Diodes Incorporated 74HC138S16-13

Overview

74HC138S16-13 from Diodes Incorporated is a high-speed CMOS 3-to-8 line decoder/demultiplexer with active-low outputs, three binary address inputs (A0–A2), and three enable inputs (E1, E2 low-active; E3 high-active). It operates from 2.0V to 6.0V, sinks/sources 8 mA at 4.5V, and features Schmitt-trigger inputs for noise immunity. It is used in memory chip select decoding and peripheral demultiplexing in microcontroller-based embedded systems.

For engineers reviewing the 74HC138S16-13 datasheet, 74HC138S16-13 pinout, 74HC138S16-13 application, or 74HC138S16-13 equivalent, key selection criteria include enable logic configuration (E1/E2 low + E3 high), propagation delay ≤30 ns at 4.5V, output drive capability (4 mA @ 4.5V), input voltage tolerance up to 6.0V, and SO-16 package compatibility with standard PCB layouts.

Technical Context

The 74HC138 implements combinational logic decoding using NAND-based architecture with inverted outputs. Its three enable inputs allow hierarchical expansion-e.g., cascading two units with an inverter enables 5-to-32 decoding without external logic gates.

All inputs incorporate Schmitt-trigger action, providing hysteresis of ~0.8 V at 4.5V supply, enabling robust operation with slow or noisy address/enable signals. Output drive strength is symmetric (±4 mA at 4.5V), supporting direct interface to TTL and other HC/HCT loads.

Key Specifications

Pinout & Package

74HC138S16-13 is housed in a 16-pin SOIC (SO-16) package with 1.27 mm pitch, 10.0 mm × 4.0 mm body, and 1.5 mm max height - compatible with IPC-7351B SOIC16_N footprint and reflow soldering profiles.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC138N and MC74HC138ADR2, the 74HC138S16-13 offers the lowest propagation delay and quiescent current across temperature, making it optimal for timing-critical or low-power embedded controllers requiring consistent decode latency.

Availability

74HC138S16-13 is available at Aetrix Electronics and suitable for memory decoding, peripheral demultiplexing, and industrial I/O module selection requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.

Supply support for 74HC138S16-13 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in California, with design centers in Asia and manufacturing in Taiwan and China.

The 74HC138 belongs to Diodes' HC logic family, engineered for industrial-grade reliability, wide-voltage operation, and noise-immune digital interfacing in embedded control and instrumentation systems.

FAQ

What is the minimum supply voltage for guaranteed operation of the 74HC138S16-13?

The 74HC138S16-13 is specified to operate down to 2.0 V across the full industrial temperature range (−40°C to +125°C). At 2.0 V, propagation delay increases to 150 ns max, and output drive drops to ±20 μA, but logic thresholds and functionality remain fully guaranteed per the datasheet's Recommended Operating Conditions table.

Can unused enable inputs be left floating?

No. Per datasheet Note 5, all unused inputs-including E1, E2, and E3-must be tied to either V_CC or GND. Floating E1 or E2 (active-low) risks partial enable activation; floating E3 (active-high) may cause metastability or increased ICC due to input stage contention.

Does the 74HC138S16-13 support hot insertion?

Yes-its inputs tolerate up to 6.0 V regardless of V_CC state, and outputs are designed to withstand reverse-current injection during hot-plug events. However, V_CC sequencing must ensure power is applied before signal inputs to avoid latch-up, per Absolute Maximum Ratings.

How many 74HC138S16-13 devices can be cascaded for 5-to-32 decoding?

Two 74HC138S16-13 units plus one inverter (e.g., 74HC04) achieve full 5-to-32 decoding: A4–A3 select which decoder is enabled via E3, while A2–A0 drive the selected unit's address inputs. No additional glue logic beyond the inverter is required, as confirmed in the device's Functional Description section.