STMicroelectronics 74ACT244TTR

Overview

74ACT244TTR from STMicroelectronics is an advanced high-speed CMOS octal non-inverting bus buffer with 3-state outputs, designed for memory address driving and TTL/CMOS/NMOS interface translation. It delivers tPD = 4.6 ns (typ), symmetrical |IOH| = IOL = 24 mA (min), 50 Ω transmission line drive capability, and operates across VCC = 4.5–5.5 V.

For engineers reviewing the 74ACT244TTR datasheet, 74ACT244TTR pinout, 74ACT244TTR application, or 74ACT244TTR equivalent, key selection criteria include propagation delay matching, 3-state enable timing (tPZL/tPHZ ≤ 11.5 ns), output drive strength at 24 mA, ESD immunity (2 kV), and TSSOP-20 package compatibility in space-constrained digital logic interfaces.

Technical Context

The device integrates two independent 4-bit non-inverting buffers, each controlled by a dedicated output-enable input (1G, 2G), enabling selective bus isolation. All inputs accept TTL-compatible thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V at VCC = 4.5–5.5 V) and feature 2 kV HBM ESD protection.

Its sub-micron C2MOS process ensures low ICC = 4 µA (max) quiescent current and balanced tPLH ≅ tPHL propagation delays. Output impedance is symmetrical, supporting clean signal integrity on 50 Ω transmission lines without external termination.

Key Specifications

Pinout & Package

TSSOP-20 package: 6.5 mm × 4.4 mm body, 0.65 mm pitch, 1.1 mm height, lead-free, RoHS-compliant surface-mount outline.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ACT244DBR and 74VHC244MTCX, the 74ACT244TTR offers superior speed (4.6 ns vs. ≥7.5 ns) and higher drive strength (24 mA vs. 8 mA for VHC), making it optimal for high-frequency address/data buffering where timing closure is critical.

Availability

74ACT244TTR is available at Aetrix Electronics and suitable for memory address buffering, microcontroller bus expansion, TTL-to-CMOS interface translation, and industrial control backplane driver applications requiring stable component supply across automotive, industrial, and communications end markets.

Supply support for 74ACT244TTR 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, delivering intelligent power, analog, MEMS, and microcontroller solutions for industrial, automotive, and consumer applications.

The 74ACT series targets high-speed, low-power 5 V logic interoperability-designed specifically for bridging legacy TTL systems with modern CMOS architectures while maintaining robust noise immunity and thermal stability.

FAQ

What is the maximum operating frequency supported by the 74ACT244TTR?

The 74ACT244TTR does not specify a maximum clock frequency directly, but its 4.6 ns typical propagation delay implies a theoretical maximum toggle rate of ~217 MHz under ideal conditions. Real-world bus operation is typically limited to ≤20 MHz due to trace capacitance, loading, and setup/hold timing constraints of connected devices like SRAM or peripherals.

Can the 74ACT244TTR operate reliably at 3.3 V?

No. The 74ACT244TTR is specified only for VCC = 4.5 V to 5.5 V. At 3.3 V, input thresholds (VIH ≥ 2.0 V) become marginal, output drive collapses below specification, and DC parameters such as VOH/VOL and ICC are not guaranteed. For 3.3 V systems, consider the 74LVC244A or similar AEC-Q100-qualified 3.3 V buffers.

How is the 3-state output behavior controlled on this device?

Each of the two 4-bit buffer groups is independently controlled by active-low enable inputs: 1G (pin 1) enables outputs 1Y1–1Y4, and 2G (pin 19) enables outputs 2Y1–2Y4. When either G input is HIGH, its corresponding outputs enter high-impedance state (Z), electrically disconnecting that bus segment regardless of input states.

Does the 74ACT244TTR require external pull-up or pull-down resistors on unused inputs?

Unused inputs should be terminated to VCC or GND to prevent floating nodes and unintended switching. While internal protection diodes exist, STMicroelectronics recommends tying all unused inputs to a defined logic level-especially in high-noise environments-to avoid increased ICC, oscillation, or ESD-induced latch-up. No pull-up/pull-down value is specified; 10 kΩ is commonly used.