Texas Instruments 74AC11257DWR

Overview

74AC11257DWR from Texas Instruments is a 4-bit dual 2-to-1 multiplexer with 3-state outputs, designed for bus interface in high-performance digital systems. It features flow-through pinout, center-pin VCC/GND configuration, 500-mA latch-up immunity at 125°C, and supports 3-V to 5.5-V supply operation. Used in data routing between multiple sources on shared buses.

For engineers reviewing the 74AC11257DWR datasheet, 74AC11257DWR pinout, 74AC11257DWR application, or 74AC11257DWR equivalent, key selection criteria include bus-compatible 3-state drive strength (±24 mA), propagation delay as low as 3.6 ns (VCC = 5 V), thermal resistance of 58°C/W, and SOIC-20 package compatibility with industrial temperature range (−40°C to 85°C).

Technical Context

This device implements four independent 2-to-1 multiplexers, each selecting between A or B inputs based on the A/B control line, with output enable (OE) controlling all four 3-state outputs simultaneously. Logic operates under positive logic convention with VIH/VIL thresholds defined per VCC level.

It uses AC-series CMOS technology with rail-to-rail output swing, guaranteed 3-state leakage ≤ ±5 µA, and input/output voltage tolerance up to VCC + 0.5 V. The flow-through architecture places inputs and outputs on opposite sides of the SOIC-20 package to minimize trace crossovers on PCBs.

Key Specifications

Pinout & Package

74AC11257DWR is housed in a 20-pin SOIC (DW) package measuring 12.8 mm × 7.5 mm × 2.35 mm, with gull-wing leads, RoHS-compliant CU NIPDAU finish, and moisture sensitivity level (MSL) 1 (260°C peak reflow).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 4-bit dual 2-to-1 multiplexer applications.

Compared with 74AC11257DWR, SN74ACT11257DWR delivers improved DC output voltage margins at the cost of higher static current, while 74LVC1257PWRE4 offers superior speed and footprint efficiency in 3.3-V domains but sacrifices 5-V interoperability and thermal robustness (θJA = 83°C/W).

Availability

74AC11257DWR is available at Aetrix Electronics and suitable for industrial PLC backplanes, automated test equipment signal routing, and embedded data acquisition systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 74AC11257DWR 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 over 50 years of innovation in high-reliability digital ICs.

The 74AC logic family was developed for high-speed, low-power bus interface applications in industrial and communications equipment, emphasizing noise immunity, latch-up robustness, and wide supply voltage tolerance.

FAQ

What is the recommended power-up sequence for 74AC11257DWR to avoid bus contention?

TI recommends tying OE to VCC through a pullup resistor (minimum value determined by driver sink capability) to ensure all outputs remain in high-impedance state during power-up. This prevents unintended bus loading before system initialization completes. The 74AC11257DWR datasheet specifies this practice to eliminate glitches on shared data lines, especially critical in hot-swap or multi-supply systems where VCC and OE may ramp at different rates.

Does 74AC11257DWR support mixed-voltage operation between input and output sides?

No - the 74AC11257DWR is a single-supply device operating from one VCC rail (3 V to 5.5 V); all inputs and outputs are referenced to that same supply. It does not provide level-shifting functionality. Input voltage limits are −0.5 V to VCC + 0.5 V, and outputs swing rail-to-rail. For true mixed-voltage interfacing, external level translators or families like LVC must be used alongside the 74AC11257DWR.

How does the center-pin VCC/GND configuration in 74AC11257DWR reduce switching noise?

The dual VCC (pins 18–19) and quad GND (pins 14–17) placements at the package center create symmetrical, low-inductance return paths for high-frequency switching currents. This geometry minimizes ground bounce and supply rail collapse during simultaneous output transitions - a key advantage confirmed by TI's characterization showing >10 dB reduction in radiated emissions versus edge-fed SOIC layouts. The 74AC11257DWR leverages this to meet industrial EMC requirements without added decoupling complexity.

Can unused inputs on 74AC11257DWR be left floating?

No - all unused inputs (including A/B, OE, and any unconnected A or B data lines) must be tied to VCC or GND. Floating CMOS inputs cause increased ICC, unpredictable logic states, and potential device malfunction due to intermediate voltage levels triggering both NMOS and PMOS transistors. TI's SCBA004 application report explicitly mandates termination for the 74AC11257DWR to ensure stable operation across −40°C to 85°C.

What is the maximum clock/data rate supported by 74AC11257DWR in a bus multiplexing application?

The 74AC11257DWR supports data rates up to ~140 MHz in ideal conditions (based on 7.2 ns max tPHL/tPLH at VCC = 5 V and 50-pF load), but practical bus timing depends on setup/hold margins, trace length, and fanout. For reliable operation in synchronous bus systems, TI recommends limiting toggle rates to ≤80 MHz with proper termination and controlled-impedance routing. The 74AC11257DWR's 3.6 ns typical propagation delay enables clean sampling at these speeds when paired with appropriate controller timing.