Texas Instruments SN74ACT245NSR

Overview

SN74ACT245NSR from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data bus communication between 5-V logic domains. It operates from 4.5 V to 5.5 V, supports TTL-compatible inputs up to 5.5 V, delivers ≤8 ns propagation delay at 5 V, and features independent direction (DIR) and output-enable (OE) controls - enabling use in industrial control backplanes and legacy microcontroller I/O expansion interfaces.

For engineers reviewing the SN74ACT245NSR datasheet, SN74ACT245NSR pinout, SN74ACT245NSR application, or SN74ACT245NSR equivalent, this page provides verified functional modes, real-world timing behavior, package-specific thermal resistance (99.7 °C/W), and validated alternatives for 5-V bus isolation and level-shifting scenarios where controlled edge rates and overvoltage-tolerant inputs are required.

Technical Context

The SN74ACT245NSR implements a dual-bus architecture with DIR-controlled signal flow direction and OE-gated 3-state output drivers. Its CMOS design ensures balanced drive strength (±24 mA per output), low power dissipation (45 pF typical Cpd), and inherent overvoltage tolerance on all inputs (up to 5.5 V regardless of VCC).

Functional operation is defined by three discrete states: DIR = L enables B→A data transfer; DIR = H enables A→B transfer; OE = H forces all outputs into high-impedance isolation. No internal latching or clocking is present - it is purely combinatorial and asynchronous.

Key Specifications

Pinout & Package

SN74ACT245NSR uses a 20-pin SOP (Small Outline Package) with 12.6 mm × 7.8 mm body size and 12.6 mm × 5.3 mm footprint. The NS package is RoHS-compliant, lead-finished with NiPdAu, and rated MSL Level-1 (260 °C reflow).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC245APWR and SN74HC245N, SN74ACT245NSR uniquely combines 5-V operation, 5.5-V input tolerance, sub-8-ns timing, and industrial temperature range in a surface-mount SOP package - making it irreplaceable in legacy 5-V systems requiring robustness and compatibility.

Availability

SN74ACT245NSR is available at Aetrix Electronics and suitable for industrial backplane interfaces, pro audio control buses, and factory automation data links requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for SN74ACT245NSR 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and logic solutions, with decades of heritage in industry-standard logic families.

SN74ACT245NSR belongs to TI's ACT (Advanced CMOS Technology) logic series, engineered for high-noise-immunity 5-V systems demanding precise timing, robust input tolerance, and reliable 3-state bus control in industrial and professional equipment.

FAQ

What is the maximum operating voltage for SN74ACT245NSR?

The SN74ACT245NSR has an absolute maximum VCC rating of 7 V, but its recommended operating range is strictly 4.5 V to 5.5 V. Inputs tolerate up to 5.5 V regardless of VCC level - a key feature enabling interoperability with overvoltage-prone 5-V buses. Operation outside 4.5–5.5 V may cause timing violations or increased ICC, and is not guaranteed by TI's characterization data for SN74ACT245NSR.

Does SN74ACT245NSR support hot-swapping or live insertion?

SN74ACT245NSR supports limited hot-swap capability due to its overvoltage-tolerant inputs (up to 5.5 V) and high-impedance 3-state outputs when OE is high. However, TI does not characterize or guarantee full hot-swap robustness. For safe live insertion, OE must be held high (via pull-up) during power-up, and VCC must ramp monotonically - verified in actual system testing for SN74ACT245NSR deployment.

Can SN74ACT245NSR interface directly between 3.3-V and 5-V logic domains?

No - SN74ACT245NSR is a 5-V-only device with VCC-referenced thresholds and no internal level-shifting. While its inputs accept up to 5.5 V, its outputs swing rail-to-rail between GND and VCC (4.5–5.5 V). To interface 3.3-V logic, external resistive dividers or dedicated level translators are required; SN74ACT245NSR itself does not translate voltages.

What is the thermal resistance (RθJA) of SN74ACT245NSR in its NS package?

The SN74ACT245NSR in the SOP (NS) package has a junction-to-ambient thermal resistance of 99.7 °C/W under standard JEDEC test conditions (1-layer board, 1-in² copper pad). This value assumes proper PCB layout with thermal vias and adequate copper pour - exceeding 70 mW dissipation requires verification of die temperature using TI's thermal models for SN74ACT245NSR.

How should unused pins be handled on SN74ACT245NSR?

All unused I/O pins (A1–A8, B1–B8) on SN74ACT245NSR must be tied to GND or VCC - floating inputs can cause excessive ICC, oscillation, or undefined bus states. DIR and OE must never float: OE should be pulled up to VCC (e.g., 10-kΩ) to ensure default high-impedance; DIR should be fixed to L or H depending on required default direction. These requirements are explicitly specified in TI's application guidance for SN74ACT245NSR.