Texas Instruments SN74LS298N

Overview

SN74LS298N from Texas Instruments is a quad 2-input multiplexer with latch function, implemented in bipolar TTL logic. It features four independent 2:1 data selectors, each with separate enable and latch control, operates at VCC = 5 V, supports propagation delay of 25 ns (max) at 25°C, and functions across 0°C to 70°C ambient temperature - used in digital data routing and register file address selection in legacy industrial controllers.

For engineers reviewing the SN74LS298N datasheet, SN74LS298N pinout, SN74LS298N application, or SN74LS298N equivalent, key selection considerations include its dual-enable architecture, latch-enabled data hold capability, TTL-compatible input thresholds, and PDIP-16 package compatibility with through-hole prototyping and repair workflows.

Technical Context

The SN74LS298N integrates four identical 2:1 multiplexer channels, each with independent strobe (G) and latch (LE) inputs that control data transparency versus latched output state. All channels share common VCC and GND, and outputs are fully buffered for fan-out of 20 LS-TTL loads.

It implements true TTL circuitry with Schottky-clamped transistors, ensuring stable switching at 5 V ±5%, with input clamp diodes for transient protection and guaranteed noise margin of 0.4 V under worst-case conditions.

Key Specifications

Pinout & Package

SN74LS298N is housed in a 16-pin plastic dual in-line package (PDIP-N), with 0.3-inch body width, 0.1-inch pin pitch, and through-hole mounting configuration. The package meets RoHS-compliant NIPDAU lead finish and is supplied in tubes of 25 units.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar multiplexer-with-latch applications.

Compared with SN74LS298N, SN74LS398N adds functional redundancy via complemented outputs at cost of power and complexity, while SN74ALS298N delivers measurable performance uplift in speed and efficiency - both retain full pin and logic compatibility for drop-in evaluation.

Availability

SN74LS298N is available at Aetrix Electronics and suitable for industrial control retrofitting, legacy test equipment repair, and educational lab kits requiring stable component supply and long-term obsolescence support.

Supply support for SN74LS298N 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 ICs with broad industrial and automotive portfolio coverage.

The SN74LS298N belongs to TI's legacy 74LS logic family, designed specifically for reliable, noise-tolerant digital signal routing in commercial-grade control and instrumentation systems of the 1970s–1990s era.

FAQ

What is the function of the latch enable (LE) input on the SN74LS298N?

The latch enable (LE) input on the SN74LS298N controls whether the output follows the selected input (LE = low) or holds the last valid value (LE = high). This feature allows asynchronous data capture independent of the strobe signal. In SN74LS298N, each of the four channels has its own LE terminal, enabling selective latching per path. This behavior is essential for glitch-free signal handoff in bus arbitration circuits.

Can SN74LS298N operate at 3.3 V?

No, SN74LS298N is strictly a 5 V TTL device and does not support 3.3 V operation. Its input thresholds, output drive strength, and internal biasing are optimized for VCC = 5 V ±5%. Attempting to power SN74LS298N at 3.3 V results in undefined logic states, excessive propagation delay, and potential output contention. Level-shifting circuitry is required for interfacing with 3.3 V systems.

Is SN74LS298N pin-compatible with SN74LS157?

No, SN74LS298N is not pin-compatible with SN74LS157. While both are quad 2:1 multiplexers, SN74LS298N includes dedicated latch and strobe inputs per channel and uses a different pin assignment - notably sharing pins for outputs and control signals. SN74LS157 lacks latch functionality entirely and has distinct enable and output pin mapping. Direct substitution would require PCB redesign.

What is the maximum clock/data rate supported by SN74LS298N?

SN74LS298N supports reliable operation up to approximately 20 MHz, based on its 25 ns maximum propagation delay and setup/hold time specifications. At 20 MHz, the 50 ns period provides sufficient margin for signal stabilization. Higher rates risk timing violations, especially under worst-case temperature and voltage conditions. For SN74LS298N, stable operation is confirmed in 8085-based systems running at 2–5 MHz with conservative timing margins.

Does SN74LS298N have ESD protection diodes on its inputs?

Yes, SN74LS298N includes integrated input clamp diodes to GND and VCC, providing basic ESD protection per MIL-STD-883 Class 3B (±2 kV HBM). These diodes limit transient overvoltage but do not replace external TVS or RC filtering in high-noise environments. TI's datasheet confirms internal clamping for all inputs, a standard feature across the 74LS family including SN74LS298N.