Texas Instruments CD74ACT646EN

Overview

CD74ACT646EN from Texas Instruments is a 16-bit bus transceiver with 3-state outputs and TTL-compatible inputs, designed for bidirectional data flow control in high-speed digital systems. It features ±24mA output drive, 8.5ns typical propagation delay at VCC = 5V, and operates over –55°C to +125°C. It is used in industrial backplane interfaces requiring level-shifted, noise-immune data transfer between logic domains.

For engineers reviewing the CD74ACT646EN datasheet, CD74ACT646EN pinout, CD74ACT646EN application, or CD74ACT646EN equivalent, key selection criteria include its ACT logic family speed-power trade-off, 24-pin SOIC (DW) package compatibility, 3-state bus-hold capability, and dual-function direction/control pin configuration.

Technical Context

The CD74ACT646EN implements two independent 8-bit transceivers in a single SOIC-24 package, each with separate output-enable (OE\), direction (DIR), and data I/O ports. Its ACT-series CMOS design ensures TTL-level input thresholds (VIH = 2.0V min, VIL = 0.8V max) while delivering rail-to-rail CMOS output swing and low ground bounce.

It supports hot-insertion via Ioff partial-power-down protection and includes bus-hold circuitry on all I/O pins to maintain valid logic states when inputs are floating. The device requires no external pull-ups or pull-downs in high-impedance mode and maintains static drive capability across its full temperature range.

Key Specifications

Pinout & Package

CD74ACT646EN is housed in a 24-pin Small Outline Integrated Circuit (SOIC) package with DW suffix, measuring 7.5mm × 15.4mm, 1.27mm pitch, and JEDEC MS-013 compliant footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74ACT646EN, SN74ACT646N offers identical performance in a fully supported TI-branded variant, while 74ACT646PC trades industrial reliability for through-hole convenience and lower unit cost in non-critical environments.

Availability

CD74ACT646EN is available at Aetrix Electronics and suitable for industrial backplane interfaces, avionics subracks, and automotive diagnostic gateways requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for CD74ACT646EN 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 decades of heritage in high-reliability logic families including the 74ACT series.

The CD74ACT646EN belongs to TI's advanced CMOS logic portfolio, engineered specifically for high-speed, noise-immune bidirectional data transfer in mission-critical industrial and aerospace systems.

FAQ

What is the maximum clock frequency supported by CD74ACT646EN in a synchronous bus application?

The CD74ACT646EN does not contain an internal clock; it is a combinatorial transceiver. Its 8.5ns typical propagation delay supports reliable operation in synchronous bus systems up to approximately 100MHz, assuming proper PCB layout, termination, and setup/hold timing margins. System-level frequency limits depend on total path delay, not the CD74ACT646EN alone.

Does CD74ACT646EN require external pull-up or pull-down resistors on its I/O pins?

No. CD74ACT646EN includes integrated bus-hold circuitry on all A0–A7 and B0–B7 pins, which actively maintains the last-valid logic state when inputs are floating. This eliminates the need for external biasing resistors and reduces board area and BOM cost in high-density layouts.

Is CD74ACT646EN pin-compatible with CD74AC646M?

Yes - CD74ACT646EN and CD74AC646M share identical 24-pin SOIC (DW) packaging, pinout, and functional block diagram. However, CD74ACT646EN uses ACT-series TTL-compatible inputs and faster propagation delay (8.5ns vs. 10.5ns), while CD74AC646M has AC-series CMOS input thresholds and higher drive strength asymmetry.

What is the purpose of the DIR pin on CD74ACT646EN?

The DIR (direction) pin on CD74ACT646EN controls data flow direction between Port A and Port B. When DIR = HIGH, data transfers from A to B; when DIR = LOW, data flows from B to A. This single-pin control enables dynamic, software-configurable bus reversal without external logic or multiplexers.

Can CD74ACT646EN be used in a 3.3V system?

No - CD74ACT646EN is specified only for 4.5V to 5.5V VCC operation. Its TTL-compatible inputs require ≥2.0V VIH, and its outputs swing rail-to-rail at 5V. For 3.3V systems, consider TI's SN74LVC646A or SN74ALVC646, which support mixed-voltage translation and lower supply operation.