Texas Instruments CD74HC126MT

Overview

CD74HC126MT from Texas Instruments is a quadruple non-inverting buffer with 3-state outputs, designed for digital bus interface and signal enable functions in industrial and automotive systems. It operates across 2 V to 6 V supply voltage, supports –55°C to +125°C ambient temperature, delivers propagation delay as low as 17 ns at 6 V, and drives up to 10 LSTTL loads.

For engineers reviewing the CD74HC126MT datasheet, CD74HC126MT pinout, CD74HC126MT application, or CD74HC126MT equivalent, key selection criteria include 3-state output control timing (enable/disable delays ≤32 ns), wide-temperature operation, CMOS input compatibility, and SOIC-14 package suitability for high-density PCB layouts.

Technical Context

This device implements four independent positive-logic buffers (Y = A) with individually controlled 3-state outputs. Each channel features standard CMOS inputs and balanced CMOS 3-state outputs capable of sourcing/sinking ≥6 mA at 4.5 V while maintaining VOH ≥3.98 V and VOL ≤0.33 V.

Functional modes are defined by OE/A inputs: when OE is low, output Y enters high-impedance state (IOZ ≤±10 µA); when OE is high, Y follows A with typical propagation delay of 21 ns (6 V, CL = 15 pF). Input transition time must be ≤400 ns at 6 V to prevent shoot-through current.

Key Specifications

Pinout & Package

CD74HC126MT is supplied in a 14-pin SOIC (D) package measuring 8.70 mm × 3.90 mm, with standard JEDEC MO-001AC footprint and moisture sensitivity level 1 (260°C peak reflow).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC125DR and MC74HC126AD, CD74HC126MT uniquely combines military-grade temperature range, robust ±6 mA drive, and industry-leading 17 ns propagation delay - making it optimal for high-reliability embedded bus gating where timing precision and environmental resilience are critical.

Availability

CD74HC126MT is available at Aetrix Electronics and suitable for industrial bus isolation, automotive sensor interface, programmable logic I/O expansion, and legacy system bus buffering requiring stable component supply across extended temperature ranges.

Supply support for CD74HC126MT 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 and embedded processing technologies, with over 90 years of innovation in high-reliability logic, power management, and signal chain solutions.

The CD74HC126MT belongs to TI's HC (High-Speed CMOS) logic family, engineered for low-power, wide-voltage, and extended-temperature operation in mission-critical industrial and automotive control systems.

FAQ

What is the maximum capacitive load the CD74HC126MT can drive while meeting all datasheet specifications?

The CD74HC126MT is specified to meet all electrical parameters with a load capacitance of ≤50 pF, as tested in Section 6.6 of the datasheet. While it can drive up to 70 pF in practice, exceeding 50 pF may degrade propagation delay, increase transition time, or raise VOL/VOH beyond guaranteed limits - especially at temperature extremes. For designs targeting worst-case timing margins, keep total node capacitance (trace + receiver input + probe) at or below 50 pF.

Does the CD74HC126MT support true bidirectional data flow like a transceiver?

No, the CD74HC126MT is a unidirectional buffer: each channel passes signal from A to Y only. It does not support automatic direction sensing or dual-path data transfer. However, two CD74HC126MT devices can be configured back-to-back (with complementary OE control) to emulate bidirectional behavior on a shared bus - though this requires external logic to coordinate enable states and avoid bus contention.

Can unused inputs on the CD74HC126MT be left floating?

No, unused inputs on the CD74HC126MT must never be left floating. Standard CMOS inputs have high impedance and undefined voltage levels when unconnected, which can cause excessive supply current, logic oscillation, or thermal overstress. All unused A and OE inputs must be tied to either VCC or GND via direct connection or a pull-up/pull-down resistor (10 kΩ recommended) to ensure stable operation and prevent malfunction.

What is the purpose of the clamp diodes in the CD74HC126MT, and how do they affect system design?

The CD74HC126MT includes internal positive and negative clamp diodes on all inputs and outputs to protect against transient overvoltage. These diodes conduct if VI or VO exceeds VCC + 0.5 V or falls below –0.5 V, limiting fault current to ±20 mA. System designs must ensure that external circuits do not force voltages beyond these clamping thresholds - otherwise, sustained conduction risks permanent damage. Always verify that driving sources and loads respect the absolute maximum ratings in Section 6.1.

How does the CD74HC126MT's 3-state output behavior differ from open-drain or open-collector configurations?

The CD74HC126MT uses active-pull CMOS 3-state outputs - meaning both high-side and low-side FETs are disabled simultaneously during high-impedance mode, resulting in near-zero DC current (IOZ ≤±10 µA). Unlike open-drain/open-collector outputs, it does not require external pull-up resistors to define logic HIGH state. This simplifies bus design and eliminates resistor-induced rise-time limitations, but also means the output floats electrically and must be externally biased if a defined voltage is needed during disable.