Texas Instruments SN74BCT2953NT

Overview

SN74BCT2953NT from Texas Instruments is an octal bus transceiver with dual 8-bit back-to-back registers for bidirectional data flow between A and B buses, operating at up to 110 MHz clock frequency, with B-port sink capability of 64 mA, A-port sink capability of 24 mA, and specified for 0°C to 70°C industrial temperature range.

For engineers reviewing the SN74BCT2953NT datasheet, SN74BCT2953NT pinout, SN74BCT2953NT application, or SN74BCT2953NT equivalent, key selection considerations include bidirectional register timing (tPLH ≤ 8 ns), output drive asymmetry (A vs. B port current ratings), clock-enable control logic, and NT-package DIP-24 mechanical compatibility in legacy board designs.

Technical Context

The SN74BCT2953NT implements two independent 8-bit edge-triggered registers: one for A→B data flow synchronized to CLKAB/CLKENAB, and another for B→A flow synchronized to CLKBA/CLKENBA. Each register latches on the low-to-high clock transition when its respective clock-enable is low.

Output-enable inputs (OEAB/OEBA) control three-state output drivers per port, with inverting logic polarity. The BiCMOS process enables high-speed operation while reducing ICCZ quiescent supply current compared to earlier bipolar-only bus transceivers.

Key Specifications

Pinout & Package

SN74BCT2953NT uses a 300-mil plastic dual-inline package (PDIP-24), pin-compatible with industry-standard DIP-24 footprints and socketing solutions for prototyping and legacy repair.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74BCT2953NT, SN74ACT2953N trades 64 mA B-port drive for lower power and better noise margin, while 74F2953PC retains identical functionality and timing but lacks BiCMOS quiescent current optimization - both require validation of load compatibility and thermal derating in target layouts.

Availability

SN74BCT2953NT is available at Aetrix Electronics and suitable for industrial control backplanes, legacy computer expansion interfaces, automated test fixture signal routing, and digital pattern generation systems requiring stable component supply and long-term obsolescence management support.

Supply support for SN74BCT2953NT 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 founded in 1930, delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74BCT2953NT belongs to TI's BCT (Bipolar-CMOS Transceiver) logic family, designed specifically for high-speed, registered bidirectional bus interfacing in commercial and industrial systems requiring robust drive strength and deterministic timing.

FAQ

What is the primary function of the SN74BCT2953NT in a digital system?

The SN74BCT2953NT functions as an octal registered bidirectional bus transceiver with two independent 8-bit back-to-back registers. It enables synchronized, clock-controlled data transfer between A and B buses - capturing data on the low-to-high clock edge when clock-enable is low, and presenting it on the output port when output-enable is asserted. Its design supports deterministic timing in bus arbitration and interface isolation scenarios.

Does the SN74BCT2953NT support 3.3-V operation?

No, the SN74BCT2953NT is rated for 4.5 V to 5.5 V supply voltage only and is not 3.3-V tolerant. Its input thresholds (VIH = 2.0 V min, VIL = 0.8 V max) and output voltage levels (VOH ≥ 2.4 V at IOH = −3 mA) are specified for 5-V TTL/CMOS compatibility. Operating below 4.5 V risks functional failure or undefined timing behavior.

How does the SN74BCT2953NT handle bus contention between A and B ports?

The SN74BCT2953NT prevents bus contention through independent output-enable controls (OEAB for A→B, OEBA for B→A) and registered data flow. Only one direction is active at a time: when OEAB is low, B-port outputs reflect A-port data (if latched), while OEBA high places A-port outputs in high-impedance. Simultaneous low states on both OE inputs are not recommended and may cause contention.

Is the SN74BCT2953NT pin-compatible with other 24-pin DIP octal transceivers?

Yes, the SN74BCT2953NT uses a standard PDIP-24 footprint with pin assignments matching industry-convention for dual-octal registered transceivers (e.g., pin 1 = B8, pin 24 = VCC). However, logic behavior - particularly clock-enable polarity, register edge sensitivity, and output drive asymmetry - differs from non-BCT families like 74LS or 74F, so electrical and timing validation is required before substitution.

What is the significance of the "BCT" designation in SN74BCT2953NT?

The "BCT" suffix denotes Texas Instruments' Bipolar-CMOS Transceiver family, combining bipolar input stages for TTL-compatible thresholds and CMOS output drivers for improved speed-power trade-offs. In the SN74BCT2953NT, this architecture achieves 110 MHz operation with significantly reduced ICCZ quiescent current versus pure bipolar predecessors like the 74F2953, while retaining robust 5-V drive capability.