Texas Instruments SN74HC126PW

Overview

SN74HC126PW from Texas Instruments is a quadruple 3-state buffer IC used for digital signal enablement 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 drives up to 10 LSTTL loads. It is commonly deployed in bidirectional data bus control and level-shifting applications.

For engineers reviewing the SN74HC126PW datasheet, SN74HC126PW pinout, SN74HC126PW application, or SN74HC126PW equivalent, key selection criteria include its TSSOP-14 package footprint, 3-state output timing (enable/disable delays), CMOS input compatibility, and thermal resistance (RθJA = 151.7°C/W) for compact PCB layouts.

Technical Context

This device implements four independent non-inverting buffers, each with a dedicated 3-state output enable (OE) input. Each channel performs Y = A in positive logic, with fully buffered inputs and balanced CMOS outputs capable of sourcing/sinking up to ±7.8 mA at 6 V.

It uses standard HCMOS process technology, features clamp diodes on all I/O pins, and requires no external pull resistors for unused inputs when tied directly to VCC or GND - enabling clean bus arbitration without signal contention or shoot-through current.

Key Specifications

Pinout & Package

TSSOP-14 package (5.00 mm × 4.40 mm), 0.65 mm pitch, thin-profile surface-mount construction optimized for space-constrained PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT126PW and 74LVC126PW, the SN74HC126PW provides the broadest supply voltage range (2–6 V) and highest absolute maximum rating (7 V), making it uniquely suitable for mixed-voltage industrial control boards where supply rails may vary across subsystems.

Availability

SN74HC126PW is available at Aetrix Electronics and suitable for industrial automation, test equipment, and embedded control systems requiring stable component supply, long-term lifecycle support, and RoHS-compliant TSSOP packaging.

Supply support for SN74HC126PW 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 IC design.

The SN74HC126PW belongs to TI's industry-standard 74HC logic family, designed specifically for robust, low-power digital interfacing in industrial, automotive, and communications equipment where wide supply range and 3-state controllability are essential.

FAQ

What is the maximum capacitive load the SN74HC126PW can reliably drive?

The SN74HC126PW is characterized for optimal switching performance with ≤70 pF total load capacitance, as confirmed in TI's application guidance. At 6 V supply and CL = 50 pF, propagation delay remains ≤31 ns (max). Driving >100 pF increases transition time and may cause ringing; a series 22–47 Ω resistor is recommended for larger loads to limit peak output current within Absolute Maximum Ratings.

Can unused inputs on the SN74HC126PW be left floating?

No - unused inputs on the SN74HC126PW must be terminated to VCC or GND. Floating CMOS inputs risk oscillation, excessive supply current, and unpredictable output states due to noise coupling. TI recommends direct connection (not pull-up/down resistors) for permanently unused channels; if dynamic control is needed, use ≤10 kΩ resistors based on leakage current limits (±1 µA max) and required edge rate.

Does the SN74HC126PW support 1.8 V logic levels?

No - the SN74HC126PW has a minimum recommended supply voltage of 2 V and is not specified for reliable operation at 1.8 V. Input thresholds scale with VCC (VIH ≈ 0.7×VCC), so at 1.8 V, VIH would be ~1.26 V - below typical 1.8 V logic HIGH definition (≥1.4 V). For 1.8 V systems, consider 74LVC126 or SN74AUP1G126 instead.

What is the thermal resistance (RθJA) of the SN74HC126PW in its TSSOP-14 package?

The SN74HC126PW in TSSOP-14 package has a junction-to-ambient thermal resistance (RθJA) of 151.7°C/W, as published in TI's SCLS103F datasheet revision F. This value assumes standard JEDEC 2-layer board conditions; actual thermal performance improves with internal copper planes, thermal vias, or localized heatsinking - critical for sustained operation near 85°C ambient.

How does the 3-state disable timing of the SN74HC126PW compare to its enable timing?

At 6 V and CL = 50 pF, the SN74HC126PW exhibits identical typical disable delay (tdis = 20 ns) and enable delay (ten = 20 ns), with matching max values of 31 ns. This symmetry ensures predictable bus release and acquisition timing - essential for synchronous data handshaking protocols where output release must align precisely with downstream sampling windows.