Nexperia USA Inc. 74HC138DB,112

Overview

74HC138DB,112 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, delivers propagation delays as low as 12 ns at VCC = 6.0 V, and supports memory chip select decoding in industrial microcontroller systems.

For engineers reviewing the 74HC138DB,112 datasheet, 74HC138DB,112 pinout, 74HC138DB,112 application, or 74HC138DB,112 equivalent, key selection considerations include enable logic polarity (E1/E2 LOW + E3 HIGH), output inversion, CMOS-level input compatibility, and SO16 package thermal derating above 110 °C.

Technical Context

The 74HC138DB,112 implements a fully static CMOS decoder architecture with no internal latches or clocks. Its function table defines strict mutual exclusivity: only one output goes LOW when all enables are satisfied and address inputs are stable - all others remain HIGH. Input clamp diodes allow safe interfacing to voltages exceeding VCC when used with current-limiting resistors.

Enable logic is hierarchical: E1 and E2 must both be LOW while E3 is HIGH for any output to activate; this triple-enable scheme enables cascading up to 1-of-32 decoding using four ICs and one inverter. As a demultiplexer, any active-LOW enable (e.g., E1) serves as data input, while remaining enables act as strobes.

Key Specifications

Pinout & Package

74HC138DB,112 uses the SO16 plastic small outline package (SOT109-1), 16-pin, 3.9 mm body width, with standard 1.27 mm lead pitch and gull-wing leads. Pin 1 index located at top-left corner with notch marking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HC138DB,112, the 74HC238PW,118 offers non-inverting outputs at the cost of added layout complexity for polarity conversion, while SN74LS138N trades CMOS efficiency and voltage flexibility for TTL interoperability in aging 5 V platforms.

Availability

74HC138DB,112 is available at Aetrix Electronics and suitable for memory decoding, industrial I/O expansion, LED matrix driving, and programmable logic enable control requiring stable component supply across automotive-grade temperature ranges.

Supply support for 74HC138DB,112 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 for industrial, automotive, and consumer markets.

The 74HC138DB,112 belongs to Nexperia's HC-series high-speed CMOS logic family, engineered for low-power, high-noise-immunity digital interfacing in space- and energy-constrained embedded systems.

FAQ

What is the maximum clock frequency supported by the 74HC138DB,112 for address decoding?

The 74HC138DB,112 has no internal clock but supports address decode rates up to 40 MHz based on its 12 ns typical propagation delay (VCC = 6.0 V, CL = 50 pF). System-level timing depends on setup/hold margins relative to the controlling microcontroller's address strobe - verified timing diagrams are provided in Figures 4 and 5 of the datasheet.

Can the 74HC138DB,112 be used with 3.3 V microcontrollers while interfacing to 5 V peripherals?

Yes - its CMOS inputs accept VIH ≥ 2.1 V (at VCC = 3.3 V) and VIL ≤ 1.35 V, making it compatible with 3.3 V logic. Outputs swing rail-to-rail (0 V to VCC), so for 5 V peripheral interfacing, operate the device at VCC = 5 V and use series resistors + input clamping diodes to protect 3.3 V MCU pins from overvoltage.

How does the enable logic of E1, E2, and E3 interact in cascade configurations?

E1 and E2 are active-LOW; E3 is active-HIGH. All three must be simultaneously asserted (E1=L, E2=L, E3=H) for decoding to occur. In cascaded 1-of-32 designs, outputs of a master '138 drive E1/E2 of slave devices, while E3 remains tied HIGH - enabling one-of-eight slaves per master output, achieving full 5-bit decode with zero external gates.

Is the 74HC138DB,112 pin-compatible with the 74HCT138DB,112 variant?

No - while both share identical pinouts and package (SO16), the 74HCT138DB,112 features TTL-compatible inputs (VIH = 2.0 V min at VCC = 4.5–5.5 V), whereas the 74HC138DB,112 requires CMOS-level inputs (VIH = 3.15 V min at VCC = 4.5 V). Swapping them may cause logic misreads in mixed-technology systems.