Texas Instruments CD74FCT245E

Overview

CD74FCT245E from Texas Instruments is a BiCMOS octal bus transceiver with 3-state outputs, designed for bidirectional data flow control between two 8-bit buses in TTL/CMOS mixed-signal systems. It features noninverted outputs, 64-mA sink capability per output, 3.7-V output voltage swing limitation to suppress EMI, and operates across 4.75–5.25 V at 0°C to 70°C.

For engineers reviewing the CD74FCT245E datasheet, CD74FCT245E pinout, CD74FCT245E application, or CD74FCT245E equivalent, key selection criteria include direction-control logic behavior, 3-state isolation timing (ten = 1.5–9.5 ns), output current drive strength, VCC bounce mitigation architecture, and PDIP-20 package compatibility with legacy through-hole designs.

Technical Context

The CD74FCT245E implements a BiCMOS output stage combining bipolar and CMOS transistors to clamp high-level output voltage to ~3.7 V (two diode drops below VCC), reducing power-bus ringing and ground bounce during simultaneous switching. Its DIR and OE inputs provide independent control of data direction and 3-state enable/disable.

Propagation delay tpd is 1.5–7 ns (A↔B), with enable/disable times ten and tdis specified at 1.5–9.5 ns and 1.5–7.5 ns respectively. Input transition rate is limited to 0–10 ns/V, and absolute maximum VCC is 6 V - exceeding standard 5-V TTL rails but requiring careful supply design.

Key Specifications

Pinout & Package

CD74FCT245E is supplied in a 20-pin plastic dual in-line package (PDIP-N), with 0.3-inch body width and standard through-hole mounting. Pin 1 is marked via corner notch or beveled edge; package conforms to JEDEC MS-001.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74F245N and 74ACT245PC, the CD74FCT245E uniquely balances 64-mA drive, EMI-suppressing 3.7-V swing, and commercial temperature range in a drop-in PDIP-20 footprint-making it optimal for retrofitting noise-sensitive industrial interfaces without layout change.

Availability

CD74FCT245E is available at Aetrix Electronics and suitable for industrial PLC backplanes, legacy bus extensions, memory-mapped I/O expansion, and automated test equipment requiring stable component supply and long-term obsolescence management.

Supply support for CD74FCT245E 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 founded in 1930, specializing in analog, embedded processing, and logic solutions with broad industrial, automotive, and communications reach.

The CD74FCT245E belongs to TI's FCT logic family-designed specifically for high-drive, low-noise, 5-V mixed-technology bus interfacing in commercial-grade industrial and instrumentation systems.

FAQ

What is the function of the DIR pin on the CD74FCT245E?

The DIR (direction-control) pin on the CD74FCT245E determines data flow direction: when DIR is LOW, data transfers from the B bus to the A bus; when DIR is HIGH, data flows from the A bus to the B bus. This bidirectional control enables flexible bus arbitration in systems where either side may act as source or sink, and is essential for implementing shared-memory or peripheral interface protocols without external logic.

How does the CD74FCT245E suppress electromagnetic interference (EMI)?

The CD74FCT245E suppresses EMI by limiting its output voltage swing to 0 V–3.7 V-two diode drops below VCC-via its BiCMOS output stage. This intentional reduction in dynamic rail excursion minimizes power-bus ringing, VCC bounce, and ground bounce during simultaneous output switching, directly lowering broadband radiated emissions. Measured noise characteristics confirm ≤1 V dynamic VOL and ≥0.5 V dynamic VOH under 50-pF load, validating its EMI-reduction architecture.

Can the CD74FCT245E operate with a 3.3-V supply?

No, the CD74FCT245E is not rated for 3.3-V operation. Its recommended VCC range is strictly 4.75 V to 5.25 V, and absolute maximum rating is 6 V. The BiCMOS output stage relies on ~5-V biasing to achieve its 3.7-V swing and 64-mA sink performance. Using 3.3 V will result in undefined logic thresholds, degraded VOL/VOH, and potential failure to meet timing specs such as tpd or ten. For 3.3-V systems, consider TI's 74LVC245A instead.

What is the correct power-up sequence for the CD74FCT245E to ensure high-impedance state?

To guarantee high-impedance outputs at power-up, the OE (output-enable) pin of the CD74FCT245E must be held HIGH before VCC reaches valid logic levels. TI recommends tying OE to VCC through a pullup resistor; the minimum value depends on the driver's sink capability but is typically 4.7 kΩ for standard TTL drivers. This prevents bus contention during power ramp-up and avoids unintended data leakage onto A or B buses before system initialization completes.

Is the CD74FCT245E pin-compatible with other 20-pin octal transceivers like the 74LS245?

Yes, the CD74FCT245E shares identical pinout and package (PDIP-20) with the 74LS245, 74F245, and 74ACT245, making it a direct physical replacement. However, functional compatibility requires verification of voltage thresholds, timing, and drive strength: the CD74FCT245E offers higher IOL (64 mA vs. 24 mA for LS), tighter VOL (0.55 V vs. 0.5 V), and BiCMOS EMI control absent in LS/F variants. Always validate timing margins and bus loading in the target application.