Document
74AC521 • 74ACT521 8-Bit Identity Comparator
November 1988 Revised November 1999
74AC521 • 74ACT521 8-Bit Identity Comparator
General Description
The AC/ACT521 is an expandable 8-bit comparator. It compares two words of up to eight bits each and provides a LOW output when the two words match bit for bit. The expansion input IA = B also serves as an active LOW enable input.
Features
s ICC reduced by 50% s Compares two 8-bit words in 6.5 ns typ s Expandable to any word length s 20-pin package s Outputs source/sink 24 mA s ACT521 has TTL-compatible inputs
Ordering Code:
Order Number 74AC521SC 74AC521SJ 74AC521PC 74ACT521SC 74ACT521SJ 74ACT521PC Package Number M20B M20D N20A M20B M20D N20A Package Description 20-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300” Wide Body 20-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide 20-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide 20-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300” Wide Body 20-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide 20-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
Device also available in Tape and Reel. Specify by appending suffix letter “X” to the ordering table.
Logic Symbols
Connection Diagram
IEEE/IEC
Pin Descriptions
Pin Names A0–A7 B0–B7 TA = B OA = B
FACT is a trademark of Fairchild Semiconductor Corporation.
Description Word A Inputs Word B Inputs Expansion or Enable Input Identity Output
© 1999 Fairchild Semiconductor Corporation
DS009964
www.fairchildsemi.com
74AC521 • 74ACT521
Truth Table
Inputs IA = B L L H H
H = HIGH Voltage Level L = LOW Voltage Level Note 1: A0 = B0, A1 = B1, A2 = B2, etc.
Logic Diagram
Outputs A, B A = B (Note 1) A≠Β A = B (Note 1) A≠Β OA = B L H H H
Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.
Applications
Ripple Expansion
Parallel Expansion
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74AC521 • 74ACT521
Absolute Maximum Ratings(Note 2)
Supply Voltage (VCC) DC Input Diode Current (IIK) VI = −0.5V VI = VCC + 0.5V DC Input Voltage (VI) DC Output Diode Current (IOK) VO = −0.5V VO = VCC + 0.5V DC Output Voltage (VO) DC Output Source or Sink Current (IO) DC VCC or Ground Current per Output Pin (ICC or IGND) Storage Temperature (TSTG) Junction Temperature (TJ) PDIP 140°C ±50 mA −65°C to +150 °C ±50 mA −20 mA +20 mA −0.5V to VCC + 0.5V −20 mA +20 mA −0.5V to VCC + 0.5V −0.5V to +7.0V
Recommended Operating Conditions
Supply Voltage (VCC) AC ACT Input Voltage (VI) Output Voltage (VO) Operating Temperature (TA) Minimum Input Edge Rate (∆V/∆t) AC Devices VIN from 30% to 70% of VCC VCC @ 3.3V, 4.5V, 5.5V Minimum Input Edge Rate (∆V/∆t) ACT Devices VIN from 0.8V to 2.0V VCC @ 4.5V, 5.5V 125 mV/ns
Note 2: Absolute maximum ratings are those values beyond which damage to the device may occur. The databook specifications should be met, without exception, to ensure that .