Nexperia USA Inc. 74HCT138D/C5J

Overview

74HCT138D/C5J from Nexperia is a 3-to-8 line inverting decoder/demultiplexer with TTL-compatible inputs, operating from 4.5 V to 5.5 V, featuring three enable inputs (E1, E2 active LOW; E3 active HIGH), eight active LOW mutually exclusive outputs (Y0–Y7), and propagation delay of 20 ns (typ) at VCC = 4.5 V, CL = 50 pF - used for memory chip select decoding and address demultiplexing in industrial control logic.

For engineers reviewing the 74HCT138D/C5J datasheet, 74HCT138D/C5J pinout, 74HCT138D/C5J application, or 74HCT138D/C5J equivalent, this page delivers verified functional behavior, SO16 package mapping, enable-input-driven demultiplexing capability, temperature-rated operation from –40 °C to +125 °C, and real-world substitution guidance against industry-standard alternatives.

Technical Context

The device implements a binary-decoded 3-input to 8-output logic function with strict mutual exclusivity: only one output goes LOW when all enables are satisfied (E1 = LOW, E2 = LOW, E3 = HIGH) and address inputs A0–A2 define the selected line. Its enable architecture supports cascading - e.g., four units plus one inverter expand to 1-of-32 decoding without external logic.

Input thresholds comply with TTL levels (VIH ≥ 2.0 V, VIL ≤ 0.8 V at VCC = 4.5–5.5 V), ensuring interoperability with legacy 5 V logic families; outputs drive ±4 mA at VOH ≥ 3.98 V and VOL ≤ 0.26 V, supporting direct interface to standard CMOS and TTL loads.

Key Specifications

Pinout & Package

74HCT138D/C5J uses the SO16 (SOT109-1) plastic small outline package: 16-pin, 3.9 mm body width, gull-wing leads, JEDEC MS-012 compliant, with pin 1 index marker on the top-left corner.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS138N, 74HCT138D/C5J cuts supply current by >70% while matching TTL input sensitivity; versus 74HC138D, it adds seamless 5 V TTL interoperability at no speed penalty - making it optimal for mixed-logic upgrades and new industrial designs.

Availability

74HCT138D/C5J is available at Aetrix Electronics and suitable for memory decoding, microcontroller peripheral selection, industrial I/O expansion, and LED matrix row driving requiring stable component supply across extended temperature ranges.

Supply support for 74HCT138D/C5J 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

Nexperia is a global semiconductor expert focused on essential efficiency technologies - delivering high-performance, reliable, and scalable logic, analog, and MOSFET solutions for automotive, industrial, and consumer markets.

The 74HCT138D/C5J belongs to Nexperia's HCT logic family, engineered specifically for seamless migration from legacy TTL systems into modern low-power, high-reliability industrial control architectures.

FAQ

Can 74HCT138D/C5J operate at 3.3 V?

No. The 74HCT138D/C5J is specified only for 4.5 V to 5.5 V operation per its recommended conditions table. At 3.3 V, input thresholds (VIH ≥ 2.0 V) may be met, but VOH drops below 2.4 V and propagation delay increases beyond specification - risking timing violations and bus contention. Use 74LVC138 or 74AHC138 for 3.3 V systems.

What is the maximum fan-out for 74HCT138D/C5J outputs?

Each output can drive up to 10 LSTTL loads (based on IOH = –4 mA and IOL = 4 mA), or 20 74HC inputs (CI = 3.5 pF, ICC < 160 μA). Fan-out is limited by capacitive loading: total CL must stay ≤ 50 pF for guaranteed 35 ns max propagation delay. Exceeding this requires local buffering or reduced clock rates.

How does the enable configuration support demultiplexing?

When E1 is used as the data input (driven HIGH/LOW), and E2/E3 serve as strobes (E2 = LOW, E3 = HIGH), the selected Yn output mirrors E1's state while all others remain HIGH - effectively distributing a single data bit across eight channels. This requires no additional logic and preserves the same timing characteristics as decoding mode.

Is 74HCT138D/C5J pin-compatible with 74HC138D?

Yes - both share identical SO16 (SOT109-1) pinout, address/enable/output assignments, and mechanical footprint. However, electrical compatibility depends on source logic: 74HC138D requires CMOS-level inputs (VIH ≥ 3.15 V at 4.5 V), whereas 74HCT138D accepts TTL-level inputs (VIH ≥ 2.0 V), making them functionally interchangeable only when driven by compatible sources.