Nexperia USA Inc. 74AHCT138D,118

Overview

74AHCT138D,118 from Nexperia is a 3-to-8 line inverting decoder/demultiplexer in SO16 package, operating at 4.5–5.5 V with TTL-compatible inputs, 8 mutually exclusive active-low outputs (Y0–Y7), and three enable inputs (E1, E2 active LOW; E3 active HIGH) for cascading up to 1-of-32 decoding. It serves as a memory chip select decoder in industrial microcontroller systems.

For engineers reviewing the 74AHCT138D,118 datasheet, 74AHCT138D,118 pinout, 74AHCT138D,118 application, or 74AHCT138D,118 equivalent, key selection considerations include TTL-level input compatibility, propagation delay ≤13.0 ns at 5 V/50 pF, -40 °C to +125 °C operation, SO16 thermal profile, and enable-input-driven demultiplexing capability.

Technical Context

The device implements a combinational logic decoder with fully decoded 3-bit binary address inputs (A0–A2) driving eight independent active-low outputs under triple-enable control. Its inverting output architecture ensures only one Yn is LOW per valid address/enable state, enabling precise chip-select routing.

Enable logic requires simultaneous assertion of both E1 and E2 (LOW) and E3 (HIGH); violation forces all outputs HIGH. This hierarchical enable scheme supports parallel expansion-e.g., four units plus one inverter yield a 5-to-32 decoder-without external gating logic.

Key Specifications

Pinout & Package

74AHCT138D,118 uses the SOT109-1 (SO16) plastic small outline package: 16-pin, 3.9 mm body width, 1.27 mm pitch, gull-wing leads, JEDEC MS-012 compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HC138PW,118 and SN74LS138N, the 74AHCT138D,118 uniquely balances TTL input compatibility, SO16 manufacturability, and industrial temperature support-making it optimal for new 5 V embedded designs requiring drop-in replaceability and production scalability.

Availability

74AHCT138D,118 is available at Aetrix Electronics and suitable for memory address decoding, peripheral multiplexing, industrial I/O expansion, and legacy system interface applications requiring stable component supply across extended temperature ranges.

Supply support for 74AHCT138D,118 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 leading semiconductor manufacturer specializing in high-performance, energy-efficient logic, analog, and MOSFET devices for industrial, automotive, and consumer markets.

The 74AHCT138D,118 belongs to Nexperia's AHCT logic family-designed specifically for seamless integration between TTL and CMOS systems, emphasizing robust input compatibility, low dynamic power, and extended temperature reliability.

FAQ

Can 74AHCT138D,118 operate with a 3.3 V supply?

No. The 74AHCT138D,118 is specified only for 4.5 V to 5.5 V operation per its Recommended Operating Conditions table. At 3.3 V, input thresholds (VIH ≥ 2.0 V) may be met, but VOH/VOL performance, propagation delay, and output drive fall outside guaranteed specs-and the device is not characterized or qualified below 4.5 V.

What happens if only one enable input is asserted?

If fewer than all three enables meet their required states-e.g., E1 = LOW but E2 = HIGH or E3 = LOW-then all eight outputs (Y0–Y7) remain HIGH regardless of A0–A2 values. This is defined in the Function Table: any invalid enable combination forces outputs HIGH as a fail-safe decode inhibition.

Is the SO16 package RoHS-compliant and lead-free?

Yes. The SOT109-1 (SO16) package used for 74AHCT138D,118 is RoHS-compliant and lead-free, meeting EU Directive 2011/65/EU and Nexperia's standard environmental compliance requirements. Full material declarations and test reports are available upon request via Aetrix Electronics' technical support.

How does the device handle unused enable inputs?

Unused enable inputs must be permanently tied to their defined active state: E1 and E2 to GND (for active LOW), E3 to VCC (for active HIGH). Floating enables risk metastability, increased ICC, or unintended output activation due to noise coupling-especially in high-noise industrial environments.