onsemi 74F543MSAX

Overview

74F543MSAX from Fairchild Semiconductor is an octal registered transceiver with dual 8-bit D-type latch sets, separate A-to-B and B-to-A control paths (CEAB/LEAB/OEAB and CEBA/LEBA/OEBA), 24 mA sink capability on A outputs, 64 mA sink on B outputs, and operates at +4.5V to +5.5V supply-used in bidirectional data bus interfacing between microprocessor subsystems and peripheral I/O buffers.

For engineers reviewing the 74F543MSAX datasheet, pinout, applications, or equivalent options, key selection criteria include independent latch/output enable timing, 3-STATE output drive asymmetry (A vs. B), propagation delays under 12.5 ns, and compatibility with TTL-level logic families in industrial control backplanes.

Technical Context

The 74F543MSAX implements two independent 8-bit register paths: A-to-B uses CEAB (enable), LEAB (latch edge-triggered), and OEAB (output enable); B-to-A mirrors this with CEBA, LEBA, and OEBA. Each path supports transparent latching and 3-STATE output control.

It features asymmetric output drive: A-side outputs rated for 24 mA sink (IOL), B-side for 64 mA sink, enabling mixed-load bus driving. Input thresholds are VIH ≥ 2.0 V and VIL ≤ 0.8 V, ensuring robust TTL compatibility across 0°C to +70°C ambient operation.

Key Specifications

Pinout & Package

74F543MSAX is housed in a 24-lead Shrink Small Outline Package (SSOP), EIAJ TYPE II, 5.3 mm wide, package code MSA24.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74F543N and 74F543SCX, the 74F543MSAX offers superior thermal performance and board density due to its 5.3 mm SSOP package, while retaining full functional and timing equivalence-making it optimal for space-constrained industrial PCBs requiring high-reliability bus interfacing.

Availability

74F543MSAX is available at Aetrix Electronics and suitable for industrial I/O expansion, microprocessor bus interface, and legacy system data buffering requiring stable component supply and long-term lifecycle support.

Supply support for 74F543MSAX 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in analog and mixed-signal ICs, acquired by ON Semiconductor in 2016; known for high-performance logic, power management, and interface solutions.

The 74F543MSAX belongs to the 74F Fast TTL logic family, designed specifically for high-speed, low-latency bidirectional data transfer in industrial control, instrumentation, and computing backplanes.

FAQ

What is the function of the CEAB and CEBA pins on the 74F543MSAX?

The CEAB (A-to-B Enable) and CEBA (B-to-A Enable) pins on the 74F543MSAX are active-LOW control inputs that gate data flow into their respective latch registers. When CEAB is LOW, data on A0–A7 can be captured by the A-to-B latches upon LEAB transition; similarly, CEBA LOW enables B0–B7 data capture into B-to-A latches. Both must be asserted for valid latching-ensuring deterministic data staging before output enable.

Does the 74F543MSAX support hot insertion or live bus swapping?

No, the 74F543MSAX does not support hot insertion. Its absolute maximum ratings specify VCC pin potential from −0.5 V to +7.0 V and input voltage range of −0.5 V to +7.0 V, but no current-limiting or bus-fault protection is integrated. Applying voltage to inputs or outputs while VCC is unpowered risks latch-up or damage-thus, power sequencing per manufacturer guidelines is required before signal application.

What is the maximum capacitive load the 74F543MSAX can drive on its B outputs?

The 74F543MSAX B outputs are characterized for CL = 50 pF in AC Electrical Characteristics, with propagation delays specified up to that load. While not explicitly rated beyond 50 pF, the 64 mA sink capability suggests stable operation into typical PCB traces and moderate fanout (e.g., ≤10 standard TTL inputs). For >50 pF loads, empirical timing validation is recommended due to increased rise/fall time degradation.

Can the 74F543MSAX operate at 3.3 V supply?

No, the 74F543MSAX is not rated for 3.3 V operation. Its Recommended Operating Conditions specify VCC = +4.5 V to +5.5 V only, and DC Electrical Characteristics (e.g., VOH, VOL, VIH, VIL) are guaranteed only within that range. At 3.3 V, input thresholds would be violated and output drive severely degraded-use a 74LVC or 74ALVC series transceiver instead for 3.3 V systems.

How does the 74F543MSAX differ from the 74F245 in bidirectional data handling?

The 74F543MSAX contains two independent 8-bit D-type latch registers with separate CE/LE/OE controls per direction, enabling true registered bidirectional transfer with storage. In contrast, the 74F245 is a non-latched octal bus transceiver with single-direction control (DIR) and output enable (OE)-no internal storage. Thus, 74F543MSAX adds setup/hold margin and eliminates metastability risk in asynchronous bus handshakes where 74F245 cannot hold data.