Texas Instruments SN74HC126PWT

Overview

SN74HC126PWT from Texas Instruments is a quadruple non-inverting buffer with 3-state outputs, designed for bus interface and signal enable functions in digital logic systems. It operates across 2 V to 6 V supply voltage, supports –40°C to +85°C ambient temperature, delivers ≤31 ns propagation delay at 6 V (CL = 50 pF), and drives up to 10 LSTTL loads. It is used in bidirectional data bus control where output isolation is required.

For engineers reviewing the SN74HC126PWT datasheet, SN74HC126PWT pinout, SN74HC126PWT application, or SN74HC126PWT equivalent, key selection criteria include 3-state output timing (enable/disable delays), CMOS input compatibility, thermal resistance (RθJA = 151.7°C/W), and TSSOP-14 package footprint constraints for high-density PCB layouts.

Technical Context

The SN74HC126PWT implements four independent positive-logic buffers (Y = A) with individual 3-state output enables (OE). Each channel features balanced CMOS outputs capable of sourcing/sinking ≥6 mA at 4.5 V and ≥7.8 mA at 6 V while maintaining VOH ≥ 3.98 V and VOL ≤ 0.33 V under load.

Its standard CMOS inputs exhibit ≤10 pF capacitance and ±1 µA leakage at 6 V, requiring input transition times ≤400 ns (at 6 V) to prevent shoot-through current. The device uses internal clamp diodes on all I/O pins and is rated for ±20 mA input/output clamp current per pin.

Key Specifications

Pinout & Package

TSSOP-14 package (5.00 mm × 4.40 mm body size, 0.65 mm pitch), thermally enhanced for surface-mount assembly in space-constrained industrial and communications PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC126APW, SN74HC126PWT supports broader voltage interoperability (2–6 V) at the cost of slightly slower timing; compared with 74HC244PW, it offers identical per-channel performance in a smaller 14-pin footprint but halves channel density.

Availability

SN74HC126PWT is available at Aetrix Electronics and suitable for industrial bus interface, microcontroller peripheral expansion, test equipment signal routing, and programmable logic interfacing requiring stable component supply and long-term production continuity.

Supply support for SN74HC126PWT 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 company delivering analog and embedded processing solutions for industrial, automotive, and personal electronics markets.

The SN74HC126PWT belongs to TI's 74HC logic family, engineered for low-power, wide-supply-voltage digital interfacing in cost-sensitive industrial and consumer applications.

FAQ

What is the maximum capacitive load the SN74HC126PWT can drive while meeting datasheet timing specifications?

The SN74HC126PWT is characterized for CL ≤ 50 pF in switching specifications, with typical performance validated up to 70 pF in design guidelines. Driving >70 pF may increase propagation delay beyond 31 ns (max at 6 V) and raise output current beyond safe limits - add a series resistor if larger loads are unavoidable. SN74HC126PWT datasheet specifies CL = 50 pF for all tpd, ten, and tdis values.

Does the SN74HC126PWT have Schmitt-trigger inputs?

No, the SN74HC126PWT uses standard CMOS inputs without hysteresis. Input transition times must be ≤400 ns at 6 V to avoid oscillation or excessive current draw. For slow or noisy signals, an external Schmitt-trigger buffer (e.g., SN74HC14) must precede SN74HC126PWT to ensure reliable operation.

Can unused inputs on the SN74HC126PWT be left floating?

No - all unused inputs on SN74HC126PWT must be terminated to VCC or GND. Floating CMOS inputs cause undefined logic states, increased power consumption, and potential device malfunction. A 10-kΩ pull-up or pull-down resistor is recommended for unused OE or A pins to maintain stable bias within VIH/VIL thresholds.

What is the purpose of the NC pins on the SN74HC126PWT TSSOP-14 package?

The SN74HC126PWT TSSOP-14 package has no NC (no-connect) pins - all 14 pins are assigned: 4× OE, 4× A, 4× Y, 1× VCC, 1× GND. NC pins appear only in the 20-pin LCCC variant (SN54HC126FK); they are unconnected internally and must remain unpopulated on PCBs using that package.

How does the thermal performance of the SN74HC126PWT compare across package types?

SN74HC126PWT (TSSOP-14) has RθJA = 151.7°C/W - higher than SOIC (133.6°C/W) or PDIP (62.5°C/W) variants due to smaller body size and reduced copper exposure. This means SN74HC126PWT requires more careful thermal layout (e.g., thermal vias, ground plane coupling) in high-ambient or high-duty-cycle applications to keep junction temperature below 150°C.