Texas Instruments SN74ACT245DGSR

Overview

SN74ACT245DGSR 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 I/O expansion and mixed-voltage system interconnects.

For engineers reviewing the SN74ACT245DGSR datasheet, SN74ACT245DGSR pinout, SN74ACT245DGSR application, or SN74ACT245DGSR equivalent, this page provides verified functional modes, real-world timing behavior, package-specific thermal resistance (RθJA = 123.5°C/W), and validated alternatives for 5-V bus isolation and level-shifting scenarios.

Technical Context

The SN74ACT245DGSR implements a dual-bus transceiver architecture with noninverting data flow controlled by DIR and OE pins. Its function table defines three operational states: A→B transfer (DIR = H, OE = L), B→A transfer (DIR = L, OE = L), and high-impedance isolation (OE = H). All eight A- and B-side I/Os are bidirectional and overvoltage tolerant to 5.5 V regardless of VCC.

It uses ACT (Advanced CMOS TTL-compatible) logic with balanced drive strength (±24 mA output current), slow edge rates to suppress ringing, and input transition rate tolerance of 8 ns/V. The device requires no external clock or timing control, making it suitable for simple, deterministic bus handshaking in legacy and mixed-signal systems.

Key Specifications

Pinout & Package

VSSOP-20 (DGS) package: 5.1 mm × 4.9 mm body size, 0.65 mm lead pitch, 1.2 mm max height, RoHS-compliant NiPdAu lead finish, MSL Level-1 (260°C peak reflow).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC245A and SN74ABT245, the SN74ACT245DGSR offers optimal balance of 5-V compatibility, moderate speed, low static power, and industrial-grade ESD/temperature specs - making it the preferred choice for cost-sensitive, thermally constrained 5-V bus isolation where extreme drive or sub-3.3-V operation is unnecessary.

Availability

SN74ACT245DGSR is available at Aetrix Electronics and suitable for industrial I/O expansion, pro audio digital bus interfaces, factory automation backplanes, and video signage controller interfaces requiring stable component supply and long-term production continuity.

Supply support for SN74ACT245DGSR 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 over 50 years of innovation in industrial, automotive, and communications markets.

The SN74ACT245DGSR belongs to TI's legacy ACT logic family, engineered specifically for robust 5-V bus interfacing in noise-prone industrial environments - emphasizing reliability, voltage tolerance, and ease of integration over ultra-high speed.

FAQ

What is the maximum operating temperature for the SN74ACT245DGSR?

The SN74ACT245DGSR is rated for operation from –40°C to +85°C. This industrial temperature range is validated per TI's recommended operating conditions and supports deployment in factory automation enclosures, outdoor signage cabinets, and other thermally demanding environments where passive cooling is used. The VSSOP package's RθJA of 123.5°C/W must be considered in thermal design.

Can the SN74ACT245DGSR interface between 3.3-V and 5-V logic domains?

The SN74ACT245DGSR does not translate voltage levels - it operates only from 4.5 V to 5.5 V and has TTL-compatible inputs. However, its inputs tolerate up to 5.5 V regardless of VCC, so it can safely receive 5-V signals while being powered by a 5-V rail. To connect a 3.3-V microcontroller, level-shifting circuitry or a compatible 3.3-V transceiver like SN74LVC245A is required upstream.

How should the OE and DIR pins be biased during power-up?

To ensure predictable high-impedance state at power-on, OE must be held HIGH (via pullup to VCC) until valid control signals are established. DIR may float briefly but should be stabilized before OE is driven LOW. TI recommends a pullup resistor ≤10 kΩ on OE - value determined by driver sink capability - to prevent bus contention during boot sequences.

What is the purpose of the slow edge-rate design in the SN74ACT245DGSR?

The intentionally slower edge rates in the SN74ACT245DGSR reduce output ringing, overshoot, and EMI - especially critical when driving unterminated or long PCB traces common in industrial backplanes and audio equipment. This design trade-off sacrifices some speed (8 ns tpd vs. 3.9 ns in ABT variants) for improved signal integrity without requiring external termination resistors.

Is the SN74ACT245DGSR pin-compatible with other packages in the SN74ACT245 family?

Yes - all SN74ACT245 variants (DB, DGS, DW, N, NS, PW, RKS) share identical 20-pin functional pinout and logic behavior. The SN74ACT245DGSR (VSSOP) matches the pin assignments shown in Figure 4-1, including DIR at Pin 1, A1–A8 at Pins 2–9, GND at Pin 10, B8–B1 at Pins 11–18, OE at Pin 19, and VCC at Pin 20 - enabling drop-in substitution where board space and thermal constraints allow.