onsemi MC74HCT244AFG

Overview

MC74HCT244AFG from onsemi is an octal 3-state noninverting buffer/line driver with LSTTL-compatible inputs, designed for bus-oriented systems including memory address drivers and clock distribution. It operates from 4.5 V to 5.5 V, delivers ±6 mA output drive per channel, supports –55°C to +125°C operation, and features two active-low output enables (OE_A, OE_B) for independent group control.

For engineers reviewing the MC74HCT244AFG datasheet, pinout, applications, or equivalent options, key selection criteria include 3-state output timing (tPLZ ≤ 39 ns), LSTTL input compatibility (VIH = 2.0 V min), high-impedance leakage (IOZ ≤ ±10 µA), and SOIC-20W/TSSOP-20 package options with Pb-free compliance.

Technical Context

The MC74HCT244AFG implements eight noninverting buffer channels split into two independently enabled groups (A1–A4/YA1–YA4 and B1–B4/YB1–YB4), each controlled by separate active-low output enable pins. Its CMOS silicon-gate process ensures TTL/NMOS input compatibility while driving CMOS, NMOS, and TTL loads directly.

It meets JEDEC Standard No. 7A for TTL-compatible logic levels and provides guaranteed DC performance across –55°C to +125°C, with propagation delays (tPLH/tPHL ≤ 30 ns) and transition times (tTLH/tTHL ≤ 18 ns) specified at VCC = 5.0 V ±10% and CL = 50 pF.

Key Specifications

Pinout & Package

MC74HCT244AFG is available in SOIC-20W (Case 751D) and TSSOP-20 (Case 948E) packages. Both are 20-pin surface-mount devices with 1.27 mm pitch (SOIC) and 0.65 mm pitch (TSSOP), Pb-free and RoHS compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal noninverting buffer applications.

Compared with SN74HCT244N and 74VHC244M, the MC74HCT244AFG uniquely combines LSTTL input compatibility, industrial temperature range, and dual-package availability-making it optimal for robust 5 V bus interfacing where legacy signal integrity and long-term supply continuity matter.

Availability

MC74HCT244AFG is available at Aetrix Electronics and suitable for memory address buffering, microcontroller bus expansion, and industrial PLC backplane interfacing requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MC74HCT244AFG 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

onsemi (formerly ON Semiconductor) is a global semiconductor manufacturer specializing in energy-efficient power, analog, sensor, and logic solutions for automotive, industrial, and cloud infrastructure markets.

The MC74HCT244AFG belongs to onsemi's high-speed CMOS logic family, engineered specifically for seamless TTL-to-CMOS interfacing and robust 3-state bus management in mission-critical industrial and automotive control systems.

FAQ

What is the maximum operating temperature for MC74HCT244AFG?

The MC74HCT244AFG is rated for continuous operation from –55°C to +125°C across all package types. This specification is guaranteed per JEDEC standards and validated in onsemi's qualification testing. The device maintains full DC and AC performance within this range, including tPLH ≤ 30 ns and IOZ ≤ ±10 µA at +125°C. Thermal derating applies above +65°C: SOIC-20W dissipates –7 mW/°C, TSSOP-20 –6.1 mW/°C.

Does MC74HCT244AFG support true TTL input levels?

Yes, MC74HCT244AFG fully supports true TTL input thresholds: VIH is guaranteed ≥ 2.0 V and VIL ≤ 0.8 V over temperature and voltage, meeting JEDEC Standard No. 7A. This allows direct connection to 74LS, 74F, and other TTL-family outputs without external level shifters. Input leakage remains ≤ ±1.0 µA at VCC = 5.5 V, ensuring minimal loading on upstream drivers.

Can MC74HCT244AFG replace a 74LS244 in existing designs?

Yes, MC74HCT244AFG is pinout-identical to the 74LS244 and functions as a direct drop-in replacement. It retains identical logic behavior, pin assignments, and mechanical footprint in SOIC-20W and TSSOP-20 packages. Key improvements include wider VCC tolerance (4.5–5.5 V vs. 4.75–5.25 V), lower ICC (≤160 µA vs. ~20 mA), and extended temperature range (–55°C to +125°C vs. 0°C to +70°C).

What is the output drive capability of MC74HCT244AFG per channel?

MC74HCT244AFG delivers ±6 mA DC output current per channel under guaranteed conditions (VCC = 4.5 V, TA ≤ 125°C), sufficient to drive 15 LSTTL loads. At room temperature and VCC = 5.0 V, VOH ≥ 4.4 V and VOL ≤ 0.26 V at ±6 mA load. This drive strength ensures signal integrity across typical PCB traces and moderate capacitive loads without external buffers.

How does the dual output-enable architecture of MC74HCT244AFG improve system design?

The MC74HCT244AFG features two independent active-low output enables (OE_A and OE_B), allowing separate control of its two four-channel groups (A and B). This enables selective bus arbitration-for example, holding Group A outputs in high-impedance while driving Group B-reducing contention in multi-master systems. Each OE pin has identical timing (tPLZ ≤ 39 ns), supporting synchronized or staggered enable sequencing without added logic.