Texas Instruments SN74HC257NSR

Overview

SN74HC257NSR from Texas Instruments is a quadruple 2-line to 1-line data selector/multiplexer with non-inverted 3-state outputs, operating from 2 V to 6 V supply. It features 9 ns typical propagation delay at 4.5 V, ±6 mA output drive, 80 µA max ICC, and supports bus interface in high-performance digital systems. Used for signal routing in microcontroller peripheral expansion and memory address selection.

For engineers reviewing the SN74HC257NSR datasheet, SN74HC257NSR pinout, SN74HC257NSR application, or SN74HC257NSR equivalent, key selection criteria include its 3-state enable control (G), dual-input per channel (A/B), non-inverting output logic, SO-16 package footprint, and compatibility with LSTTL loads in industrial control and instrumentation bus architectures.

Technical Context

The SN74HC257NSR implements four independent 2:1 multiplexers sharing common address (A/B) and active-low output-enable (G) inputs. Each channel selects between two data inputs (A or B) based on the A/B logic level, with G controlling high-impedance state entry/exit. All outputs are non-inverted and tri-state capable.

Its CMOS HC-family design ensures low power consumption and TTL-compatible voltage thresholds across 2–6 V operation. Propagation delay varies with supply voltage and load capacitance: 25 ns max at 6 V/50 pF, 32 ns max at 6 V/150 pF, enabling timing-critical data path selection in synchronous digital systems.

Key Specifications

Pinout & Package

SN74HC257NSR uses a 16-pin SOP (Small Outline Package) with 6.20 mm × 5.30 mm body size and 1.27 mm pitch. Pin numbering follows standard SOIC/SOP top-view convention with Pin 1 in bottom-left corner.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar multiplexer applications.

Compared with SN74HC157D and SN74LVC257APW, SN74HC257NSR uniquely balances wide-voltage operation (2–6 V), integrated 3-state control, and proven industrial temperature range (−40°C to +85°C) - making it the only drop-in solution for legacy 5 V bus systems requiring future-proof 3.3 V compatibility.

Availability

SN74HC257NSR is available at Aetrix Electronics and suitable for industrial control panels, programmable logic controllers, and test instrumentation requiring stable component supply with long-term lifecycle support.

Supply support for SN74HC257NSR 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 delivering analog and embedded processing solutions for industrial, automotive, and personal electronics markets.

The SN74HC257NSR belongs to TI's 74HC logic family, designed for robust, low-power digital signal routing in noise-immune industrial environments with wide supply tolerance and reliable 3-state bus control.

FAQ

What is the maximum recommended supply voltage for SN74HC257NSR?

The absolute maximum supply voltage for SN74HC257NSR is 7 V, but the recommended operating range is 2 V to 6 V. Operating continuously above 6 V risks permanent damage and violates TI's specified conditions. For reliable long-term performance in industrial applications, maintain VCC ≤ 6 V with proper decoupling - the SN74HC257NSR achieves optimal speed-power tradeoff at 4.5–5.5 V.

Does SN74HC257NSR support 3.3 V logic levels?

Yes, SN74HC257NSR fully supports 3.3 V operation: VIH(min) = 2.0 V and VIL(max) = 0.8 V at VCC = 3.3 V, exceeding standard 3.3 V TTL thresholds. Its 2–6 V supply range allows direct interfacing with 3.3 V microcontrollers without level shifters, and the SN74HC257NSR maintains 9 ns typical propagation delay and ±6 mA drive at 3.3 V.

How does the G (strobe) pin function on SN74HC257NSR?

The G pin on SN74HC257NSR is an active-low output enable: when G = HIGH, all Y0–Y3 outputs enter high-impedance (Z) state regardless of A/B or input states; when G = LOW, outputs reflect selected inputs (A or B). To ensure safe power-up, TI recommends tying G to VCC via a pull-up resistor - the SN74HC257NSR guarantees Z-state entry within 32 ns of G assertion.

Can SN74HC257NSR replace older 74LS257 devices?

Yes, SN74HC257NSR is a functional and pin-compatible upgrade for 74LS257 in most applications: same SO-16 footprint, identical pinout, non-inverting logic, and 3-state outputs. Key improvements include wider voltage range (2–6 V vs 4.75–5.25 V), lower power (80 µA vs ~20 mA ICC), and higher noise immunity. The SN74HC257NSR also drives 15 LSTTL loads - matching LS-series fanout capability.

What thermal considerations apply to SN74HC257NSR in continuous operation?

SN74HC257NSR in SOP-16 (NS) package has RθJA = 64°C/W. At 6 V and full output loading (±6 mA per Y), worst-case power dissipation is ~25 mW - resulting in <2°C junction rise above ambient. No heatsinking is required; however, TI specifies maximum junction temperature of 150°C. For sustained 85°C ambient operation, keep board copper area ≥1 cm² around GND/VCC pads to maintain margin - the SN74HC257NSR remains within spec under these conditions.