Texas Instruments SN74ALS29846NT

Overview

SN74ALS29846NT from Texas Instruments is an 8-bit transparent D-type latch with inverting data inputs and three-state outputs, designed for bus interface applications. It operates at 5 V, delivers ±24 mA high-level and 48 mA low-level output drive, and supports 0°C to 70°C industrial temperature range. Used in bidirectional bus drivers and I/O ports where data inversion and bus isolation are required.

For engineers reviewing the SN74ALS29846NT datasheet, SN74ALS29846NT pinout, SN74ALS29846NT application, or SN74ALS29846NT equivalent, key selection factors include its inverting D-input logic, triple output control (OC1–OC3), power-up high-impedance state, and compatibility with standard 24-pin NT (plastic DIP) packaging.

Technical Context

This device implements eight independent D-type latches with asynchronous preset (PRE) and clear (CLR) inputs, enabling immediate output forcing regardless of clock state. Its three buffered output controls (OC1, OC2, OC3) operate independently of internal latch timing and place all outputs simultaneously into high-impedance without affecting stored data.

The SN74ALS29846NT uses Advanced Low-Power Schottky (ALS) technology, delivering propagation delays as low as 2 ns (tPLH/tPHL, CL = 50 pF) and output enable/disable times under 10 ns (tPZH/tPLZ). It maintains bus integrity via high-impedance during power-up/down and supports direct driving of capacitive bus loads up to 300 pF.

Key Specifications

Pinout & Package

SN74ALS29846NT is supplied in a 24-pin plastic dual in-line package (NT), 300-mil width, with through-hole mounting and bus-structured pinout optimized for PCB layout density and signal routing efficiency.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-bit bus interface latch applications.

Compared with SN74ALS29845NT and SN74F29846N, the SN74ALS29846NT uniquely combines inverting data logic, guaranteed power-up high-impedance, and ALS power-efficiency-making it optimal for bus-isolated I/O and parity applications where deterministic startup behavior is essential.

Availability

SN74ALS29846NT is available at Aetrix Electronics and suitable for memory address latching, parallel I/O port expansion, and parity bus interface applications requiring stable component supply and long-term obsolescence support.

Supply support for SN74ALS29846NT 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 with global manufacturing and quality certification.

The SN74ALS29846NT belongs to TI's legacy Advanced LS (ALS) logic family, engineered for high-speed, low-power bus interfacing in industrial and computing systems requiring TTL compatibility and robust drive capability.

FAQ

What logic polarity does the SN74ALS29846NT implement on its data inputs?

The SN74ALS29846NT features inverting D-type inputs: a logic high applied to any D pin produces a low at the corresponding Q output after latching. This is confirmed in the device description and function table, distinguishing it from the noninverting SN74ALS29845. The SN74ALS29846NT is selected specifically when data inversion is required within the latch stage itself.

Does the SN74ALS29846NT enter high-impedance state automatically during power-up?

Yes, the SN74ALS29846NT guarantees a high-impedance output state at power-up, preventing bus contention before system initialization completes. This behavior is explicitly stated in the datasheet description and is a key differentiator from standard TTL latches. The SN74ALS29846NT maintains this state until all output controls (OC1–OC3) are actively driven low.

How many output control inputs does the SN74ALS29846NT have, and how do they operate?

The SN74ALS29846NT has three dedicated output control inputs: OC1, OC2, and OC3. All three must be held low to enable normal logic-level outputs; if any one is high, all eight Q outputs enter high-impedance. These inputs are buffered to minimize loading on upstream control logic, and their operation is independent of the clock or latch state - the SN74ALS29846NT retains stored data even while outputs are disabled.

What package type is used for the SN74ALS29846NT variant?

The SN74ALS29846NT uses a 24-pin plastic dual in-line package (NT), 300-mil width, with through-hole mounting. This matches the "NT Package (Top View)" designation in the datasheet and differs from the FN (flatpack) and DW (SOIC) variants. The SN74ALS29846NT pinout is identical to SN74ALS29845NT, supporting drop-in replacement where logic polarity permits.

Can the SN74ALS29846NT be used alongside SN74ALS29845 devices on the same bus?

Yes, the SN74ALS29846NT and SN74ALS29845 share identical pinouts, timing, drive strength, and electrical specifications - differing only in D-input polarity. They can coexist on the same bus when their respective data paths require complementary logic polarity. System designers must ensure that the SN74ALS29846NT's inverting behavior aligns with upstream signal definitions, as the SN74ALS29846NT will invert data relative to the SN74ALS29845NT.