SN74ALS518NE4 Texas Instruments Integrated Circuit (Dual-In-Line Packages) In Stock
The SN74ALS518NE4 is an 8-bit identity comparator IC from Texas Instruments in the ALS logic family, featuring non-inverting open-collector outputs with built-in pull-up resistors, cascadable architecture, 50 pF load capacitance rating, and a 20-pin PDIP package for address comparison and data matching in digital systems.
- Manufacturer
- Texas Instruments
- Package
- Dual-In-Line Packages
- Pin Count
- 20
- Lifecycle
- OBSOLETE
- Datasheet
- SN74ALS518NE4 Datasheet PDF
- Category
- Integrated Circuit
- Temp Range
- ?°C to 70.0°C
- RoHS
- Compliant
- Lead Time
- 3–7 business days
- Shipping
- DHL Express · Worldwide
What are the key features of SN74ALS518NE4?
- 8-bit identity comparator with cascadable architecture for wider word comparisons
- Open-collector outputs allow wired-AND bus sharing across multiple comparator ICs
- Built-in pull-up resistors on Q inputs reduce external component count
- ALS logic family for low-power, high-speed TTL-compatible operation
- 20-pin PDIP through-hole package rated to 50 pF load capacitance
- Non-inverting output polarity for straightforward logic integration
What is SN74ALS518NE4 used for?
The SN74ALS518NE4 is used in address decoding and memory management units of embedded systems and industrial controllers where an 8-bit data bus value must be continuously compared against a programmable reference word. Its cascadable design allows two or more devices to be chained for 16-bit or wider comparisons, making it a practical solution for position decoders, content-addressable memory interfaces, and protocol-framing state machines in 5 V TTL logic environments.
What are the specifications of SN74ALS518NE4?
| Pbfree Code | Yes |
| YTEOL | 0 |
| Additional Feature | WITH PULL-UP RESISTORS ON Q INPUTS; CASCADABLE |
| Family | ALS |
| JESD-30 Code | R-PDIP-T20 |
| JESD-609 Code | e4 |
| Load Capacitance (CL) | 50pF |
| Logic IC Type | IDENTITY COMPARATOR |
| Number of Bits | 8 |
| Number of Functions | 1 |
| Output Characteristics | OPEN-COLLECTOR |
| Output Polarity | TRUE |
| Package Body Material | PLASTIC/EPOXY |
| Package Equivalence Code | DIP20,.3 |
| Package Shape | RECTANGULAR |
| Package Style | IN-LINE |
| Packing Method | TUBE |
| Power Supply Current-Max (ICC) | 17mA |
| Propagation Delay (tpd) | 33ns |
| Qualification Status | Not Qualified |
| Supply Voltage-Max (Vsup) | 5.5V |
| Supply Voltage-Min (Vsup) | 4.5V |
| Supply Voltage-Nom (Vsup) | 5V |
| Surface Mount | NO |
| Technology | TTL |
| Temperature Grade | COMMERCIAL |
| Terminal Finish | NICKEL PALLADIUM GOLD |
| Terminal Form | THROUGH-HOLE |
| Terminal Pitch | 2.54mm |
| Terminal Position | DUAL |
| Package | Dual-In-Line Packages |
Compliance & Regulatory
| RoHS Status | Compliant |
| Lead-Free | Yes (Pb-Free) |
| HTS Code | 8542.39.00.60 |
Where can I find the SN74ALS518NE4 datasheet?
SN74ALS518NE4 Datasheet DownloadOfficial datasheet from Texas Instruments
What are equivalent replacements for SN74ALS518NE4?
Compatible alternatives and drop-in replacements for SN74ALS518NE4:
Frequently Asked Questions
How does the cascadable design of SN74ALS518NE4 enable comparisons wider than 8 bits?
The SN74ALS518NE4 cascades by connecting the open-collector equality output of the first device to the enable input of a second SN74ALS518NE4, so both 8-bit stages must simultaneously report equality for the combined output to assert. This allows 16-bit, 24-bit, or wider word comparisons using multiple devices without additional glue logic, at the cost of only one additional propagation delay per extra 8-bit stage—typically a few nanoseconds in the ALS family.
Why are the built-in pull-up resistors on the Q inputs of SN74ALS518NE4 an advantage in address-decoding circuits?
Unused or tri-stated bus lines can float to undefined logic levels and cause spurious comparisons without termination. The on-chip pull-up resistors on the Q inputs of SN74ALS518NE4 bias floating lines to a logic HIGH, guaranteeing a defined comparison state and eliminating the need for external 1 kΩ to 10 kΩ pull-up networks on every input pin. This simplifies board layout and reduces the passive component count on address-bus decoder cards.
In a 5 V TTL system, what propagation delay can be expected from the SN74ALS518NE4 and how does it compare to standard LS logic comparators?
The ALS (Advanced Low-power Schottky) logic family delivers propagation delays typically in the 5 ns to 10 ns range at 5 V with a 50 pF load, compared to the 15 ns to 25 ns typical of older standard LS 74LS family comparators. This improvement allows the SN74ALS518NE4 to operate at bus clock frequencies exceeding 50 MHz while consuming less supply current than equivalent LS devices, making it a preferred upgrade for performance-sensitive address comparison paths in legacy 5 V digital systems.
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About Texas Instruments
Texas Instruments (TI) is a global semiconductor company headquartered in Dallas, Texas. TI designs and manufactures analog and embedded processing chips used in industrial, automotive, consumer, communications, and enterprise systems.
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