Texas Instruments SN74AHCT245DBR

Overview

SN74AHCT245DBR from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between 5 V buses. It operates from 4.5 V to 5.5 V, accepts TTL-compatible inputs (VIH = 2 V, VIL = 0.8 V), delivers ±8 mA output drive, and supports –40°C to 125°C industrial temperature range - used in microcontroller-to-peripheral bus isolation and level-shifting interfaces.

For engineers reviewing the SN74AHCT245DBR datasheet, SN74AHCT245DBR pinout, SN74AHCT245DBR application, or SN74AHCT245DBR equivalent, key selection criteria include direction-control logic behavior, 3-state enable timing (tPZH/tPHZ ≤ 16 ns @ 50 pF), thermal resistance (RθJA = 113.1°C/W for DB package), and SSOP-20 mechanical compatibility with legacy 5 V system designs.

Technical Context

The SN74AHCT245DBR implements dual-bus bidirectional data flow controlled by DIR (direction) and OE (output enable) inputs. Its CMOS design with TTL-compatible input thresholds enables reliable interfacing between 3.3 V controllers and 5 V peripherals while maintaining low dynamic power consumption (ICC ≤ 40 µA).

Each of the eight A↔B channels operates independently under shared DIR/OE control. The device enters high-impedance state when OE is high, isolating both buses; DIR determines signal direction (A→B when high, B→A when low), with propagation delays tPLH/tPHL ≤ 10 ns (CL = 15 pF) and edge-rate limiting to suppress output ringing.

Key Specifications

Pinout & Package

SN74AHCT245DBR uses a 20-pin SSOP (Shrink Small Outline Package) with 0.65 mm lead pitch, body size 7.50 mm × 5.30 mm, and exposed pad not present. Pin 1 is marked via dot or bevel; pin numbering follows standard counter-clockwise layout from top-left corner.

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 SN74AHCT245DBR uniquely combines 5 V operation, TTL-compatible inputs, and SSOP-20 packaging - making it optimal for mixed-voltage upgrades where legacy 5 V peripherals coexist with newer 3.3 V controllers without added translation circuitry.

Availability

SN74AHCT245DBR is available at Aetrix Electronics and suitable for industrial PLC backplanes, automotive body control modules, microcontroller GPIO expansion, and legacy instrument cluster upgrades requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN74AHCT245DBR 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 delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and consumer applications - with over 90 years of innovation in logic and interface ICs.

The SN74AHCT245DBR belongs to TI's AHCT logic family, engineered specifically for robust 5 V bus interfacing with TTL compatibility, low power, and extended temperature operation - targeting industrial control, automotive subsystems, and legacy system modernization.

FAQ

What is the recommended power supply bypassing scheme for SN74AHCT245DBR?

Place a 0.1 µF ceramic capacitor between VCC (Pin 20) and GND (Pin 10), located within 3 mm of the package. For systems with multiple VCC sources or high-noise environments, add a 1 µF bulk capacitor in parallel. Avoid shared vias between bypass caps and signal returns to maintain low-impedance ground paths critical for clean 3-state transitions in SN74AHCT245DBR.

Can SN74AHCT245DBR interface directly with a 3.3 V microcontroller output?

Yes - SN74AHCT245DBR accepts VIH = 2 V minimum, which is satisfied by standard 3.3 V CMOS outputs (typically VOH ≥ 2.4 V). No level shifter is required. However, ensure the microcontroller's output drive strength meets SN74AHCT245DBR's input capacitance (Ci = 10 pF) and that OE/DIR control signals also meet the 2 V VIH threshold for reliable operation.

What happens to the A and B ports during power-up or power-down of SN74AHCT245DBR?

During power sequencing, SN74AHCT245DBR does not guarantee high-impedance states unless OE is actively held high. To prevent bus contention, tie OE to VCC via a pullup resistor (e.g., 10 kΩ) so the device remains disabled until supply stabilizes. This ensures safe power-up behavior in systems where A/B buses may be live before VCC reaches regulation.

Is SN74AHCT245DBR pin-compatible with other 20-pin octal transceivers like 74LS245?

No - although SN74AHCT245DBR shares the same 20-pin SSOP footprint and functional pinout (DIR, A1–A8, GND, B8–B1, OE, VCC), its electrical characteristics differ significantly from bipolar 74LS245 (e.g., input current, drive strength, propagation delay). Direct substitution requires validation of timing margins, loading, and DC compatibility in the target application.

Does SN74AHCT245DBR support hot-swap operation on live 5 V buses?

SN74AHCT245DBR supports hot-swap when OE is asserted (high) before bus connection, placing all I/O pins in high-impedance state. Its absolute maximum ratings allow VI up to 5.5 V independent of VCC, and latch-up immunity exceeds 250 mA per JESD17 - enabling safe insertion into powered-backplane systems if OE control is sequenced correctly prior to physical mating.