onsemi 74ACT652SC

Overview

74ACT652SC 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 real-time or registered data routing between two 8-bit buses. It operates from 4.5 V to 5.5 V across −40°C to +85°C and is used in bidirectional data buffering and synchronized bus interfacing in industrial control backplanes.

For engineers reviewing the 74ACT652SC datasheet, pinout, applications, or equivalent options, key selection criteria include clock-controlled register storage, independent OEAB/OEBA enable logic, SAB/SBA multiplexing for real-time vs. stored data routing, and SOIC-24 package compatibility with JEDEC MS-013 footprint.

Technical Context

The 74ACT652SC integrates two independent 8-bit D-type flip-flop registers-one per bus-with separate clock inputs (CPAB, CPBA) and select inputs (SAB, SBA) enabling four operational modes: real-time A→B, real-time B→A, stored A→B, and stored B→A. Data latching occurs on LOW-to-HIGH clock transitions regardless of OE or S states.

Output enable logic is asymmetric: OEAB controls A-bus outputs, OEBA controls B-bus outputs, and both must be LOW to enable bidirectional transceiver mode. The device supports simultaneous storage into both registers and isolated hold functions via selective OE assertion-e.g., OEAB = HIGH + OEBA = LOW holds A bus while storing B bus data.

Key Specifications

Pinout & Package

74ACT652SC is housed in a 24-lead Small Outline Integrated Circuit (SOIC) package per JEDEC MS-013, 0.300-inch wide, with gull-wing leads and standard thermal/mechanical dimensions for surface-mount reflow assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74ACT652SC, the 74F652PC trades higher static power for improved speed, while the SN74ACT652N retains identical logic behavior in a through-hole form factor-making the SOIC variant optimal for production-scale surface-mount manufacturing with thermal and density advantages.

Availability

74ACT652SC is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus bridging, and programmable logic I/O expansion requiring stable component supply, long-term obsolescence mitigation, and consistent SOIC-24 sourcing.

Supply support for 74ACT652SC 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, discrete, and logic ICs before its acquisition by ON Semiconductor in 2016; its ACT logic family remains widely deployed in industrial and automotive systems.

The 74ACT652SC belongs to Fairchild's Advanced CMOS Technology (ACT) logic series, designed specifically for 5 V systems requiring TTL compatibility, high noise immunity, and robust drive capability in harsh electromagnetic environments.

FAQ

What is the maximum clock frequency supported by the 74ACT652SC?

The 74ACT652SC supports a maximum clock frequency of 50 MHz under recommended operating conditions (VCC = 5.0 V ± 0.5 V, CL = 50 pF, TA = −40°C to +85°C). This is derived from the maximum propagation delay of 10.5 ns (tPLH/tPHL, bus-to-bus) and accounts for setup/hold timing margins. The 74ACT652SC does not include internal PLLs or frequency multipliers-its clock limit is strictly governed by combinational and register path delays.

Does the 74ACT652SC support hot-swap or live-insertion?

The 74ACT652SC is not rated for hot-swap operation. Its absolute maximum ratings specify DC input diode current limits of ±20 mA and prohibit operation outside VCC = −0.5 V to +7.0 V, with no built-in bus-hold, power-up sequencing, or I²C-style slew-rate control. Applying signal or power before VCC stabilization may cause latch-up or excessive current flow. For hot-swap applications, external protection circuitry or dedicated hot-swap controllers must be used alongside the 74ACT652SC.

Can the 74ACT652SC operate with a 3.3 V supply?

No, the 74ACT652SC requires a minimum VCC of 4.5 V and is not specified for 3.3 V operation. Its TTL-compatible input thresholds (VIH = 2.0 V min, VIL = 0.8 V max) and output voltage levels (VOH ≥ 4.4 V at VCC = 4.5 V) are optimized for 5 V systems. Using 3.3 V violates the recommended operating conditions and will result in undefined logic states, insufficient noise margin, and potential failure to drive downstream TTL loads. For 3.3 V systems, consider ACT-family variants explicitly rated for mixed-voltage operation or level translators paired with the 74ACT652SC.

How does the 74ACT652SC handle bus contention during direction switching?

The 74ACT652SC avoids bus contention through controlled 3-state output enable logic: OEAB and OEBA independently place A0–A7 and B0–B7 into high-impedance states. During direction change, asserting either OE input disables its respective bus drivers before enabling the opposite side-ensuring no simultaneous drive. The 74ACT652SC does not include automatic direction-sensing or slew-rate limiting; proper sequencing of OEAB/OEBA transitions must be implemented in system firmware or external logic to guarantee clean handover.

Is the 74ACT652SC pin-compatible with the 74LS652 or 74ALS652?

Yes-the 74ACT652SC shares identical pinout, terminal assignment, and functional logic with the 74LS652 and 74ALS652, including A0–A7, B0–B7, CPAB, CPBA, SAB, SBA, OEAB, OEBA, VCC, and GND positions on the 24-pin SOIC package. However, electrical behavior differs: the 74ACT652SC offers higher output drive (±24 mA vs. ±8 mA for LS), faster timing (≤10.5 ns vs. ≤25 ns), and lower ICC (80 µA vs. 30 mA typical for LS). System-level validation is required to confirm timing closure and loading compatibility when substituting.