Texas Instruments SN74LS244NSR

Overview

SN74LS244NSR from Texas Instruments is an octal non-inverting 3-state buffer/line driver in a 20-pin SSOP package, designed for memory address and bus line driving. It features dual 4-bit channels with independent active-low output-enable (1G, 2G), 24 mA low-level output drive, 15 ns maximum propagation delay at 5 V, and hysteresis-enhanced noise immunity. It is used in server backplanes to isolate and strengthen address/data bus signals between CPU and memory modules.

For engineers reviewing the SN74LS244NSR datasheet, SN74LS244NSR pinout, SN74LS244NSR application, or SN74LS244NSR equivalent, key selection criteria include 3-state bus-driving capability, TTL-compatible input thresholds, thermal resistance (RθJA = 94.3°C/W), PNP-input DC loading reduction, and compatibility with mixed 3.3-V/5-V logic systems.

Technical Context

The SN74LS244NSR implements two independent 4-bit non-inverting buffer sections, each controlled by a dedicated active-low output-enable input (1G and 2G). Its PNP input structure reduces DC loading on upstream drivers, while built-in input hysteresis provides 400 mV noise margin. The device operates strictly within 4.75–5.25 V supply range and supports bidirectional bus isolation when paired with complementary devices.

Each channel drives up to 24 mA sink current at VOL ≤ 0.5 V and delivers VOH ≥ 2.4 V at IOH = –3 mA. Output enable timing includes tPZH ≤ 23 ns and tPLZ ≤ 20 ns (CL = 45 pF, RL = 667 Ω), enabling reliable high-speed bus arbitration in legacy TTL-based systems.

Key Specifications

Pinout & Package

SN74LS244NSR uses a 20-pin SSOP (DB) package measuring 7.20 mm × 5.30 mm, optimized for high-density PCB layouts while maintaining surface-mount manufacturability.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS240NSR, SN74LS244NSR avoids signal inversion-critical for address/data bus transparency-while matching all timing, drive, and noise specs. Against SN74LS244N, it trades thermal performance for 40% smaller footprint and automated assembly compatibility.

Availability

SN74LS244NSR is available at Aetrix Electronics and suitable for memory address buffering, server backplane signal integrity, LED display column driving, and industrial I/O expander interface applications requiring stable component supply across extended product lifecycles.

Supply support for SN74LS244NSR 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 founded in 1930, delivering analog and embedded processing solutions across industrial, automotive, and communications markets.

The SN74LS244NSR belongs to TI's legacy LS-TTL logic family, engineered specifically for high-reliability bus driving, memory address expansion, and signal restoration in industrial control and computing infrastructure.

FAQ

What is the recommended operating voltage range for SN74LS244NSR?

The SN74LS244NSR is specified for operation between 4.75 V and 5.25 V. Operation outside this range may cause unreliable 3-state control, increased VOL, or permanent damage. The device draws ICC = 27–46 mA depending on output state, and its internal PNP inputs require stable VCC to maintain VIH/VIL thresholds per the datasheet's Recommended Operating Conditions table.

How does SN74LS244NSR handle mixed-voltage logic interfaces?

SN74LS244NSR accepts 2.5-V and 3.3-V logic inputs while powered at 5 V, due to its input tolerance down to 2 V and hysteresis-enhanced thresholds. This allows direct connection to modern microcontrollers without level shifters. However, outputs remain 5-V TTL levels, so downstream 3.3-V receivers must be 5-V tolerant or buffered accordingly. The SN74LS244NSR itself does not translate output voltage levels.

What is the function of pins 1G and 19 (2G/2G) on SN74LS244NSR?

Pins 1 (1G) and 19 (2G/2G) are active-low output-enable inputs controlling Channel 1 and Channel 2 independently. When pulled LOW, each channel passes non-inverted data from its A-side inputs (e.g., pins 2,4,6,8) to Y-side outputs (e.g., pins 18,16,14,12). When HIGH, the corresponding outputs enter high-impedance state. For reliable power-up behavior, both G pins must be tied to VCC via pullup resistors to prevent bus contention.

Can SN74LS244NSR drive terminated transmission lines?

Yes, SN74LS244NSR is explicitly rated to drive terminated lines down to 133 Ω, supporting impedance-matched routing on backplanes or long cables. Its 24 mA IOL ensures VOL ≤ 0.5 V into such loads, preserving noise margins. For optimal signal integrity, TI recommends using series termination near the driver and avoiding stubs longer than 1/10 wavelength of the highest significant frequency component (typically <10 cm for 15 ns edges).

What thermal considerations apply to SN74LS244NSR in SSOP packaging?

SN74LS244NSR in SSOP (DB) package has RθJA = 94.3°C/W. At maximum ICC = 54 mA and 5.25 V, worst-case power dissipation is ~284 mW, resulting in ~26.8°C junction rise above ambient. To maintain reliability, keep ambient temperature below 70°C and ensure adequate copper pour under the package. Avoid placing heat-generating components nearby, and verify thermal performance using actual board layout simulations or IR imaging.