Texas Instruments SN74HCS126DR

Overview

SN74HCS126DR from Texas Instruments is a quadruple CMOS buffer with 3-state outputs and Schmitt-trigger inputs, designed for signal conditioning in noisy or slow-transition environments. It operates from 2 V to 6 V, delivers ±7.8 mA output drive at 6 V, supports –40°C to +125°C ambient temperature, and features typical supply current of 100 nA - enabling low-power digital isolation in industrial sensor interfaces and switch debouncing circuits.

For engineers reviewing the SN74HCS126DR datasheet, SN74HCS126DR pinout, SN74HCS126DR application, or SN74HCS126DR equivalent, key selection criteria include Schmitt-trigger hysteresis (ΔVT ≥ 0.6 V at 6 V), 3-state enable timing (tdis ≤ 14 ns at 6 V), output drive capability under load, and SOIC-14 package compatibility with legacy board layouts.

Technical Context

This device implements four independent positive-logic buffers (Y = A) with active-high 3-state enable (OE) per channel. Each input incorporates Schmitt-trigger architecture with hysteresis (ΔVT = 0.6–1.6 V depending on VCC), enabling reliable operation with slow-rising signals or high-noise margins.

The balanced CMOS 3-state outputs support bidirectional current sourcing/sinking up to ±7.8 mA at 6 V while maintaining high-impedance leakage < 2 µA. Propagation delay is 7–26 ns across 2–6 V supply, and input leakage remains ±100 nA typical at 6 V - critical for battery-powered and thermally constrained embedded systems.

Key Specifications

Pinout & Package

SN74HCS126DR is supplied in a 14-pin SOIC (D) package measuring 9.90 mm × 3.90 mm, with standard 1.27 mm pitch and gull-wing leads compatible with automated SMT assembly and IPC-7351B footprints.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCS126DR, SN74HCS125DR preserves timing and power traits but inverts logic - requiring redesign of upstream logic or downstream interpretation. SN74LVC126ADBR offers faster switching and lower-voltage operation but forfeits Schmitt-trigger noise rejection, making it unsuitable for direct replacement in noisy or slow-edge applications.

Availability

SN74HCS126DR is available at Aetrix Electronics and suitable for industrial sensor interfaces, switch debounce circuits, LED driver control, and legacy bus isolation requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN74HCS126DR 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, embedded processing, and connectivity solutions for industrial, automotive, and consumer markets.

The SN74HCS126DR belongs to TI's HCS logic family - designed specifically for high-noise-immunity, low-power, wide-supply applications in harsh environments where reliability and signal integrity outweigh raw speed.

FAQ

What is the maximum capacitive load SN74HCS126DR can drive while meeting datasheet timing specs?

The SN74HCS126DR is characterized to meet all timing specifications (tpd, ten, tdis) with a total output load capacitance ≤ 50 pF. Exceeding this value increases propagation delay and transition time - for example, at 100 pF, tpd may increase by ~30% at 6 V. Always verify timing margins in final layout using worst-case load models.

Does SN74HCS126DR require external pull-up or pull-down resistors on unused inputs?

Yes - all unused inputs of SN74HCS126DR must be terminated to either VCC or GND to prevent floating states that cause excessive current draw and erratic output behavior. A 10 kΩ resistor is recommended for most cases; direct connection is acceptable if the logic state is fixed and no dynamic switching is expected.

Can SN74HCS126DR outputs be paralleled for higher current drive?

Yes - two or more channels of SN74HCS126DR with identical inputs and enables can be wired in parallel to increase effective output drive strength, provided all corresponding OE and A pins are tied together. This configuration maintains timing alignment and avoids shoot-through, but does not reduce VOL or VOH beyond datasheet limits.

What is the minimum input voltage threshold (VT−) for SN74HCS126DR at 3.3 V supply?

At VCC = 3.3 V, the negative switching threshold VT− for SN74HCS126DR is specified as 0.9 V (typical) to 2.2 V (max). This means an input must fall below 0.9 V to guarantee recognition as a logic LOW - critical for designing RC-based switch debouncers or comparator hysteresis windows.

Is SN74HCS126DR suitable for automotive applications?

Yes - SN74HCS126DR is rated for –40°C to +125°C ambient operation and meets AEC-Q100 HBM ESD Class 2 (±4 kV), making it suitable for under-dash, engine bay–adjacent, and ADAS subsystems where extended temperature and ESD robustness are required. Always confirm qualification status per specific part marking and lot traceability.