Texas Instruments SN74AHCT244NSR

Overview

SN74AHCT244NSR from Texas Instruments is an octal 3-state buffer/driver IC designed for bus interface and memory address driving in 5-V digital systems. It features TTL-compatible inputs (VIH = 2 V, VIL = 0.8 V), ±8 mA output drive, 5.5 ns typical propagation delay (CL = 15 pF), and operates from –40°C to +85°C. It enables bidirectional signal isolation in PC motherboard data buses and industrial I/O expansion modules.

For engineers reviewing the SN74AHCT244NSR datasheet, SN74AHCT244NSR pinout, SN74AHCT244NSR application, or SN74AHCT244NSR equivalent, this page delivers verified electrical specs, SOP-20 package mapping, functional mode behavior, real-world use cases in bus buffering, and two validated alternative parts with documented differences.

Technical Context

The SN74AHCT244NSR implements two independent 4-bit non-inverting buffers, each controlled by a dedicated 3-state output-enable input (1OE, 2OE). Its CMOS design with TTL-level input thresholds allows seamless interfacing between 3.3-V logic sources and 5-V bus loads. The device uses slow-edge-rate outputs to suppress ringing on unterminated transmission lines.

Each buffer section operates with rail-to-rail output swing (VOH ≥ 3.8 V at IOH = –8 mA, VOL ≤ 0.44 V at IOL = 8 mA) and exhibits low quiescent current (ICC ≤ 40 µA). Input hysteresis is not present; switching thresholds are fixed at VIH = 2 V and VIL = 0.8 V across the full operating temperature range.

Key Specifications

Pinout & Package

SOP-20 (NS) package: 12.60 mm × 7.80 mm body size, 12.6 mm × 5.30 mm footprint, 1.75 mm max height, gull-wing leads, RoHS-compliant NiPdAu finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AHCT244NSR, SN74LVC244APWR offers higher speed and lower voltage operation but requires external level translation in 5-V environments, while 74ACT244SCX provides greater drive strength but sacrifices input overvoltage safety-making SN74AHCT244NSR optimal for robust, mixed-signal bus isolation.

Availability

SN74AHCT244NSR is available at Aetrix Electronics and suitable for PC motherboard I/O expansion, industrial PLC backplane interface, and network switch management bus applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for SN74AHCT244NSR 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 leader specializing in analog, embedded processing, and logic solutions with over 90 years of innovation in industrial, automotive, and communications markets.

The SN74AHCT244NSR belongs to TI's AHCT logic family, engineered for TTL-compatible interfacing in 5-V systems where noise immunity, bus contention control, and reliable 3-state operation are critical.

FAQ

What is the maximum input voltage rating for SN74AHCT244NSR?

The SN74AHCT244NSR supports input voltages up to 5.5 V regardless of VCC level, as confirmed in Section 5.1 Absolute Maximum Ratings. This overvoltage tolerance allows safe connection to 3.3-V, 5-V, or mixed-voltage signal sources without external clamping, making SN74AHCT244NSR ideal for system bring-up and debug interfaces where voltage domains overlap.

Does SN74AHCT244NSR require external pull-up resistors on its OE pins?

Yes - to ensure outputs remain in high-impedance state during power-up or brownout, SN74AHCT244NSR OE pins (1OE, 2OE) must be pulled high via external resistors. Section 7.1 Overview specifies that OE should connect to VCC through a pullup; minimum resistance depends on driver sink capability but typically ranges from 4.7 kΩ to 10 kΩ for standard microcontroller outputs.

Can SN74AHCT244NSR drive a 50-pF load at 100 MHz?

No - SN74AHCT244NSR is rated for CL = 15 pF and CL = 50 pF in switching characteristics tables, with tPLH/tPHL ≤ 9.5 ns at 50 pF. At 100 MHz (10 ns period), timing margin is insufficient for reliable toggling. SN74AHCT244NSR is intended for asynchronous or low-frequency synchronous bus buffering (≤30 MHz sustained), not high-speed clock distribution.

What is the thermal resistance (RθJA) of SN74AHCT244NSR in SOP-20 package?

The junction-to-ambient thermal resistance (RθJA) for SN74AHCT244NSR in SOP-20 (NS) package is 77.6°C/W, as specified in Section 5.4 Thermal Information. This value assumes standard JEDEC 2S2P board layout; actual performance improves with copper pour and thermal vias under the exposed pad (if applicable) - though NS package has no exposed pad.

Is SN74AHCT244NSR pin-compatible with SN74AHCT244N (PDIP-20)?

Yes - SN74AHCT244NSR (SOP-20) and SN74AHCT244N (PDIP-20) share identical pin numbering, pin functions, and logic behavior per Figure 4-1 and Table 4-1. Both follow the same 20-pin dual-inline functional map, enabling direct PCB footprint substitution where board space and reflow profile allow.