Diodes Incorporated 74HCT138T16-13

Overview

74HCT138T16-13 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 4.5 V to 5.5 V, sinks 4 mA at VO = 0.26 V, and delivers propagation delays as low as 17 ns at 5.0 V. It is used in memory chip select decoding and peripheral demultiplexing in industrial microcontroller systems.

For engineers reviewing the 74HCT138T16-13 datasheet, 74HCT138T16-13 pinout, 74HCT138T16-13 application, or 74HCT138T16-13 equivalent, key selection criteria include enable logic configuration (dual low + single high), output drive capability under 4 mA load, guaranteed operation from –40°C to +125°C, and TSSOP-16 package compatibility with high-density PCB layouts.

Technical Context

The 74HCT138T16-13 implements combinational logic decoding using standard TTL-compatible input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) and Schmitt-trigger action on all inputs for noise immunity. Its output stage is designed for active-low open-drain–like behavior with defined VOL (0.26 V @ 4 mA) and VOH (3.7 V @ –4 mA).

Enable architecture supports hierarchical expansion: parallel connection of multiple units enables 4-to-16 or 5-to-32 decoding without external gates-E1/E2/E3 logic allows cascading via Y outputs driving downstream E inputs while maintaining deterministic high-Z disable state (all outputs high when disabled).

Key Specifications

Pinout & Package

TSSOP-16 package: 4.9 mm × 6.4 mm body, 0.65 mm pitch, 1.08 mm max height, lead-free and RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT138DR and 74VHC138MTCX, the 74HCT138T16-13 offers optimal trade-off of compact TSSOP-16 footprint, full industrial temperature support, and proven 5 V system interoperability-making it preferred for new designs targeting high-reliability embedded control.

Availability

74HCT138T16-13 is available at Aetrix Electronics and suitable for memory decoding, peripheral demultiplexing, bus isolation control, and legacy interface adaptation requiring stable component supply across industrial temperature ranges and long production lifecycles.

Supply support for 74HCT138T16-13 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, specializing in high-reliability components for industrial, computing, and consumer applications.

The 74HCT logic family targets pin-compatible upgrades of legacy TTL systems, delivering CMOS power efficiency with guaranteed 5 V TTL signal compatibility and enhanced ESD/latch-up robustness.

FAQ

What is the maximum clock frequency supported for address changes?

The 74HCT138T16-13 is a purely combinational device with no internal clock; its usable frequency depends on propagation delay and system setup/hold timing. With 17 ns typical tPD at 5.0 V, it reliably supports address bus toggling up to ~30 MHz in synchronous systems where enable signals are stable before address transitions.

Can E1, E2, and E3 be driven directly from a 3.3 V microcontroller?

Yes-inputs tolerate up to 6.0 V and recognize VIH ≥ 2.0 V. A 3.3 V logic high exceeds the 2.0 V minimum VIH threshold across all temperature ranges, making direct connection safe without level shifting, provided VCC remains at 4.5–5.5 V.

What happens to outputs during power-up or brown-out conditions?

During VCC ramp-up, outputs remain in high-impedance until VCC exceeds ~1.5 V, then default to high state once internal biasing stabilizes (~100 μs after VCC > 2.0 V). All outputs stay high if any enable input is inactive, preventing spurious peripheral activation during power sequencing.

Is thermal derating required above 85°C ambient?

Yes-the datasheet specifies absolute max junction temperature of 150°C and recommends limiting power dissipation. At 125°C ambient, total power (ICC × VCC + switching losses) must be kept below ~300 mW to maintain TJ < 150°C, requiring careful PCB copper area and airflow consideration in sealed enclosures.