STMicroelectronics 74ACT245MTR

Overview

74ACT245MTR from STMicroelectronics is an octal non-inverting bus transceiver with 3-state outputs, designed for bidirectional asynchronous data bus interfacing between TTL, CMOS, and NMOS systems. It features 5.4 ns typical propagation delay at 5 V, ±24 mA symmetrical output drive, and operates across 4.5–5.5 V supply range. Used in system-level bus isolation and level translation in industrial control backplanes.

For engineers reviewing the 74ACT245MTR datasheet, 74ACT245MTR pinout, 74ACT245MTR application, or 74ACT245MTR equivalent, key selection criteria include directional control (DIR), output enable (G), 3-state bus isolation timing, and 50 Ω transmission line driving capability under industrial temperature range (-55°C to +125°C).

Technical Context

The device implements a dual-bus architecture with independent A- and B-side I/Os controlled by DIR (data direction) and G (output enable). All 16 I/O pins support bidirectional flow: when G = L and DIR = L, A→B transfer occurs; when G = L and DIR = H, B→A transfer occurs. High-impedance state is asserted on both buses when G = H.

Input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V at VCC = 4.5–5.5 V) ensure TTL compatibility. ESD protection (2 kV HBM) and latch-up immunity are built-in. The IC uses sub-micron C2MOS technology, enabling low ICC (4 µA max) and fast switching without external biasing.

Key Specifications

Pinout & Package

74ACT245MTR is supplied in a 20-pin SOIC (Small Outline Integrated Circuit) package, 7.5 mm wide, with 1.27 mm pitch and gull-wing leads. RoHS-compliant, surface-mount compatible, and rated for reflow soldering per JEDEC J-STD-020.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ACT245DBR and 74VHC245M, the 74ACT245MTR delivers optimal balance of speed, drive strength, and industrial temperature compliance in standard SOIC packaging-making it preferred for new designs targeting reliability-critical bus isolation.

Availability

74ACT245MTR is available at Aetrix Electronics and suitable for industrial PLC backplanes, automotive body control modules, and test equipment data acquisition systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 74ACT245MTR 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 consumer markets.

The 74ACT series targets high-speed, low-power TTL-compatible logic applications-specifically engineered for robust bus interfacing in harsh environments with guaranteed AC performance and enhanced ESD/latch-up resilience.

FAQ

What is the maximum recommended capacitive load for 74ACT245MTR outputs?

The device is characterized with CL = 50 pF in AC specifications, and its 24 mA drive capability supports stable switching into 50 Ω transmission lines. Driving loads > 50 pF may increase propagation delay and cause ringing; for >100 pF, external series termination or buffer staging is advised per application note AN2012.

Can DIR and G be tied together for unidirectional operation?

No-DIR and G serve independent functions: DIR controls data direction (A↔B), while G enables/disables all outputs. Tying them risks undefined states during transitions. For unidirectional use, fix DIR to constant logic level and control bus activity solely via G, as confirmed in the truth table on page 2 of the STMicroelectronics datasheet.

Is pull-up or pull-down resistance required on floating bus terminals?

Yes-the datasheet explicitly requires external pull-up or pull-down resistors on bus terminals in high-impedance state to prevent floating inputs. This avoids unintended switching, noise coupling, and increased ICC. Typical values are 4.7 kΩ to VCC or GND, depending on bus topology and noise environment.

Does 74ACT245MTR support hot-swap insertion?

No-hot-swap is not supported. The absolute maximum rating specifies that signals must not be applied to any terminal while the device is in output mode or while a bus terminal is floating. Power sequencing (VCC before inputs) and bus isolation via G assertion are mandatory prior to live connection.