Texas Instruments CAHCT257QWBQBRQ1

Overview

CAHCT257QWBQBRQ1 from Texas Instruments is an automotive-grade quad 2-input data selector/multiplexer with three-state non-inverting outputs, operating from 4.5 V to 5.5 V, delivering 4.3 ns typical propagation delay at 25°C/5V, and qualified per AEC-Q100 Grade 1 (–40°C to +125°C) for use in vehicle body control modules and infotainment data routing.

For engineers reviewing the CAHCT257QWBQBRQ1 datasheet, CAHCT257QWBQBRQ1 pinout, CAHCT257QWBQBRQ1 application, or CAHCT257QWBQBRQ1 equivalent, key selection criteria include its TTL-compatible inputs, balanced CMOS 3-state output drive (±8 mA), latch-up immunity (>250 mA), wettable-flank WQFN-16 package, and shared A/B and OE control logic across all four channels.

Technical Context

The CAHCT257QWBQBRQ1 implements four independent 2:1 multiplexers sharing a common data-select (A/B) input and active-low output-enable (OE) signal. Each channel routes either input A or B to its respective Y output based on the A/B logic level, with simultaneous 3-state control via OE.

Its TTL-compatible CMOS inputs accept standard 5-V logic thresholds (VIH = 2 V min, VIL = 0.8 V max), while outputs provide rail-to-rail swing (VOH ≥ 3.94 V, VOL ≤ 0.36 V at 8 mA) and support bus-oriented systems through high-impedance tri-state operation with tPHZ/tPLZ ≤ 8.5 ns (CL = 15 pF).

Key Specifications

Pinout & Package

CAHCT257QWBQBRQ1 is packaged in a 3.6 mm × 2.6 mm wettable-flank WQFN-16 (BQB) with exposed thermal pad. The package supports automated optical inspection (AOI) and enhanced thermal dissipation in space-constrained automotive PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AHCT257QPWRQ1 and MC74VHC257DTG, CAHCT257QWBQBRQ1 uniquely combines wettable-flank WQFN packaging, Grade 1 thermal rating, and AEC-Q100 certification-making it the sole option qualified for volume production in thermally demanding, safety-aware automotive subsystems.

Availability

CAHCT257QWBQBRQ1 is available at Aetrix Electronics and suitable for body control modules, instrument clusters, infotainment head-units, and ADAS camera arbitration systems requiring stable component supply across automotive production lifecycles.

Supply support for CAHCT257QWBQBRQ1 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 automotive ICs, with decades of experience delivering high-reliability components for transportation systems.

The SN74AHCT257-Q1 product line delivers automotive-qualified logic solutions optimized for data routing, signal selection, and bus interface functions in harsh-temperature electronic control units.

FAQ

What is the maximum capacitive load supported by CAHCT257QWBQBRQ1 while maintaining specified timing?

CAHCT257QWBQBRQ1 maintains full switching specification compliance up to 50 pF load capacitance. At CL = 15 pF, propagation delays are 3.7–6.4 ns; at CL = 50 pF, delays increase to 4.9–13.5 ns depending on signal path. Exceeding 50 pF may degrade timing margins and increase power consumption, so PCB trace length and receiver input capacitance must be carefully managed in CAHCT257QWBQBRQ1 designs.

Does CAHCT257QWBQBRQ1 support mixed-voltage operation between inputs and VCC?

No, CAHCT257QWBQBRQ1 does not support mixed-voltage operation. All inputs must remain within 0 V to VCC (max 5.5 V), and VCC must be stable between 4.5 V and 5.5 V. Input voltages exceeding VCC or falling below GND violate absolute maximum ratings and risk damage. The device's TTL-compatible inputs require VIH ≥ 2 V and VIL ≤ 0.8 V when VCC = 5 V, and these thresholds scale proportionally with VCC - confirming strict 5-V domain operation for CAHCT257QWBQBRQ1.

How is the thermal pad on the CAHCT257QWBQBRQ1 WQFN package intended to be used?

The exposed thermal pad on CAHCT257QWBQBRQ1 is designed to be soldered to a PCB copper pour connected to GND. Doing so improves thermal resistance (RθJB = 75.4°C/W) and enhances long-term reliability in high-ambient-temperature automotive environments. While the datasheet states the pad may be left floating, TI recommends GND connection for production designs using CAHCT257QWBQBRQ1 to ensure junction temperature remains within safe limits under continuous operation.

Can unused inputs on CAHCT257QWBQBRQ1 be left unconnected?

No, unused inputs on CAHCT257QWBQBRQ1 must never be left floating. TTL-compatible CMOS inputs require defined logic states to prevent oscillation, excessive power draw, or undefined output behavior. Each unused input (e.g., spare A/B, OE, or channel inputs) must be tied directly to VCC or GND - or via a 10 kΩ pull-up/pull-down resistor if dynamic control is needed later. This requirement applies strictly to all CAHCT257QWBQBRQ1 implementations per TI's design guidelines.

Is CAHCT257QWBQBRQ1 pin-compatible with non-automotive variants like SN74AHCT257N?

No, CAHCT257QWBQBRQ1 is not pin-compatible with commercial-grade SN74AHCT257N (DIP-16) or SN74AHCT257D (SOIC-16). It shares identical logic functionality and pin numbering with SN74AHCT257QPWRQ1 (TSSOP-16), but differs physically from DIP/SOIC packages due to its 3.6 mm × 2.6 mm WQFN-16 footprint and wettable flank geometry. Pin mapping matches the BQB package definition in the CAHCT257QWBQBRQ1 datasheet - not legacy through-hole or SOIC variants.