Nexperia USA Inc. 74HC138BQ,115

Overview

74HC138BQ,115 from Nexperia is a 3-to-8 line inverting decoder/demultiplexer with three binary address inputs (A0–A2), eight active-LOW mutually exclusive outputs (Y0–Y7), and three enable inputs (E1, E2 = active LOW; E3 = active HIGH). It operates from 2.0 V to 6.0 V, supports -40 °C to +125 °C ambient range, and features CMOS-level input compatibility. It is used for memory chip select decoding and parallel expansion to 1-of-32 decoding in embedded control logic.

For engineers reviewing the 74HC138BQ,115 datasheet, 74HC138BQ,115 pinout, 74HC138BQ,115 application, or 74HC138BQ,115 equivalent, key selection considerations include its inverting output logic, triple-enable architecture for cascading, DHVQFN16 thermal-enhanced packaging, and guaranteed static/dynamic performance across industrial temperature extremes.

Technical Context

The device implements a combinational logic decoder with strict mutual exclusivity: only one output goes LOW when all enables are satisfied (E1 = LOW, E2 = LOW, E3 = HIGH) and a unique 3-bit address is applied. Its enable hierarchy allows hierarchical expansion-e.g., four units plus one inverter yield a 5-to-32 decoder without external logic gates.

Input clamping diodes permit safe interfacing to voltages exceeding VCC when used with current-limiting resistors. All outputs drive standard CMOS loads with guaranteed VOH ≥ 4.4 V and VOL ≤ 0.26 V at VCC = 4.5 V and IO = ±4 mA, supporting direct connection to downstream logic without level-shifting.

Key Specifications

Pinout & Package

DHVQFN16 package (SOT763-1): 2.5 mm × 3.5 mm × 0.85 mm body, no leads, exposed thermal pad (non-soldered by default), 16 terminals, pin 1 index marked on top surface.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HCT138BQ,115, the 74HC138BQ,115 offers superior voltage flexibility and lower static power but requires CMOS-level input drive; versus SN74LS138DR, it enables modern low-voltage operation and cuts quiescent current by >99%, though with different noise margin trade-offs.

Availability

74HC138BQ,115 is available at Aetrix Electronics and suitable for memory address decoding, peripheral select logic, bus multiplexing, and FPGA configuration interfaces requiring stable component supply across industrial temperature ranges.

Supply support for 74HC138BQ,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 specializing in high-performance, energy-efficient logic, analog, and MOSFET solutions for automotive, industrial, and consumer markets.

The 74HC138BQ,115 belongs to Nexperia's industry-standard HC logic family, designed for robust, low-power combinational decoding in space-constrained embedded systems operating across extended temperature ranges.

FAQ

What is the maximum clock frequency supported by the 74HC138BQ,115?

The 74HC138BQ,115 is a purely combinational device with no internal clock - its effective operating frequency depends on propagation delay and system timing margins. With tpd = 12 ns (typ) at VCC = 6.0 V, it supports address decode cycles up to approximately 40 MHz in synchronous bus architectures, assuming setup/hold times are met by the driving controller.

Can the 74HC138BQ,115 be used as a demultiplexer?

Yes - configure E3 as the data input (active HIGH), and use E1/E2 as strobe controls while holding A0–A2 constant. Each Yn output reflects the inverted E3 state when its corresponding enable condition is satisfied, enabling 1-to-8 signal distribution without additional logic.

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

No - the thermal pad (terminal 1) has no electrical function and requires no solder connection. If soldered, it must remain electrically floating or be connected to GND; improper grounding may cause latch-up or increased ground impedance.

How does the 74HC138BQ,115 differ from the 74HCT138BQ,115 in practical design?

The 74HC138BQ,115 uses CMOS-compatible input thresholds (VIH ≈ 0.7×VCC), making it ideal for mixed-voltage 3.3 V/2.5 V systems. The 74HCT138BQ,115 uses fixed TTL thresholds (VIH = 2.0 V min), ensuring compatibility with legacy 5 V TTL outputs but limiting use below 4.5 V supply.