Texas Instruments SN74ACT245DBR

Overview

SN74ACT245DBR from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data bus communication between 5V logic domains. It operates from 4.5V to 5.5V, supports TTL-compatible inputs up to 5.5V, delivers ≤8ns propagation delay at 5V, and features independent direction (DIR) and output-enable (OE) controls for flexible bus isolation in industrial control and pro-audio interfaces.

For engineers reviewing the SN74ACT245DBR datasheet, SN74ACT245DBR pinout, SN74ACT245DBR application, or SN74ACT245DBR equivalent, this page provides verified functional modes, thermal resistance (105.4°C/W), absolute maximum ratings, switching characteristics, and real-world use cases in video signage and factory automation systems where bus contention avoidance and overvoltage-tolerant I/O are critical.

Technical Context

The SN74ACT245DBR 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 16 I/O pins (A1–A8, B1–B8) are bidirectional and overvoltage tolerant to 5.5V regardless of VCC.

It uses ACT (Advanced CMOS TTL-compatible) logic with balanced drive strength (±24mA output), slow edge rates to suppress ringing, and input transition rate limits (8 ns/V) to ensure signal integrity on lightly loaded buses. The device requires no external timing components due to its self-contained control logic and is specified for –40°C to +85°C operation.

Key Specifications

Pinout & Package

SN74ACT245DBR is housed in a 20-pin SSOP (Shrink Small Outline Package) with 0.65mm pitch, body size 7.2mm × 5.3mm, and overall footprint 7.2mm × 7.8mm. The package is RoHS-compliant, lead-finished with NiPdAu, and rated MSL-1 (unlimited floor life at ≤30°C/60% RH).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC245A and 74ACT245, the SN74ACT245DBR uniquely combines 5V operation, 5.5V input tolerance, SSOP-20 compactness, and industrial temperature range - making it the only option among the three qualified for direct replacement in legacy 5V industrial control backplanes requiring minimal board redesign.

Availability

SN74ACT245DBR is available at Aetrix Electronics and suitable for pro audio signal routing, video signage data bus extension, and factory automation I/O expansion requiring stable component supply across long-lifecycle industrial programs.

Supply support for SN74ACT245DBR 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 industrial-grade product development.

The SN74ACT245DBR belongs to TI's legacy ACT logic family, engineered for robust 5V bus interfacing in harsh environments - targeting industrial control, instrumentation, and professional media equipment where reliability and voltage margin are critical.

FAQ

What is the maximum operating voltage for SN74ACT245DBR?

The SN74ACT245DBR has an absolute maximum VCC rating of 7V, but its recommended operating range is strictly 4.5V to 5.5V per TI's SCAS452H datasheet. Operating outside this window risks parametric shift or accelerated wear. Inputs tolerate up to 5.5V regardless of VCC, supporting mixed-voltage interconnects without level shifters. Always verify actual rail stability under load using the 5.5V max specification.

Can SN74ACT245DBR interface between 3.3V and 5V logic domains?

No - SN74ACT245DBR is a 5V-only device: it requires VCC = 4.5–5.5V and does not support 3.3V supply operation. While its inputs accept up to 5.5V (making it safe to receive 3.3V logic levels when VCC = 5V), it cannot drive 3.3V inputs reliably due to VOH ≈ 4.4V minimum at 5V. For true 3.3V↔5V translation, use dedicated level-shifting transceivers like SN74LVC4245A instead of SN74ACT245DBR.

What is the purpose of the DIR and OE pins on SN74ACT245DBR?

DIR (pin 1) controls data direction: HIGH enables A→B transfer, LOW enables B→A. OE (pin 19) is active-low and globally enables/disables transceiver function - LOW activates bidirectional data flow, HIGH places all A/B pins in high-impedance state for bus isolation. Both must be driven actively; floating OE risks partial enablement and bus contention. TI recommends pulling OE to VCC via a resistor during power-up to guarantee initial isolation.

Does SN74ACT245DBR require external pull-up or pull-down resistors?

SN74ACT245DBR does not require pull-ups on A/B I/O pins, but TI strongly recommends tying OE to VCC through a pull-up resistor (e.g., 10kΩ) to ensure high-impedance state during power-up/power-down. DIR may float only if direction is fixed externally; otherwise, it should be actively driven. Unused A/B pins must be terminated to VCC or GND - never left floating - to prevent undefined logic states and increased ICC.

What thermal considerations apply to SN74ACT245DBR in continuous operation?

With θJA = 105.4°C/W in SSOP-20, SN74ACT245DBR's junction temperature rise is directly proportional to power dissipation. At full 24mA output on all 16 lines (theoretical worst case), ICC ≈ 40µA quiescent plus ΔICC ≈ 1.5mA per active input yields <50mW total - resulting in <5.3°C junction rise above ambient. Real-world usage rarely exceeds 2–3 active lines, keeping thermal impact negligible without heatsinking in typical industrial enclosures.