Texas Instruments SN74S139AN3

Overview

SN74S139AN from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in a 16-pin PDIP package, featuring TTL-compatible inputs and outputs, propagation delay of 11 ns (typ) at V_CC = 5 V, output drive capability of –20 mA sink / +10 mA source, and operating temperature range of 0°C to 70°C. It is used in address decoding for memory systems and data routing in industrial control logic.

For engineers reviewing the SN74S139AN datasheet, SN74S139AN pinout, SN74S139AN application, or SN74S139AN equivalent, this page provides verified functional specifications, validated pin assignments, confirmed industrial and computing use cases, and two technically documented alternative parts with explicit interface and timing differences.

Technical Context

The SN74S139AN implements two independent 2-to-4 line decoders, each with active-low enable (G̅) and active-low outputs (Y₀–Y₃). Each decoder accepts two binary address inputs (A, B) and generates four mutually exclusive low-active outputs based on input state and enable assertion.

It uses Schottky-clamped TTL circuitry for improved speed over standard LS variants, with guaranteed fan-out of 20 TTL loads per output and input clamp diodes for transient protection. The device operates strictly from a single 5-V supply and does not support mixed-voltage or open-collector configurations.

Key Specifications

Pinout & Package

SN74S139AN 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 compatibility.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS139AN and SN74HC139N, the SN74S139AN delivers the fastest propagation delay in the 74xx139 family while maintaining full TTL voltage and current compatibility - making it the sole choice for timing-critical commercial-grade decoding where speed outweighs power efficiency.

Availability

SN74S139AN is available at Aetrix Electronics and suitable for memory address decoding, industrial PLC I/O expansion, test equipment signal routing, and legacy computer bus arbitration requiring stable component supply and long-term commercial-grade availability.

Supply support for SN74S139AN 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 for industrial, automotive, and communications markets.

The SN74S139AN belongs to TI's 74S logic family, designed specifically for high-speed commercial applications where propagation delay and drive strength are prioritized over static power consumption.

FAQ

What is the maximum operating frequency supported by SN74S139AN?

The SN74S139AN does not specify a maximum clock frequency because it is a combinational logic device without internal clocking. Its usable switching rate is determined by propagation delay (11 ns typ) and system setup/hold timing margins. In practice, SN74S139AN reliably supports address decode operations in systems with clock periods ≥44 ns (i.e., ≤22.7 MHz sustained toggle rate on inputs), assuming clean signal edges and proper load termination.

Does SN74S139AN support mixed-voltage operation or level translation?

No, SN74S139AN operates exclusively from a single 5-V supply (4.75 V to 5.25 V) and is not designed for mixed-voltage interfaces. Its input thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V) and output voltage levels (V_OL ≤ 0.5 V, V_OH ≥ 2.7 V) are fixed for TTL compatibility. Interfacing with 3.3 V or CMOS logic requires external level-shifting circuitry; SN74S139AN itself provides no level translation capability.

Can SN74S139AN be used as a 1-to-4 demultiplexer?

Yes, SN74S139AN can function as a 1-to-4 demultiplexer by tying one address input (e.g., B) low and using the other (A) plus the active-low enable (G̅) as data and select lines. When G̅ = LOW and B = LOW, inputs A and G̅ jointly determine which of Y₀–Y₃ is asserted - effectively routing a single data line to one of four destinations. This configuration is explicitly supported in TI's application notes for SN74S139AN and preserves all timing and drive specifications.

Is SN74S139AN pin-compatible with SN74LS139AN?

Yes, SN74S139AN and SN74LS139AN share identical 16-pin PDIP packaging, pin assignments, and terminal functions - including identical enable, input, output, V_CC, and GND locations. Both devices may be substituted on the same PCB footprint without layout changes, though timing and power characteristics differ significantly (SN74S139AN offers faster speed but higher supply current).

What is the recommended bypass capacitor for SN74S139AN?

Texas Instruments recommends a 0.1 µF ceramic capacitor placed as close as possible to the V_CC (Pin 16) and GND (Pin 8) pins of SN74S139AN to suppress high-frequency supply noise generated during output transitions. For boards with multiple SN74S139AN devices or high-speed adjacent logic, adding a bulk 4.7 µF tantalum or aluminum electrolytic capacitor near the power entry point further stabilizes the 5-V rail. This bypassing is essential to maintain specified 11 ns propagation delay and prevent output glitches.