onsemi MC74AC125MG

Overview

MC74AC125MG from onsemi is a quad 3-state buffer with low-enable logic, designed for bidirectional data bus isolation and signal routing in CMOS systems. It features four independent buffer channels, 5.5 V absolute maximum supply voltage, ±24 mA output drive capability, propagation delay as low as 7.0 ns at 5.0 V, and operates across −40°C to +85°C ambient temperature - used in industrial control backplanes and digital instrumentation interfaces.

For engineers reviewing the MC74AC125MG datasheet, pinout, applications, or equivalent options, this page delivers verified electrical specifications, SOIC-14 package details, functional truth table behavior, real-world use cases in bus-hold and level-shifting contexts, and two validated alternative parts with documented parameter differences.

Technical Context

The MC74AC125MG implements four identical non-inverting 3-state buffers, each controlled by an active-low enable input (Bn). Its silicon-gate CMOS architecture ensures TTL-compatible output levels while maintaining CMOS input thresholds (VIH = 2.1 V min at VCC = 3.0 V), enabling mixed-voltage interface bridging between 3.3 V and 5 V domains. Each output supports high-impedance state with <±5.0 µA off-state leakage.

It exhibits rail-to-rail output swing (VOH ≥ 4.4 V, VOL ≤ 0.1 V at IOL/IOH = ±24 mA, VCC = 4.5 V), fast enable/disable timing (tPZH/tPHZ ≤ 8.0 ns max at 5.0 V), and robust ESD protection (>2000 V HBM). The device lacks Schmitt-trigger inputs and requires monotonic input transitions within specified rise/fall time limits (≤25 ns/V at VCC = 5.5 V).

Key Specifications

Pinout & Package

MC74AC125MG is supplied in a Pb-free SOIC-14 (Case 751A) package, 8.55–8.75 mm × 3.80–4.00 mm body size, 1.27 mm pitch, with 1.35–1.75 mm height. Pin 1 is marked by notch or beveled corner.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC74AC125MG, SN74AC125N offers identical electrical behavior and direct interchangeability, while 74LVC125APW trades wider voltage range for reduced speed and package flexibility - making MC74AC125MG optimal for cost-sensitive, 5 V industrial backplanes requiring proven SOIC reliability.

Availability

MC74AC125MG is available at Aetrix Electronics and suitable for industrial control backplanes, digital test instrumentation, programmable logic interfacing, and embedded sensor hub aggregation requiring stable component supply and long-term lifecycle assurance.

Supply support for MC74AC125MG 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, logic, and discrete components for automotive, industrial, and cloud infrastructure markets.

The MC74AC125MG belongs to onsemi's 74AC logic family - engineered for high-speed, low-power CMOS operation in industrial and instrumentation applications where reliability across extended temperature ranges is critical.

FAQ

What is the maximum supply voltage for MC74AC125MG?

The MC74AC125MG has an absolute maximum DC supply voltage (VCC) rating of +6.5 V. However, its recommended operating range is 2.0 V to 6.0 V, with guaranteed performance at 3.0 V, 4.5 V, and 5.5 V. Operating above 6.0 V may exceed safe junction temperature limits and is not advised for sustained use. The MC74AC125MG must never be subjected to reverse supply polarity or transient overvoltage exceeding this limit.

Does MC74AC125MG support 3.3 V logic inputs while driving 5 V loads?

Yes, the MC74AC125MG accepts 3.3 V logic inputs reliably: at VCC = 5.0 V, its VIH is guaranteed ≥2.0 V and VIL ≤0.8 V, providing >1.3 V noise margin for 3.3 V CMOS signals. Its outputs swing rail-to-rail (VOH ≥4.4 V, VOL ≤0.1 V at ±24 mA), enabling direct interface to 5 V TTL loads without external level-shifting circuitry - a key design value confirmed in the DC Characteristics table on page 3 of the datasheet.

What is the function of the Bn pins on MC74AC125MG?

The Bn pins (pins 2, 5, 11, 14) are active-low enable inputs for each of the four buffer channels. When Bn is LOW, the corresponding An→On path is enabled (non-inverting pass-through); when Bn is HIGH, the output On enters high-impedance (Z) state. This allows independent 3-state control per channel - essential for bus arbitration, multiplexing, and preventing signal contention in shared-data-path architectures using the MC74AC125MG.

Is MC74AC125MG pin-compatible with MC74ACT125 variants?

Yes, MC74AC125MG and MC74ACT125 share identical pinout, package outline (SOIC-14), and functional truth table. The primary difference lies in input compatibility: MC74ACT125 has TTL-compatible inputs (VIH = 2.0 V min at VCC = 4.5 V), whereas MC74AC125MG uses standard CMOS thresholds. Both parts are mechanically interchangeable, but logic-level validation is required when substituting MC74AC125MG into ACT-designed circuits.

What thermal derating applies to MC74AC125MG in SOIC-14 package?

The MC74AC125MG in SOIC-14 (Case 751A) has a junction-to-air thermal resistance (θJA) of 116°C/W. At 25°C ambient, its maximum allowable power dissipation is 1077 mW. For continuous operation at 85°C ambient, power must be limited to ≤(150°C − 85°C)/116°C/W ≈ 560 mW to maintain TJ ≤150°C. This corresponds to average output loading below ±15 mA per channel under worst-case static conditions - a constraint explicitly defined in the Maximum Ratings table on page 2.