Texas Instruments SN74LVC646ADWR

Overview

SN74LVC646ADWR from Texas Instruments is an octal bus transceiver and register with 3-state outputs, designed for bidirectional data flow between two 8-bit buses (A and B) under clocked register control. It operates from 1.65 V to 3.6 V, supports mixed-mode 5-V/3.3-V I/O, and features Ioff partial-power-down protection. Used in system-level bus isolation, data buffering, and synchronous bus arbitration in industrial controllers and FPGA interconnects.

For engineers reviewing the SN74LVC646ADWR datasheet, SN74LVC646ADWR pinout, SN74LVC646ADWR application, or SN74LVC646ADWR equivalent, this page delivers verified functional identity, precise SOIC-24 pin mapping, real-time vs. registered transfer modes, Ioff behavior, and validated alternatives for bus interface design.

Technical Context

The SN74LVC646ADWR integrates eight D-type flip-flops per bus, dual clock inputs (CLKAB/CLKBA), direction (DIR), output-enable (OE), and select-control (SAB/SBA) logic to enable four distinct bus-management functions: real-time A→B/B→A transfer, stored-data transfer, simultaneous A/B storage, and high-impedance isolation. Its architecture allows independent latching of A- or B-bus data on rising clock edges while maintaining transparent or registered paths based on DIR and OE states.

It supports voltage translation across 3.3-V and 5-V domains via 5.5-V-tolerant inputs and Ioff-enabled power-down isolation. The device implements true 3-state outputs with controlled enable/disable timing (ten = 10.2 ns, tdis = 8.9 ns at VCC = 3.3 V), ensuring glitch-free bus handover during mode transitions.

Key Specifications

Pinout & Package

SN74LVC646ADWR is packaged in a 24-pin SOIC (DW) body measuring 7.5 mm × 15.4 mm with 1.27 mm pitch. The package is RoHS-compliant, moisture sensitivity level 1, and rated for reflow up to 260°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC646APWR and SN74LVC646ADBR, the SN74LVC646ADWR provides optimal thermal performance (θJA = 46°C/W) and mechanical robustness in SOIC packaging, making it preferred for high-reliability industrial applications requiring manual rework or extended thermal cycling.

Availability

SN74LVC646ADWR is available at Aetrix Electronics and suitable for industrial PLC backplanes, FPGA-to-MCU bridges, and automotive body control modules requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for SN74LVC646ADWR 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 innovation in industrial, automotive, and communications markets.

The SN74LVC646ADWR belongs to TI's LVC logic family - engineered for low-voltage, high-speed, mixed-signal interfacing in space- and power-constrained embedded systems.

FAQ

What is the primary function of the SN74LVC646ADWR in a digital system?

The SN74LVC646ADWR serves as an octal bus transceiver and register with 3-state outputs, enabling bidirectional, clock-synchronized data transfer between two 8-bit buses (A and B). It supports both real-time (transparent) and registered (latched) modes, allowing flexible bus arbitration, isolation, and voltage translation in industrial and embedded systems. Its core value lies in deterministic timing control and mixed-voltage interoperability.

Does the SN74LVC646ADWR support 5-V input signals while operating at 1.65 V VCC?

Yes, the SN74LVC646ADWR accepts input voltages up to 5.5 V regardless of VCC level (1.65–3.6 V), enabling direct interfacing with 5-V logic without external level shifters. This feature is explicitly specified in the Absolute Maximum Ratings and Recommended Operating Conditions tables of the TI datasheet, and applies to all control and data inputs (CLKAB, DIR, OE, A1–A8, B1–B8).

How does the Ioff feature of the SN74LVC646ADWR protect system-level designs?

The Ioff circuitry in the SN74LVC646ADWR disables all outputs and blocks current backflow when VCC = 0 V, preventing damaging current from flowing through the device during partial power-down or hot-swap events. This is critical in modular systems like PLC backplanes or server blades where subsystems may power up/down independently while sharing common buses.

What are the key timing parameters that define reliable operation of the SN74LVC646ADWR?

Key timing parameters include maximum clock frequency (150 MHz), propagation delay tpd = 7.4 ns (at VCC = 3.3 V), setup time tsu = 1.6 ns, hold time th = 1.7 ns, and 3-state enable/disable times (ten = 10.2 ns, tdis = 8.9 ns). These values ensure glitch-free bus handover, synchronous data capture, and compatibility with high-speed microcontrollers and FPGAs operating at ≤150 MHz.

Can the SN74LVC646ADWR replace the SN74LVC646ADW in an existing design?

Yes - SN74LVC646ADWR is the tape-and-reel version of the same SOIC-24 device as SN74LVC646ADW (tube-packaged), with identical electrical specifications, pinout, and thermal characteristics. Both share the same top-side marking "LVC646A", same JEDEC MO-153-compliant package outline, and identical recommended operating conditions. No PCB or firmware changes are required for substitution.