Toshiba Semiconductor and Storage 74HCT245D

Overview

74HCT245D from Toshiba is a high-speed CMOS octal bus transceiver in SOIC20 package, featuring bidirectional data flow control via DIR input, 3-state outputs enabled by G, and TTL-compatible inputs (VIH ≥ 2.0 V, VIL ≤ 0.8 V). It operates from 4.5 V to 5.5 V, delivers 11 ns typical propagation delay at 5.5 V, and supports industrial temperature range (–40 °C to +125 °C) for robust two-way bus interfacing in embedded control systems.

For engineers reviewing the 74HCT245D datasheet, 74HCT245D pinout, 74HCT245D application, or 74HCT245D equivalent, this device serves as a low-power, high-speed level-shifting transceiver for isolating and routing parallel data between microcontroller buses, peripheral interfaces, and memory subsystems under mixed-logic-voltage conditions.

Technical Context

The 74HCT245D implements an 8-bit bidirectional buffer with independent direction (DIR) and output-enable (G) controls, enabling asynchronous, non-inverted data transfer between two 8-bit busses. Its C2MOS silicon gate process ensures TTL-level input compatibility while maintaining CMOS quiescent current (ICC ≤ 4.0 µA max at 25 °C).

All I/O pins support 3-state high-impedance outputs when G is high, and internal input protection circuits guard against ESD and transient overvoltage. Propagation delays are balanced (tPLH ≈ tPHL), and output transition times remain consistent across VCC (4.5–5.5 V) and temperature (–40 to +125 °C).

Key Specifications

Pinout & Package

Package: SOIC20 (Small Outline Integrated Circuit, 20-pin, 7.5 mm width, 0.5 mm pitch, 0.51 g typical weight).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT245N and 74VHC245M, the 74HCT245D offers optimal balance of industrial-grade SOIC packaging, guaranteed TTL compatibility, and proven thermal reliability across extended temperature - making it the preferred choice for volume-manufactured embedded controllers requiring long-term supply stability.

Availability

74HCT245D is available at Aetrix Electronics and suitable for microcontroller bus expansion, memory interface isolation, industrial I/O module interfacing, and legacy system protocol translation requiring stable component supply across automotive, industrial automation, and medical device OEM programs.

Supply support for 74HCT245D 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

Toshiba Electronic Devices & Storage Corporation designs and manufactures high-reliability semiconductor components for industrial, automotive, and consumer applications, with emphasis on logic, power, and memory solutions.

The 74HCT245D belongs to Toshiba's HCT-series high-speed CMOS logic family, engineered specifically for seamless interoperability between TTL and CMOS systems while delivering low static power and robust noise immunity in harsh operating environments.

FAQ

What is the maximum operating temperature for the 74HCT245D?

The 74HCT245D is rated for continuous operation from –40 °C to +125 °C, meeting industrial and extended-temperature requirements. This specification is verified across all electrical parameters in the datasheet's Section 12 (Ta = –40 to +125 °C), including propagation delay, output drive, and leakage current limits - making the 74HCT245D suitable for under-hood automotive ECUs and factory-floor PLCs where ambient heat exceeds 85 °C.

Does the 74HCT245D support 3.3 V logic inputs?

No - the 74HCT245D is designed for 5 V operation only, with VCC specified from 4.5 V to 5.5 V. Its input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) are optimized for TTL compatibility, not 3.3 V CMOS levels. Applying 3.3 V signals risks marginal VIH recognition; for mixed-voltage systems, use the 74VHC245M or add a level-shifter. The 74HCT245D itself does not tolerate VCC < 4.5 V or input voltages exceeding VCC + 0.5 V.

How does the DIR pin control data flow direction in the 74HCT245D?

The DIR pin is a static control input: when DIR = Low, data flows from Bus A to Bus B (A→B); when DIR = High, data flows from Bus B to Bus A (B→A). This direction setting is latched and remains active until DIR changes - no clock or edge triggering is involved. The 74HCT245D performs non-inverting, real-time bidirectional buffering, and both busses retain their logic states during direction transitions as long as G remains active.

What happens to the 74HCT245D outputs when the G pin is high?

When G = High (active-low enable asserted), all A0–A7 and B0–B7 pins enter high-impedance (Hi-Z) state, electrically disconnecting both busses. Output leakage current is limited to ≤ 0.1 µA (max), ensuring minimal bus loading. This isolation is critical for multi-master bus architectures - for example, allowing a second transceiver to take control without contention. The 74HCT245D maintains Hi-Z even if DIR changes while G is high.

Is the 74HCT245D pin-compatible with other octal transceivers like the 74LS245?

No - while the 74HCT245D shares identical pinout (SOIC20) and functional mapping with industry-standard 74-series octal transceivers (including 74LS245, 74ALS245, and 74F245), it is not a drop-in replacement due to differences in DC drive strength, AC timing, and input protection. The 74HCT245D draws significantly less quiescent current (4.0 µA vs. ~20 mA for 74LS245) and exhibits faster propagation (11 ns vs. ~20 ns), requiring layout and timing verification. Always validate the 74HCT245D in-system before substitution.