Texas Instruments SN74HC139N-NG

Overview

SN74HC139N-NG from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in PDIP-16 package, operating across 2 V to 6 V supply range. It delivers 10 ns typical propagation delay at 5 V, ±4 mA output drive, and supports high-speed memory decoding and data routing with two independent active-low enable inputs (G1, G2). Used in address decoding for SRAM/ROM systems where low-latency signal selection is critical.

For engineers reviewing the SN74HC139N-NG datasheet, SN74HC139N-NG pinout, SN74HC139N-NG application, or SN74HC139N-NG equivalent, key selection criteria include its dual-decoder architecture with separate strobe control, LSTTL-compatible output drive (up to 10 loads), and operation over industrial temperature range (−40°C to +85°C) in through-hole PDIP packaging.

Technical Context

The SN74HC139N-NG integrates two independent CMOS decoders, each accepting two binary inputs (A, B) and one active-low enable (G) to select one of four outputs (Y0–Y3) in low state while others remain high. Its fully buffered inputs present only one normalized load, minimizing fanout burden on upstream logic.

Each decoder operates synchronously but independently: enabling one channel does not affect the other. The device uses standard HC-series CMOS logic levels, with VIH/VIL thresholds scaling with VCC (e.g., VIH = 3.15 V at VCC = 4.5 V), and features low input current (≤1 μA max) and quiescent ICC ≤80 μA at 6 V.

Key Specifications

Pinout & Package

SN74HC139N-NG is housed in a 16-pin plastic dual in-line package (PDIP) with 0.300-inch body width and 0.100-inch lead pitch, optimized for through-hole prototyping and legacy PCB assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC139N-NG, SN74HCT139N offers superior TTL input compatibility at the cost of higher static power, while 74AC139PC delivers significantly faster switching but mandates SMT layout - making SN74HC139N-NG optimal for industrial through-hole systems balancing speed, power, and drop-in replaceability.

Availability

SN74HC139N-NG is available at Aetrix Electronics and suitable for memory decoding, peripheral selection, bus expansion, and legacy system repair requiring stable component supply and long-term obsolescence management.

Supply support for SN74HC139N-NG 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 specializing in analog, embedded processing, and logic ICs, with over 50 years of innovation in industrial, automotive, and communications markets.

The SN74HC139N-NG belongs to TI's 74HC logic family, designed specifically for high-speed, low-power memory decoding and data-routing applications in industrial and commercial systems.

FAQ

What is the maximum operating frequency supported by SN74HC139N-NG in a memory decode application?

The SN74HC139N-NG does not specify a maximum clock frequency, but its 12 ns maximum propagation delay at 6 V enables reliable operation in address decode paths up to approximately 25 MHz. In practice, system timing depends on combined delays of address generation, decoder, and memory access - SN74HC139N-NG contributes minimal latency, allowing tight timing margins in SRAM/ROM interfaces. Always verify setup/hold times against target memory datasheets.

Can SN74HC139N-NG interface directly with 3.3 V microcontrollers?

Yes, SN74HC139N-NG can interface directly with 3.3 V microcontrollers when operated at VCC = 3.3 V. Its input thresholds scale with supply voltage (VIH ≈ 0.7×VCC), so a 3.3 V controller's 2.4 V high output exceeds the required VIH of 2.31 V. Outputs swing rail-to-rail, providing clean 0 V / 3.3 V logic levels compatible with HC-series inputs downstream.

Is SN74HC139N-NG pin-compatible with the obsolete 74LS139?

Yes, SN74HC139N-NG is pin-compatible and functionally equivalent to 74LS139 in PDIP-16 packaging, including identical pin assignments for G, A, B, Y0–Y3, VCC, and GND. However, SN74HC139N-NG uses CMOS inputs (higher impedance, lower drive) and requires attention to unused input termination per TI guidelines - unlike LS, floating inputs must be tied to VCC or GND.

What decoupling capacitor value is recommended for SN74HC139N-NG?

Texas Instruments recommends a 0.1 μF ceramic capacitor placed as close as possible to the VCC (pin 16) and GND (pin 8) pins of SN74HC139N-NG. For systems with high-frequency noise or multiple logic devices, paralleling a 1 μF tantalum or ceramic capacitor improves low-frequency bypassing. Mounting distance should be ≤5 mm from the IC leads to minimize inductance and ensure effective high-speed transient suppression.

Does SN74HC139N-NG support cascading for larger decode matrices?

Yes, SN74HC139N-NG supports cascading via its dual enable inputs (G1, G2): one decoder's outputs can drive the G input of another to construct 3-to-8 or 4-to-16 decoders. For example, using A2 as a master enable controlling G1/G2 allows selection of eight outputs across two SN74HC139N-NG devices. This preserves timing integrity because each stage adds only one tpd delay, avoiding combinatorial logic bottlenecks.