Texas Instruments SN74HC139NG4

Overview

SN74HC139NG4 from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in PDIP-16 package, operating from 2 V to 6 V with typical propagation delay of 10 ns at 5 V, ±4-mA output drive, and low ICC of 80 μA max - used for high-speed memory decoding and address demultiplexing in microcontroller-based systems.

For engineers reviewing the SN74HC139NG4 datasheet, SN74HC139NG4 pinout, SN74HC139NG4 application, or SN74HC139NG4 equivalent, this page delivers verified functional modes, real-world timing behavior, true output drive capability under load, and confirmed package-specific thermal and layout constraints - all aligned to TI's SCLS108E production data sheet (Rev. FEBRUARY 2022).

Technical Context

The SN74HC139NG4 integrates two independent decoders, each with active-low enable (G) and binary-select inputs (A, B), producing four active-low outputs (Y0–Y3). Its fully buffered CMOS inputs present only one normalized load, minimizing fan-out burden on upstream logic.

Each decoder operates in two functional states: when G is high, all outputs are forced high; when G is low, exactly one output goes low per A/B combination (00→Y0, 01→Y1, etc.). This enables cascading via G as a data line in demultiplexing and simplifies hierarchical address decoding without external gating.

Key Specifications

Pinout & Package

Packaged in 16-pin plastic dual in-line package (PDIP), SN74HC139NG4 has 5.08 mm lead pitch, 19.31 mm × 6.35 mm body size, and through-hole mounting compatibility - suitable for prototyping, legacy board repair, and industrial control panels requiring mechanical robustness.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC139NG4, SN74HC139N offers identical performance with standard RoHS finish, while 74HCT139N trades speed and power for guaranteed TTL-level compatibility - making the G4 variant optimal for cost-sensitive, mixed-voltage 3.3/5 V embedded control where HC logic thresholds are sufficient.

Availability

SN74HC139NG4 is available at Aetrix Electronics and suitable for industrial control panels, legacy system repairs, and microcontroller-based I/O expansion requiring stable component supply and long-term obsolescence management.

Supply support for SN74HC139NG4 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 with broad industrial, automotive, and aerospace qualification programs.

SN74HC139NG4 belongs to TI's HC logic family - designed for high-speed, low-power CMOS applications requiring TTL-compatible output drive and wide supply voltage tolerance in space-constrained or thermally demanding environments.

FAQ

What is the maximum clock frequency supported by SN74HC139NG4?

SN74HC139NG4 is not a clocked device and has no clock input; it is a combinational decoder. Its usable signal frequency depends on propagation delay and system timing margins. With 10 ns typical tpd at 5 V, it supports address/data transitions up to ~50 MHz in well-designed layouts - but actual limit is set by board-level signal integrity and load capacitance, not internal clocking.

Can SN74HC139NG4 operate reliably at 3.3 V supply?

Yes, SN74HC139NG4 is fully specified from 2 V to 6 V. At 3.3 V, VIH = 2.31 V min and VIL = 0.99 V max per datasheet Section 5.2, ensuring clean logic thresholds with standard 3.3 V microcontrollers. Output drive drops to ±3.2 mA, still sufficient for 10 LSTTL loads or direct interface with most 3.3 V logic inputs.

How should unused inputs be handled on SN74HC139NG4?

All unused inputs on SN74HC139NG4 must be tied to VCC or GND - floating CMOS inputs cause increased ICC, noise susceptibility, and potential oscillation. For example, if only one decoder section is used, tie A2, B2, and G2 to VCC or GND per functional intent; never leave them open. TI application report SCBA004 details implications.

Is SN74HC139NG4 pin-compatible with SN74LS139N?

Yes, SN74HC139NG4 is pin-compatible with SN74LS139N in PDIP-16 package - identical pinout, same VCC (pin 16) and GND (pin 8) locations, and matching decoder input/output assignments. However, HC logic has higher noise immunity, lower power, and wider voltage range, making it a drop-in upgrade where LS speed requirements are met.

Does SN74HC139NG4 require a bypass capacitor?

Yes, TI recommends a 0.1-μF ceramic bypass capacitor between VCC (pin 16) and GND (pin 8), placed as close as possible to the pins. This suppresses supply noise generated during output switching and prevents false triggering or increased propagation delay variation - especially critical in high-density or fast-switching PCB layouts.