STMicroelectronics 74ACT245TTR

Overview

74ACT245TTR from STMicroelectronics is an octal non-inverting bus transceiver with 3-state outputs, designed for bidirectional asynchronous data bus communication 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 between mixed-logic subsystems.

For engineers reviewing the 74ACT245TTR datasheet, 74ACT245TTR pinout, 74ACT245TTR application, or 74ACT245TTR equivalent, key selection criteria include directional control (DIR), output enable (G), 3-state bus isolation capability, 50 Ω transmission line drive, and ESD immunity up to 2 kV.

Technical Context

The device implements a dual-bus bidirectional interface with independent DIR and G inputs controlling data flow direction and output state. All 16 I/O pins (A1–A8, B1–B8) support high-impedance tri-state operation when G is high, enabling bus contention avoidance.

It uses sub-micron C2MOS technology with double-layer metal wiring, delivering TTL-compatible input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V), symmetrical tPLH/tPHL delays, and robust latch-up immunity. Input/output protection includes 2 kV HBM ESD rating and diode clamping.

Key Specifications

Pinout & Package

TSSOP-20 package: 6.4 mm × 6.5 mm body, 0.65 mm pitch, 1.1 mm height, lead-free and RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74LVC245APW and SN74ACT245N, the 74ACT245TTR uniquely combines 5 V operation, TSSOP packaging, and full 50 Ω line drive-making it optimal for industrial upgrades requiring pin-compatible 5 V logic with compact layout.

Availability

74ACT245TTR is available at Aetrix Electronics and suitable for industrial PLC backplanes, automotive body control modules, and medical diagnostic imaging interfaces requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 74ACT245TTR 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 family delivers advanced CMOS performance with TTL compatibility, targeting high-reliability bus interface applications in harsh-environment systems where speed, noise immunity, and wide temperature operation are critical.

FAQ

What is the maximum clock/data rate supported by the 74ACT245TTR?

The 74ACT245TTR does not operate on a clock; it is an asynchronous transceiver. Its 5.4 ns typical propagation delay supports data rates up to ~100 MHz on well-terminated 50 Ω lines, assuming setup/hold margins and board-level signal integrity constraints are met per application design.

Can the DIR and G inputs be driven directly from a 3.3 V microcontroller?

Yes - the 74ACT245TTR accepts 3.3 V logic levels on DIR and G: its VIH minimum is 2.0 V at VCC = 5 V, and VIL maximum is 0.8 V, making it compatible with standard 3.3 V CMOS outputs without level shifters.

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

Yes - STMicroelectronics explicitly requires external pull-up or pull-down resistors on A/B bus terminals when in high-impedance state to prevent undefined logic levels, oscillation, or excessive current draw due to floating inputs.

Does the 74ACT245TTR support hot-swap or live-insertion?

No - the device lacks built-in hot-swap protection circuitry. Applying signals to A/B pins while in output mode or allowing bus terminals to float violates absolute maximum ratings and risks latch-up or ESD damage. System-level hot-swap requires external protection circuitry.