Texas Instruments SN74AS874NT

Overview

SN74AS874NT from Texas Instruments is a dual 4-bit D-type edge-triggered flip-flop with noninverting 3-state outputs, designed as a bus-oriented register driver. It features asynchronous clear (CLR), true logic outputs, 125 MHz max clock frequency, 48 mA output drive capability, and operates from 4.5 V to 5.5 V across 0°C to 70°C. It is used in high-speed bidirectional bus interfaces and I/O port buffering.

For engineers reviewing the SN74AS874NT datasheet, SN74AS874NT pinout, SN74AS874NT application, or SN74AS874NT equivalent, key selection considerations include its 24-pin plastic DIP (NT) package, 3-state bus-driving capability, asynchronous reset timing (min 2 ns pulse width), propagation delays under 10.5 ns, and compatibility with TTL-level signaling in legacy industrial control and data acquisition systems.

Technical Context

This device implements two independent 4-bit edge-triggered D flip-flop sections, each with individual clock (CLK), clear (CLR), and output-enable (OE) controls. Data is latched on the low-to-high transition of CLK; CLR asynchronously forces Q outputs low regardless of clock state.

The 3-state outputs support direct bus connection with controlled enable/disable timing-tPZH/tPHZ (2–6 ns) and tPZL/tPLZ (2–7.5 ns) ensure fast bus release and acquisition. Its AS-family silicon delivers higher speed and stronger drive than ALS variants while maintaining TTL-compatible input thresholds and output voltage levels.

Key Specifications

Pinout & Package

SN74AS874NT is supplied in a 24-pin plastic dual-in-line package (DIP), 300-mil width, with through-hole mounting and standard JEDEC MO-058 AA footprint. Pin 1 is located at the top-left corner with notch or dot marking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ALS874BN, SN74AS874NT delivers 4× higher clock rate and 2× stronger drive for demanding bus applications; versus SN74AS874DW, it provides through-hole reliability and serviceability in field-replaceable modules, albeit with larger board area.

Availability

SN74AS874NT is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, legacy test equipment data capture, and embedded controller bus interface applications requiring stable component supply and long-term obsolescence management.

Supply support for SN74AS874NT 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 founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74AS874NT belongs to TI's 74AS advanced Schottky TTL logic family, engineered for high-speed, high-drive parallel bus interfacing in legacy and upgrade systems where 5 V TTL compatibility and deterministic timing are essential.

FAQ

What is the maximum clock frequency supported by the SN74AS874NT?

The SN74AS874NT supports a maximum clock frequency of 125 MHz under recommended operating conditions (VCC = 4.5 V to 5.5 V, CL = 50 pF). This specification is verified per TI's SDAS061C datasheet, with tPLH/tPHL propagation delays guaranteed ≤ 10.5 ns. The SN74AS874NT achieves this performance using advanced Schottky TTL process technology, making it suitable for high-speed synchronous register applications where timing precision is critical.

Does the SN74AS874NT have inverting or noninverting outputs?

The SN74AS874NT has noninverting Q outputs, consistent with the SN74AS874 family designation. Each of its two 4-bit sections produces true logic outputs (Q, not Q̅), and its function table confirms that Q follows D on the rising clock edge when CLR is inactive and OE is low. This distinguishes it from the SN74AS876 variant, which provides inverting outputs. The SN74AS874NT's noninverting behavior simplifies data path design in register-to-bus transfer applications.

What package type is used for the SN74AS874NT?

The SN74AS874NT uses a 24-pin plastic dual-in-line package (DIP), designated "NT" by Texas Instruments, with 300-mil width and through-hole leads. Mechanical drawings confirm compliance with JEDEC MO-058 AA and MIL-STD-1835 GDIP3-T24 standards. This package supports socket-based prototyping, field replacement, and legacy board assembly - unlike the SOIC-24 (DW) variant, the NT package is not surface-mount and requires wave or hand soldering.

Can the SN74AS874NT be used as a bidirectional bus driver?

Yes, the SN74AS874NT can serve as a bidirectional bus driver when paired with complementary devices or used in systems where direction control is managed externally. Its dual 4-bit structure, independent OE inputs per section, and 3-state outputs allow selective enabling/disabling of each 4-bit bank onto a shared bus. While it does not integrate direction control logic internally, its bus-structured pinout and strong ±48 mA drive make it ideal for implementing discrete bidirectional data paths in industrial backplanes and test instrumentation, as confirmed in TI's functional description.

What is the purpose of the CLR input on the SN74AS874NT?

The CLR (clear) input on the SN74AS874NT is an asynchronous, active-low control that forces the corresponding Q outputs low immediately - independent of the clock signal. Each 4-bit section has its own CLR pin (Pin 1 for Section 1, Pin 24 for Section 2), enabling independent reset of register banks. This function is essential for system initialization, error recovery, and deterministic state clearing in real-time control applications. The minimum CLR pulse width is specified as 2 ns, ensuring compatibility with fast logic families in the SN74AS874NT's timing budget.