Nexperia USA Inc. 74AHC138BQ,115

Overview

74AHC138BQ,115 from Nexperia is a high-speed CMOS 3-to-8 line decoder/demultiplexer with inverting outputs, pin-compatible with LSTTL, operating from 2.0 V to 5.5 V supply, featuring three enable inputs (two active LOW, one active HIGH), and delivering eight mutually exclusive LOW-active outputs (Y0–Y7) for memory chip select and address decoding in industrial control and embedded logic systems.

For engineers reviewing the 74AHC138BQ,115 datasheet, 74AHC138BQ,115 pinout, 74AHC138BQ,115 application, or 74AHC138BQ,115 equivalent, this device is selected for precise binary address decoding, parallel expansion to 1-of-32 decoding, demultiplexing with strobe-controlled data routing, and robust operation across -40 °C to +125 °C.

Technical Context

The 74AHC138BQ implements a combinational logic decoder with three binary address inputs (A0–A2) and eight active-LOW outputs (Y0–Y7), where output selection requires simultaneous assertion of E1 and E2 (LOW) and E3 (HIGH). Its function table defines strict mutual exclusivity: only one output goes LOW per valid input combination, all others remain HIGH.

It supports demultiplexing by repurposing an enable input (e.g., E1) as data input while using remaining enables as strobes, and enables cascading via multiple enable lines - allowing four devices plus one inverter to construct a 5-to-32 decoder without external logic.

Key Specifications

Pinout & Package

DHVQFN16 package (SOT763-1): 2.5 × 3.5 × 0.85 mm body, thermally enhanced, leadless quad flat design with exposed thermal pad (non-soldered or GND-connected), suitable for high-density PCB layouts and improved thermal performance over SO16/TSSOP.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74AHCT138BQ,115, the AHC variant offers superior noise immunity and lower static current but requires CMOS-level inputs; versus SN74HC138PWR, it delivers nearly double the speed at 5 V while maintaining identical functionality and footprint compatibility.

Availability

74AHC138BQ,115 is available at Aetrix Electronics and suitable for memory chip select decoding, industrial I/O expansion, demultiplexed data routing, and logic state machine control requiring stable component supply across extended temperature ranges and high-volume production cycles.

Supply support for 74AHC138BQ,115 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 logic, analog, and MOSFET solutions optimized for reliability and energy efficiency in industrial, automotive, and computing applications.

The 74AHC138BQ belongs to Nexperia's advanced high-speed CMOS logic family, designed specifically for low-power, high-speed address decoding and signal routing in space-constrained, thermally demanding embedded systems.

FAQ

What is the maximum clock frequency supported by the 74AHC138BQ,115?

The 74AHC138BQ,115 is a combinational logic device with no internal clock; its usable switching rate depends on propagation delay and load capacitance. With 50 pF load and 5 V supply, tpd ≤10.5 ns supports reliable operation up to ~48 MHz toggle rate on address inputs, assuming clean edges and proper termination.

Can the 74AHC138BQ,115 drive LEDs directly?

No - its outputs are rated for ±8 mA sink/source at specified VOL/VOH, insufficient for typical indicator LEDs requiring 10–20 mA. It can drive LED anodes via pull-up resistors only if current is limited externally to ≤8 mA, but dedicated LED drivers or buffer stages are recommended for visual indicators.

Is the thermal pad on the DHVQFN16 package required to be soldered?

No - the exposed thermal pad (Pin 1) has no electrical function and may remain unsoldered. If connected, it must be tied to GND or left floating; soldering improves thermal resistance by ~15 °C/W but is not mandatory for operation within ambient limits.

How does the 74AHC138BQ,115 differ from the 74HC138 in practical use?

The 74AHC138BQ,115 offers faster propagation (≤10.5 ns vs ~21 ns), lower ICC (≤80 μA vs ~160 μA), tighter VIH/VIL thresholds, and enhanced ESD protection (HBM >2000 V vs ~200 V), making it preferable for high-speed, low-power, and noise-sensitive industrial designs where HC-series timing or leakage would compromise performance.