Texas Instruments CD74HC238EG4

Overview

CD74HC238EG4 from Texas Instruments is a high-speed CMOS 3-to-8 line decoder/demultiplexer with active-high outputs, 16-pin PDIP package, 2 V to 6 V supply range, -55°C to 125°C operating temperature, and typical propagation delay of 13 ns at V_CC = 5 V, C_L = 15 pF. It serves as an I/O port or memory selector in industrial control logic and address decoding circuits.

For engineers reviewing the CD74HC238EG4 datasheet, CD74HC238EG4 pinout, CD74HC238EG4 application, or CD74HC238EG4 equivalent, this page delivers verified functional behavior, exact pin roles, real-world use cases, and validated alternative options for memory decoding, demultiplexing, and enable-controlled routing in harsh-environment digital systems.

Technical Context

The CD74HC238EG4 implements a 3-input address decoder with three independent strobe inputs (G2, G1, G0) - one standard-active and two active-low - enabling precise output gating and cascading. Its logic function forces all eight Y0–Y7 outputs low when any strobe is asserted, and only the selected output high when strobes are inactive.

This device operates as a noninverting decoder: decoded outputs are active-high, contrasting with the inverting '138 family. It supports demultiplexing by using one strobe input as data while A2–A0 select the destination output line.

Key Specifications

Pinout & Package

CD74HC238EG4 uses a 16-pin plastic dual in-line package (PDIP) with 25.40 mm × 6.35 mm body size, through-hole mounting, and industry-standard pin spacing (0.1 inch).

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74HC138E and SN74HC238N, the CD74HC238EG4 offers identical active-high decode functionality and PDIP packaging, but differs in part marking, RoHS status (G4 suffix indicates lead-free), and availability channel - making it suitable for legacy-replacement scenarios requiring documented Pb-free compliance.

Availability

CD74HC238EG4 is available at Aetrix Electronics and suitable for industrial control systems, test equipment signal routing, memory address decoding, and legacy bus interface logic requiring stable component supply across extended temperature ranges.

Supply support for CD74HC238EG4 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 company specializing in analog and embedded processing solutions, with leadership in logic, power management, and signal chain technologies.

The CD74HC238EG4 belongs to TI's HC-series high-speed CMOS logic family, designed for low-power, wide-voltage-range digital interfacing in industrial, military, and automotive applications where reliability and temperature resilience are critical.

FAQ

What is the key functional difference between CD74HC238EG4 and CD74HC138E?

The CD74HC238EG4 provides active-high outputs (Y0–Y7 go high when selected), whereas CD74HC138E provides active-low outputs (Y0–Y7 go low when selected). Both share identical pinout, supply range (2–6 V), propagation delay (~13 ns), and strobe architecture (G2, G1, G0), but their output polarity dictates interface compatibility with downstream logic or peripherals requiring true-high enables.

Does CD74HC238EG4 support 3.3 V logic systems?

Yes, CD74HC238EG4 operates from 2 V to 6 V, making it fully compatible with 3.3 V logic systems. At V_CC = 3.3 V, its input thresholds (V_IL ≤ 0.99 V, V_IH ≥ 2.31 V) provide >30% noise margin, and output drive (±4 mA) meets standard 3.3 V CMOS loading requirements. No level-shifting circuitry is needed when interfacing with 3.3 V MCUs or FPGAs.

Can CD74HC238EG4 be used as a demultiplexer?

Yes, CD74HC238EG4 functions as a 1-to-8 demultiplexer: apply data to any strobe input (e.g., G2), use A2–A0 to select the output channel, and route the data to the corresponding Y0–Y7 line. When G2 is high and G1/G0 are low, the selected output mirrors G2's state - enabling clean serial-to-parallel conversion without additional gates.

What is the maximum fanout capability of CD74HC238EG4?

At full temperature range, CD74HC238EG4 drives up to 10 LSTTL loads on standard outputs. This equates to approximately 10 × 0.4 mA = 4 mA sink/source per output - verified at V_CC = 4.5 V. For heavier loads or longer traces, buffer stages are recommended. Fanout is reduced at lower V_CC (e.g., 2 V) due to diminished drive strength.

Is CD74HC238EG4 pin-compatible with CD74HC238E?

Yes, CD74HC238EG4 is a direct replacement for CD74HC238E in PDIP-16 packaging. The "G4" suffix denotes lead-free (RoHS-compliant) finish and updated packaging standards, but electrical characteristics, pinout, and mechanical dimensions remain identical. No PCB layout changes are required when upgrading from CD74HC238E to CD74HC238EG4.