Texas Instruments SN74F257DR

Overview

SN74F257DR from Texas Instruments is a quad 2-line to 1-line data selector/multiplexer with 3-state outputs, designed for bus-organized systems requiring signal routing from dual 4-bit sources to shared 4-bit data lines. It operates at 4.5–5.5 V, supports 0°C to 70°C ambient, and delivers tPLH/tPHL propagation delays as low as 2.2 ns/1.2 ns (A/B → Y) and 3.7 ns/2.7 ns (A/B control → Y), enabling high-speed bus interface in TTL-compatible logic systems.

For engineers reviewing the SN74F257DR datasheet, SN74F257DR pinout, SN74F257DR application, or SN74F257DR equivalent, key selection criteria include its 3-state bus-driving capability, guaranteed 24 mA low-level output drive, 16-pin SOIC (D) package compatibility with JEDEC MS-012, and direct replacement suitability in legacy F-series TTL bus multiplexing designs.

Technical Context

The SN74F257DR implements four independent 2:1 multiplexers sharing a common A/B select line and a single 3-state output enable (OE) input. Each channel routes either the A-input or B-input to its corresponding Y-output based on the logic level of A/B, while OE controls all four outputs simultaneously into high-impedance state when high.

Its electrical behavior conforms to standard TTL voltage thresholds (VIL = 0.8 V, VIH = 2.0 V), supports 24 mA sink current per output, and maintains specified switching performance across CL = 50 pF load conditions - confirming its role as a robust, drop-in-compatible bus interface component in industrial and computing backplane applications.

Key Specifications

Pinout & Package

SN74F257DR is housed in a 16-pin small-outline integrated circuit (SOIC) package per JEDEC MS-012, with 1.27 mm pitch, 10.0–10.4 mm body width, and maximum 2.00 mm height - optimized for space-constrained PCB layouts and reflow soldering.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS257N and SN74HC257DR, the SN74F257DR delivers superior speed and drive strength for demanding TTL bus environments, while retaining pin-for-pin compatibility with the LS variant and avoiding CMOS-level translation overhead required by the HC variant.

Availability

SN74F257DR is available at Aetrix Electronics and suitable for industrial control systems, legacy computing upgrades, and test instrumentation requiring stable component supply and long-term obsolescence management.

Supply support for SN74F257DR 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 founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74F257DR belongs to TI's 74F family of fast TTL logic devices, engineered specifically for high-speed bus interface and data routing in computing and real-time control systems where propagation delay and drive strength are critical.

FAQ

What is the operating temperature range for the SN74F257DR?

The SN74F257DR is characterized for operation from 0°C to 70°C, meeting commercial-grade environmental requirements. This range supports deployment in office equipment, industrial controllers, and embedded computing platforms where ambient thermal conditions remain within standard room-temperature specifications. The SN74F257DR does not support extended or military temperature ranges - those are covered by the SN54F257 variant.

Does the SN74F257DR support true 3-state outputs, and how is output enable controlled?

Yes, the SN74F257DR features fully compliant 3-state outputs controlled by an active-low Output Enable (OE) input on Pin 1. When OE is high, all four Y-outputs enter high-impedance state, electrically isolating them from the bus. When OE is low, outputs actively drive logic levels based on the A/B select condition. This behavior is confirmed in the FUNCTION TABLE and absolute maximum ratings, where IOZL/IOZH leakage is specified at ±50 µA.

What package type and dimensions does the SN74F257DR use?

The SN74F257DR uses a 16-pin SOIC (D) package per JEDEC MS-012, with 1.27 mm lead pitch, 10.0–10.4 mm body width, and maximum 2.00 mm height. Its tape-and-reel packaging (2500 units per reel) follows standard EIA-481 specifications, and the pin 1 quadrant is Q1 per TI's tape orientation documentation. This package is distinct from PDIP (N) and SOP (NS) variants of the same logic function.

Can the SN74F257DR be used as a direct replacement for the SN74LS257 in existing designs?

Yes, the SN74F257DR is pin-compatible and functionally identical to the SN74LS257, sharing the same pinout, logic diagram, and truth table. However, it offers faster propagation delays (2.2 ns vs. ~15 ns) and higher output drive (24 mA vs. 8 mA), making it a performance upgrade. No PCB changes are required, but designers should verify timing margins and bus loading in high-frequency operation due to the improved speed.

What are the absolute maximum ratings for supply voltage and input voltage on the SN74F257DR?

The SN74F257DR has an absolute maximum supply voltage (VCC) of −0.5 V to 7 V and input voltage range of −1.2 V to 7 V. Exceeding these limits may cause permanent damage. These ratings are defined in the Absolute Maximum Ratings table of the SDFS065A datasheet and apply regardless of operating temperature. For reliable operation, VCC must be maintained between 4.5 V and 5.5 V per recommended conditions.