Texas Instruments SN74F126NSR

Overview

SN74F126NSR from Texas Instruments is a quadruple bus buffer gate with 3-state outputs, designed for bidirectional data bus isolation and memory address register buffering in TTL-compatible systems. It operates from 4.5 V to 5.5 V, delivers 6.5 ns max propagation delay at 5 V, and supports ±64 mA low-level output drive per channel.

For engineers reviewing the SN74F126NSR datasheet, SN74F126NSR pinout, SN74F126NSR application, or SN74F126NSR equivalent, key selection criteria include 3-state enable timing (tPZL/tPHZ ≤ 8.5 ns), thermal performance (θJA = 76°C/W), and compatibility with legacy F-series TTL logic families in industrial control and instrumentation interfaces.

Technical Context

The SN74F126NSR implements four independent noninverting buffers, each with dedicated active-high output-enable (OE) control. Each channel transitions to high-impedance when OE is low, enabling shared-bus arbitration without external gating logic.

It adheres to standard F-series TTL electrical characteristics: VIH = 2 V min, VIL = 0.8 V max, VOL = 0.55 V max at IOL = 64 mA, and IOZH/IOZL ≤ ±50 µA in 3-state mode - ensuring interoperability with SN74Fxx and compatible logic families across 0°C to 70°C operation.

Key Specifications

Pinout & Package

SN74F126NSR is housed in a 14-pin SOP (NS) package with 1.27 mm pitch, 8.75 mm × 3.9 mm body, and 1.75 mm max height - optimized for automated surface-mount assembly and thermal dissipation in space-constrained designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74F126NSR, SN74LS126N trades speed and drive for lower power, while SN74ACT126DR offers faster switching and voltage flexibility at reduced output current - making SN74F126NSR optimal for legacy 5-V TTL bus systems demanding robust drive and precise timing.

Availability

SN74F126NSR is available at Aetrix Electronics and suitable for memory address buffering, parallel bus isolation, and legacy system interface applications requiring stable component supply and long-term industrial availability.

Supply support for SN74F126NSR 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 industrial, automotive, and communications markets.

The SN74F126NSR belongs to TI's legacy F-series TTL logic family, engineered for high-speed, high-drive 5-V digital interfacing in industrial control, test equipment, and computer peripheral subsystems.

FAQ

What is the recommended pull-down resistor value for OE pins on the SN74F126NSR?

The SN74F126NSR datasheet specifies that OE should be tied to GND through a pulldown resistor to ensure high-impedance state at power-up. The minimum resistor value depends on the driver's current-sourcing capability; typical values range from 1 kΩ to 10 kΩ. For most applications using standard TTL drivers, a 4.7 kΩ resistor provides sufficient noise immunity and fast discharge without excessive current draw. Always verify against actual board-level noise and rise-time requirements when selecting the final value for SN74F126NSR.

Does the SN74F126NSR support hot insertion or live bus swapping?

The SN74F126NSR is not rated for hot insertion. Its absolute maximum ratings specify that output voltages must remain within –0.5 V to 5.5 V when disabled, and inputs must stay within –1.2 V to 7 V. During live insertion, uncontrolled voltage transients or bus contention can exceed these limits, risking latch-up or permanent damage. For hot-swap applications, dedicated hot-swap controllers or buffers with built-in protection (e.g., SN74CBT16210) are required. SN74F126NSR must be powered and stabilized before bus connection.

Can the SN74F126NSR drive a 50-pF capacitive load with full timing compliance?

Yes - the SN74F126NSR's switching characteristics are explicitly characterized at CL = 50 pF, RL = 500 Ω, and TA = 25°C. All published delays (tPLH, tPHL, tPZL, etc.) meet specification under this exact load condition. At 5 V supply, tPLH/tPHL are guaranteed ≤6.5 ns and ≤8.5 ns respectively, and enable/disable times remain within 8.5 ns. For heavier loads (>50 pF), timing margins degrade predictably; derating curves are provided in the TI application report SCBA004.

Is the SN74F126NSR RoHS compliant and lead-free?

Yes - according to TI's Packaging Information Addendum, SN74F126NSR (ordered as SN74F126DR or SN74F126NSR) carries "Yes" for RoHS compliance and uses NIPDAU (nickel/palladium/gold) lead finish. The NS package variant is supplied in tape-and-reel format with MSL Level-1 rating (unlimited floor life at ≤30°C/60% RH). Full compliance documentation, including material declarations and test reports, is accessible via TI's Quality & Environmental page using the SN74F126NSR part number.

How does the SN74F126NSR differ from the SN74F125 in practical design use?

The SN74F126NSR features noninverting buffers with active-high OE, whereas the SN74F125 has inverting buffers with active-low OE (/OE). This affects control logic polarity: SN74F126NSR enables outputs when OE = H, matching standard enable conventions in bus arbitration logic, while SN74F125 requires inverted enable signals. Both share identical timing, drive, and package specs - so SN74F126NSR is preferred when minimizing external inverters or aligning with positive-logic system architecture.