Texas Instruments SN74S244N

Overview

SN74S244N from Texas Instruments is an octal non-inverting 3-state buffer/line driver designed for memory address and bus-oriented applications. It features two independent 4-bit channels, 5-V operation, maximum propagation delay of 9 ns (tPLH/tPHL), ±15 mA output drive capability, and PNP input structure reducing DC loading on bus lines. It is used in server memory subsystems to isolate and strengthen address signals between CPU and DRAM modules.

For engineers reviewing the SN74S244N datasheet, SN74S244N pinout, SN74S244N application, or SN74S244N equivalent, key selection criteria include 3-state enable timing (tPZH/tPLZ), high-noise-margin hysteresis inputs, compatibility with 3.3-V/5-V mixed logic systems, and thermal performance under sustained bus loading conditions.

Technical Context

The SN74S244N implements Schottky transistor logic (S-TTL) with PNP input stages that reduce input current draw and improve fan-in. Its dual 4-bit architecture uses active-low output-enable (1G, 2G) controls to place each channel's outputs into high-impedance state independently.

It delivers 64 mA low-level output current (IOL) and –15 mA high-level output current (IOH) at VCC = 5 V, enabling direct drive of terminated transmission lines down to 133 Ω. Input hysteresis (0.2–0.4 V) enhances noise immunity in electrically noisy server and telecom backplane environments.

Key Specifications

Pinout & Package

SN74S244N is supplied in a 20-pin plastic dual in-line package (PDIP-N), measuring 24.33 mm × 6.35 mm, with through-hole mounting and standard 0.3-inch row spacing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS244N and 74ACT244PC, SN74S244N provides superior speed and drive strength for legacy TTL bus systems but consumes more power and requires careful G-pin biasing-making it optimal for high-reliability, high-speed address/data buffering where S-TTL compatibility is mandatory.

Availability

SN74S244N is available at Aetrix Electronics and suitable for server memory subsystems, telecom infrastructure backplanes, industrial I/O expanders, and LED display drivers requiring stable component supply across extended product lifecycles.

Supply support for SN74S244N 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 specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74S244N belongs to TI's legacy S-TTL logic family, engineered for high-speed, high-drive bus interface applications in systems where compatibility with 1980s-era TTL architectures remains essential.

FAQ

What is the maximum recommended operating temperature for SN74S244N?

The SN74S244N is rated for 0°C to +70°C ambient operating temperature. Exceeding +70°C risks parametric shift in propagation delay and output drive capability; thermal derating above 50°C is advised when sustained IOL > 40 mA per output is required. The PDIP package has RθJA = 50.6°C/W, so junction temperature must remain below 125°C under worst-case power dissipation.

Does SN74S244N require external pull-up resistors on its G pins?

Yes, SN74S244N requires pull-up resistors on pins 1 (1G) and 19 (2G) to ensure outputs remain in high-impedance state during power-up and power-down sequences. TI recommends ≥10-kΩ pull-ups to VCC; values below 4.7 kΩ increase ICC without improving enable timing. This prevents bus contention before firmware initializes the enable logic.

Can SN74S244N interface directly with 3.3-V microcontrollers?

Yes, SN74S244N accepts 3.3-V logic-high inputs reliably: its VIH specification is 2.0 V minimum, and it exhibits hysteresis (0.2–0.4 V), making it robust against noise when driven from 3.3-V CMOS outputs. However, its outputs swing to ~3.4 V (VOH) at –15 mA, so level-shifting may be needed for 3.3-V receivers expecting rail-to-rail input thresholds.

What is the short-circuit current rating for SN74S244N outputs?

SN74S244N is not characterized for continuous short-circuit operation. Per datasheet Section 6.5, "Not more than one output must be shorted at a time, and duration of the short-circuit must not exceed one second." Sustained shorts risk permanent damage due to localized heating in the S-TTL output stage; external current-limiting resistors or fault protection circuitry are recommended in safety-critical designs.

How does SN74S244N differ from SN74LS244N in bus-driving capability?

SN74S244N delivers 64 mA low-level output current (IOL) versus 24 mA for SN74LS244N, enabling direct drive of heavily loaded or long-trace buses (e.g., 133-Ω terminated lines). Its tPLH/tPHL is 4.5 ns (typ) vs. 12 ns (typ) for LS, and it achieves this with higher ICC (95–160 mA vs. 27–46 mA), reflecting the trade-off between speed, drive, and power in S-TTL versus LS families.