Texas Instruments CY74FCT157ATQCT

Overview

CY74FCT157ATQCT from Texas Instruments is a quad 2-input multiplexer with 3-state outputs, designed for data routing in TTL- and FCT-compatible digital systems. It features 5 ns propagation delay (max), ±32 mA output drive, Ioff partial-power-down support, and operates across –40°C to 85°C. Used in bus multiplexing, function generation, and register-to-bus data selection.

For engineers reviewing the CY74FCT157ATQCT datasheet, CY74FCT157ATQCT pinout, CY74FCT157ATQCT application, or CY74FCT157ATQCT equivalent, key selection criteria include 3-state output timing, Ioff-enabled power-down isolation, TTL-level input compatibility, and QSOP-16 package suitability for high-density PCB layouts.

Technical Context

The CY74FCT157ATQCT implements four independent 2:1 multiplexers sharing one common select (S) and active-low enable (E) control. Each Y output reflects I0a/I1a, I0b/I1b, I0c/I1c, or I0d/I1d based on S state when E is low; all outputs go high-impedance when E is high.

Its edge-rate control circuitry limits slew rate to reduce switching noise, while matched rise/fall times ensure clean signal transitions. The device supports mixed-voltage interfacing via TTL-compatible inputs (VIH = 2 V min, VIL = 0.8 V max) and CMOS-level outputs (VOH = 3.3 V typ at VCC = 5 V).

Key Specifications

Pinout & Package

Package: QSOP-16 (DBQ), 3.9 mm × 4.9 mm body, 0.635 mm pitch, moisture sensitivity level 2 (260°C peak reflow).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74FCT157ATSOCT and 74AC157MTCX, the CY74FCT157ATQCT uniquely combines QSOP-16 miniaturization, Ioff-enabled power management, and FCT-family noise immunity-making it optimal for space-constrained industrial controllers requiring robust hot-swap operation.

Availability

CY74FCT157ATQCT is available at Aetrix Electronics and suitable for bus multiplexing, register file selection, function generation, and industrial control logic requiring stable component supply across long production lifecycles.

Supply support for CY74FCT157ATQCT 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 for industrial, automotive, and communications markets.

The CY74FCT157ATQCT belongs to TI's FCT logic family, engineered for high-speed, low-noise, TTL-compatible digital interfacing in mission-critical embedded systems.

FAQ

What is the maximum propagation delay of CY74FCT157ATQCT across its operating temperature range?

The CY74FCT157ATQCT has a maximum propagation delay of 5 ns (tPLH/tPHL) from any input (S, E, or data) to output Y over –40°C to +85°C, as specified in the switching characteristics table for the 'AT' speed grade. This value applies under standard load conditions (CL = 50 pF) and VCC = 4.75–5.25 V. The CY74FCT157ATQCT maintains consistent timing performance without derating across its full temperature range.

Does CY74FCT157ATQCT support partial-power-down mode, and how is it implemented?

Yes, the CY74FCT157ATQCT supports partial-power-down mode via its Ioff feature. When VCC = 0 V, the Ioff circuitry limits output leakage to ±1 µA even if input/output voltages reach 4.5 V, preventing damaging current backflow. This allows safe insertion into live backplanes or operation in multi-rail systems where other sections remain powered. The CY74FCT157ATQCT achieves this without external circuitry or configuration pins.

What package type and dimensions does CY74FCT157ATQCT use, and what are its assembly requirements?

The CY74FCT157ATQCT uses a QSOP-16 (DBQ) package measuring 3.9 mm × 4.9 mm with 0.635 mm lead pitch. It has moisture sensitivity level 2, requiring bake-out if exposed to ambient >60% RH for >1 year before reflow. Peak reflow temperature is 260°C (1 minute max), and pin 1 orientation follows quadrant Q1 per TI tape-and-reel standards. The CY74FCT157ATQCT requires standard SSOP solder paste stencil design and 250°C preheat profile.

How does CY74FCT157ATQCT handle TTL-level inputs while operating from a 5 V supply?

The CY74FCT157ATQCT accepts TTL-level inputs directly: VIH(min) = 2.0 V and VIL(max) = 0.8 V at VCC = 4.75–5.25 V, matching standard 74LS logic thresholds. Its input structure includes Schmitt-trigger hysteresis (Vhys = 0.2 V) for noise rejection, and it draws only ±1 µA input current. No external pull-ups or level shifters are needed-the CY74FCT157ATQCT interfaces natively with legacy TTL families while delivering CMOS-level outputs.

Can CY74FCT157ATQCT be used as a function generator, and what logic functions does it support?

Yes, the CY74FCT157ATQCT can implement any of the 16 possible 2-variable Boolean functions by configuring I0 and I1 inputs as constant logic levels (0/1) and using S as the function select. For example: setting I0 = A, I1 = B, and S = A yields XOR; I0 = 1, I1 = A̅ gives implication. The CY74FCT157ATQCT's 4-channel architecture allows concurrent generation of up to four distinct functions, making it ideal for compact PLD replacements in control logic.