Texas Instruments SN74LS155ANE4

Overview

SN74LS155ANE4 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, 15 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 retro-computing peripheral interfaces.

For engineers reviewing the SN74LS155ANE4 datasheet, SN74LS155ANE4 pinout, SN74LS155ANE4 application, or SN74LS155ANE4 equivalent, key selection criteria include its dual independent decoder architecture, active-low enable and output logic, TTL-level compatibility, and through-hole PDIP-16 packaging for prototyping and repair scenarios.

Technical Context

The SN74LS155ANE4 integrates two identical 2-to-4 line decoders on a single die, each with separate 2-bit binary address inputs (A₀, A₁), individual active-low strobe inputs (G̅₁, G̅₂), and four active-low decoded outputs (Y₀–Y₃ per section). Both sections share no internal signal coupling - enabling fully independent operation.

Each decoder implements standard binary decoding logic: when its strobe is low and inputs are stable, exactly one output goes low corresponding to the 2-bit input code; all other outputs remain high. Input thresholds and output voltage levels comply with LS-TTL specifications, ensuring interoperability with SN74LSxx-series logic families without level-shifting.

Key Specifications

Pinout & Package

SN74LS155ANE4 uses a 16-pin plastic dual in-line package (PDIP-N) with 0.3-inch body width and standard through-hole pitch (2.54 mm). Pin 1 is marked by a notch or dot; leads are tin-lead free (NIPDAU) and RoHS compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS155ANE4, SN74LS139N offers identical functionality and pin compatibility for seamless substitution, while SN74HC139N introduces CMOS advantages at the cost of interface compatibility and timing trade-offs in mixed-logic systems.

Availability

SN74LS155ANE4 is available at Aetrix Electronics and suitable for industrial control panels, retro-computing restoration projects, and educational lab kits requiring stable component supply and long-term obsolescence support.

Supply support for SN74LS155ANE4 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 products with broad industrial and automotive qualification.

The SN74LS155ANE4 belongs to TI's legacy 74LS logic family, designed specifically for reliable, low-power TTL-compatible digital interfacing in commercial-grade systems from the 1970s onward.

FAQ

What is the maximum clock frequency supported by SN74LS155ANE4?

The SN74LS155ANE4 is not a clocked device - it is a combinational decoder with no internal clock. Its usable switching rate depends on propagation delay (22 ns max) and system setup/hold timing. In practice, it reliably supports address decode and control signal routing in systems with bus cycles ≥50 ns, such as classic 8-bit microprocessors like the Z80 or 6502.

Does SN74LS155ANE4 require external pull-up resistors on its outputs?

No - SN74LS155ANE4 features totem-pole (push-pull) outputs capable of actively driving high or low. External pull-ups are unnecessary unless interfacing with open-collector buses or specific legacy designs requiring wired-AND logic, which is not the intended use case for this part.

Can SN74LS155ANE4 replace SN74LS139N in an existing design?

Yes - SN74LS155ANE4 and SN74LS139N are functionally identical, share the same 16-pin PDIP package, pinout, and electrical specifications. They are interchangeable without PCB or schematic changes, making SN74LS155ANE4 a valid drop-in alternative where SN74LS139N is unavailable.

What is the meaning of the "E4" suffix in SN74LS155ANE4?

The "E4" suffix in SN74LS155ANE4 indicates a specific TI packaging and marking variant: it denotes the PDIP-N package with NiPdAu (NIPDAU) lead finish, RoHS compliance, and standard commercial temperature range (0°C to +70°C), consistent with TI's internal ordering nomenclature for legacy logic devices.

Is SN74LS155ANE4 suitable for new designs today?

SN74LS155ANE4 remains viable for new designs targeting legacy system compatibility, repair, education, or environments where proven reliability and through-hole assembly are prioritized over power efficiency or miniaturization. It is not recommended for battery-powered or high-density PCBs where modern CMOS alternatives offer better integration.