Texas Instruments SN54AS873JT

Overview

SN54AS873JT from Texas Instruments is a dual 4-bit D-type latch with 3-state outputs, designed for bus driving in military-grade digital systems. It features independent latch-enable (LE), clear (CLR), and output-enable (OE) controls per latch bank, operates across –55°C to 125°C, supports 5 V supply, and delivers ±48 mA output drive capability. It is used in high-reliability I/O port buffering and bidirectional data bus interfacing.

For engineers reviewing the SN54AS873JT datasheet, SN54AS873JT pinout, SN54AS873JT application, or SN54AS873JT equivalent, key selection considerations include its military temperature range, 3-state bus-driving architecture, dual-latch timing parameters (e.g., tPLH ≤ 9 ns), and JT ceramic DIP package compatibility with legacy board layouts.

Technical Context

This device implements two independent 4-bit transparent D latches, each with separate LE, CLR, and OE inputs. Latching occurs on LE falling edge; CLR asynchronously forces Q outputs low; OE places outputs in high-impedance state when high. The logic is TTL-compatible with AS-series speed and drive strength.

It uses bipolar Schottky (AS) technology for fast propagation (tPHL ≤ 7 ns from D to Q), low setup/hold times (tsu = 2 ns, th = 4.5 ns), and robust noise immunity (VIH = 2 V, VIL = 0.8 V). All timing and DC specs are fully characterized over –55°C to 125°C for SN54AS873JT.

Key Specifications

Pinout & Package

Ceramic Dual In-Line Package (JT), 24-pin, through-hole mount. Pin 1 marked by notch or dot; pin numbering follows standard DIP convention (counter-clockwise from top-left corner).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual 4-bit latch applications.

Compared with SN54AS873JT, SN54ALS873B-JT offers lower power and relaxed timing at the expense of speed and drive strength, while SN74AS873A-DW provides identical electrical performance in a smaller, commercial-grade package - making SN54AS873JT the sole choice for high-speed, high-reliability through-hole military designs.

Availability

SN54AS873JT is available at Aetrix Electronics and suitable for avionics data acquisition, ruggedized industrial PLCs, military communications backplanes, and test equipment I/O ports requiring stable component supply across extended temperature ranges and long lifecycle support.

Supply support for SN54AS873JT 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 innovator founded in 1930, delivering analog, embedded processing, and logic solutions for industrial, automotive, and aerospace markets.

The SN54AS873JT belongs to TI's military-grade TTL logic family, engineered specifically for high-speed, high-reliability digital interfacing in mission-critical systems where timing precision and environmental resilience are non-negotiable.

FAQ

What is the maximum operating temperature for SN54AS873JT?

The SN54AS873JT is fully characterized and guaranteed to operate from –55°C to 125°C. This military-grade temperature range is validated per MIL-STD-883 Class B requirements and applies across all specified electrical parameters including propagation delay, output drive, and noise margins - ensuring reliable performance in avionics, ground vehicles, and space-qualified subsystems where thermal extremes are routine.

Does SN54AS873JT support true bidirectional bus operation?

The SN54AS873JT does not implement automatic direction control like a transceiver, but enables bidirectional bus operation through coordinated use of its dual latch banks and 3-state outputs. By assigning one bank to input capture (with OE low) and the other to output driving (with OE low), and using shared or independent LE/CLR signals, designers can manage data flow in both directions on the same physical bus - a method widely adopted in legacy MIL-STD-1553 and VMEbus interface designs.

What is the purpose of the NC pins on SN54AS873JT?

SN54AS873JT has four NC (no internal connection) pins: 4, 11, 25, and 26. These pins serve no electrical function and must remain unconnected in the PCB layout. They exist due to package pinout standardization across the SN54AS873/SN54ALS873 family and ceramic JT footprint compatibility. Leaving them floating avoids unintended coupling; soldering or routing to ground/power would risk internal damage or signal integrity degradation.

How does the clear (CLR) function interact with latch-enable (LE) in SN54AS873JT?

In SN54AS873JT, CLR is asynchronous and dominant over LE: when CLR goes low, the corresponding Q outputs (Q1–Q4) force immediately to logic low regardless of LE state or data inputs. This override behavior persists until CLR returns high, after which normal LE-controlled latching resumes. This design allows hard reset of latch contents without disrupting the LE timing sequence - critical for fault recovery in safety-critical control systems.

Can SN54AS873JT be used with 3.3 V logic systems?

SN54AS873JT is a 5 V TTL device and is not 3.3 V compatible. Its input thresholds (VIH = 2.0 V, VIL = 0.8 V) and output swing (VOH ≈ 3.2 V min at 15 mA) are specified only for VCC = 4.5–5.5 V operation. Driving it from 3.3 V CMOS outputs may result in marginal VIH margin, and connecting its 5 V outputs to 3.3 V inputs risks overvoltage damage. Level-shifting circuitry or a 3.3 V–compatible alternative (e.g., SN74LVC873A) is required for mixed-voltage systems.