Texas Instruments SN74LS670N3

Overview

SN74LS670N3 from Texas Instruments is a 4×4-bit register file with three-state outputs, designed for temporary data storage and addressable read/write operations in TTL-based digital systems. It features 16-word × 4-bit organization, asynchronous write enable, and independent read/write addressing - enabling use in microprocessor auxiliary registers, ALU operand staging, and early minicomputer data path buffering.

For engineers reviewing the SN74LS670N3 datasheet, SN74LS670N3 pinout, SN74LS670N3 application, or SN74LS670N3 equivalent, key selection considerations include its 16-pin PDIP package, TTL-compatible input thresholds, 3-state output control timing, and compatibility with LS-family bus loading requirements in legacy control logic and educational hardware platforms.

Technical Context

The SN74LS670N3 implements a fully synchronous 4-bit-wide register file using bipolar TTL circuitry, with separate 2-bit address inputs for read (A0–A1) and write (B0–B1) ports. Its internal architecture supports concurrent read and write operations to different addresses without bus contention, enabled by independent address decoders and gated output drivers.

Three-state output control is managed via an active-low Output Enable (OE) pin, allowing direct connection to shared data buses. Write operation requires both Write Enable (WE) low and valid B-address; read operation activates only when OE is low and A-address is stable - all timing referenced to TTL-level signal edges with guaranteed setup/hold margins.

Key Specifications

Pinout & Package

SN74LS670N3 is supplied in a 16-pin plastic dual in-line package (PDIP-N), with 0.3-inch body width and through-hole mounting. Pin spacing follows standard 0.1-inch grid; pin 1 marked by notch or dot.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar register file applications.

Compared with SN74LS670N and generic 74LS670 variants, the SN74LS670N3 offers guaranteed TI-specified timing, commercial-grade temperature rating, and documented traceability - making it preferred for production systems requiring consistent LS-family interoperability and long-term supply stability.

Availability

SN74LS670N3 is available at Aetrix Electronics and suitable for microprocessor auxiliary register, ALU operand staging buffer, and TTL-based logic training platform applications requiring stable component supply across legacy electronics refurbishment, industrial controller maintenance, and academic lab procurement cycles.

Supply support for SN74LS670N3 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic ICs with broad industrial, automotive, and educational market reach.

The SN74LS670N3 belongs to TI's classic 74LS logic family - engineered for reliable, low-power TTL operation in discrete digital systems where deterministic timing, bus compatibility, and long-term availability are essential.

FAQ

What is the function of the SN74LS670N3 in a digital system?

The SN74LS670N3 functions as a 4×4-bit addressable register file with independent read and write ports and three-state outputs. It stores 16 bits of data across four 4-bit words, enabling concurrent access to different locations - commonly used for operand buffering, status storage, or microcode data tables in TTL-based systems. Its asynchronous operation and LS-TTL compatibility make it ideal for integration with classic processors like the Z80 or 6502.

Does the SN74LS670N3 require a clock signal to operate?

No, the SN74LS670N3 operates asynchronously - it has no clock input. Data is written when Write Enable (WE) is low and a valid write address (B0/B1) is present; data is read when Output Enable (OE) is low and a valid read address (A0/A1) is present. This eliminates timing constraints associated with clock distribution and simplifies control logic in systems where precise edge-aligned sequencing is unnecessary.

What is the significance of the "N3" suffix in SN74LS670N3?

The "N3" suffix in SN74LS670N3 indicates a specific packaging and revision variant within TI's PDIP-16 product line - denoting the plastic dual in-line package (N) with a particular date code, assembly lot, or minor process revision (3). It is functionally identical to SN74LS670N and shares the same pinout, timing, and electrical specifications per SDLS193 datasheet revision March 1988.

Can SN74LS670N3 be used alongside modern microcontrollers?

Yes, the SN74LS670N3 can interface with modern microcontrollers via level-shifting and timing adaptation - for example, using GPIO pins to emulate address/data/control signals and software-controlled delays to meet its 35 ns propagation and setup/hold requirements. Its 5 V tolerance and 3-state outputs simplify connection to 3.3 V MCU I/O with appropriate buffer or translator ICs, especially in retro-computing or hybrid prototyping contexts.

How does the SN74LS670N3 differ from static RAM devices like the 2114?

The SN74LS670N3 differs from static RAMs such as the 2114 in architecture and interface: it uses dual 2-bit address buses (A0/A1 for read, B0/B1 for write), lacks chip select or byte enable, and relies on 3-state outputs instead of bidirectional data buses. Unlike the 2114's 1K×4 organization and address multiplexing, the SN74LS670N3 offers only 4×4-bit capacity but enables true concurrent read/write - making it better suited for small-scale, low-latency register file tasks rather than general-purpose memory expansion.