Texas Instruments CD74HCT126MT

Overview

CD74HCT126MT from Texas Instruments is a quadruple non-inverting buffer with 3-state outputs, designed for digital bus interface and signal enable functions in industrial control and embedded systems. It operates across 4.5 V to 5.5 V supply voltage, supports –55°C to +125°C temperature range, delivers propagation delay ≤25 ns (VCC = 4.5 V, CL = 50 pF), and drives up to 10 LSTTL loads.

For engineers reviewing the CD74HCT126MT datasheet, CD74HCT126MT pinout, CD74HCT126MT application, or CD74HCT126MT equivalent, key selection criteria include its TTL-compatible input thresholds, guaranteed 3-state leakage (±10 µA), low power consumption (ICC ≤ 80 µA at 6 V), and SOIC-14 packaging for high-density PCB layouts.

Technical Context

This device implements four independent positive-logic buffers (Y = A) with active-low 3-state output enables. Each channel features balanced CMOS outputs capable of sourcing/sinking ≥6 mA while maintaining VOH ≥ 3.98 V and VOL ≤ 0.33 V under load.

It uses standard CMOS inputs with VIH = 2.0 V (min) and VIL = 0.8 V (max) at VCC = 4.5 V, enabling direct interfacing with TTL logic families. The 3-state control architecture allows bidirectional bus management without external direction signals.

Key Specifications

Pinout & Package

CD74HCT126MT is supplied in a 14-pin SOIC (D) package measuring 8.70 mm × 3.90 mm, with standard JEDEC MO-001AC footprint and gull-wing leads for surface-mount assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT125DR and 74LVC126APW, CD74HCT126MT uniquely provides active-low 3-state control with full 5-V tolerance and extended temperature support-making it the only option qualified for legacy industrial controllers and high-reliability aerospace subsystems requiring direct TTL interoperability.

Availability

CD74HCT126MT is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, automotive body control modules, and avionics data acquisition interfaces requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HCT126MT 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 and embedded processing solutions, with over 90 years of innovation in logic, power management, and signal chain technologies.

CD74HCT126MT belongs to TI's HCT logic family, engineered specifically for seamless integration between TTL and CMOS systems in mission-critical industrial and defense applications where reliability across extreme temperatures is mandatory.

FAQ

What is the maximum capacitive load the CD74HCT126MT can drive while maintaining specified timing?

The CD74HCT126MT is characterized for CL = 50 pF in switching specifications, with propagation delay ≤25 ns at VCC = 4.5 V. Driving loads >70 pF increases transition time and may violate setup/hold margins; TI recommends limiting total load to ≤70 pF or adding series termination resistors if higher capacitance is unavoidable. The CD74HCT126MT datasheet specifies CL = 50 pF as the test condition for all timing parameters.

Does the CD74HCT126MT support mixed-voltage operation between 3.3 V and 5 V logic domains?

No, the CD74HCT126MT is strictly a 5-V device with VCC operating range 4.5 V to 5.5 V. Its TTL-compatible inputs accept 3.3-V logic highs (VIH = 2.0 V min), but it cannot be powered from 3.3 V. For true mixed-voltage translation, use dedicated level shifters; the CD74HCT126MT serves only as a 5-V bus buffer with TTL-input compatibility.

How should unused inputs and outputs be terminated on the CD74HCT126MT?

Unused inputs must be tied to VCC or GND-never left floating-to prevent undefined states and excessive current draw. Unused outputs may be left unconnected (floating) since they enter high-impedance mode when disabled. TI's layout guidelines explicitly show unused inputs tied to VCC and outputs left floating, as confirmed in Figure 11-1 of the CD74HCT126MT datasheet.

What is the thermal resistance (RθJA) of the CD74HCT126MT in its SOIC-14 package?

The CD74HCT126MT in SOIC-14 (D) package has RθJA = 133.6°C/W, per TI's SCHS144D datasheet revision June 2021. This value assumes standard JEDEC 2-layer board conditions; actual thermal performance improves with internal copper planes and thermal vias. Junction temperature must remain ≤150°C under all operating conditions.

Is the CD74HCT126MT pin-compatible with the CD74HC126M variant?

Yes, CD74HCT126MT and CD74HC126M share identical SOIC-14 pinout, terminal functions, and mechanical footprint. However, CD74HCT126MT uses TTL-compatible input thresholds (VIH/VIL), while CD74HC126M uses CMOS thresholds (VIH = 0.7×VCC, VIL = 0.3×VCC). Electrical behavior differs significantly-CD74HCT126MT is not a drop-in replacement without verifying input signal compatibility.