STMicroelectronics M74HC125B1R

Overview

M74HC125B1R from STMicroelectronics is a high-speed CMOS quad 3-state bus buffer with independent enable control per channel, operating from 2V to 6V supply, delivering 8ns typical propagation delay at 6V and ±6mA symmetrical output drive, widely used in bidirectional bus isolation and data routing in industrial control logic systems.

For engineers reviewing the M74HC125B1R datasheet, M74HC125B1R pinout, M74HC125B1R application, or M74HC125B1R equivalent, key selection criteria include 3-state output timing (tPZL/tPLZ), input noise immunity (28% VCC), quiescent current (4μA max), and DIP-14 package compatibility with legacy 74-series designs.

Technical Context

The M74HC125B1R implements four independent non-inverting buffers, each with a dedicated active-low enable input (G) that places the corresponding Y output into high-impedance state when asserted high. All inputs feature ESD protection circuits compliant with IEC 61000-4-2.

It uses silicon gate C2MOS technology for low power consumption and rail-to-rail output swing. Propagation delays are balanced (tPLH ≅ tPHL), and output impedance is symmetrical (|IOH| = IOL ≥ 6mA), enabling clean signal integrity in shared-bus environments across -55°C to +125°C operating range.

Key Specifications

Pinout & Package

Package: Plastic DIP-14 (Dual In-line Package, 0.3" width), JEDEC MS-001, lead finish Sn/Pb.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC125N and MC74HC125ANG, the M74HC125B1R offers superior noise immunity (28% vs. 20% VCC), lower quiescent current (4μA vs. 8μA), and extended temperature support (-55°C to +125°C), making it preferred for mission-critical industrial and automotive control layers.

Availability

M74HC125B1R is available at Aetrix Electronics and suitable for industrial PLC backplanes, automotive body control modules, and test equipment signal routing requiring stable component supply and long-term obsolescence management.

Supply support for M74HC125B1R 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, digital, and mixed-signal ICs for industrial, automotive, and consumer markets.

The M74HC125B1R belongs to ST's high-speed HC logic family, engineered for low-power, high-noise-immunity bus interface applications in harsh environments where reliability and longevity are critical.

FAQ

What is the maximum clock frequency supported by M74HC125B1R in a bus-switching application?

The M74HC125B1R is not a clocked device but a combinational buffer; its usable frequency depends on propagation delay and load. With 8ns typical tPD and 50pF load, it supports clean signal edges up to ~50MHz in point-to-point routing. For bus multiplexing, system-level timing must account for worst-case tPLZ (120ns) and tPZL (110ns) to avoid contention.

Can M74HC125B1R operate reliably at 2.0V supply voltage?

Yes - the device is fully specified from 2.0V to 6.0V. At 2.0V, VOH is guaranteed ≥1.9V and VOL ≤0.1V with 20μA load, and tPD increases to 75ns (max). Input thresholds scale proportionally (VIH = 1.5V min), ensuring robust logic discrimination even at minimum VCC.

Is there a RoHS-compliant version of M74HC125B1R?

The M74HC125B1R is an obsolete part marked "Obsolete Product(s)" in the official ST datasheet (Rev. August 2001). ST replaced it with RoHS-compliant variants like M74HC125M1R (SO-14) and M74HC125TTR (TSSOP-14), which share identical logic and AC/DC specs but use lead-free terminations and green molding compound.

How does the 3-state enable behavior differ between M74HC125B1R and 74LS125?

M74HC125B1R uses active-high enable (G = HIGH → high-Z), matching 74LS125 pinout and function. However, HC logic draws μA-level ICC versus mA-level for LS, and HC outputs swing rail-to-rail (VOH = VCC – 0.1V), unlike LS (VOH ≈ 3.4V at 5V), enabling direct interfacing with modern CMOS loads without pull-ups.