Texas Instruments SN74ABT646ADBR

Overview

SN74ABT646ADBR from Texas Instruments is a 24-pin SSOP bus transceiver with dual 8-bit registers, direction control (DIR), output enable (OE), and dual clock inputs (CLKAB/CLKBA) for synchronous data latching. It delivers high-drive outputs (−32 mA IOH, 64 mA IOL), supports partial-power-down via Ioff, and operates across −40°C to 85°C. It enables real-time or registered bidirectional data transfer between A and B buses in industrial control backplanes.

For engineers reviewing the SN74ABT646ADBR datasheet, SN74ABT646ADBR pinout, SN74ABT646ADBR application, or SN74ABT646ADBR equivalent, this page provides verified functional architecture, timing-critical switching parameters (e.g., tPLH ≤ 5.6 ns, fmax = 125 MHz), register storage behavior, and validated alternative options for bus isolation and multiplexed data routing.

Technical Context

The SN74ABT646ADBR integrates two independent 8-bit D-type flip-flop registers with separate clock inputs (CLKAB for A→B, CLKBA for B→A), enabling synchronized capture of data from either bus. Its DIR input selects data flow direction during OE-active operation, while SAB/SBA inputs select between real-time or stored data paths.

It implements true bidirectional bus management: when OE is low, one bus drives while the other samples; when OE is high, both buses enter high-impedance isolation while retaining independently latched data. Ioff circuitry ensures <±100 µA leakage at VCC = 0 V, preventing backflow during partial power-down sequences.

Key Specifications

Pinout & Package

SN74ABT646ADBR uses a 24-pin SSOP (Shrink Small Outline Package) with 0.65 mm pitch, 7.8 mm × 4.4 mm body, and 1.2 mm max height. Pin 1 is located in Quadrant Q1 per tape-and-reel orientation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ABT245DBR and SN74LVC16245ADGGR, the SN74ABT646ADBR uniquely combines registered data storage, dual-clock synchronization, and industrial-grade Ioff protection - making it irreplaceable in deterministic real-time bus architectures requiring hold-and-forward functionality.

Availability

SN74ABT646ADBR is available at Aetrix Electronics and suitable for industrial backplane interfaces, automated test equipment data routing, legacy bus extension, and hot-swappable module interfaces requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN74ABT646ADBR 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 for industrial, automotive, and communications markets.

The SN74ABT646ADBR belongs to TI's ABT logic family, engineered for high-speed, high-drive 5-V bus management in noise-sensitive industrial environments with strict partial-power-down requirements.

FAQ

What is the maximum clock frequency supported by the SN74ABT646ADBR?

The SN74ABT646ADBR supports a maximum clock frequency of 125 MHz under recommended operating conditions (VCC = 5 V, TA = 25°C). This value is guaranteed across the full industrial temperature range (−40°C to +85°C) with appropriate layout practices, including proper decoupling and controlled-impedance routing. The SN74ABT646ADBR achieves this performance through optimized internal logic paths and low-propagation-delay design.

Does the SN74ABT646ADBR support partial-power-down operation?

Yes, the SN74ABT646ADBR supports partial-power-down operation via its Ioff circuitry, which limits current to ±100 µA when VCC = 0 V and any input or output is biased to ≤4.5 V. This feature prevents damaging backflow current during hot-swap or staged power sequencing, meeting JEDEC JESD78 reliability requirements. The SN74ABT646ADBR retains register state during Ioff activation if OE remains asserted.

How does the SN74ABT646ADBR handle bus direction control?

The SN74ABT646ADBR uses the DIR pin to determine data flow direction when OE is low: DIR = LOW enables B→A transfer, while DIR = HIGH enables A→B transfer. Direction selection is independent of clock edges and takes effect immediately upon DIR transition. The SN74ABT646ADBR maintains bus isolation when OE is high, regardless of DIR state, preserving register contents on both sides.

What package type is used for the SN74ABT646ADBR?

The SN74ABT646ADBR uses a 24-pin SSOP (Shrink Small Outline Package) with 0.65 mm lead pitch, 7.8 mm × 4.4 mm body dimensions, and 1.2 mm maximum height. It is supplied in tape-and-reel format (2000 units per reel) with RoHS-compliant NiPdAu lead finish and Moisture Sensitivity Level 1 (unlimited floor life at ≤30°C/60% RH). The SN74ABT646ADBR pin 1 orientation follows Quadrant Q1 per JEDEC standards.

Can the SN74ABT646ADBR operate with 3.3-V logic levels?

No, the SN74ABT646ADBR is designed exclusively for 5-V operation (4.5 V to 5.5 V supply range) and is not 3.3-V compatible. Its input thresholds (VIH = 2.0 V, VIL = 0.8 V) and output drive characteristics are specified only at 5 V. For 3.3-V systems, TI recommends alternatives such as SN74LVC16245A; interfacing the SN74ABT646ADBR directly with 3.3-V devices risks undervoltage recognition and excessive current draw.