Texas Instruments CD74FCT2952AM

Overview

CD74FCT2952AM from Texas Instruments is a BiCMOS octal bus transceiver and register with dual 8-bit back-to-back registers, 3-state outputs, buffered inputs, noninverted data flow, and 64-mA sink capability. It operates at 4.75–5.25 V over 0°C to 70°C and is used in bidirectional data buffering between system buses in industrial control and legacy computing interfaces.

For engineers reviewing the CD74FCT2952AM datasheet, CD74FCT2952AM pinout, CD74FCT2952AM application, or CD74FCT2952AM equivalent, key selection considerations include its dual-clock-enable architecture, controlled output edge rates for EMI reduction, 3.7-V output swing limitation at 5-V VCC, and SOIC-24 package compatibility with TTL/CMOS mixed-signal systems.

Technical Context

The CD74FCT2952AM implements two independent 8-bit register paths (A↔B), each with dedicated clock (CLKAB/CLKBA), clock-enable (CLKENAB/CLKENBA), and 3-state output-enable (OEAB/OEBA) controls. Data latching occurs on the low-to-high transition of CLKAB or CLKBA when the corresponding CLKEN is low.

Its BiCMOS output stage combines bipolar and CMOS transistors to limit VOH to ~3.7 V at VCC = 5 V-reducing power-bus ringing, VCC bounce, and ground bounce during simultaneous switching-while sustaining 64-mA sink current per output and supporting 48-mA IOL under recommended conditions.

Key Specifications

Pinout & Package

Packaged in a 24-pin plastic small-outline integrated circuit (SOIC) with standard DW footprint and 0.300-inch body width. Pin mapping validated per TI SCBS720 datasheet Figure M (top view).

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74FCT2952AM, SN74FCT2952M offers identical performance and drop-in replacement capability, while 74ACT2952PC trades EMI-safe output swing for raw speed and higher drive voltage-making it less suitable for noise-sensitive backplane or mixed-voltage interfacing.

Availability

CD74FCT2952AM is available at Aetrix Electronics and suitable for industrial PLC backplanes, legacy computer bus extenders, and automated test equipment requiring stable component supply and long-term obsolescence management support.

Supply support for CD74FCT2952AM 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 CD74FCT2952AM belongs to TI's FCT (Fast CMOS Technology) logic series, designed for high-speed, low-noise bidirectional bus interfacing in industrial, computing, and instrumentation systems requiring TTL compatibility and EMI resilience.

FAQ

What is the maximum output sink current specification for CD74FCT2952AM?

The CD74FCT2952AM is rated for 64-mA output sink current per pin under recommended operating conditions (VCC = 4.75 V, TA = 25°C). This value is confirmed in the "electrical characteristics" table of the SCBS720 datasheet and supports direct driving of multiple TTL loads or moderate-capacitance PCB traces without external buffers. The absolute maximum rating is 70 mA, but sustained operation should remain within the 64-mA limit for reliability.

Does CD74FCT2952AM support hot-swapping or live insertion into a powered bus?

Yes, CD74FCT2952AM supports controlled hot-insertion due to its input/output isolation from VCC and SCR latch-up-resistant BiCMOS process. When OE is held high (3-state), all outputs enter high-impedance mode regardless of VCC sequencing. TI recommends tying OE to VCC via a pullup resistor during power-up to ensure defined initial state. The device's VIH/VIL thresholds and clamping diodes further enhance robustness during partial-power transitions.

What is the purpose of the 3.7-V output voltage limit at VCC = 5 V in CD74FCT2952AM?

The 3.7-V VOH limit in CD74FCT2952AM arises from its BiCMOS output stage design, which uses two series diode drops below VCC. This intentional voltage swing reduction lowers power-bus ringing and mitigates VCC/ground bounce during simultaneous switching-critical for signal integrity in dense backplane or multi-drop bus environments. It does not impair TTL compatibility, as VOH remains well above the 2.0-V VIH threshold.

Can CD74FCT2952AM operate with a 3.3-V supply?

No, CD74FCT2952AM is specified only for 4.75–5.25-V operation per its recommended conditions and absolute maximum ratings. Applying 3.3 V violates the minimum VCC requirement and will result in undefined logic behavior, insufficient noise margin, and potential failure to meet timing specifications. For 3.3-V systems, consider TI's ALVC or LVC series transceivers instead of CD74FCT2952AM.

How does the dual-clock-enable architecture of CD74FCT2952AM improve system timing flexibility?

The CD74FCT2952AM features independent CLKENAB and CLKENBA inputs, allowing selective activation of A→B or B→A data latching without affecting the opposite path. This enables asymmetric timing control-for example, capturing sensor data on the B bus while simultaneously forwarding processed results to the A bus-without requiring synchronized clocks or additional glue logic. Each register path operates autonomously, increasing design modularity and reducing timing-critical dependencies.