STMicroelectronics 74AC244TTR

Overview

74AC244TTR from STMicroelectronics is an advanced high-speed CMOS octal non-inverting bus buffer with 3-state outputs, designed for memory address/data bus driving and system-level signal isolation. It features 3.8 ns typical propagation delay at 5V, ±24 mA symmetrical output drive, 2 V to 6 V operating voltage range, and 2 kV ESD immunity. Used in industrial control backplanes and legacy 5V TTL-compatible logic interfaces.

For engineers reviewing the 74AC244TTR datasheet, 74AC244TTR pinout, 74AC244TTR application, or 74AC244TTR equivalent, key selection criteria include 3-state enable timing (tPZL/tPLZ ≤ 10.5 ns), transmission-line driving capability into 50 Ω, balanced tPLH/tPHL symmetry, and latch-up immunity for robust board-level interfacing.

Technical Context

The 74AC244TTR implements two independent 4-bit non-inverting 3-state buffer groups, each controlled by a dedicated output-enable input (1G and 2G). Its sub-micron C2MOS process enables rail-to-rail input compatibility (VI = 0 to VCC) and symmetrical ±24 mA output sourcing/sinking at VCC = 5.5 V.

It supports mixed-voltage interfacing across 2–6 V operation, delivers 50 Ω transmission-line drive without external termination, and guarantees incident-wave switching on low-impedance lines - critical for noise-sensitive data bus applications in legacy industrial systems.

Key Specifications

Pinout & Package

TSSOP-20 package: 6.5 mm × 4.4 mm body, 0.65 mm pitch, thin shrink small outline with exposed pad not present. RoHS-compliant, lead-free finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HC244PW and SN74ACT244PWR, the 74AC244TTR uniquely combines 3.8 ns speed, ±24 mA drive, and Class II latch-up immunity - making it optimal for high-reliability 5 V industrial backplanes where signal fidelity and fault tolerance are co-critical.

Availability

74AC244TTR is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy memory subsystems, automotive body control modules, and test equipment signal conditioning requiring stable component supply and long-term lifecycle support.

Supply support for 74AC244TTR 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, digital, and mixed-signal ICs for industrial, automotive, and power applications.

The 74AC logic family targets high-speed, low-noise, and latch-up-immune replacements for legacy TTL and 74HC devices in mission-critical industrial control and instrumentation systems.

FAQ

Is the 74AC244TTR pin-compatible with standard 74-series 244 devices?

Yes - it uses the same TSSOP-20 footprint and pin assignment as 74LS244 and 74HC244 variants. All input/output and enable pins match functionally and physically, enabling direct PCB replacement without layout changes. The device retains identical logic behavior and truth table, including active-low 3-state control on G inputs.

What is the maximum recommended capacitive load for stable 3-state switching?

The 74AC244TTR is characterized for CL = 50 pF in AC testing, and its 50 Ω transmission-line drive capability supports stable edge integrity into ≤30 pF total load (including trace + receiver input). Exceeding 50 pF may increase tPZL/tPLZ beyond 10.5 ns and induce ringing; add series damping only if measured overshoot exceeds 10 % VCC.

Can the 74AC244TTR operate reliably at 3.3 V supply?

Yes - it is fully specified from 2 V to 6 V, with guaranteed VIH/VIL thresholds (e.g., VIH = 2.25 V min. at VCC = 4.5 V) that ensure clean logic recognition at 3.3 V. VOH/VOL remain compliant (VOH ≥ 3.1 V, VOL ≤ 0.44 V at IO = ±24 mA), supporting robust interfacing with 3.3 V microcontrollers and FPGAs.

Does the 74AC244TTR require external power supply decoupling?

Yes - STMicroelectronics specifies a minimum 100 nF ceramic capacitor placed within 3 mm of VCC (pin 20) and GND (pin 10). This suppresses high-frequency supply noise induced by simultaneous 3-state transitions, preventing false triggering or increased propagation delay variation. Omitting this capacitor risks timing violations above 10 MHz operation.