onsemi MC74VHCT126AMEL

Overview

MC74VHCT126AMEL from onsemi is a quad noninverting bus buffer with 3-state control inputs, designed for high-speed level translation between 3.3 V and 5.0 V logic domains. It features TTL-compatible inputs (VIL = 0.8 V, VIH = 2.0 V), 3.8 ns typical propagation delay at VCC = 5.0 V, ±25 mA output drive, and operates across 4.5–5.5 V supply range. It serves as an interface buffer in mixed-voltage digital systems such as industrial controllers and communication modules.

For engineers reviewing the MC74VHCT126AMEL datasheet, pinout, applications, or equivalent options, key selection criteria include 3-state enable timing (tPZL/tPHZ ≤ 7.5 ns), input overvoltage tolerance up to 7.0 V, 5.5 V absolute maximum input voltage, and SOIC-14 package compatibility with legacy VHCT/TTL designs.

Technical Context

The MC74VHCT126AMEL implements four independent noninverting buffers, each with active-high 3-state control (OE). Its silicon gate CMOS architecture delivers bipolar-Schottky TTL speed while maintaining CMOS power efficiency. Input structures tolerate 0–7.0 V regardless of VCC, enabling safe interfacing of 5.0 V systems to 3.0 V subsystems without external level shifters.

Each buffer stage includes internal noise immunity enhancement via balanced propagation paths and a dedicated output-stage protection network. The device supports hot insertion and battery-backup scenarios due to VCC = 0 V tolerant outputs and input protection against supply–input voltage mismatch.

Key Specifications

Pinout & Package

MC74VHCT126AMEL is housed in a 14-pin SOIC package (case 751A), with 1.27 mm pitch and standard JEDEC MS-012 outline. Pin 1 is marked by a beveled corner or notch; pin numbering follows counterclockwise convention from the top-left corner when viewed from the top with marking side up.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad bus buffer applications.

Compared with SN74LVC126APWR and 74LCX126MTCX, the MC74VHCT126AMEL uniquely supports full 5.0 V operation with 7.0 V input overvoltage tolerance and VCC = 0 V safe outputs - making it the only choice for industrial backplanes and automotive modules requiring mixed-supply interoperability and fault resilience.

Availability

MC74VHCT126AMEL is available at Aetrix Electronics and suitable for industrial PLC backplanes, automotive body control modules, and medical diagnostic equipment requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.

Supply support for MC74VHCT126AMEL 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensors, and logic solutions for automotive, industrial, and cloud infrastructure markets.

The MC74VHCT126AMEL belongs to the VHCT logic family, engineered specifically for pin-compatible migration from bipolar TTL into low-power CMOS while preserving timing, drive strength, and interface compatibility in mixed-voltage digital systems.

FAQ

What is the maximum input voltage rating for MC74VHCT126AMEL?

The MC74VHCT126AMEL supports DC input voltages from –0.5 V to +7.0 V, independent of VCC level. This overvoltage tolerance allows safe interfacing of 5.0 V signals into systems powered at 3.3 V or lower, eliminating external clamping components. The specification is validated across –40°C to +85°C operating temperature and confirmed in the Absolute Maximum Ratings table of the official onsemi datasheet (Rev. 11, October 2016).

Does MC74VHCT126AMEL support hot insertion?

Yes, MC74VHCT126AMEL supports hot insertion due to its VCC = 0 V output protection and input structures rated for 0–7.0 V regardless of supply state. When VCC is unpowered, outputs remain in high-impedance mode without leakage or latch-up risk, preventing bus contention. This behavior is explicitly documented in the "Power Down Protection Provided on Inputs" feature and verified in the Maximum Ratings section of the onsemi datasheet.

What is the recommended decoupling for MC74VHCT126AMEL?

A 0.1 µF ceramic capacitor placed as close as possible to the VCC (pin 14) and GND (pin 7) terminals is the recommended decoupling for MC74VHCT126AMEL. This minimizes high-frequency supply noise and stabilizes output transitions, especially critical given its 3.8 ns propagation delay and ±25 mA drive capability. The requirement is derived from AC electrical characteristics testing conditions and noise performance validation in the onsemi datasheet (Figure 5 test circuit and NOISE CHARACTERISTICS section).

Can MC74VHCT126AMEL operate at 3.3 V supply?

No, MC74VHCT126AMEL is not specified for reliable operation at 3.3 V supply. Its Recommended Operating Conditions require VCC between 4.5 V and 5.5 V. While some DC parameters may function marginally at lower voltages, AC performance (e.g., tPD = 5.6 ns @ 3.3 V) degrades significantly, and input thresholds (VIH = 2.0 V min) violate TTL compatibility. For 3.3 V systems, consider SN74LVC126A or 74LCX126 instead.

Is MC74VHCT126AMEL pin-compatible with standard 74-series TTL buffers?

Yes, MC74VHCT126AMEL is pin- and function-compatible with industry-standard 74HCT126 and 74LS126 devices in SOIC-14 packaging. Pin assignments for A1–A4, OE1–OE4, Y1–Y4, VCC, and GND match exactly, enabling drop-in replacement without PCB modification. This compatibility is stated in the "Pin and Function Compatible with Other Standard Logic Families" feature and confirmed in Figure 2 (PIN ASSIGNMENT) of the onsemi datasheet.