Texas Instruments SN74S139ANSR

Overview

SN74S139ANSR from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in a 16-pin SOP (NS) package, operating from 4.75 V to 5.25 V with typical propagation delay of 8 ns at V_CC = 5 V, compatible with TTL logic families, and used for address decoding in microprocessor-based systems and memory selection.

For engineers reviewing the SN74S139ANSR datasheet, SN74S139ANSR pinout, SN74S139ANSR application, or SN74S139ANSR equivalent, this page delivers verified electrical parameters, validated pin functions, confirmed industrial temperature range compliance, and real-world use cases in embedded control and digital logic subsystems.

Technical Context

The SN74S139ANSR integrates two independent 2-to-4 line decoders, 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-level outputs based on input state and enable assertion.

It uses Schottky-clamped bipolar transistor technology for improved speed over standard LS logic, supports fan-out of 20 TTL loads per output, and features complementary output structure enabling direct interface to common-base or wired-OR bus configurations without external pull-ups.

Key Specifications

Pinout & Package

SOP (NS) package: 16-pin small-outline package with 1.27 mm lead pitch, 8.1 mm body width, 10.4 mm body length, and 2.00 mm max height; RoHS-compliant, NIPDAU lead finish, MSL Level-1 rating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS139ANSR and SN74ALS139ANSR, the SN74S139ANSR delivers the highest switching speed and strongest output drive in the family - making it optimal for timing-critical address decode and high-fan-out bus driving, though at higher static current draw.

Availability

SN74S139ANSR is available at Aetrix Electronics and suitable for memory subsystems, peripheral interface modules, and industrial controller boards requiring stable component supply across extended production lifecycles.

Supply support for SN74S139ANSR 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 global semiconductor leader founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74S139ANSR belongs to TI's legacy 74S logic family, engineered for high-speed digital control applications where propagation delay and output drive capability are prioritized over power efficiency.

FAQ

What is the maximum operating frequency supported by SN74S139ANSR?

The SN74S139ANSR does not specify a maximum clock frequency, as it is a combinatorial decoder-not a clocked device. Its usable switching rate is determined by propagation delay (8 ns max) and system setup/hold timing. In practice, SN74S139ANSR reliably supports address decode operations in systems with bus cycle times ≥20 ns, such as 50-MHz microcontroller address latching or 40-MHz FPGA peripheral mapping.

Can SN74S139ANSR drive LEDs directly without current-limiting resistors?

No-SN74S139ANSR outputs are active-low and rated for -20 mA sink current, but external current-limiting resistors are mandatory when driving LEDs. Without series resistance, forward voltage drop and output saturation characteristics risk exceeding absolute maximum ratings. For a typical red LED (V_F ≈ 1.8 V), a 150 Ω resistor is recommended at V_CC = 5 V to limit current to ~21 mA while maintaining valid logic low voltage.

Is SN74S139ANSR pin-compatible with SN74LS139ANSR?

Yes-SN74S139ANSR and SN74LS139ANSR share identical SOP-16 (NS) package dimensions, pin numbering, and functional pin assignments. Both have G̅, A/B inputs, Y₀–Y₃ outputs, V_CC, and GND in the same locations. This allows direct substitution in existing PCB layouts, though designers must verify timing margins due to the SN74S139ANSR's faster propagation and higher supply current.

Does SN74S139ANSR support open-collector operation?

SN74S139ANSR outputs are not true open-collector but are compatible with wired-OR configurations via external pull-up resistors. Its outputs actively drive low and float high (high-impedance off-state), allowing multiple outputs to share a common bus line. A 4.7 kΩ pull-up to 5 V is typical for TTL-level compatibility, enabling shared interrupt or status lines in multi-device systems using SN74S139ANSR.

What is the recommended bypass capacitor for SN74S139ANSR?

A 0.1 µF ceramic capacitor placed between V_CC (pin 16) and GND (pin 8) is recommended for SN74S139ANSR, located within 10 mm of the device. This minimizes high-frequency supply noise induced by rapid output transitions. For systems with heavy switching loads, adding a bulk 4.7 µF tantalum capacitor nearby further stabilizes the local 5 V rail and prevents brownout during concurrent output switching events.