Texas Instruments SN74LVC646ANSR

Overview

SN74LVC646ANSR 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 SN74LVC646ANSR datasheet, SN74LVC646ANSR pinout, SN74LVC646ANSR application, or SN74LVC646ANSR equivalent, this page delivers verified electrical specs, functional timing behavior, package-validated pin mapping, real-world bus management use cases, and technically grounded alternative part comparisons - all specific to the SSOP-24 (NS) packaged SN74LVC646ANSR.

Technical Context

The SN74LVC646ANSR integrates eight D-type flip-flops per bus side, dual clock inputs (CLKAB and CLKBA), direction (DIR), output-enable (OE), and select-control (SAB/SBA) logic to enable four distinct bus operations: real-time A→B or B→A transfer, stored-data forwarding, 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 SAB/SBA states.

It implements true 3-state outputs with Ioff circuitry that disables outputs and blocks current backflow during power-down, and accepts input voltages up to 5.5 V regardless of VCC (1.65–3.6 V), enabling robust level translation in mixed-voltage systems without external resistors or translators.

Key Specifications

Pinout & Package

SN74LVC646ANSR is packaged in a 24-pin SSOP (Shrink Small Outline Package) with 0.65 mm lead pitch, 7.5 mm × 5.3 mm body size, and 1.2 mm max height - optimized for space-constrained PCB layouts while maintaining hand-solderability and automated assembly compatibility.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC646ANSR, SN74LVC646APWR offers improved thermal dissipation in compact TSSOP form, while 74LVC646ADBR provides identical SSOP-24 functionality with alternate marking and sourcing - both retain full functional equivalence but differ in package qualification, thermal metrics, and manufacturing traceability.

Availability

SN74LVC646ANSR is available at Aetrix Electronics and suitable for industrial automation, automotive body electronics, and test equipment requiring stable component supply, long-term lifecycle support, and guaranteed SSOP-24 packaging consistency.

Supply support for SN74LVC646ANSR 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 expertise in high-reliability interface ICs and industrial-grade timing products.

The SN74LVC646ANSR belongs to TI's LVC logic family - engineered for low-voltage operation, mixed-signal interoperability, and robust bus management in harsh electromagnetic environments typical of factory automation and transportation systems.

FAQ

What is the maximum clock frequency supported by SN74LVC646ANSR?

The SN74LVC646ANSR supports a maximum clock frequency of 150 MHz when operated at VCC = 3.3 V, as specified in the timing characteristics table. At lower supply voltages (e.g., 1.8 V), the maximum usable frequency is not published in the datasheet, and design margins should be conservatively applied. This 150 MHz rating applies to both CLKAB and CLKBA inputs and enables high-throughput data staging in real-time control loops.

Does SN74LVC646ANSR support 5-V tolerant inputs while powered from 1.8 V?

Yes, SN74LVC646ANSR supports input voltages up to 5.5 V regardless of VCC level (1.65–3.6 V), including at 1.8 V operation. This is explicitly confirmed in the Recommended Operating Conditions table under "VI Input voltage" (0 to 5.5 V). The feature enables direct interfacing with legacy 5-V peripherals without external level shifters - a key advantage in mixed-voltage system upgrades.

What is the purpose of the SAB and SBA pins on SN74LVC646ANSR?

SAB (Select A→B) and SBA (Select B→A) control whether real-time or registered data is forwarded across the transceiver. When SAB = L, real-time A-bus data passes to B-bus; when SAB = H, stored-A data is transferred. Similarly, SBA selects real-time vs. stored-B data for A-bus output. These pins, combined with DIR and OE, define the four fundamental bus-management functions shown in Figure 1 of the datasheet.

Can SN74LVC646ANSR be used in partial-power-down applications?

Yes, SN74LVC646ANSR includes Ioff circuitry that disables outputs and limits off-state current to ±10 µA when VCC = 0 V but input/output pins remain biased up to 5.5 V. This meets JESD78 requirements and is validated for use in hot-pluggable modules, modular PLC backplanes, and systems where subsystems power up/down independently - ensuring no damaging back-current flows through the device.

Is SN74LVC646ANSR pin-compatible with other packages in the LVC646A family?

Yes, SN74LVC646ANSR (SSOP-24, NS package) shares identical pin numbering and signal assignment with SN74LVC646ADBR (SSOP-24, DB), SN74LVC646APW/PWR (TSSOP-24, PW), and SN74LVC646ADW (SOIC-24, DW). All variants implement the same logic diagram, timing behavior, and electrical specifications - making them functionally interchangeable at the schematic level, though PCB footprints differ.