Renesas 74FCT621TSOG

Overview

74FCT621TSOG from Renesas Electronics (formerly IDT) is an octal bus transceiver with open-drain outputs in both A→B and B→A directions, designed for asynchronous bidirectional data bus interfacing. It operates at 5V ±5%, supports industrial temperature range (–40°C to +85°C), sinks up to 64mA per B-bus output, and features TTL-compatible inputs/outputs with VOH = 3.3V (typ.) and VOL = 0.3V (typ.). It enables live insertion via power-off disable outputs.

For engineers reviewing the 74FCT621TSOG datasheet, 74FCT621TSOG pinout, 74FCT621TSOG application, or 74FCT621TSOG equivalent, key selection considerations include open-drain bidirectional drive capability, 64mA B-bus sink current, JEDEC 18 compliance, SOIC-20 package compatibility, and industrial-grade thermal performance.

Technical Context

The 74FCT621TSOG implements dual-directional bus communication using two independent enable controls (GBA and GAB), allowing selective data flow from A-to-B, B-to-A, or simultaneous bidirectional operation. Its open-drain architecture requires external pull-ups and supports wired-AND logic and mixed-voltage interface bridging.

It meets JEDEC Standard No. 18 for fast CMOS devices, delivers propagation delays as low as 1.5ns (tPHL, B→A), and maintains ≤1µA input/output leakage across temperature. Power-off disable ensures high-impedance outputs when VCC = 0V, enabling hot-plug capability without bus contention.

Key Specifications

Pinout & Package

74FCT621TSOG is housed in a 20-pin Small Outline IC (SOIC) package with standard 0.3-inch body width and 1.27mm pitch. Pin 1 is marked by a notch or dot; pin numbering follows counter-clockwise top-view convention.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74F245N and 74ACT16245QG, the 74FCT621TSOG uniquely combines open-drain bidirectionality, 64mA B-bus sink strength, power-off disable, and industrial temperature qualification - making it irreplaceable for hot-swappable, contention-managed, or high-capacitance bus applications.

Availability

74FCT621TSOG is available at Aetrix Electronics and suitable for industrial backplane interfacing, legacy system bus bridging, and hot-swappable I/O module designs requiring stable component supply and long-term lifecycle support.

Supply support for 74FCT621TSOG 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

Renesas Electronics Corporation is a global semiconductor leader delivering microcontrollers, analog, power, and connectivity solutions for automotive, industrial, and IoT applications.

The 74FCT621TSOG belongs to Renesas' legacy IDT fast CMOS logic family, engineered specifically for robust, low-latency, bidirectional bus interfacing in industrial control and communications infrastructure.

FAQ

What is the maximum sink current capability of the B-bus outputs on the 74FCT621TSOG?

The 74FCT621TSOG B-bus outputs (B1–B8) each support a maximum sink current of 64mA under VCC = 5.0V min and TA = –40°C to +85°C. This rating applies per output when up to eight outputs are active simultaneously; total device sink current is limited to 384mA for industrial-grade operation. The 74FCT621TSOG datasheet specifies this value in the DC Electrical Characteristics table under "VOL Output LOW Voltage" test condition.

Does the 74FCT621TSOG support live insertion, and how is it implemented?

Yes, the 74FCT621TSOG supports live insertion through its power-off disable feature. When VCC = 0V, all outputs enter a high-impedance state with IOFF leakage ≤ ±1µA, preventing back-driving of the bus. This behavior is guaranteed in the Absolute Maximum Ratings and DC Electrical Characteristics sections of the 74FCT621TSOG datasheet and enables safe hot-swap of daughter cards or modules without disrupting system operation.

What package type and pin count does the 74FCT621TSOG use?

The 74FCT621TSOG uses a 20-pin Small Outline IC (SOIC) package with standard 0.3-inch body width and 1.27mm lead pitch. It is designated as "SO" in Renesas' ordering information and matches JEDEC MS-013AC. The 74FCT621TSOG pinout includes dual enable inputs (GAB, GBA), eight A-side I/Os (A1–A8), eight B-side I/Os (B1–B8), one VCC, and one GND.

How does the 74FCT621TSOG differ from standard tri-state transceivers like the 74F245?

The 74FCT621TSOG differs fundamentally by using open-drain outputs instead of tri-state outputs - enabling wired-AND logic, inherent bus arbitration, and compatibility with external pull-up networks at different voltages. Unlike the 74F245, the 74FCT621TSOG provides power-off disable, lower leakage (≤1µA), and higher B-bus sink current (64mA vs. ~20mA). These traits make the 74FCT621TSOG suitable for contention-prone or hot-swap environments where the 74F245 cannot operate safely.

Is the 74FCT621TSOG compliant with any industry standards?

Yes, the 74FCT621TSOG meets or exceeds JEDEC Standard No. 18 for fast CMOS logic devices. This certification confirms interoperability with TTL and other 5V logic families, defines AC/DC electrical limits, and validates timing parameters including propagation delay, setup/hold times, and noise margins. Compliance is explicitly stated in the Features section of the 74FCT621TSOG datasheet and verified across the full industrial temperature range.