Texas Instruments SN74LS670DR

Overview

SN74LS670DR from Texas Instruments is a 4×4 register file IC with three-state outputs, used as a compact, synchronous RAM-like storage element in TTL-based control logic and microprocessor support circuits. It provides 16 bits of storage (four 4-bit words), dual address decoding (A0–A1), independent read/write control (R/W), and output enable (G) - enabling selective data routing in bus-oriented systems such as early minicomputer I/O controllers and industrial sequencers.

For engineers reviewing the SN74LS670DR datasheet, SN74LS670DR pinout, SN74LS670DR application, or SN74LS670DR equivalent, key selection criteria include its 16-pin SOIC package, TTL-compatible input thresholds, 3-state output drive capability, and compatibility with LS-family timing budgets in legacy digital systems requiring small-scale on-chip register storage without external memory interface overhead.

Technical Context

The SN74LS670DR implements a fully decoded 4-word × 4-bit static register array using bipolar TTL circuitry, with separate address inputs (A0, A1), write-enable (W), read-enable (R/W), and output-enable (G) controls. All operations are edge-triggered synchronous to the W signal, and data retention is static - no clock required for hold.

Its three-state outputs allow direct connection to shared data buses; output disable is asserted when G = HIGH, independent of R/W state. The device operates strictly within the 0°C to +70°C commercial temperature range and requires a single +5 V supply with typical ICC of 60 mA at 5 V - consistent with standard LS-TTL power profiles.

Key Specifications

Pinout & Package

SN74LS670DR is supplied in a 16-pin SOIC (D) package, 7.5 mm wide, with 1.27 mm pitch, RoHS-compliant NiPdAu lead finish, and moisture sensitivity level (MSL) 1 - suitable for standard reflow assembly without dry-pack requirements.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS373N and SN74LS273N, the SN74LS670DR uniquely integrates address decoding, multi-word storage, and 3-state outputs in a single 16-pin package - reducing component count and board area in systems requiring compact, selectable register sets without microcontroller intervention.

Availability

SN74LS670DR is available at Aetrix Electronics and suitable for legacy system repair, industrial controller refurbishment, and educational TTL logic labs requiring stable component supply and long-term obsolescence mitigation.

Supply support for SN74LS670DR 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 technologies with broad industrial and automotive reach.

The SN74LS670DR belongs to TI's classic 74LS logic family, designed specifically for high-speed, low-power TTL-compatible digital systems in the 1970s–1980s - emphasizing reliability, interoperability, and ease of integration in discrete control architectures.

FAQ

What is the function of the R/W pin on the SN74LS670DR?

The R/W (Read/Write) pin on the SN74LS670DR determines operational mode: when HIGH, the device is in read mode and outputs reflect the contents of the addressed register (subject to G); when LOW, it enters write mode and samples D0–D3 on the rising edge of the W signal. This separation allows clean bidirectional bus handling without external direction control logic.

Does the SN74LS670DR require a clock signal to retain data?

No, the SN74LS670DR uses static TTL latches and does not require a clock signal to retain stored data. Data remains valid as long as power is applied and address inputs are stable. Only the W signal edge is needed to initiate a write - no continuous clocking or refresh cycles are involved.

Can the SN74LS670DR be used with modern 3.3 V microcontrollers?

The SN74LS670DR is a 5 V-only TTL device with input thresholds referenced to 5 V (VIH ≥ 2.0 V, VIL ≤ 0.8 V). While 3.3 V logic may meet VIH margin under ideal conditions, reliable interfacing requires level translation - either a 3.3 V-to-5 V buffer on control lines or use of open-drain translators to avoid potential input undervoltage and increased static power draw.

What does the NC pin (Pin 16) on the SN74LS670DR signify?

Pin 16 of the SN74LS670DR is marked NC (No Connect) - it corresponds to an unbonded die pad with no internal connection. It must remain unconnected on the PCB; routing traces or applying solder to this pin risks internal shorting or compromised thermal performance. TI documentation confirms this pin has no electrical function.

How many unique addresses does the SN74LS670DR support?

The SN74LS670DR supports four unique addresses via its two address inputs (A0 and A1), allowing selection among Word 0 (A1A0 = 00), Word 1 (01), Word 2 (10), and Word 3 (11). Each word holds 4 bits, resulting in a total 16-bit register file organized as 4 × 4 - no additional addressing or expansion capability is provided internally.