onsemi 74ACT652SCX

Overview

74ACT652SCX from Fairchild Semiconductor is an octal bus transceiver/register IC with dual D-type flip-flop registers, independent A/B bus control, 24 mA output drive, TTL-compatible inputs, and operation over −40°C to +85°C at 4.5–5.5 V. It enables multiplexed real-time or stored data transfer between two 8-bit buses in industrial control backplanes and memory-mapped I/O interfaces.

For engineers reviewing the 74ACT652SCX datasheet, pinout, applications, or equivalent options, key selection criteria include clock-to-bus propagation delay (max 10.5 ns), output enable timing (tPZH/tPHZ), register storage capability per bus, 3-STATE output control via OEAB/OEBA, and SOIC-24 package compatibility with legacy 74-series board layouts.

Technical Context

The 74ACT652SCX integrates two independent 8-bit D-type registers synchronized to separate clock inputs (CPAB, CPBA), allowing asynchronous capture of A- or B-bus data on LOW-to-HIGH transitions. Its transceiver logic supports four operating modes-real-time transfer, register storage, bidirectional stored-data exchange, and isolated bus hold-controlled by SAB/SBA select and OEAB/OEBA enable signals.

Unlike standard transceivers, the 74ACT652SCX allows simultaneous register loading and 3-STATE output control without conflict: data input functions remain always enabled, while output direction and drive state are decoupled from clock activity via dedicated enable pins and internal bus isolation logic.

Key Specifications

Pinout & Package

74ACT652SCX is housed in a 24-lead Small Outline Integrated Circuit (SOIC) package, JEDEC MS-013 compliant, 0.300 inch wide, with standard gull-wing lead form for surface-mount assembly and thermal performance suitable for industrial ambient conditions.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74ACT652SCX, the 74F652PC trades industrial temperature tolerance for marginal speed gain, while the SN74ACT652N preserves full electrical equivalence but requires manual soldering or socketing due to its PDIP package-making 74ACT652SCX optimal for volume SMT deployment in ruggedized systems.

Availability

74ACT652SCX is available at Aetrix Electronics and suitable for industrial backplane interfaces, memory-mapped I/O bridges, and programmable logic controller bus arbiters requiring stable component supply, long-term lifecycle support, and consistent SOIC-24 footprint compatibility.

Supply support for 74ACT652SCX 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, power management, and logic families before its acquisition by ON Semiconductor in 2016.

The 74ACT652SCX belongs to Fairchild's ACT (Advanced CMOS Technology) logic family, designed specifically for high-speed, low-noise, industrial-grade bus interface applications requiring TTL compatibility and robust ESD tolerance.

FAQ

What is the maximum clock frequency supported by the 74ACT652SCX?

The 74ACT652SCX supports a maximum clock frequency of 100 MHz, derived from its guaranteed maximum propagation delay of 10.5 ns (tPLH/tPHL) under standard load (CL = 50 pF) and VCC = 5.0 V ± 0.5 V. This allows reliable use in synchronous bus systems operating up to 50 MHz with setup/hold margin. The 74ACT652SCX does not specify fMAX directly but defines timing limits that imply this operational ceiling.

Does the 74ACT652SCX support hot-swapping or live insertion?

The 74ACT652SCX is not explicitly rated for hot-swap operation. While its absolute maximum ratings include VI = −0.5 V to VCC + 0.5 V and IOK = ±20 mA, it lacks integrated hot-swap protection features such as slew-rate controlled outputs or undervoltage lockout. Safe live insertion requires external current limiting and sequencing circuitry. The 74ACT652SCX should be powered and stabilized before bus connection in modular systems.

Can the 74ACT652SCX operate with a 3.3 V supply?

No, the 74ACT652SCX is specified only for 4.5 V to 5.5 V operation. Its DC electrical characteristics-including VOH (min 4.4 V at VCC = 4.5 V) and VIH (min 2.0 V)-are defined exclusively within this range. Operation at 3.3 V falls outside recommended conditions and risks failure to meet logic thresholds, increased static current, or undefined register behavior. For 3.3 V systems, consider ACTQ or LVT logic families instead of the 74ACT652SCX.

How does the 74ACT652SCX handle bus contention during mode transitions?

The 74ACT652SCX prevents bus contention through strict 3-STATE control: OEAB and OEBA independently disable A→B and B→A outputs, while SAB/SBA select only the source (real-time or stored) without enabling conflicting drivers. During clock or select transitions, outputs remain in high-impedance until the new state is fully established. The 74ACT652SCX does not auto-isolate; proper external sequencing of OE and clock signals is required to avoid overlap.

Is the 74ACT652SCX pin-compatible with the 74LS652 or 74ALS652?

No, the 74ACT652SCX is not pin-compatible with 74LS652 or 74ALS652. Although all three share identical pin names and 24-pin SOIC packaging, the 74LS652 uses different internal logic architecture (no dual-clock register structure) and incompatible timing-particularly in clock-to-output and enable timing relationships. Substituting the 74ACT652SCX into an LS/ALS-designed board may cause metastability or functional failure without layout and firmware revision.