STMicroelectronics 74AC245MTR

Overview

74AC245MTR from STMicroelectronics is an advanced high-speed CMOS octal bus transceiver with 3-state non-inverting outputs, designed for bidirectional asynchronous data bus communication. It features 4.5 ns typical propagation delay at 5 V, ±24 mA symmetrical output drive, and operates across 2 V to 6 V supply range. Used in legacy industrial control backplanes and memory-mapped I/O expansion interfaces where direction-controlled bus isolation is required.

For engineers reviewing the 74AC245MTR datasheet, 74AC245MTR pinout, 74AC245MTR application, or 74AC245MTR equivalent, key selection criteria include directional control logic (DIR), output enable timing (tPZL/tPLZ ≤ 9.0 ns at 5 V), 50 Ω transmission line drive capability, and latch-up immunity for mixed-voltage system interfacing.

Technical Context

The device implements a dual-bus architecture with independent A- and B-side 8-bit I/O ports controlled by DIR (data flow direction) and G (output enable). Directional control is synchronous with enable: when G = L, outputs reflect A→B or B→A based on DIR; when G = H, all outputs enter high-impedance state.

It uses sub-micron silicon gate C2MOS technology with double-layer metal wiring, enabling low ICC (4 µA max at 25°C) while maintaining rail-to-rail input thresholds (VIH/VIL = 2.1 V/1.5 V at VCC = 3.0 V) and robust ESD protection (2 kV HBM).

Key Specifications

Pinout & Package

74AC245MTR is supplied in a 20-pin SOIC (Small Outline Integrated Circuit) package per JEDEC MS-013, with 0.300-inch body width and 1.27 mm pitch. Pin 1 is marked by a beveled corner or notch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74AC245MTR, the 74ACT245PW offers stronger TTL input compatibility at the cost of higher quiescent current, while the SN74LVC245APWR provides optimized 3.3 V performance and space savings but sacrifices 5 V interoperability and mixed-voltage flexibility.

Availability

74AC245MTR is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy microcontroller I/O expansion, and memory-mapped peripheral bridging requiring stable component supply across extended temperature ranges (–55°C to +125°C).

Supply support for 74AC245MTR 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, specializing in automotive, industrial, and power discrete solutions with vertical manufacturing capabilities.

The 74AC logic family targets high-speed, low-power digital interfacing in industrial and telecom infrastructure, emphasizing robustness, wide supply range, and legacy system compatibility.

FAQ

What is the maximum operating frequency supported by the 74AC245MTR?

The 74AC245MTR does not specify a maximum clock frequency, but its 4.5 ns typical propagation delay at 5 V supports reliable data toggling up to approximately 100 MHz in point-to-point configurations with proper layout and termination. System-level timing depends on bus capacitance, trace length, and load conditions - measured AC characteristics assume CL = 50 pF and RL = 500 Ω.

Can the 74AC245MTR operate with mixed 3.3 V and 5 V supplies on A and B sides?

No - the 74AC245MTR has a single VCC pin and requires identical supply voltage on both sides. It supports operation from 2 V to 6 V, enabling use in either 3.3 V or 5 V systems, but cannot translate between different supply domains. For true level translation, separate voltage translators or families like 74LVC are required.

How does the DIR pin interact with the G (enable) input during state transitions?

DIR is sampled only when G is low (active). When G transitions high, both A and B ports immediately enter high-impedance regardless of DIR state. DIR changes while G = H have no effect on outputs; valid direction control occurs only after G returns low, ensuring glitch-free bus arbitration during enable/disable cycles.

Is the 74AC245MTR pin-compatible with standard 74LS245 devices?

Yes - it is pin- and function-compatible with the 74 series 244/245 family, including 74LS245, sharing identical 20-pin DIP/SOIC/TSSOP footprints and truth table behavior. However, AC245 offers superior speed (4.5 ns vs. ~15 ns), lower power (µA vs. mA ICC), and higher drive strength (24 mA vs. 8 mA), making it a direct performance upgrade without layout changes.