STMicroelectronics 74ACT240MTR

Overview

74ACT240MTR from STMicroelectronics is an advanced high-speed CMOS octal bus buffer with 3-state inverted outputs, designed for memory address driving and bidirectional bus interfacing in TTL/CMOS/NMOS mixed-signal systems. It delivers 5 ns typical propagation delay at 5 V, ±24 mA symmetrical output drive, and operates across 4.5–5.5 V supply with 4 µA max quiescent current.

For engineers reviewing the 74ACT240MTR datasheet, 74ACT240MTR pinout, 74ACT240MTR application, or 74ACT240MTR equivalent, key selection criteria include 3-state enable timing (tPZL/tPHZ ≤ 10.5 ns), 50 Ω transmission line drive capability, ESD immunity (2 kV HBM), and strict VIH/VIL compatibility with TTL logic thresholds.

Technical Context

The device integrates eight independent inverting buffers grouped into two 4-bit sections, each controlled by a dedicated active-low output enable (1G, 2G). Each buffer supports true 3-state operation with high-impedance outputs when enabled low, enabling bidirectional data flow on shared buses.

It employs sub-micron silicon gate C2MOS technology with double-layer metal wiring, delivering balanced tPLH ≅ tPHL propagation delays and symmetrical |IOH| = IOL ≥ 24 mA drive strength-critical for clean signal integrity on 50 Ω transmission lines without external termination.

Key Specifications

Pinout & Package

74ACT240MTR is supplied in a 20-pin SOIC (Small Outline Integrated Circuit) package, 7.5 mm body width, with 1.27 mm pitch and gull-wing leads. Pin 1 marked by bevelled corner or notch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74ACT240MTR, the M variant offers identical performance in tube packaging for flexibility, while SN74ACT240N provides through-hole compatibility at the cost of board area and thermal efficiency-both retain full functional equivalence but differ in mechanical integration and volume handling.

Availability

74ACT240MTR is available at Aetrix Electronics and suitable for memory address buffering, industrial PLC backplane interface, legacy TTL-to-CMOS translation, and test equipment signal conditioning requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 74ACT240MTR 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 automotive, industrial, and consumer markets.

The 74ACT series targets high-speed, low-power logic interfacing-specifically engineered to bridge TTL, CMOS, and NMOS systems while maintaining robustness in harsh operating conditions.

FAQ

What is the maximum clock frequency supported by 74ACT240MTR in a bus application?

The 74ACT240MTR does not operate on a clock; it is an asynchronous buffer. Its 5 ns typical propagation delay supports reliable operation in parallel bus systems running up to approximately 100 MHz for short traces (<10 cm) with proper termination. Maximum usable frequency depends on total path delay, including PCB routing and load capacitance-not an internal clock rate.

Can 74ACT240MTR drive multiple loads on the same bus line?

Yes-it is explicitly rated for 50 Ω transmission line driving and supports fan-out to multiple CMOS/TTL inputs when used with appropriate bus topology. However, total capacitive load must remain ≤50 pF per output to maintain specified tPD and edge rates; exceeding this requires buffer replication or series termination.

Is 74ACT240MTR compatible with 3.3 V logic systems?

No-its absolute maximum VCC is 7 V, but recommended operating range is strictly 4.5–5.5 V. Input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) are optimized for 5 V logic families. Direct connection to 3.3 V systems risks undervoltage operation and marginal noise margins; level-shifting circuitry is required.

Does 74ACT240MTR require external pull-up or pull-down resistors on its 3-state outputs?

No-outputs enter high-impedance (Z) state with leakage ≤ ±5 µA when G is inactive; no external resistors are needed for bus idle-state biasing. However, system-level bus keepers or terminators may still be required depending on host controller architecture and signal integrity requirements.