Texas Instruments CD74HCT126M

Overview

CD74HCT126M from Texas Instruments is a quadruple 3-state buffer IC used for digital signal routing and bus isolation in logic systems. It features buffered CMOS inputs, operates from 4.5 V to 5.5 V, supports –55°C to +125°C temperature range, delivers propagation delay ≤25 ns at 5 V, and drives up to 10 LSTTL loads. It enables bidirectional data bus control in industrial controllers and test equipment.

For engineers reviewing the CD74HCT126M datasheet, CD74HCT126M pinout, CD74HCT126M application, or CD74HCT126M equivalent, key selection criteria include its TTL-compatible input thresholds, guaranteed 3-state leakage (±10 µA), output drive capability (±6 mA), and SOIC-14 package suitability for high-density PCB layouts with thermal constraints.

Technical Context

This device implements four independent non-inverting buffers, each with an active-low 3-state output enable (OE) controlling Y = A logic function. All channels operate synchronously under a single VCC supply, with no internal inter-channel coupling or shared timing paths.

Its HCT logic family ensures TTL-level input compatibility (VIH = 2.0 V min, VIL = 0.8 V max at 5 V), while maintaining CMOS-level output swing (VOH ≥ 4.4 V, VOL ≤ 0.33 V at IO = ±6 mA). The balanced output structure provides matched sourcing/sinking capability without internal pull-ups or level-shifting circuitry.

Key Specifications

Pinout & Package

CD74HCT126M is housed in a 14-pin SOIC (D) package measuring 8.70 mm × 3.90 mm, with standard JEDEC MO-001AC footprint and gull-wing leads suitable for reflow soldering.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT125N and 74VHC126M, CD74HCT126M offers guaranteed TTL-compatible inputs across its full rated VCC range and active-low OE alignment with legacy industrial control architectures, making it optimal for retrofitting into existing 5-V backplane systems requiring minimal logic changes.

Availability

CD74HCT126M is available at Aetrix Electronics and suitable for industrial PLC backplanes, automotive ECU diagnostics, test equipment signal gating, and avionics data acquisition requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HCT126M 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 90 years of innovation in industrial, automotive, and aerospace electronics.

CD74HCT126M belongs to TI's HCT logic family, engineered specifically for seamless integration between TTL and CMOS systems in mission-critical industrial and transportation applications.

FAQ

What is the maximum capacitive load supported by CD74HCT126M while maintaining specified timing?

CD74HCT126M maintains guaranteed switching characteristics (tpd ≤25 ns, ten ≤31 ns) with a 50-pF load capacitance at VCC = 5 V and TA = 25°C. While operation with up to 70 pF is feasible per layout guidelines, exceeding 50 pF may increase propagation delay beyond datasheet limits and require empirical validation in target PCB environments. Always verify timing margins using actual board-level measurements for CD74HCT126M deployments.

Does CD74HCT126M support operation at 3.3 V supply voltage?

No, CD74HCT126M is not characterized or guaranteed for operation at 3.3 V. Its recommended operating range is strictly 4.5 V to 5.5 V, and TTL-compatible input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) are only validated within that range. For 3.3-V systems, consider TI's SN74LVC126A or similar LVC-family devices explicitly rated for 3.3-V operation. CD74HCT126M must be powered from a regulated 5-V rail to ensure functional compliance.

How should unused inputs and outputs be handled on CD74HCT126M?

Unused inputs on CD74HCT126M must be terminated to either VCC or GND using direct connections or 10-kΩ pull-up/down resistors to prevent floating states and undefined logic behavior. Unused outputs may be left unconnected (floating), but must never be tied directly to VCC or GND. This applies equally to all four channels - for example, if Channel 3 is unused, tie 3A and 3OE to VCC or GND, and leave 3Y open. Proper termination ensures stable CD74HCT126M operation across its full temperature range.

What is the thermal resistance (RθJA) of CD74HCT126M in its SOIC-14 package?

The junction-to-ambient thermal resistance (RθJA) for CD74HCT126M in the SOIC-14 (D) package is 133.6°C/W, as specified in the datasheet's Thermal Information table. This value assumes standard JEDEC 2-layer board conditions. Actual thermal performance depends on PCB copper area, airflow, and nearby heat sources. For high-reliability applications, ensure peak junction temperature remains below 150°C by calculating power dissipation (P = ICC × VCC + Σ(VO × IO)) and applying RθJA to determine allowable ambient rise for CD74HCT126M.

Is CD74HCT126M pin-compatible with CD74HC126M?

Yes, CD74HCT126M and CD74HC126M share identical SOIC-14 pinouts, terminal functions, and physical dimensions. However, they differ electrically: CD74HCT126M has TTL-compatible inputs (VIH/VIL thresholds fixed at ~2.0 V/0.8 V), while CD74HC126M uses CMOS thresholds (VIH = 0.7×VCC, VIL = 0.3×VCC). Substituting CD74HCT126M for CD74HC126M is safe in 5-V systems with TTL sources, but CD74HC126M cannot replace CD74HCT126M in such cases without risking input recognition failure. Verify signal source compatibility before interchange of CD74HCT126M and CD74HC126M.