Texas Instruments SNJ54HC251J

Overview

SNJ54HC251J from Texas Instruments is a high-speed 8-to-1 data selector/multiplexer with complementary 3-state outputs, designed for military-grade bus interfacing and parallel-to-serial conversion. It operates across 2 V to 6 V, delivers ±6 mA output drive at 5 V, exhibits typical propagation delay of 35 ns (VCC = 6 V, CL = 50 pF), and supports full binary decoding of three select lines (A, B, C) to route one of eight data inputs (D0–D7) to true (Y) and inverted (W) outputs.

For engineers reviewing the SNJ54HC251J datasheet, SNJ54HC251J pinout, SNJ54HC251J application, or SNJ54HC251J equivalent, this device is critical in legacy aerospace, defense, and industrial control systems requiring wide-voltage operation, high-current 3-state bus driving, and guaranteed −55°C to +125°C performance with CDIP packaging.

Technical Context

The SNJ54HC251J implements full binary decoding logic to select exactly one of eight data inputs based on the 3-bit address (A, B, C), with strobe-controlled enable (OE) gating both complementary outputs (Y and W) into high-impedance state when asserted high. Its CMOS architecture ensures low input current (≤1 μA max) and low quiescent power (ICC ≤ 80 μA at 6 V).

It features dual 3-state outputs-Y (true) and W (inverted)-both simultaneously enabled or disabled by OE, allowing synchronized bus arbitration. The device meets SN54HC logic family specifications, including absolute maximum ratings up to 7 V supply and junction temperature limits of 150°C, making it suitable for harsh-environment embedded timing and data routing.

Key Specifications

Pinout & Package

SNJ54HC251J uses a 16-pin Ceramic Dual In-line Package (CDIP) with 24.38 mm × 6.92 mm body size, hermetically sealed for high-reliability military use. Pin numbering follows JEDEC MS-012 standard for J-package devices.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-to-1 multiplexer applications.

Compared with SN74HC251N, SNJ54HC251J offers guaranteed operation at −55°C and hermetic reliability, while SNJ54HC251FK trades through-hole ease-of-use for compactness-neither is pin-compatible, requiring physical redesign for substitution.

Availability

SNJ54HC251J is available at Aetrix Electronics and suitable for aerospace data acquisition, avionics sensor multiplexing, and military communication interfaces requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SNJ54HC251J 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 logic solutions, with over 50 years of heritage in high-reliability military IC design.

The SN54HC logic family-including SNJ54HC251J-is engineered for defense, aerospace, and industrial applications demanding extended temperature operation, radiation tolerance, and long-term supply chain stability.

FAQ

What is the maximum clock frequency supported by SNJ54HC251J for reliable data selection?

The SNJ54HC251J does not operate on a clock signal-it is combinatorial logic. Its maximum usable data rate is determined by propagation delay: at VCC = 6 V and CL = 50 pF, tpd is 35 ns max, supporting input address changes up to ~10 MHz for stable output settling. For SNJ54HC251J, timing margins must account for worst-case select-line setup/hold relative to data validity windows.

Does SNJ54HC251J support 3.3 V logic systems?

Yes, SNJ54HC251J operates across 2 V to 6 V, including 3.3 V nominal supply. At VCC = 3.3 V, VIH is 2.31 V min and VIL is 0.99 V max per datasheet Section 5.2, ensuring compatibility with standard 3.3 V CMOS logic families. However, output drive strength reduces to ~±4 mA, sufficient for most 3.3 V loads.

Can SNJ54HC251J be used without pull-up or pull-down resistors on unused inputs?

No. Per TI application report SCBA004, all unused inputs-including select lines A/B/C and data inputs D0–D7-must be tied to VCC or GND. Floating inputs cause increased ICC, erratic output behavior, and potential latch-up. For SNJ54HC251J, tie unused D inputs to GND and unused select lines to VCC unless actively driven.

What is the meaning of "complementary outputs" in SNJ54HC251J?

SNJ54HC251J provides two simultaneous, logically inverted outputs: Y delivers the selected Dn value, while W delivers its inverse (!Dn). Both share the same 3-state enable (OE) control. This eliminates need for external inverters in applications requiring true/inverted bus pairs, such as differential signaling or active-low enable paths.

Is SNJ54HC251J RoHS compliant?

No. SNJ54HC251J uses SnPb (tin-lead) lead finish and is explicitly marked "No" for RoHS compliance in TI's Package Option Addendum. It is intended for legacy military/aerospace systems where Pb-based soldering and hermetic CDIP packaging remain mandatory. For RoHS-compliant alternatives, consider SN74HC251DBR (SSOP) or SN74HC251PWR (TSSOP).