Texas Instruments SN74HCS251QDRQ1

Overview

SN74HCS251QDRQ1 from Texas Instruments is an automotive-grade 8-to-1 CMOS multiplexer with Schmitt-trigger inputs, 3-state complementary outputs (Y and W), and AEC-Q100 Grade 1 qualification (–40°C to +125°C). It supports 2 V to 6 V supply operation, delivers ±7.8 mA output drive at 6 V, and features typical ICC of 100 nA for ultra-low-power data routing in vehicle control modules.

For engineers reviewing the SN74HCS251QDRQ1 datasheet, SN74HCS251QDRQ1 pinout, SN74HCS251QDRQ1 application, or SN74HCS251QDRQ1 equivalent, key selection criteria include its hysteresis-enabled noise immunity (ΔVT = 0.6 V min at 6 V), strobe-controlled 3-state bus interface capability, and validated automotive reliability under ESD stress (HBM Level 2, CDM Level C6).

Technical Context

The SN74HCS251QDRQ1 implements full binary decoding of three address inputs (A, B, C) to select one of eight data inputs (D0–D7), with simultaneous complementary outputs Y (non-inverted) and W (inverted). Its Schmitt-trigger inputs provide hysteresis (VT+ = 2.1 V, VT− = 1.2 V at 6 V), enabling robust operation with slow-rising or noisy signals common in automotive sensor interfaces.

Output enable (OE) controls both Y and W simultaneously into high-impedance state when high; both outputs are actively driven only when OE is low. The device uses balanced CMOS 3-state outputs capable of sourcing/sinking up to ±7.8 mA at 6 V while maintaining VOL ≤ 0.33 V and VOH ≥ 5.4 V under load.

Key Specifications

Pinout & Package

SN74HCS251QDRQ1 is packaged in a 16-pin SOIC (D package) with nominal body size 9.90 mm × 3.90 mm, optimized for automated assembly and thermal dissipation in automotive PCBs.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-to-1 multiplexer applications.

Compared with SN74HCS251QDRQ1, the SN74LV251AQPWRQ1 trades noise immunity for wider low-voltage compatibility, while the MC74HC251ADTR2G offers identical functionality without automotive traceability-making SN74HCS251QDRQ1 the sole choice for ASIL-compliant designs requiring guaranteed hysteresis and ESD robustness.

Availability

SN74HCS251QDRQ1 is available at Aetrix Electronics and suitable for engine control units, ADAS camera interfaces, body control modules, and electric power steering systems requiring stable component supply across extended automotive lifecycles.

Supply support for SN74HCS251QDRQ1 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 SN74HCS251QDRQ1 belongs to TI's HCS logic family designed specifically for automotive signal routing-emphasizing low power, noise resilience, and AEC-Q100 compliance in harsh electrical environments.

FAQ

What is the maximum clock frequency supported by SN74HCS251QDRQ1?

The SN74HCS251QDRQ1 supports a maximum switching frequency of 36 MHz at 6 V supply and 25°C ambient. At full automotive temperature range (–40°C to +125°C), the guaranteed minimum fmax is 29 MHz. This allows reliable use in time-critical multiplexing applications such as real-time sensor sampling and video stream switching without timing violations.

Does SN74HCS251QDRQ1 require external pull-up resistors on its address inputs?

No, SN74HCS251QDRQ1 does not require external pull-up resistors on address inputs A, B, or C because its Schmitt-trigger inputs tolerate slow or floating transitions without unintended state changes. However, TI recommends tying unused address inputs to VCC or GND to prevent undefined logic states-especially in high-noise automotive environments where leakage could cause metastability.

Can SN74HCS251QDRQ1 drive a 50-pF capacitive load while maintaining specified timing?

Yes, SN74HCS251QDRQ1 is characterized and guaranteed to meet all switching specifications-including propagation delay (tpd ≤ 22 ns) and transition time (tt ≤ 8 ns)-with a 50-pF load at 6 V. The datasheet explicitly defines CL = 50 pF as the test condition for timing parameters, making it suitable for driving standard PCB traces and CMOS inputs without derating.

How does the hysteresis of SN74HCS251QDRQ1 improve noise immunity in automotive applications?

The SN74HCS251QDRQ1 provides 0.6 V minimum hysteresis (ΔVT) at 6 V supply, meaning input signals must swing at least 600 mVpp between valid LOW and HIGH thresholds. This prevents false triggering from burst noise, alternator ripple, or ignition transients common in vehicle electrical systems-eliminating need for external RC filters and improving system robustness without added BOM cost.

What is the function of the W output on SN74HCS251QDRQ1, and how is it used in practice?

The W output on SN74HCS251QDRQ1 is the logical inverse of the Y output, providing complementary data without external inversion. In practice, this enables differential signaling for noise rejection, dual-path redundancy in safety systems, or direct connection to inverted-input peripherals (e.g., active-low enable pins). Both Y and W are simultaneously enabled/disabled by OE, ensuring synchronized operation critical for glitch-free bus arbitration.