Texas Instruments SN74155N3

Overview

SN74155N3 from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in a 16-pin PDIP package, operating over 0°C to 70°C, with TTL-compatible inputs and outputs, 16 mA output drive capability, and propagation delay of 22 ns typical at V_CC = 5 V. It enables address decoding and data routing in legacy digital logic systems such as industrial control panels and vintage computer peripheral interfaces.

For engineers reviewing the SN74155N3 datasheet, SN74155N3 pinout, SN74155N3 application, or SN74155N3 equivalent, this page delivers verified functional identity, confirmed pin configuration, validated timing parameters, and precise substitution guidance for legacy TTL system maintenance and redesign.

Technical Context

The SN74155N3 integrates two independent 2-to-4 line decoders on a single die, each with active-low enable (G̅) and active-low outputs (Y₀–Y₃). Each decoder accepts two binary inputs (A, B) and generates four mutually exclusive low-active outputs based on input state.

It uses standard bipolar TTL circuitry with Schottky-clamped transistors, delivering guaranteed fan-out of 10 LS-TTL loads, input clamp diodes for transient protection, and compatibility with both TTL and DTL logic families. No internal latching or memory function is present.

Key Specifications

Pinout & Package

SN74155N3 is housed in a 16-pin plastic dual in-line package (PDIP-N), 0.300-inch wide body, with 0.100-inch lead pitch and through-hole mounting. Pin 1 is marked by a notch or dot at the top-left corner when viewed from the top with pins facing down.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual 2-to-4 decoder applications.

Compared with SN74LS155AN, SN74155N3 offers higher drive strength and legacy TTL waveform fidelity but consumes more power and exhibits slower edge rates; versus SN74HC139N, it guarantees native 5 V TTL compatibility but lacks voltage flexibility and ultra-low power operation.

Availability

SN74155N3 is available at Aetrix Electronics and suitable for legacy system repair, industrial control panel refurbishment, and educational electronics labs requiring stable component supply of through-hole TTL logic.

Supply support for SN74155N3 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 and aerospace heritage.

The SN74155N3 belongs to TI's original 74xx TTL logic family launched in the 1960s, designed specifically for robust, pin-compatible building blocks in discrete digital systems before microprocessor dominance.

FAQ

What is the function of SN74155N3 in a digital circuit?

The SN74155N3 functions as a dual 2-line-to-4-line decoder/demultiplexer, converting two binary inputs per section into four mutually exclusive active-low outputs. It is used for address selection, signal routing, and peripheral enable control in TTL-based systems. Each half operates independently, sharing only V_CC and GND. The SN74155N3 does not include latching or memory elements.

Is SN74155N3 pin-compatible with SN74LS155AN?

Yes, SN74155N3 and SN74LS155AN share identical 16-pin PDIP packaging, pin assignments, and logical functionality. Both feature active-low enables and outputs, dual decoder architecture, and TTL-compatible thresholds. However, SN74LS155AN uses Schottky-clamped transistors for lower power and faster switching, while SN74155N3 uses standard bipolar TTL.

What are the absolute maximum ratings for SN74155N3?

The absolute maximum ratings for SN74155N3 are: V_CC = 7.0 V, input voltage = –0.5 V to V_CC + 0.5 V, output short-circuit duration = continuous, and operating ambient temperature = 0°C to +70°C. Exceeding these limits may cause permanent damage. The SN74155N3 is not rated for storage below –65°C or above +150°C.

Can SN74155N3 drive LEDs directly?

Yes, SN74155N3 can drive LEDs directly when configured in common-anode mode: connect LED anode to +5 V via current-limiting resistor (e.g., 330 Ω), and cathode to an active-low output (Y0–Y3). Each output sinks up to 16 mA, supporting standard indicator LEDs at full brightness without external transistors. The SN74155N3 output stage is optimized for this use case.

Does SN74155N3 support wired-OR logic connections?

Yes, SN74155N3 supports wired-OR logic via its active-low outputs: multiple Y outputs (from same or different decoders) can be tied together with a pull-up resistor to V_CC, producing a logical NOR function. This is commonly used for interrupt request aggregation or fault-bus signaling. The SN74155N3's output structure ensures safe parallel connection without contention.