Texas Instruments CD74HC238EE4

Overview

CD74HC238EE4 from Texas Instruments is a high-speed CMOS 3-to-8 line decoder/demultiplexer with noninverting outputs, operating from 2 V to 6 V, featuring 13 ns typical propagation delay at 5 V/15 pF, -55°C to +125°C temperature range, and three enable inputs (E1, E2 active-low; E3 active-high) for cascading. It serves as a memory address decoder or data-routing selector in industrial control logic systems.

For engineers reviewing the CD74HC238EE4 datasheet, CD74HC238EE4 pinout, CD74HC238EE4 application, or CD74HC238EE4 equivalent, this page delivers verified electrical specs, truth table behavior, package-specific thermal data, and real-world use context for reliable system integration and replacement evaluation.

Technical Context

The CD74HC238EE4 implements a binary-decoded 3-input (A0–A2) to 8-output logic function where all eight outputs are normally low and one goes high when enabled - distinct from the inverting '138 family. Its enable architecture (two active-low, one active-high) allows hierarchical decoding without external gating.

It uses silicon-gate CMOS technology with balanced rise/fall times, fanout of 10 LSTTL loads over full temperature range, and input noise immunity of 30% of VCC at 5 V. Propagation delay varies with supply voltage and load: 13 ns (typ) at 5 V/15 pF, 26 ns (max) at 6 V/50 pF.

Key Specifications

Pinout & Package

CD74HC238EE4 is supplied in a 16-lead plastic dual in-line package (PDIP), with 0.3-inch body width and through-hole mounting. Thermal resistance θJA = 67°C/W enables stable operation up to 125°C ambient under typical PCB layout conditions.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74HC138EE4, the CD74HC238EE4 eliminates external inversion for active-high systems, while SN74HC238N provides identical functionality with alternate logistics packaging - making CD74HC238EE4 optimal for new designs requiring guaranteed extended-temperature support and RoHS compliance.

Availability

CD74HC238EE4 is available at Aetrix Electronics and suitable for industrial control systems, memory expansion modules, and programmable logic interfaces requiring stable component supply across extreme temperature ranges and long production lifecycles.

Supply support for CD74HC238EE4 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 over 90 years of innovation in high-reliability components.

The CD74HC238EE4 belongs to TI's HC-series high-speed CMOS logic family, designed specifically for low-power, high-noise-immunity digital interfacing in industrial, aerospace, and automotive applications where extended temperature operation is mandatory.

FAQ

What is the key functional difference between CD74HC238EE4 and CD74HC138EE4?

The CD74HC238EE4 features noninverting outputs - its selected output goes high when enabled - whereas the CD74HC138EE4 has inverting outputs where the selected output goes low. Both share identical pinout, supply range (2–6 V), propagation delay (13 ns typ at 5 V), and enable structure (E1/E2 low, E3 high). This polarity difference dictates whether external inverters are needed in active-high chip-select architectures.

Does CD74HC238EE4 support 3.3 V logic systems?

Yes, CD74HC238EE4 fully supports 3.3 V operation within its specified 2 V to 6 V supply range. At VCC = 3.3 V, it maintains valid CMOS input thresholds (VIH ≥ 2.1 V, VIL ≤ 1.1 V), delivers VOH ≥ 3.1 V and VOL ≤ 0.1 V under 4 mA load, and achieves ~20 ns typical propagation delay - making it interoperable with standard 3.3 V microcontrollers and FPGAs without level-shifting.

Can CD74HC238EE4 be used in place of CD74HCT238EE4?

No - CD74HC238EE4 and CD74HCT238EE4 are not interchangeable without circuit review. The HC version operates from 2–6 V and has CMOS-compatible inputs, while the HCT version is strictly 4.5–5.5 V and features TTL-compatible inputs (VIH ≥ 2.0 V, VIL ≤ 0.8 V). Substituting CD74HC238EE4 in an HCT-designed board may cause input threshold violations and logic errors at 5 V with marginal noise margins.

What is the maximum capacitive load CD74HC238EE4 can drive reliably?

CD74HC238EE4 is characterized up to 50 pF load capacitance in switching specifications, with propagation delay increasing from 13 ns (15 pF) to 26 ns (50 pF) at 6 V. For reliable operation beyond 50 pF, add series termination or buffer stages. Output drive strength remains ±25 mA per pin, but transition times degrade linearly with load - verify timing margins using TI's provided CPD = 67 pF power dissipation capacitance model.

Is CD74HC238EE4 pin-compatible with other package variants like CD74HC238M or CD74HC238PW?

Yes - all CD74HC238 variants (EE4/PDIP, M/SOIC, PW/TSSOP, NSR/SOP) share identical 16-pin functional pinout and logic behavior. Mechanical dimensions, thermal resistance (θJA = 67°C/W for PDIP vs. 73°C/W for SOIC), and moisture sensitivity level (MSL) differ, but PCB footprint and signal routing remain interchangeable across packages when accounting for soldering profile and board space constraints.