Texas Instruments SN74LS244NS

Overview

SN74LS244NS from Texas Instruments is an octal non-inverting 3-state buffer/line driver in a 20-pin SOP (NS) package, designed for memory address and bus driving applications. It features two independent 4-bit channels with active-low output-enable inputs (1G, 2G/2G), 24 mA low-level output drive, 18 ns maximum propagation delay at 5 V, and PNP input structure reducing DC loading on buses.

For engineers reviewing the SN74LS244NS datasheet, SN74LS244NS pinout, SN74LS244NS application, or SN74LS244NS equivalent, this device is selected for high-density bus interfacing where controlled 3-state isolation, noise-immune inputs with hysteresis, and compatibility with both 5-V TTL and 3.3-V logic levels are required in industrial control, telecom infrastructure, and LED display systems.

Technical Context

The SN74LS244NS implements dual 4-bit non-inverting buffer architecture with separate active-low output-enable controls per channel (1G and 2G/2G). Each channel passes A-side inputs to Y-side outputs when its G input is low; outputs enter high-impedance state when G is high.

It uses Schottky-clamped TTL (LS) logic with PNP input stages to minimize input current draw and built-in input hysteresis (0.2–0.4 V) to improve noise immunity. The device operates across 4.75–5.25 V supply and supports terminated line driving down to 133 Ω.

Key Specifications

Pinout & Package

SN74LS244NS is housed in a 20-pin SOP (Small Outline Package) with body size 7.80 mm × 12.60 mm, surface-mount footprint, and standard JEDEC MS-012AC outline.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal non-inverting 3-state buffer applications.

Compared with SN74LS240NS and SN74LS244N, the SN74LS244NS offers identical logic functionality and performance in a smaller surface-mount package-reducing PCB area by 68% versus PDIP while maintaining full drop-in compatibility with other SN74LS24x variants in SOP format.

Availability

SN74LS244NS is available at Aetrix Electronics and suitable for memory address buffering, LED display driving, telecom backplane interfacing, and industrial I/O expansion requiring stable component supply across long-lifecycle embedded programs.

Supply support for SN74LS244NS 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 global semiconductor company headquartered in Dallas, Texas, delivering analog and embedded processing solutions for industrial, automotive, and communications markets.

The SN74LS24x family was developed to provide high-density, low-power 3-state bus interface solutions for memory subsystems and control logic in 1980s-era computing and instrumentation platforms, emphasizing reliability, noise immunity, and backward compatibility.

FAQ

What is the recommended operating voltage range for SN74LS244NS?

The SN74LS244NS is specified for operation at 4.75 V to 5.25 V. Operation outside this range may cause unreliable 3-state control, increased ICC, or failure to meet VOH/VOL specifications. TI recommends using a tightly regulated 5-V supply with local 0.1 µF ceramic decoupling at the VCC pin to ensure stable SN74LS244NS performance under dynamic load conditions.

How does the SN74LS244NS handle input signals from 3.3-V logic devices?

The SN74LS244NS accepts 3.3-V logic inputs reliably because its VIH minimum is 2.0 V, well below typical 3.3-V CMOS VOH (≈3.0 V). No level-shifting circuitry is required. This compatibility is confirmed in the "Inputs Tolerant Down to 2 V" feature and validated across the recommended operating conditions table in the SN74LS244NS datasheet.

What is the purpose of the hysteresis on SN74LS244NS inputs?

The SN74LS244NS incorporates 0.2–0.4 V of input hysteresis (VT+ − VT−) to increase noise immunity on shared bus lines. This prevents false triggering due to slow-rising edges or electrical noise, especially in industrial or telecom environments. The hysteresis is inherent to the LS-TTL input structure and applies to all A and G inputs of the SN74LS244NS.

Can SN74LS244NS outputs drive terminated transmission lines?

Yes - the SN74LS244NS can drive terminated lines down to 133 Ω, as explicitly stated in the device description. Its 24 mA sink capability and 15 ns typical propagation delay make it suitable for short-to-medium-length PCB traces in memory and control buses where impedance matching is required to suppress reflections.

What happens to SN74LS244NS outputs during power-up or power-down?

During power-up or power-down, SN74LS244NS outputs enter undefined states unless output-enable inputs (1G, 2G/2G) are held high via pullup resistors to VCC. TI recommends connecting both 1G and 2G/2G to VCC through ≥10 kΩ resistors to force high-impedance mode before VCC stabilizes, preventing bus contention and protecting downstream devices in the SN74LS244NS system.