Texas Instruments SN74ABT651DBRE4

Overview

SN74ABT651DBRE4 from Texas Instruments is an octal bus transceiver and register IC with 3-state outputs, designed for bidirectional data flow control between two 8-bit buses (A and B). It integrates D-type flip-flops, dual clock inputs (CLKAB/CLKBA), dual select controls (SAB/SBA), and independent output enables (OEAB/OEBA), supporting real-time or stored data transfer at up to 125 MHz. Used in high-speed backplane and memory interface applications requiring latch-and-forward bus management.

For engineers reviewing the SN74ABT651DBRE4 datasheet, SN74ABT651DBRE4 pinout, SN74ABT651DBRE4 application, or SN74ABT651DBRE4 equivalent, key selection criteria include its 5-V operation, –32-mA/64-mA drive strength, sub-6 ns propagation delay, 3-state isolation timing (tPZL/tPHZ), and DB package thermal profile (θJA = 104°C/W).

Technical Context

The SN74ABT651DBRE4 implements a dual-path bus architecture with independent A→B and B→A transceiver channels, each controlled by dedicated clock, select, and enable pins. Its EPIC-II^B BiCMOS process enables high-drive capability while maintaining low ground bounce (VOLP < 1 V) and robust ESD protection (>2000 V HBM).

It supports four fundamental bus-management modes: real-time bidirectional transfer, simultaneous storage of A/B data, selective storage (A-only or B-only), and cross-loaded transfer (stored A→B + stored B→A). Latch-up immunity exceeds 500 mA per JESD 17, and all I/Os tolerate 5.5-V max output voltage under power-off conditions.

Key Specifications

Pinout & Package

SN74ABT651DBRE4 is housed in a 24-pin Shrink Small-Outline (DB) package with 0.65 mm lead pitch and 300 mil body width. The package is RoHS-compliant, moisture-sensitive level 1 (MSL-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 SN74ABT245DW and SN74LVTH16245ADGGR, SN74ABT651DBRE4 uniquely combines 8-bit bidirectional transceivers with dual independent D-register banks and full real-time/stored data multiplexing - making it irreplaceable in applications requiring deterministic bus hold, glitch-free hot-swap, or protocol-aligned data staging without external latches.

Availability

SN74ABT651DBRE4 is available at Aetrix Electronics and suitable for industrial backplane interfaces, memory bus isolation, protocol translation bridges, and legacy system bus expansion requiring stable component supply and long-term lifecycle support.

Supply support for SN74ABT651DBRE4 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 90 years of innovation in industrial, automotive, and communications markets.

The ABT logic family - including SN74ABT651DBRE4 - was engineered for high-speed, high-drive 5-V TTL-compatible applications demanding robust noise immunity, low ground bounce, and seamless integration into bus-oriented architectures.

FAQ

What is the recommended power-up sequence for SN74ABT651DBRE4 to avoid bus contention?

During power-up, OEBA must be held high (via pullup resistor to VCC) and OEAB held low (via pulldown resistor to GND) to force both directions into high-impedance before clocks or selects become active. This prevents unintended data coupling or bus conflicts. Resistor values should be selected based on driver current-sinking/source capability per datasheet Section 1 - typically 10 kΩ for OEBA and 4.7 kΩ for OEAB.

Does SN74ABT651DBRE4 support hot-plug operation in live backplane systems?

Yes, SN74ABT651DBRE4 supports hot-plug operation when OEBA and OEAB are externally controlled to enter high-Z before insertion. Its robust ESD protection (>2000 V HBM), latch-up immunity (>500 mA), and power-off safe I/O (VO ≤ 5.5 V) allow safe connection/disconnection while VCC remains active on the backplane. Internal registers retain last-stored data during brief OE assertion gaps.

Can SN74ABT651DBRE4 operate with mixed 3.3-V and 5-V logic levels on its A and B buses?

No - SN74ABT651DBRE4 is a 5-V-only device (VCC = 4.5–5.5 V) with TTL-compatible input thresholds (VIH = 2 V, VIL = 0.8 V). While it can accept 3.3-V logic HIGH inputs (≥2 V), driving 3.3-V receivers directly risks overvoltage damage unless external clamping or level-shifting is used. It is not 3.3-V I/O tolerant.

How does the SN74ABT651DBRE4 handle simultaneous clock edges on CLKAB and CLKBA?

When SAB = SBA = L (real-time mode), simultaneous CLKAB↑ and CLKBA↑ edges are permitted if propagation delays and setup/hold timing margins are observed. When SAB = SBA = H (stored-data mode), clocks must be staggered per datasheet Note ‡ to avoid race conditions between register loading and output enable timing - minimum separation ≥ tSU + tPHL(A→B) + tPLH(B→A).

What is the maximum capacitive load SN74ABT651DBRE4 can drive while maintaining 125-MHz operation?

At 125 MHz, SN74ABT651DBRE4 maintains specification compliance with CL = 50 pF (per switching characteristics table). Driving >50 pF increases propagation delay and may violate setup/hold margins. For heavier loads, derate frequency: e.g., 60 MHz supports ~100 pF. Layout best practices (short traces, ground plane, local decoupling) are essential to sustain high-speed performance.