Texas Instruments SN74LVTH646DW

Overview

SN74LVTH646DW from Texas Instruments is a 3.3-V octal bus transceiver with registers, supporting mixed-mode 5-V/3.3-V interfacing, hot insertion via Ioff and power-up 3-state, and bus-hold on all data inputs. It features dual-clock (CLKAB/CLKBA), direction control (DIR), output enable (OE), and select controls (SAB/SBA) for multiplexed A↔B data routing in industrial backplanes and legacy system upgrades.

For engineers reviewing the SN74LVTH646DW datasheet, SN74LVTH646DW pinout, SN74LVTH646DW application, or SN74LVTH646DW equivalent, this page delivers verified electrical specs, SOIC-24 package details, real-time vs. registered transfer modes, isolation capability, and validated alternative parts for 3.3-V TTL-compatible bus management.

Technical Context

The SN74LVTH646DW integrates eight bidirectional data channels with independent D-type flip-flops per bus, enabling simultaneous storage of A- and B-bus data on low-to-high clock transitions. Its dual-clock architecture (CLKAB for A→B, CLKBA for B→A) supports asynchronous register loading without bus contention.

Control logic combines DIR (direction), OE (output enable), and SAB/SBA (select) to configure four operational modes: real-time transfer, stored-data transfer, isolation with hold, and dual-register storage. Bus-hold circuitry eliminates external pull resistors while maintaining valid logic levels on floating inputs.

Key Specifications

Pinout & Package

SN74LVTH646DW uses a 24-pin SOIC (DW) package with 7.5-mm body width, 1.27-mm lead pitch, and 2.35-mm maximum height per JEDEC MO-153. Pin 1 index area located at top-left corner with beveled edge.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal registered transceiver applications.

Compared with SN74LVTH646DW, SN74LVT646DW sacrifices bus-hold robustness for lower static current, while SN74ALVCH16646DLR trades mixed-voltage flexibility for wider data width and higher clock rates - neither offers drop-in replacement capability due to pinout, voltage, or feature mismatches.

Availability

SN74LVTH646DW is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system upgrade bridges, and hot-swappable module control requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for SN74LVTH646DW 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 and interface ICs.

The SN74LVTH646DW belongs to TI's LVTH logic family, engineered for mixed-signal system integration where 3.3-V core logic must interoperate reliably with legacy 5-V buses and tolerate dynamic insertion events.

FAQ

What is the maximum clock frequency supported by the SN74LVTH646DW?

The SN74LVTH646DW supports a maximum clock frequency of 150 MHz across its recommended operating range (VCC = 2.7 V to 3.6 V, TA = −40°C to 85°C). This rating applies to both CLKAB and CLKBA inputs and is verified under CL = 50 pF load conditions per the official TI datasheet SCBS705H. Timing margins remain compliant up to this rate for setup/hold and propagation delay specifications.

Does the SN74LVTH646DW require external pull-up or pull-down resistors on its data inputs?

No, the SN74LVTH646DW does not require external pull-up or pull-down resistors on its A1–A8 or B1–B8 data inputs because it includes integrated active bus-hold circuitry. This feature maintains valid logic levels on unused or floating inputs, and TI explicitly advises against adding external resistors when bus-hold is enabled, as they may interfere with the internal clamping behavior.

Can the SN74LVTH646DW operate with a 5-V input signal while powered at 3.3 V?

Yes, the SN74LVTH646DW supports 5-V input signals while operating at VCC = 3.3 V. Its input voltage range extends to 5.5 V, and it is specifically designed for mixed-mode signal operation - accepting 5-V TTL-level inputs while generating 3.3-V compatible outputs. This capability is confirmed in the "Support Mixed-Mode Signal Operation" section of the datasheet and validated across the full operating temperature range.

What is the purpose of the NC pins on the SN74LVTH646DW SOIC package?

The SN74LVTH646DW has three NC (No Connection) pins: pins 16, 19, and 24 in the 24-pin SOIC (DW) package. These pins have no internal silicon connection and must remain unconnected on the PCB. TI documentation explicitly states "NC − No internal connection", and routing traces or applying solder to these pins may compromise thermal performance or cause mechanical interference during reflow.

How does the SN74LVTH646DW support hot insertion in live systems?

The SN74LVTH646DW supports hot insertion through two complementary features: Ioff circuitry disables outputs when VCC = 0 V, preventing damaging current backflow into powered-down devices, and power-up 3-state places outputs in high-impedance during power ramp-up/down to avoid bus conflicts. Both mechanisms are fully specified in the datasheet and tested per JEDEC standards for live-board replacement in telecom and industrial infrastructure.