Renesas 74FCT257CTQG8

Overview

74FCT257CTQG8 from Renesas Electronics (formerly IDT) is a fast CMOS quad 2-input multiplexer with 3-state outputs, designed for bus-oriented data routing in industrial 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).

For engineers reviewing the 74FCT257CTQG8 datasheet, 74FCT257CTQG8 pinout, 74FCT257CTQG8 application, or 74FCT257CTQG8 equivalent, key selection criteria include its 16-pin QSOP package, common select (S) and active-low output enable (OE), propagation delays ≤4.3 ns (FCT257CT grade), and compliance with JEDEC Std 18.

Technical Context

The 74FCT257CTQG8 implements four independent 2:1 multiplexers sharing one select (S) and one active-low output enable (OE) control line. 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 robust bus interfacing - including live-insertion support via power-off disable outputs.

Key Specifications

Pinout & Package

74FCT257CTQG8 is housed in a 16-pin Quarter-size Small Outline Package (QSOP), green-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 74AC257SCX, the 74FCT257CTQG8 uniquely combines industrial temperature rating, JEDEC Std 18 compliance, 3-state bus interface, and sub-5 ns propagation - making it optimal for ruggedized embedded control where timing integrity and bus coexistence are critical.

Availability

74FCT257CTQG8 is available at Aetrix Electronics and suitable for industrial PLC backplanes, legacy microcontroller bus expansion, and automated manufacturing fixtures requiring stable component supply and long-term lifecycle support.

Supply support for 74FCT257CTQG8 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 formed through the merger of NEC Electronics and Renesas Technology, specializing in microcontrollers, analog, power, and timing solutions.

The 74FCT257CTQG8 belongs to the IDT FCT logic family, originally developed for high-speed, low-power, bus-friendly digital interfacing in industrial and communications infrastructure - emphasizing TTL compatibility, 3-state control, and robustness across temperature extremes.

FAQ

What is the operating voltage range for the 74FCT257CTQG8?

The 74FCT257CTQG8 operates at a nominal VCC of 5.0 V ±5%, meaning 4.75 V to 5.25 V. It is not rated for operation outside this range. The device's input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) and output drive characteristics (VOH ≥ 2.4 V at –8 mA) are specified only under these conditions. Using the 74FCT257CTQG8 at voltages outside this window may result in undefined logic states or degraded timing margins.

Does the 74FCT257CTQG8 support live insertion in backplane systems?

Yes, the 74FCT257CTQG8 supports live insertion due to its power-off disable feature: when VCC = 0 V, input/output leakage remains ≤±1 µA, preventing back-driving of powered slots. This behavior is explicitly guaranteed in the datasheet under "IOFF Input/Output Power Off Leakage." The 74FCT257CTQG8 leverages this to safely integrate into modular industrial backplanes where cards are inserted or removed while the system remains operational.

What is the maximum clock/data toggle frequency supported by the 74FCT257CTQG8?

The 74FCT257CTQG8 does not have a specified maximum toggle frequency, but its propagation delay (≤4.3 ns) and output enable/disable times (≤6 ns) imply reliable operation up to ~100 MHz for short trace lengths with proper termination. Total supply current (IC) calculations in the datasheet assume up to 10 MHz output toggling (four bits); sustained higher-frequency use requires thermal validation and attention to dynamic power dissipation and PCB layout parasitics.

Is the 74FCT257CTQG8 pin-compatible with the 74FCT257AT or 74FCT257DT variants?

Yes - the 74FCT257CTQG8 shares identical pinout, function table, and AC/DC specifications with the 74FCT257AT and 74FCT257DT, differing only in propagation delay grading (CT = 4.3 ns max, DT = 3.9 ns max, AT = 5.0 ns max) and operating temperature validation. All three use the same QSOP-16 package and are drop-in replacements in designs where timing margin allows the selected grade's delay specification.

Can the 74FCT257CTQG8 be used in new designs despite its obsolete status?

Although marked "Obsolete" and "Not Recommended for New Designs" by Renesas, the 74FCT257CTQG8 remains actively stocked and supported by Aetrix Electronics with full traceable sourcing and lifecycle coordination. Its proven reliability in industrial applications, JEDEC Std 18 compliance, and lack of functional alternatives with identical timing/package make it viable for maintenance, replacement, and cost-sensitive legacy upgrades - provided long-term supply risk is mitigated through forward-buy or dual-sourcing strategies.