Renesas 74FCT257DTQG8

Overview

74FCT257DTQG8 from Renesas Electronics (formerly IDT) is a fast CMOS quad 2-input multiplexer with 3-state outputs, designed for bus-oriented digital systems. It features true TTL input/output compatibility (VOH = 3.3 V typ., VOL = 0.3 V typ.), high drive capability (–15 mA IOH, 48 mA IOL), and industrial temperature operation (–40°C to +85°C). It is used in data routing, address selection, and bus arbitration applications.

For engineers reviewing the 74FCT257DTQG8 datasheet, 74FCT257DTQG8 pinout, 74FCT257DTQG8 application, or 74FCT257DTQG8 equivalent, key selection criteria include its 16-pin QSOP package, active-low Output Enable (OE), common select input (S), and guaranteed JEDEC Std-18 compliance for interoperability in legacy TTL/CMOS hybrid systems.

Technical Context

The 74FCT257DTQG8 implements four independent 2:1 multiplexers sharing one select line (S) and one active-low output enable (OE). Each channel routes either I0x or I1x to Zx based on S, with outputs placed in high-impedance state when OE is high.

It uses advanced dual-metal CMOS technology to achieve TTL-compatible voltage thresholds (VIH = 2.0 V min, VIL = 0.8 V max), low leakage (≤1 µA), and fast propagation delays (tPLH/tPHL ≤ 3.9 ns at VCC = 5.0 V, CL = 50 pF, RL = 500 Ω).

Key Specifications

Pinout & Package

74FCT257DTQG8 is housed in a 16-pin Quarter-size Small Outline Package (QSOP), green RoHS-compliant, with 0.65 mm lead pitch and body dimensions of 4.4 mm × 5.5 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad 2-input multiplexer applications.

Compared with SN74F257N and 74ACT257SCX, the 74FCT257DTQG8 uniquely combines industrial temperature rating, power-off disable, and sub-4 ns propagation delay - making it optimal for ruggedized bus arbitration where reliability and timing predictability are critical.

Availability

74FCT257DTQG8 is available at Aetrix Electronics and suitable for industrial automation, legacy system upgrades, and test equipment requiring stable component supply and long-term lifecycle support.

Supply support for 74FCT257DTQG8 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

Renesas Electronics Corporation is a global semiconductor leader delivering microcontrollers, analog, power, and connectivity solutions for automotive, industrial, and infrastructure markets.

The 74FCT257DTQG8 belongs to the legacy IDT FCT logic family, engineered specifically for high-speed, low-noise 5 V bus interfacing in industrial and telecom systems where TTL compatibility and robustness are mandatory.

FAQ

What is the operating voltage range for the 74FCT257DTQG8?

The 74FCT257DTQG8 operates at a nominal VCC of 5.0 V ±5%, meaning its valid supply range is 4.75 V to 5.25 V. This tight tolerance ensures stable TTL-compatible logic thresholds and output drive performance across industrial temperature extremes (–40°C to +85°C). Operation outside this range may violate VOH/VOL specifications or cause functional failure. The 74FCT257DTQG8 does not support 3.3 V or dual-supply operation.

Does the 74FCT257DTQG8 support live insertion into powered systems?

Yes, the 74FCT257DTQG8 supports live insertion due to its power-off disable feature: when VCC = 0 V, all outputs enter a high-impedance state regardless of OE or input states. This prevents bus contention during hot-swap events in backplane or modular instrumentation systems. This behavior is explicitly characterized in the datasheet's DC Electrical Characteristics table under IOFF (input/output power-off leakage ≤ ±1 µA).

What is the maximum propagation delay for the 74FCT257DTQG8 under industrial conditions?

The maximum propagation delay for the 74FCT257DTQG8 is 3.9 ns for both tPLH and tPHL (S → Zx path) under industrial conditions (TA = –40°C to +85°C, VCC = 4.75 V, CL = 50 pF, RL = 500 Ω). This value is specified for the DT grade in the Switching Characteristics table and reflects worst-case timing for reliable synchronous bus design using the 74FCT257DTQG8.

How many independent multiplexers are integrated in the 74FCT257DTQG8?

The 74FCT257DTQG8 integrates four independent 2:1 multiplexers (channels A–D) sharing one common select input (S) and one active-low output enable (OE). Each channel accepts two data inputs (I0x and I1x) and delivers a buffered, non-inverting output (Zx). All four outputs are 3-state capable, enabling direct connection to shared data buses without external isolation.

Is the 74FCT257DTQG8 pin-compatible with other members of the FCT257 family?

Yes, the 74FCT257DTQG8 is pin-compatible with the entire IDT74FCT257A/CT/DT series, including 74FCT257AT and 74FCT257CT. All share identical 16-pin QSOP (QG) and SOIC (SO) footprints, pin functions, and logic behavior. Differences are limited to speed grade (AT = 5 ns, CT = 4.3 ns, DT = 3.9 ns max tPD) and temperature qualification - the 74FCT257DTQG8 is rated for industrial temperature range.