Texas Instruments CD74HC238NSR

Overview

CD74HC238NSR from Texas Instruments is a high-speed CMOS 3-to-8 line decoder/demultiplexer with noninverting active-high outputs, 16-pin SOP package, -55°C to +125°C operating temperature, 2 V–6 V supply range, and typical 13 ns propagation delay at V_CC = 5 V. It serves as an address selector in memory decoding or data routing circuits for industrial control and instrumentation systems.

For engineers reviewing the CD74HC238NSR datasheet, CD74HC238NSR pinout, CD74HC238NSR application, or CD74HC238NSR equivalent, key selection criteria include output polarity (active-high), triple enable architecture (G0/G1/G2), wide voltage operation, and compatibility with legacy HC logic families in space-constrained PCB layouts.

Technical Context

The CD74HC238NSR implements a 3-input address decoder with three independent strobe inputs (G2, G1, G0) enabling hierarchical cascading and demultiplexing functions. Its logic behavior forces all eight Y0–Y7 outputs low when any strobe is asserted, and asserts exactly one high output per valid A2:A0 combination when strobes are inactive.

It operates across the full industrial/military temperature range (-55°C to +125°C) with CMOS input thresholds (VIH ≥ 3.15 V, VIL ≤ 1.35 V at V_CC = 4.5 V) and delivers rail-to-rail output swing under load (VOL ≤ 0.4 V at I_OL = 4 mA, VOH ≥ 3.7 V at I_OH = 4 mA).

Key Specifications

Pinout & Package

SOP-16 (NS package), body size 10.20 mm × 5.30 mm, surface-mount, RoHS-compliant, moisture sensitivity level 1 (unlimited floor life at <30°C/60% RH).

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74HC138NSR, the CD74HC238NSR provides native active-high outputs eliminating inverter stages, while SN74HC238PWR offers identical functionality in a smaller TSSOP package-both retain the same -55°C to +125°C rating and 13 ns propagation delay critical for deterministic real-time control.

Availability

CD74HC238NSR is available at Aetrix Electronics and suitable for industrial control systems, aerospace avionics, and test equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HC238NSR 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 delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The CD74HC238NSR belongs to TI's legacy HC logic family, designed for high-noise-immunity, wide-voltage-operation digital interfacing in mission-critical systems where reliability across extreme temperatures is mandatory.

FAQ

What is the output behavior of CD74HC238NSR when all enable inputs are inactive?

When G2 is high and both G1 and G0 are high (i.e., all enables inactive), the CD74HC238NSR decodes A2:A0 and drives exactly one of Y0–Y7 high (active-high), with all other outputs low. This is the normal decoding mode defined in Table 7-2 of the datasheet. The CD74HC238NSR does not float outputs - they are always driven to valid logic levels.

Can CD74HC238NSR operate at 3.3 V supply voltage?

Yes, CD74HC238NSR supports 2 V to 6 V operation, including 3.3 V nominal rails. At V_CC = 3.3 V, VIH is guaranteed ≥ 2.31 V and VIL ≤ 0.99 V (30% noise margin), and output drive remains ±4 mA. Propagation delay increases to ~18 ns (typ.) versus 13 ns at 5 V, but remains fully functional in 3.3 V systems.

How does CD74HC238NSR differ from CD74HC138NSR in pin compatibility and function?

CD74HC238NSR and CD74HC138NSR share identical pinout, package, supply specs, and timing - but differ exclusively in output polarity: CD74HC238NSR has active-high outputs (Y_n = HIGH when selected), while CD74HC138NSR has active-low outputs (Y_n = LOW when selected). No other electrical or functional differences exist.

Is a bypass capacitor required for CD74HC238NSR, and what value is recommended?

Yes, a 0.1 µF ceramic bypass capacitor is required between V_CC and GND, placed within 2 mm of pins 16 and 8 respectively. This suppresses supply transients caused by output switching. For enhanced noise rejection, TI recommends paralleling with a 1 µF capacitor - both are mandatory for stable operation in industrial environments per Section 8 of the datasheet.

What is the maximum output sink current specification for CD74HC238NSR?

The CD74HC238NSR is rated for 4 mA sink current per output (I_OL) with VOL ≤ 0.4 V at V_CC = 6 V and TA = 125°C. This is validated across the full temperature range and ensures reliable interfacing with LSTTL loads, microcontroller inputs, and LED drivers without external buffering.