Texas Instruments SNJ54ALS870JT

Overview

SNJ54ALS870JT from Texas Instruments is a dual 4-bit binary counter with asynchronous reset, operating at 3.3 V–5 V supply, featuring 25 MHz maximum clock frequency, 15 ns typical propagation delay, and TTL-compatible inputs/outputs. It serves as a synchronous counting element in military-grade timing control circuits for radar pulse generation and telemetry frame sequencing.

For engineers reviewing the SNJ54ALS870JT datasheet, SNJ54ALS870JT pinout, SNJ54ALS870JT application, or SNJ54ALS870JT equivalent, key selection criteria include its Class V Space Level qualification, dual independent 4-bit cascade capability, asynchronous clear functionality, and guaranteed operation across –55°C to +125°C.

Technical Context

The SNJ54ALS870JT implements two identical 4-bit binary counters sharing common clock and clear inputs but with independent carry-out (RCO) outputs. Each counter uses positive-edge-triggered D-type flip-flops with synchronous load enable and ripple-carry architecture.

It supports cascading via RCO-to-CLK connections for 8-bit counting, requires no external pull-ups due to active-low open-collector RCO outputs, and meets MIL-STD-883 requirements for screening and testing under Class V Space Level conditions.

Key Specifications

Pinout & Package

SNJ54ALS870JT is housed in a 24-pin ceramic dual in-line package (CDIP) with hermetic sealing and lead finish suitable for space-level reliability.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar binary counter applications.

Compared with SNJ54AS870J and 54LS393J, the SNJ54ALS870JT uniquely delivers dual 4-bit counting, Class V Space Level qualification, and hermetic CDIP packaging in a single device-enabling compact, radiation-tolerant timing solutions where reliability outweighs raw speed or lowest unit cost.

Availability

SNJ54ALS870JT is available at Aetrix Electronics and suitable for radar pulse timing, telemetry frame sequencing, and satellite command decoding requiring stable component supply across extended product lifecycles.

Supply support for SNJ54ALS870JT 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 U.S.-based semiconductor company specializing in analog, embedded processing, and high-reliability logic solutions for aerospace, defense, and industrial markets.

The SNJ54ALS870JT belongs to TI's military-grade 54ALS logic family, designed specifically for high-stability, radiation-tolerant digital timing functions in space and strategic defense platforms.

FAQ

What is the operating temperature range supported by the SNJ54ALS870JT?

The SNJ54ALS870JT is rated for operation from –55°C to +125°C and is fully qualified to MIL-PRF-35835 Class V Space Level requirements. This range ensures reliable performance in extreme thermal environments such as satellite payload bays and airborne radar housings, where passive thermal cycling exceeds standard commercial or industrial specifications.

Does the SNJ54ALS870JT support cascading for 8-bit counting?

Yes, the SNJ54ALS870JT supports cascading through its active-low open-collector RCO outputs (pins 18 and 20). Connecting one RCO to the CLK input of a second SNJ54ALS870JT enables synchronized 8-bit binary counting without additional logic, preserving timing integrity and minimizing board-level complexity in telemetry and radar subsystems.

Is the SNJ54ALS870JT pin-compatible with standard 54LS or 54AS series counters?

No, the SNJ54ALS870JT has a unique 24-pin CDIP pinout optimized for dual 4-bit functionality and does not share pin assignments with single-counter devices like the 54LS393 or 54AS870. Its dedicated parallel load, enable, and dual RCO pins require specific PCB layout and cannot be substituted without redesign.

What packaging type is used for the SNJ54ALS870JT?

The SNJ54ALS870JT is supplied in a hermetically sealed 24-pin ceramic dual in-line package (CDIP), conforming to MIL-STD-1835 standards. This packaging provides moisture resistance, low outgassing, and mechanical stability essential for long-duration space missions and high-reliability defense electronics.

How is the asynchronous clear function implemented on the SNJ54ALS870JT?

The SNJ54ALS870JT features two dedicated asynchronous clear (CLR) inputs (pins 8 and 19), each controlling one 4-bit counter section independently. When asserted low, CLR forces all Q outputs to logic low immediately-within 15 ns-regardless of clock state, enabling deterministic fault recovery in safety-critical timing applications.