Texas Instruments SN74AHC257PWR

Overview

SN74AHC257PWR from Texas Instruments is a quad 2-input data selector/multiplexer with three-state non-inverting outputs, operating across 2V–5.5V V_CC. It integrates four independent 2:1 multiplexers sharing A/B select and active-low OE control, delivering 9.5ns max propagation delay at 5V/50pF and supporting bus-oriented data routing in digital logic systems.

For engineers reviewing the SN74AHC257PWR datasheet, SN74AHC257PWR pinout, SN74AHC257PWR application, or SN74AHC257PWR equivalent, key selection criteria include its 16-pin TSSOP (PW) package, guaranteed 3-state output drive (±8mA at 5V), latch-up immunity (>250mA per JESD 17), and compatibility with mixed-voltage 3.3V/5V system interfaces.

Technical Context

The SN74AHC257PWR implements four identical 2:1 multiplexer channels with fully synchronous three-state output control via a shared active-low OE input. Each channel selects between two inputs (xA/xB) using a common A/B select line, enabling compact 4-bit data path switching without per-channel enable logic.

Its balanced CMOS three-state outputs support bidirectional bus driving with matched sourcing/sinking capability (±8mA at 5V), while standard CMOS inputs require fast transitions (<20 ns/V at 5V) to prevent oscillation and excessive power draw. The device complies with JEDEC JESD 17 latch-up specifications and features integrated negative clamp diodes on all inputs.

Key Specifications

Pinout & Package

SN74AHC257PWR uses the PW (16-pin TSSOP) package: 6.4mm × 5.0mm body size, 5.0mm × 4.4mm footprint, 1.2mm max height. Thermal pad not present - no thermal pad connection required.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad 2:1 multiplexer applications.

Compared with SN74AHC257PWR, SN74LVC257PWR trades 5V compatibility for ultra-low quiescent current in 3.3V-only designs, while 74AHC257D,118 offers identical performance in a larger SO16 package-making SN74AHC257PWR optimal for space-constrained, mixed-voltage industrial PCBs requiring proven TI reliability.

Availability

SN74AHC257PWR is available at Aetrix Electronics and suitable for industrial automation, automotive body electronics, and test equipment requiring stable component supply, long-term manufacturability, and full traceability across production batches.

Supply support for SN74AHC257PWR 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, with decades of experience in high-reliability industrial and automotive components.

The SN74AHC257PWR belongs to TI's advanced high-speed CMOS (AHC) logic family, designed specifically for low-power, high-noise-immunity digital interfacing in harsh electromagnetic environments.

FAQ

What is the maximum capacitive load SN74AHC257PWR can drive while maintaining specified timing?

The SN74AHC257PWR is characterized and guaranteed to meet all switching specifications-including 9.5ns max propagation delay-at 50pF load capacitance. Driving loads exceeding 50pF will increase propagation delay and may degrade noise margins; TI recommends limiting total output capacitance to ≤50pF for full spec compliance. For heavier loads, consider buffering or layout optimization to reduce trace capacitance.

Can SN74AHC257PWR operate reliably at 2.5V supply voltage?

Yes, SN74AHC257PWR is fully specified from 2V to 5.5V, including operation at 2.5V. At 2.5V, it delivers VOH ≥ 2.35V and VOL ≤ 0.2V under IOL = 4mA, with typical propagation delay of 12.8ns (CL = 50pF). This makes SN74AHC257PWR suitable for mixed-voltage systems integrating 2.5V FPGAs or legacy logic.

How should unused inputs be handled on SN74AHC257PWR?

All unused inputs on SN74AHC257PWR-including A/B, OE, and any unconnected xA/xB pins-must be terminated to a valid logic level (V_CC or GND) to prevent floating states that cause excessive current draw, oscillation, or undefined outputs. TI recommends 10kΩ pull-up or pull-down resistors for flexibility; direct connection is acceptable if the signal is permanently inactive.

Does SN74AHC257PWR support hot insertion or live insertion into a powered backplane?

No, SN74AHC257PWR does not support hot insertion. Its absolute maximum ratings specify VI and VO limits of –0.5V to 7V, but the absence of power-on reset, bus-hold, or I²C-style slew-rate control means uncontrolled voltage sequencing during insertion can exceed clamp diode current limits (±20mA) and risk damage. Always power-cycle the system before inserting SN74AHC257PWR.

What is the thermal resistance (R_θJA) of SN74AHC257PWR in its TSSOP package?

The SN74AHC257PWR in the PW (TSSOP-16) package has a junction-to-ambient thermal resistance (R_θJA) of 135.9°C/W, measured under standard JEDEC JESD51-2 conditions (single-layer board, 1-inch² copper). This value assumes no thermal vias or heatsinking; adding two thermal vias per power pin reduces R_θJA by ~15°C/W in typical 4-layer PCBs.