Texas Instruments CD74FCT543M

Overview

CD74FCT543M from Texas Instruments is a BiCMOS octal registered transceiver with 3-state outputs, designed for bidirectional data flow control in TTL-compatible bus systems. It features dual independent latch/enable paths (A↔B), 64-mA sink current per output, 3.7-V limited high-level output swing, and operation across 4.75–5.25 V at 0°C to 70°C.

For engineers reviewing the CD74FCT543M datasheet, CD74FCT543M pinout, CD74FCT543M application, or CD74FCT543M equivalent, key selection criteria include controlled edge rates for EMI reduction, bus-hold inputs for floating-input immunity, and separate CE/LE/OE controls enabling independent A-to-B and B-to-A register staging in memory interfaces and backplane drivers.

Technical Context

The CD74FCT543M implements two parallel sets of eight D-type latches with fully independent control logic: CEAB/LEAB/OEAB governs A→B flow, while CEBA/LEBA/OEBA manages B→A flow. Each path supports transparent latch mode (LE low) and storage mode (LE rising edge), with 3-state output enable/disable decoupled from latching.

Its BiCMOS output stage clamps VOH to ~3.7 V (two diode drops below VCC), reducing power-bus ringing and ground bounce during simultaneous switching. Input isolation from VCC, active bus-hold circuitry, and SCR latch-up resistance further enhance robustness in noisy industrial and computing environments.

Key Specifications

Pinout & Package

CD74FCT543M is housed in a 24-pin plastic small-outline (SOIC) package (DW drawing), with 300-mil body width and gull-wing leads. Thermal impedance θJA = 46°C/W enables stable operation under sustained 64-mA per-pin loading without forced airflow.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74F543N and 74ACT543SCX, the CD74FCT543M uniquely balances EMI-safe 3.7-V output swing, integrated bus-hold, and 64-mA drive in a single BiCMOS device-making it optimal for noise-sensitive industrial backplanes where layout space precludes external termination or biasing.

Availability

CD74FCT543M is available at Aetrix Electronics and suitable for memory interface buffering, backplane data transceivers, legacy system bus extension, TTL-to-logic-level translation, and industrial controller I/O expansion requiring stable component supply and long-term obsolescence management.

Supply support for CD74FCT543M 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 decades of heritage in high-reliability logic families.

The CD74FCT543M belongs to TI's FCT (Fast CMOS TTL-compatible) logic series, engineered for low-noise, high-drive 5-V bus interfacing in industrial and computing systems where EMI control and latch-based data staging are essential.

FAQ

What is the maximum sink current capability of each output pin on the CD74FCT543M?

Each output pin on the CD74FCT543M supports up to 64 mA of sink current under recommended operating conditions (VCC = 4.75 V, TA = 25°C). This rating is confirmed in the electrical characteristics table and enables direct drive of multiple TTL inputs or termination networks without external buffers. The CD74FCT543M maintains this performance across its full 0°C to 70°C operating range, with derating only required above 70°C.

Does the CD74FCT543M include bus-hold circuitry, and how does it function?

Yes, the CD74FCT543M integrates active bus-hold circuitry on all data inputs (A1–A8 and B1–B8). This feature maintains unused or floating inputs at their last-valid logic state using weak feedback, eliminating the need for external pull-up or pull-down resistors. The bus-hold current is self-limiting and operates across the full supply and temperature range, ensuring deterministic behavior in partial-population backplane or modular system designs where some lines may be unconnected.

What is the purpose of the 3.7-V output voltage limit on the CD74FCT543M?

The CD74FCT543M limits VOH to approximately 3.7 V (two diode drops below VCC) via its BiCMOS output stage. This intentional voltage swing reduction minimizes power-bus ringing, VCC bounce, and ground bounce during simultaneous output switching-key contributors to electromagnetic interference (EMI). The CD74FCT543M achieves this without sacrificing noise margin, as VIH remains at 2 V and VOL stays at 0.55 V, preserving TTL compatibility while enhancing signal integrity in dense PCB layouts.

How are the latch-enable and output-enable functions separated for each direction in the CD74FCT543M?

The CD74FCT543M provides fully independent control logic for A-to-B and B-to-A data paths: CEAB/LEAB/OEAB manage A→B flow, while CEBA/LEBA/OEBA handle B→A flow. LEAB/LEBA control latch transparency vs. storage mode (rising-edge triggered), and OEAB/OEBA independently enable/disable 3-state outputs-allowing latched data to be held while outputs remain high-impedance. This separation enables complex handshaking protocols and prevents bus contention in bidirectional memory or peripheral interfaces using the CD74FCT543M.

Is the CD74FCT543M compatible with 3.3-V logic systems?

The CD74FCT543M is a 5-V-only device (VCC = 4.75–5.25 V) and is not 3.3-V tolerant on inputs or outputs. Its VIH minimum is 2.0 V and VIL maximum is 0.8 V, making it compatible with 3.3-V CMOS outputs driving into it-but its 3.7-V VOH exceeds safe input limits for most 3.3-V receivers. To interface with 3.3-V systems, level-shifting circuitry or a dedicated 3.3-V transceiver like the SN74LVC543A must be used alongside the CD74FCT543M.