Texas Instruments SN74HC257DR

Overview

SN74HC257DR from Texas Instruments is a quadruple 2-line to 1-line data selector/multiplexer with non-inverted 3-state outputs, operating across 2 V–6 V supply range, delivering 9 ns typical propagation delay at 4.5 V, ±6 mA output drive at 5 V, and 80 µA max ICC - used for bus arbitration and signal routing in industrial control logic and digital instrumentation.

For engineers reviewing the SN74HC257DR datasheet, SN74HC257DR pinout, SN74HC257DR application, or SN74HC257DR equivalent, key selection criteria include its 16-pin SOIC (D) package, non-inverting output polarity, 3-state enable control via active-low G input, and compatibility with LSTTL loads in mixed-voltage logic systems.

Technical Context

The SN74HC257DR 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 all outputs entering high-impedance state when G is high.

Its CMOS design ensures low static current (≤1 µA input leakage), rail-to-rail output swing, and robust noise immunity. The device supports bus interface applications by enabling multiple data sources to share a common data path without contention, controlled entirely through synchronous address and enable signals.

Key Specifications

Pinout & Package

SN74HC257DR is housed in a 16-pin SOIC (D) package measuring 9.90 mm × 3.90 mm, with standard 1.27 mm pitch and gull-wing leads. Pin numbering follows JEDEC MS-012, with Pin 1 located at top-left corner marked by index notch or dot.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC157DR and SN74LVC257APW, the SN74HC257DR uniquely balances 2–6 V operation, proven 5 V bus compatibility, and 9 ns speed - making it the preferred choice for mixed-voltage industrial control upgrades where pinout stability and supply flexibility are mandatory.

Availability

SN74HC257DR is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, digital test equipment signal routing, and embedded system bus arbitration requiring stable component supply and long-term production continuity.

Supply support for SN74HC257DR 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 ICs, with over 90 years of innovation in industrial, automotive, and communications markets.

The SN74HC257DR belongs to TI's 74HC logic family - designed specifically for high-speed, low-power, pin-compatible replacements of legacy TTL devices in industrial control, instrumentation, and legacy interface applications.

FAQ

What is the function of the G pin on the SN74HC257DR?

The G pin on the SN74HC257DR is the active-low output-enable terminal. When G is logic high, all four Y outputs enter a high-impedance (Hi-Z) state, effectively disconnecting them from the bus. When G is logic low, the outputs become active and reflect the selected A or B input based on the A/B address line. This enables clean bus sharing without contention, and TI recommends tying G to VCC via a pull-up resistor during power-up to ensure Hi-Z default state.

Does the SN74HC257DR support 3.3 V operation?

Yes, the SN74HC257DR fully supports 3.3 V operation within its specified 2 V–6 V supply range. At VCC = 3.3 V, it maintains guaranteed logic thresholds (VIH ≥ 2.31 V, VIL ≤ 0.99 V), delivers ≥±4 mA output drive, and achieves ~15 ns typical propagation delay (CL = 50 pF). Its CMOS inputs are compatible with both 3.3 V and 5 V logic families, making it ideal for mixed-voltage board designs.

Is the SN74HC257DR pin-compatible with the SN74LS257?

No, the SN74HC257DR is not pin-compatible with the SN74LS257. While both are quadruple 2:1 multiplexers with 3-state outputs, the SN74LS257 uses a different pin assignment: its G (enable) is on Pin 1, whereas SN74HC257DR places G on Pin 16. Additionally, SN74LS257 has inverted outputs and requires separate VCC/GND per package quadrant. Direct replacement requires PCB redesign or adapter logic.

What is the maximum capacitive load the SN74HC257DR can drive reliably?

The SN74HC257DR is characterized for reliable operation with up to 50 pF load capacitance, where tpd = 9 ns (typ) and tt = 15 ns (max) at VCC = 4.5 V. At 150 pF, tpd increases to 32 ns (max) and tt to 45 ns (max). For loads exceeding 50 pF, TI recommends verifying timing margins in the target application and using series termination or local buffering if setup/hold violations occur - especially in high-speed bus environments.

How does the SN74HC257DR differ from the SN74HC258DR?

The SN74HC257DR and SN74HC258DR share identical pinout, package, and functional architecture, but differ in output polarity: SN74HC257DR provides non-inverted outputs (Y = A or B), while SN74HC258DR provides inverted outputs (Y = NOT A or NOT B). Both have identical timing, drive strength, and supply specifications. Selection depends strictly on required signal polarity in the target data path - no other electrical or mechanical differences exist between the two parts.