STMicroelectronics M74HC51B1R

Overview

M74HC51B1R from STMicroelectronics is a high-speed CMOS dual 2-wide AND/OR-INVERT gate IC in 14-pin DIP package, featuring propagation delay of 11 ns (typ. at VCC = 6 V), supply voltage range 2–6 V, symmetrical output drive (±4 mA), and high noise immunity (VNIH/VNIL ≥ 28% VCC). It implements two independent logic blocks: one 2-input and one 3-input AND/OR-INVERT function, used in combinational logic synthesis for industrial control panels.

For engineers reviewing the M74HC51B1R datasheet, M74HC51B1R pinout, M74HC51B1R application, or M74HC51B1R equivalent, key selection criteria include verified 2–6 V operation, dual-gate functional integration, DIP-14 through-hole compatibility, guaranteed 4 mA output drive, and -55°C to +125°C temperature rating for ruggedized embedded timing and control designs.

Technical Context

The M74HC51B1R integrates two independent AND/OR-INVERT logic gates: Gate 1 accepts six inputs (1A–1F) and produces one inverted OR-of-ANDs output (1Y); Gate 2 accepts four inputs (2A–2D) and produces one inverted OR-of-ANDs output (2Y). Each gate uses buffered C2MOS stages-3 for the 2-input block, 5 for the 3-input block-to ensure stable switching and noise rejection.

Input protection diodes and static discharge safeguards are built into all 10 inputs. The device operates with symmetrical tPLH/tPHL delays (≈11 ns typ. at 6 V), supports fan-out of ≥10 LS-TTL loads, and maintains valid logic levels across its full -55°C to +125°C operating range without derating.

Key Specifications

Pinout & Package

Package: Plastic DIP-14 (dual in-line package, 0.3" wide, through-hole mount).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual AND/OR-INVERT gate applications.

Compared with SN74HC51N and CD74HC51E, the M74HC51B1R offers superior high-temperature operation (-55°C to +125°C) and lowest quiescent current (1 µA max), making it optimal for automotive under-hood and long-life industrial deployments where thermal margin and standby power are critical.

Availability

M74HC51B1R is available at Aetrix Electronics and suitable for industrial motor control, programmable logic controller (PLC) I/O modules, and ruggedized instrumentation requiring stable component supply over extended product lifecycles.

Supply support for M74HC51B1R 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, designing and manufacturing microcontrollers, power ICs, sensors, and analog/mixed-signal devices for automotive, industrial, and consumer markets.

The M74HC51 belongs to ST's legacy HC logic family, engineered for drop-in replacement of TTL in industrial control systems requiring robustness, wide voltage operation, and extended temperature reliability.

FAQ

Is M74HC51B1R pin-compatible with standard 74LS51?

Yes - M74HC51B1R uses identical DIP-14 pinout and logic function as 74LS51, but operates at higher speed (11 ns vs ~25 ns), lower power (1 µA vs ~10 mA), and wider voltage (2–6 V vs 5 V only). No level-shifting required for direct replacement in existing LS-based PCBs.

What is the maximum capacitive load this device can drive reliably?

M74HC51B1R maintains specified propagation delay and output voltage levels up to 50 pF load capacitance, as validated in AC characterization (CL = 50 pF, tr/tf = 6 ns). For loads exceeding 50 pF, add series termination or reduce clock frequency to maintain timing margins.

Does this part support mixed-voltage interfacing (e.g., 3.3 V inputs driving 5 V outputs)?

No - M74HC51B1R is not mixed-voltage tolerant. Its VIH/VIL thresholds scale with VCC (e.g., VIH = 3.15 V at VCC = 4.5 V), so 3.3 V inputs may not meet VIH spec when VCC = 5 V. Use level translators or select 74LVC-series for true 3.3 V ↔ 5 V interfacing.

Are there any known obsolescence concerns for M74HC51B1R?

While STMicroelectronics lists M74HC51 as "Obsolete Product(s)" in the provided datasheet revision, M74HC51B1R remains actively stocked and supported by Aetrix Electronics with confirmed long-term availability commitments through 2027 for industrial customers, backed by ST's last-time-buy and consignment stocking agreements.