Texas Instruments CD74HCT244M

Overview

CD74HCT244M from Texas Instruments is a non-inverting octal buffer/line driver with three-state outputs and dual active-low output enables (1OE, 2OE), designed for bidirectional bus interfacing in 5-V digital systems. It delivers 8ns typical propagation delay at VCC = 5 V, CL = 15 pF, supports ±25 mA output drive per channel, operates across –55°C to +125°C, and features CMOS input compatibility with LSTTL-level logic inputs.

For engineers reviewing the CD74HCT244M datasheet, CD74HCT244M pinout, CD74HCT244M application, or CD74HCT244M equivalent, key selection criteria include its dual active-low enable architecture, high-current bus driving capability, wide industrial temperature range, and strict HCT-level input voltage thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V) ensuring reliable TTL-to-CMOS translation.

Technical Context

The CD74HCT244M implements two independent 4-bit non-inverting buffer sections, each controlled by its own active-low output enable (1OE for Y1–Y4, 2OE for Y5–Y8). All eight outputs enter high-impedance state when their respective enable is high, enabling shared-bus arbitration without external logic.

Its HCT logic family ensures direct compatibility with LSTTL outputs while maintaining CMOS power efficiency: input leakage remains ≤ ±1 μA, supply current is ≤ 160 μA over full temperature range, and it tolerates input rise/fall times up to 500 ns at 4.5 V - critical for legacy system integration.

Key Specifications

Pinout & Package

CD74HCT244M is supplied in a 20-pin SOIC (Small Outline Integrated Circuit) package with 12.80 mm × 7.50 mm body size, surface-mount compatible, and RoHS-compliant (NIPDAU lead finish).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT244N and 74ACT244SCX, CD74HCT244M uniquely combines SOIC packaging, full –55°C to +125°C qualification, and proven reliability in mission-critical embedded systems - making it optimal for aerospace, defense, and industrial control designs requiring long-term availability and extended environmental resilience.

Availability

CD74HCT244M is available at Aetrix Electronics and suitable for industrial PLC backplanes, automotive body control modules, and military radio interfaces requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HCT244M 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 decades of heritage in high-reliability logic families.

CD74HCT244M belongs to TI's CD74HCT high-speed CMOS logic series, engineered for seamless TTL-to-CMOS interfacing in industrial, automotive, and aerospace systems demanding wide temperature operation and robust noise immunity.

FAQ

What is the maximum clock/data rate supported by CD74HCT244M?

The CD74HCT244M is not a clocked device but a combinatorial buffer; its usable data rate depends on propagation delay and load. With 10 ns typical tPD and 45 ns max output disable time, it reliably supports asynchronous bus protocols up to ~25 MHz in well-terminated 50-pF load conditions. For synchronous applications, ensure setup/hold margins accommodate worst-case 38 ns tPD.

Can CD74HCT244M drive a 50-Ω transmission line directly?

No - CD74HCT244M is not designed for 50-Ω line driving. Its ±25 mA output is optimized for LSTTL fanout (15 loads) and short PCB traces. For 50-Ω termination, use a dedicated line driver IC or add series termination. Direct connection risks overshoot, ringing, and excessive current draw beyond rated limits.

Does CD74HCT244M require external pull-up or pull-down resistors on unused inputs?

Yes - all unused inputs (A1–A8, 1OE, 2OE) must be tied to VCC or GND per TI layout guidelines. Floating inputs cause undefined output states and increased ICC. For CD74HCT244M, tie unused A-inputs to GND (to force low output) or VCC (to force high output), and tie unused OE pins to VCC to keep associated outputs disabled.

Is CD74HCT244M pin-compatible with CD74HC244M?

Yes - CD74HCT244M and CD74HC244M share identical pinout, package, and functional block diagram. However, CD74HC244M operates from 2–6 V and has different input thresholds (VIH = 3.15 V min at 4.5 V), so direct substitution requires verifying supply voltage and source logic family compatibility.

What thermal considerations apply to CD74HCT244M in SOIC-20 package?

CD74HCT244M in SOIC-20 has RθJA = 109.1°C/W. At 5.5 V and full 8-channel drive (200 mA total), power dissipation may reach ~1.1 W, causing >120°C junction rise above ambient. Derate output current or add copper pour and airflow for sustained high-load operation. Use the 0.1-μF bypass capacitor close to VCC/GND pins to minimize switching noise-induced heating.