Texas Instruments CD74HC238PWRE4

Overview

CD74HC238PWRE4 from Texas Instruments is a high-speed CMOS 3-to-8 line decoder/demultiplexer with active-high outputs, 2 V to 6 V supply operation, -55°C to 125°C temperature range, and typical 13 ns propagation delay at VCC = 4.5 V and CL = 15 pF. It serves as an address decoder in memory subsystems and data routing in industrial control logic.

For engineers reviewing the CD74HC238PWRE4 datasheet, CD74HC238PWRE4 pinout, CD74HC238PWRE4 application, or CD74HC238PWRE4 equivalent, key selection factors include its noninverting output logic, three enable inputs for cascading, LSTTL-compatible fanout (10 loads), wide voltage tolerance, and TSSOP-16 packaging for space-constrained PCB layouts.

Technical Context

The CD74HC238PWRE4 implements a 3-input address decoding function with three independent strobe inputs (G2, G1, G0) - one standard (G2) and two active-low (G1, G0) - enabling hierarchical demultiplexing and multi-level enable control. Its logic architecture forces all eight Y0–Y7 outputs low when any strobe is asserted, and asserts exactly one high output per valid 3-bit address when enabled.

Unlike the '138 variant, the '238 family uses noninverting output polarity: selected output goes high while unselected outputs remain low. This eliminates external inverters in applications requiring active-high enable signals for peripheral selection or LED drivers, reducing component count and propagation latency.

Key Specifications

Pinout & Package

TSSOP-16 package (5.00 mm × 4.40 mm body size, 0.65 mm pitch), 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 CD74HC138PWR, CD74HC238PWRE4 eliminates inverter stages in active-high routing, saving 2–3 ns per stage and one passive component per channel; versus SN74LV138APWR, it retains full 5 V interoperability but trades 3 ns speed for broader voltage flexibility.

Availability

CD74HC238PWRE4 is available at Aetrix Electronics and suitable for industrial control systems, test equipment signal routing, memory address decoding, and LED display multiplexing requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HC238PWRE4 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 headquartered in Dallas, Texas, delivering analog and embedded processing solutions for industrial, automotive, and personal electronics markets.

The CD74HC238PWRE4 belongs to TI's HC (High-Speed CMOS) logic family, designed for pin-compatible upgrades from LS-TTL with lower power, wider voltage range, and improved noise immunity in industrial and instrumentation applications.

FAQ

What is the maximum clock frequency supported by CD74HC238PWRE4 for reliable address decoding?

The CD74HC238PWRE4 does not operate on a clock signal - it is combinational logic. Its maximum usable frequency is determined by propagation delay: with 13 ns typical tpd at VCC = 4.5 V, it supports address transitions up to approximately 30 MHz in systems where setup/hold margins allow. For synchronous systems, ensure address stability ≥13 ns before strobe assertion. The CD74HC238PWRE4 datasheet specifies no maximum toggle rate, only timing limits under defined load conditions.

Can CD74HC238PWRE4 be used with a 3.3 V microcontroller without level shifting?

Yes. The CD74HC238PWRE4 operates from 2 V to 6 V and has CMOS input thresholds (VIH = 1.8 V min. at VCC = 3.3 V), making it fully compatible with 3.3 V logic. Inputs accept 3.3 V signals directly, and outputs swing rail-to-rail - producing ≥3.1 V high and ≤0.2 V low at VCC = 3.3 V - ensuring robust interfacing with 3.3 V MCUs without level shifters.

How do the three enable inputs (G2, G1, G0) interact in CD74HC238PWRE4?

In CD74HC238PWRE4, all outputs go low when *any* enable condition fails: G2 must be high, and both G1 and G0 must be low. If G2 = low, or G1 = high, or G0 = high, all Y0–Y7 are forced low regardless of A2–A0 state. This enables hierarchical enable trees - e.g., G2 from system master enable, G1 from subsystem ID, G0 from mode register - allowing fine-grained control without external logic.

Is CD74HC238PWRE4 pin-compatible with CD74HC138PWR?

Yes - CD74HC238PWRE4 and CD74HC138PWR share identical TSSOP-16 pinout, supply ratings, timing, and enable logic. The sole functional difference is output polarity: CD74HC238PWRE4 outputs go high when selected (noninverting), while CD74HC138PWR outputs go low (inverting). No PCB changes are required for substitution, but firmware or downstream logic must accommodate the polarity inversion.

What thermal considerations apply to CD74HC238PWRE4 in high-density PCB layouts?

CD74HC238PWRE4 has a junction-to-ambient thermal resistance (RθJA) of 108°C/W in TSSOP-16. At maximum ICC = 160 µA and worst-case 6 V supply, static power dissipation is <1 mW - negligible for thermal design. However, under heavy capacitive loading (e.g., 50 pF per output), dynamic power rises; maintain ≥0.1 µF ceramic decoupling at VCC and avoid routing high-frequency traces near the device to prevent localized heating. No heatsink is required.