Texas Instruments SN74LVC646ADBR

Overview

SN74LVC646ADBR 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 FPGA-to-ASIC interconnect, memory-mapped peripheral bridging, and level-translating data paths in industrial controllers.

For engineers reviewing the SN74LVC646ADBR datasheet, SN74LVC646ADBR pinout, SN74LVC646ADBR application, or SN74LVC646ADBR equivalent, key selection criteria include its dual-clock register architecture (CLKAB/CLKBA), DIR/OE/SAB/SBA control logic, 7.4 ns max propagation delay at 3.3 V, 24-pin SSOP (DB) package, and guaranteed 3.6-V tolerant inputs.

Technical Context

The SN74LVC646ADBR integrates eight D-type flip-flops per bus side, enabling synchronous latching of A→B or B→A data on low-to-high clock transitions. Its DIR input selects directionality while OE enables/disables 3-state outputs, and SAB/SBA select real-time or registered data routing - supporting four distinct bus-management modes: real-time transfer, stored-data transfer, isolation, and storage from either or both buses.

It implements Ioff circuitry to disable outputs during power-down, preventing backflow current when VCC = 0 V, 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

SN74LVC646ADBR uses a 24-pin Shrink Small-Outline Package (SSOP-DB) with 0.65-mm lead pitch, 7.8-mm body width, and 1.2-mm max height. Pin 1 is located in Quadrant Q1 per tape-and-reel orientation standards.

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 SN74LVC646ADW, the SN74LVC646ADBR offers optimal balance of compact SSOP size, thermal performance, and high-volume tape-and-reel logistics - making it the default choice for industrial and automotive production programs requiring IPC-compliant assembly and thermal margin.

Availability

SN74LVC646ADBR is available at Aetrix Electronics and suitable for industrial PLC backplane interfaces, FPGA-to-ASIC data bridges, and automotive body control modules requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant sourcing.

Supply support for SN74LVC646ADBR 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 connectivity solutions, with over 50 years of innovation in logic, power management, and signal chain technologies.

The SN74LVC646ADBR belongs to TI's LVC (Low-Voltage CMOS) logic family, engineered for high-speed, low-power, mixed-voltage interfacing in industrial automation, automotive electronics, and communications infrastructure.

FAQ

What is the maximum clock frequency supported by the SN74LVC646ADBR?

The SN74LVC646ADBR supports a maximum clock frequency of 150 MHz across its full operating voltage range (1.65 V to 3.6 V), as verified in TI's official datasheet SCAS302J. This applies to both CLKAB and CLKBA inputs under recommended conditions (VCC = 3.3 V ± 0.3 V, TA = –40°C to +85°C). The device achieves this with a typical propagation delay of 7.4 ns at 3.3 V, making SN74LVC646ADBR suitable for high-throughput synchronous bus applications.

Does the SN74LVC646ADBR support level translation between 5-V and 3.3-V logic domains?

Yes, the SN74LVC646ADBR supports true bidirectional level translation: its inputs tolerate up to 5.5 V regardless of VCC (1.65–3.6 V), allowing direct connection to 5-V TTL/CMOS outputs, while its outputs swing rail-to-rail within the VCC range. This enables SN74LVC646ADBR to serve as a seamless interface between legacy 5-V peripherals and modern 3.3-V or 1.8-V processors without external resistors or translators.

How does the Ioff feature function in the SN74LVC646ADBR during power-down sequences?

The Ioff circuitry in SN74LVC646ADBR disables all outputs when VCC = 0 V, preventing current backflow from live A/B buses into the unpowered device. This protects downstream circuitry and meets JEDEC JESD78 latch-up immunity requirements (>250 mA). For SN74LVC646ADBR, Ioff is active across the full temperature range and requires no external bias - a critical feature for hot-swap and partial-power-down systems.

What are the key timing parameters that define the SN74LVC646ADBR's synchronous operation?

Key timing parameters for SN74LVC646ADBR include: tsu = 1.6 ns (data setup before CLK↑), th = 1.7 ns (data hold after CLK↑), tpd = 7.4 ns (max propagation delay from CLK to output), ten = 8.2 ns (enable time from OE↓ to valid output), and tdis = 7.5 ns (disable time from OE↑ to high-Z). These values are specified at VCC = 3.3 V and ensure deterministic synchronization in clocked bus architectures using SN74LVC646ADBR.

Is the SN74LVC646ADBR pin-compatible with other packages in the same family?

Yes, the SN74LVC646ADBR shares identical pin numbering and signal assignment with SN74LVC646ADW (SOIC), SN74LVC646APW (TSSOP), and SN74LVC646ANSR (SOP), as confirmed in TI's SCAS302J datasheet Figure 1 and Package Option Addendum. All variants use the same 24-pin functional mapping - meaning SN74LVC646ADBR can be substituted for these parts at the schematic level, though PCB layout must match the SSOP-DB footprint.