Texas Instruments SNJ54HC138J

Overview

SNJ54HC138J from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in CDIP-16 package, designed for high-speed memory decoding and data routing. It operates across –55°C to +125°C, supports 2 V–6 V supply, delivers ±4 mA output drive at 5 V, and achieves 15 ns typical propagation delay (VCC = 6 V). It is used in military-grade timing-critical address decoding within avionics and ruggedized industrial controllers.

For engineers reviewing the SNJ54HC138J datasheet, SNJ54HC138J pinout, SNJ54HC138J application, or SNJ54HC138J equivalent, key selection criteria include its triple-enable architecture (G1, G2A, G2B), active-low outputs, wide temperature range, and compatibility with legacy TTL loads in high-reliability systems.

Technical Context

The SNJ54HC138J implements CMOS-based binary decoding logic with three select inputs (A, B, C) and three enable terminals (G1 active-high; G2A, G2B active-low). All outputs are active-low open-drain compatible, enabling wired-OR expansion without external inverters.

Its functional mode requires simultaneous assertion of G1 = HIGH and G2A = G2B = LOW to activate decoding; any enable violation forces all eight Y0–Y7 outputs HIGH. Propagation delay is specified down to 15 ns at VCC = 6 V and CL = 50 pF, with input transition times supported as slow as 400 ns (VCC = 6 V).

Key Specifications

Pinout & Package

SNJ54HC138J uses a 16-pin Ceramic Dual In-line Package (CDIP) with 21.34 mm × 6.92 mm body size and through-hole mounting. Pin numbering follows standard D, DB, J, N, NS, PW, and W package conventions per TI SCLS107G.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC138N and MC14513BCP, SNJ54HC138J uniquely combines military temperature range, hermetic CDIP packaging, and triple-enable architecture - making it irreplaceable in systems requiring guaranteed operation at –55°C or requiring MIL-STD-883 compliance.

Availability

SNJ54HC138J is available at Aetrix Electronics and suitable for avionics address decoding, industrial PLC I/O expansion, ruggedized LED matrix displays, and military data acquisition systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SNJ54HC138J 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and high-reliability logic solutions with over 50 years of aerospace and defense component experience.

The SNJ54HC138J belongs to TI's military-grade HC logic family, engineered for high-speed, low-power decoding in mission-critical systems where extended temperature operation and process consistency are mandatory.

FAQ

What is the operating temperature range of the SNJ54HC138J?

The SNJ54HC138J is rated for –55°C to +125°C operation, meeting MIL-PRF-38535 requirements for military and aerospace applications. This range is validated across all electrical parameters in the datasheet, including propagation delay, output drive, and input thresholds - unlike commercial variants such as SN74HC138N, which only operate from –40°C to +85°C.

Does the SNJ54HC138J support 3.3 V logic levels?

Yes, the SNJ54HC138J supports 3.3 V operation within its 2 V–6 V supply range. At VCC = 3.3 V, VIH is guaranteed ≥2.31 V and VIL ≤1.0 V per Section 6.3 of the datasheet, ensuring reliable interfacing with 3.3 V microcontrollers and FPGAs without level shifters.

How many enable inputs does the SNJ54HC138J have, and what are their polarities?

The SNJ54HC138J has three enable inputs: G1 (active-high), G2A (active-low), and G2B (active-low). All three must be simultaneously asserted (G1 = HIGH, G2A = G2B = LOW) for decoding to occur; any violation forces all Y0–Y7 outputs HIGH - a feature used for hierarchical chip selection and data reception gating.

Can the SNJ54HC138J drive LEDs directly?

Yes, the SNJ54HC138J can directly sink LED current via its active-low outputs. Each output delivers up to 4 mA at 5 V, sufficient for low-current indicator LEDs or column driving in multiplexed 8×8 matrices. For higher-current LEDs, an external NPN transistor or MOSFET is recommended to avoid exceeding absolute maximum ratings.

Is the SNJ54HC138J pin-compatible with other HC138 variants?

Yes, the SNJ54HC138J shares identical pinout and logic function with all SNx4HC138 variants in D, DB, N, NS, PW, and W packages (per Pin Functions table, page 3 of SCLS107G). However, mechanical dimensions, thermal characteristics, and temperature ratings differ - CDIP (J) offers hermetic sealing and extended temperature range not found in plastic SOIC or TSSOP versions.