Texas Instruments SN74HC138NG4

Overview

SN74HC138NG4 from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in 16-pin PDIP package, operating from 2 V to 6 V with typical propagation delay of 15 ns at 6 V, ±4-mA output drive at 5 V, and active-low outputs enabling direct LED column sinking in matrix displays.

For engineers reviewing the SN74HC138NG4 datasheet, SN74HC138NG4 pinout, SN74HC138NG4 application, or SN74HC138NG4 equivalent, this device serves as a high-speed memory decoder and data-routing IC with three enable inputs for cascading, low-power CMOS logic compatibility, and precise binary-select decoding for industrial control and embedded I/O expansion.

Technical Context

The SN74HC138NG4 implements a 3-to-8 binary decoder with three select inputs (A, B, C) and three enable pins (G1 active-high, G2A/G2B active-low), where only one output Y0–Y7 goes LOW per valid input combination while all others remain HIGH. Its function table defines strict enable hierarchy: all three enables must be asserted to activate decoding.

Designed for high-performance memory systems, it minimizes system decoding delay-its tpd (15 ns typ. at 6 V) and fast enable path ensure negligible contribution to total memory access time when paired with high-speed memories and fast enable circuits.

Key Specifications

Pinout & Package

SN74HC138NG4 uses a 16-pin plastic dual in-line package (PDIP) with 19.32 mm × 6.35 mm body size, through-hole mounting, and industry-standard pin spacing (0.1 inch). Pin 1 is located at the top-left corner with notch orientation marking.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 3-to-8 decoder applications.

Compared with 74HC238D, SN74HC138NG4 delivers lower propagation delay and simpler enable architecture; compared with CD74HC138E, it provides identical functionality with updated environmental compliance and packaging markings.

Availability

SN74HC138NG4 is available at Aetrix Electronics and suitable for industrial I/O expansion, LED matrix display control, and memory address decoding requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN74HC138NG4 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 solutions, with decades of leadership in high-reliability logic families.

The SN74HC138NG4 belongs to TI's 74HC high-speed CMOS logic series, designed for low-power, high-noise-immunity digital interfacing in industrial, computing, and communications equipment.

FAQ

What is the operating temperature range for SN74HC138NG4?

The SN74HC138NG4 is rated for operation from –40°C to +85°C, matching the commercial-grade specification of the SN74HC138 family. This range supports deployment in industrial control panels, network infrastructure equipment, and consumer electronics environments where ambient temperatures remain within standard commercial limits. The PDIP package provides robust thermal performance with RθJA = 54.8°C/W.

Does SN74HC138NG4 support 3.3 V logic systems?

Yes, SN74HC138NG4 fully supports 3.3 V operation: its recommended VCC range is 2 V to 6 V, and input thresholds (VIH = 2.0 V min, VIL = 0.8 V max at VCC = 3.3 V) ensure reliable interfacing with 3.3 V microcontrollers and FPGAs. Output drive remains ±4 mA at 3.3 V, sufficient for driving standard CMOS loads and small-signal transistors.

How many enable inputs does SN74HC138NG4 have, and what are their polarities?

SN74HC138NG4 has three enable inputs: G1 (active-high), G2A (active-low), and G2B (active-low). All three must be simultaneously asserted - G1 HIGH and both G2A/G2B LOW - for any output Y0–Y7 to respond to A/B/C inputs. This configuration allows flexible hierarchical decoding and simplifies cascading without external inverters.

Can SN74HC138NG4 drive LEDs directly?

Yes, SN74HC138NG4 can drive LEDs directly in low-side configuration: each output sinks up to 4 mA at 5 V (or ~2.6 mA at 3.3 V), sufficient for indicator LEDs or low-current segments in multiplexed displays. Its active-low outputs align naturally with common-anode LED matrices, and the 15 ns propagation delay ensures crisp column scanning without ghosting.

Is SN74HC138NG4 pin-compatible with other 74HC138 variants?

Yes, SN74HC138NG4 shares identical pinout and function with all PDIP-packaged 74HC138 variants including CD74HC138E and SN74HC138N. It is not pin-compatible with SOIC, SSOP, TSSOP, or surface-mount versions due to differing package footprints and lead forms - mechanical layout must match PDIP-16 dimensions (19.32 mm × 6.35 mm, 0.1″ pitch).