TYPE
INPUT
PULLUP
OUTPUT FUNCTION
AND
RESISTOR CONFIGURATION
SN74ALS518 Yes P = Q open collector
′ALS520 Yes P = Q totem pole
SN74ALS521
‡
No P = Q totem pole
‡
SN74ALS521 is identical to ′ALS688.
description
These identity comparators perform comparisons
on two 8-bit binary or BCD words. The
SN74ALS518 provides P = Q outputs, while the
′ALS520 and SN74ALS521 provide P = Q
outputs. The SN74ALS518 has an open-collector
output. The SN74ALS518 and ′ALS520 feature
20-kΩ pullup resistors on the Q inputs for analog
or switch data.
The SN54ALS520 is characterized for operation
over the full military temperature range of –55°C
to 125°C. The SN74ALS518, SN74ALS520, and
SN74ALS521 are characterized for operation
from 0°C to 70°C.
FUNCTION TABLE
INPUTS OUTPUTS
DATA
P, Q
ENABLE
G
P = Q P = Q
P = Q L H L
P > Q LLH
P < Q LLH
XHLH
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
G
P0
Q0
P1
Q1
P2
Q2
P3
Q3
GND
V
CC
P = Q/P = Q
†
Q7
P7
Q6
P6
Q5
P5
Q4
P4
SN54ALS520 ...J PACKAGE
SN74ALS518, SN74ALS520,
SN74ALS521 ...DW OR N PACKAGE
(TOP VIEW)
3212019
910111213
4
5
6
7
8
18
17
16
15
14
Q7
P7
Q6
P6
Q5
P1
Q1
P2
Q2
P3
SN54ALS520 . . . FK PACKAGE
(TOP VIEW)
Q0 P0 G
Q4
P5
P
= Q
Q3
GND
P4
V
CC
†
P = Q for SN74ALS518
P = Q for ′ALS520 and SN74ALS521
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.