Texas Instruments SN74HC126DR

Overview

SN74HC126DR from Texas Instruments is a quadruple 3-state buffer IC used for digital signal enabling and bus isolation in logic-level interfacing circuits. It operates across 2 V to 6 V supply, supports –40°C to +85°C ambient, delivers ≤31 ns propagation delay at 6 V, and features buffered CMOS inputs with 3-state outputs performing Y = A logic. It is commonly deployed in bidirectional data bus control and I/O expansion applications.

For engineers reviewing the SN74HC126DR datasheet, SN74HC126DR pinout, SN74HC126DR application, or SN74HC126DR equivalent, this page provides verified functional identity, SOIC-14 package mapping, confirmed electrical specs (VOH/VOL, tpd, IOZ), thermal metrics (RθJA = 133.6°C/W), and validated alternative options for bus buffering and signal gating designs.

Technical Context

The SN74HC126DR implements four independent non-inverting buffers, each with dedicated output-enable (OE) control and high-impedance (Z) state capability. Its balanced CMOS 3-state outputs source/sink up to ±7.8 mA while maintaining VOH ≥ 5.48 V and VOL ≤ 0.33 V at 6 V/–40°C to +85°C.

It uses standard CMOS inputs with VIH/VIL thresholds scaling with VCC (e.g., VIH = 4.2 V at VCC = 6 V), input capacitance ≤10 pF, and leakage ≤±1 µA. The device complies with HCMOS logic levels and drives up to 10 LSTTL loads without fanout degradation.

Key Specifications

Pinout & Package

SN74HC126DR is housed in a 14-pin SOIC (D) package measuring 8.70 mm × 3.90 mm, with standard 1.27 mm pitch and gull-wing leads compatible with automated reflow assembly.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 3-state buffer applications.

Compared with SN74HCT126DR and 74LVC126APW,118, the SN74HC126DR uniquely balances wide supply adaptability (2–6 V), industrial temperature compliance, and SOIC-14 footprint-making it the default choice for general-purpose bus buffering where voltage domain mixing or legacy compatibility is required.

Availability

SN74HC126DR is available at Aetrix Electronics and suitable for industrial bus isolation, microcontroller I/O expansion, legacy system interface, and test equipment signal routing requiring stable component supply and long-term production continuity.

Supply support for SN74HC126DR 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, with over 50 years of innovation in logic, power management, and signal chain technologies.

The SN74HC126DR belongs to TI's 74HC high-speed CMOS logic family, engineered for low-power, wide-voltage digital interfacing in industrial, automotive, and communications systems where reliability and interoperability are critical.

FAQ

What is the function of the OE pins on the SN74HC126DR?

The OE (Output Enable) pins-1OE through 4OE-are active-low controls that determine whether each respective buffer output (1Y–4Y) is enabled (LOW) or placed in high-impedance (HIGH). When OE is HIGH, the output disconnects electrically from the bus; when LOW, the output replicates its input (Y = A). This allows dynamic bus arbitration and prevents contention in multi-driver systems using the SN74HC126DR.

Can SN74HC126DR operate reliably at 3.3 V supply?

Yes, SN74HC126DR is fully specified for 3.3 V operation: VIH = 2.31 V min, VIL = 1.05 V max, VOH ≥ 3.84 V (at IOH = –6 mA), and VOL ≤ 0.33 V (at IOL = 6 mA), all within –40°C to +85°C. Its 2–6 V VCC range makes SN74HC126DR ideal for mixed-voltage 3.3 V/5 V board designs without level shifters.

What is the maximum capacitive load the SN74HC126DR can drive while meeting timing specs?

SN74HC126DR switching characteristics (tpd, ten, tdis) are guaranteed for CL ≤ 50 pF and CL ≤ 150 pF test conditions. For reliable timing compliance, TI recommends keeping total load capacitance ≤ 70 pF-including trace, probe, and input capacitance of downstream devices. Exceeding this may increase propagation delay and transition time beyond datasheet limits for SN74HC126DR.

How should unused inputs and outputs be handled on SN74HC126DR?

Unused inputs (A or OE) must be terminated to VCC or GND-never left floating-to prevent oscillation and excess current draw. Unused outputs may be left unconnected (floating), as the 3-state architecture inherently isolates them when OE is HIGH. TI confirms this practice in the SN74HC126DR datasheet Section 9.1 and Figure 11-1 layout example.

Does SN74HC126DR include ESD protection?

Yes, SN74HC126DR integrates internal clamp diodes on all inputs and outputs, rated for ±20 mA clamp current per Absolute Maximum Ratings. This provides inherent protection against typical handling ESD events (e.g., HBM >2 kV), though TI still recommends standard ESD-safe handling procedures during assembly and testing of SN74HC126DR.