Texas Instruments CY74FCT2257CTQCT

Overview

CY74FCT2257CTQCT from Texas Instruments is a quad 2-input multiplexer with 3-state outputs in a 16-pin QSOP package, operating at 4.75–5.25 V, delivering 12 mA sink / 15 mA source drive, 4.7 ns max propagation delay (S→Y), and integrated 25-Ω output series resistors for reflection noise suppression - used in bus-multiplexed data routing in industrial control backplanes.

For engineers reviewing the CY74FCT2257CTQCT datasheet, CY74FCT2257CTQCT pinout, CY74FCT2257CTQCT application, or CY74FCT2257CTQCT equivalent, key selection criteria include TTL-compatible logic levels, Ioff-enabled partial-power-down support, 3-state bus contention management, and edge-rate controlled switching for EMI-sensitive digital systems.

Technical Context

The CY74FCT2257CTQCT implements four independent 2:1 multiplexers sharing one common select (S) and one active-low output-enable (OE) input. Each channel routes either I0a/I0b/I0c/I0d or I1a/I1b/I1c/I1d to Ya/Yb/Yc/Yd based on S logic level, with noninverting output polarity and simultaneous 3-state control via OE.

Its FCT-family architecture integrates edge-rate control circuitry and on-die 25-Ω series termination resistors per output, reducing transmission-line reflections without external components. Ioff protection disables outputs when VCC = 0 V, preventing backflow current during partial power-down sequences.

Key Specifications

Pinout & Package

Package: 16-pin QSOP (SSOP, DBQ), 3.9 mm × 4.9 mm body, 1.75 mm max height, pitch 0.635 mm, RoHS-compliant NIPDAU finish, MSL Level-2-260°C-1 year.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74FCT257D and 74LVC257PW, the CY74FCT2257CTQCT uniquely combines 5-V TTL compatibility, integrated trace-matching termination, and Ioff safety - making it optimal for retrofitting noise-sensitive industrial backplanes without redesigning signal integrity paths.

Availability

CY74FCT2257CTQCT is available at Aetrix Electronics and suitable for industrial automation, test equipment, and legacy bus interface applications requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for CY74FCT2257CTQCT 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 for industrial, automotive, and communications markets.

The CY74FCT2257CTQCT belongs to TI's FCT logic family, engineered for noise-immune, high-speed 5-V digital interfacing in mission-critical industrial and instrumentation systems.

FAQ

What logic family does the CY74FCT2257CTQCT belong to, and how does it differ from standard TTL?

The CY74FCT2257CTQCT belongs to Texas Instruments' FCT (Fast CMOS Technology) logic family. Unlike standard TTL, it uses CMOS input structure with TTL-compatible voltage thresholds (VIH = 2.0 V, VIL = 0.8 V), consumes significantly less static power (ICC ≤ 0.2 mA), and integrates edge-rate control and 25-Ω output series resistors - features absent in 74LS or 74F devices. The CY74FCT2257CTQCT maintains pinout and functional equivalence with FCT257-series parts while improving noise immunity and bus driving capability.

Does the CY74FCT2257CTQCT support hot-swap or partial-power-down operation?

Yes, the CY74FCT2257CTQCT supports partial-power-down operation via its Ioff feature. When VCC = 0 V, the Ioff circuitry limits off-state input/output leakage to ±1 µA, preventing damaging current backflow from live bus lines into the unpowered device. This makes the CY74FCT2257CTQCT suitable for systems with staggered power sequencing or hot-plug modules - provided OE is held high during power-off to maintain high-impedance outputs.

What is the maximum clock/data rate supported by the CY74FCT2257CTQCT in multiplexed bus applications?

The CY74FCT2257CTQCT supports data rates up to approximately 200 MHz in well-terminated environments, based on its 4.7 ns max propagation delay (S→Y) and 5 ns max 3-state enable/disable times. For reliable operation, signal rise/fall times should exceed 2 ns, and trace lengths should be ≤15 cm with controlled impedance (50–75 Ω). The integrated 25-Ω series resistors help dampen reflections at these speeds, allowing the CY74FCT2257CTQCT to replace discrete termination networks in compact layouts.

Can the CY74FCT2257CTQCT be used with 3.3-V microcontrollers?

No - the CY74FCT2257CTQCT is strictly a 5-V device with recommended VCC = 4.75–5.25 V and TTL-compatible input thresholds (VIH = 2.0 V min). While a 3.3-V microcontroller's high output (~3.3 V) exceeds VIH and will register as logic high, its low output (~0 V) satisfies VIL. However, driving the CY74FCT2257CTQCT inputs directly from 3.3-V GPIO risks violating absolute maximum ratings if VCC is powered - and more critically, the CY74FCT2257CTQCT's 5-V outputs are not 3.3-V tolerant. A level-shifter or buffer is required for bidirectional interfacing.

How does the CY74FCT2257CTQCT prevent bus contention when multiple 3-state devices share a common data line?

The CY74FCT2257CTQCT prevents bus contention through strict 3-state control: all outputs (Ya–Yd) enter high-impedance mode simultaneously when OE is high, regardless of S or input states. To avoid contention, system design must ensure that only one CY74FCT2257CTQCT (or other 3-state driver) has OE low at any time - typically enforced via dedicated bus arbitration logic or software-coordinated enable sequencing. The datasheet explicitly warns that overlapping OE activation across devices can exceed absolute maximum output current ratings (120 mA per pin) and cause permanent damage.