STMicroelectronics M74HC42B1R

Overview

M74HC42B1R from STMicroelectronics is a high-speed CMOS BCD-to-decimal decoder in 16-pin DIP package, operating from 2V to 6V supply, with typical propagation delay of 14ns at 6V, symmetrical output drive (±4mA), and guaranteed low-power quiescent current ≤4µA at 25°C. It decodes four BCD inputs (A–D) to ten active-low decimal outputs (Y0–Y9), supporting code conversion, address decoding, and memory selection in industrial control panels.

For engineers reviewing the M74HC42B1R datasheet, M74HC42B1R pinout, M74HC42B1R application, or M74HC42B1R equivalent, key selection criteria include its 2–6V wide VCC range, ±4mA output drive capability, 14ns typical tPD, high noise immunity (28% VCC), and compatibility with legacy 74-series 42 logic functions.

Technical Context

The M74HC42B1R implements a fixed-function BCD-to-10-line decoder using silicon gate C2MOS technology, with all inputs protected against ESD and transient overvoltage. Its logic behavior is defined by a truth table where only one output goes low per valid BCD input (0–9); invalid codes (10–15) force all outputs high.

It supports dual-mode operation: as a standard BCD decoder when all four inputs are used, or as a 3-to-8 line decoder with D input serving as an enable/disable control. Propagation delays tPLH and tPHL are balanced (tPLH ≅ tPHL), and output impedance is symmetrical for sourcing and sinking.

Key Specifications

Pinout & Package

Package: Plastic DIP-16 (0.300″ wide), 16-pin through-hole, JEDEC MS-001 compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar BCD-to-decimal decoder applications.

Compared with SN74HC42N and 74HCT42N, the M74HC42B1R offers superior temperature range (−55°C to +125°C), lowest quiescent current (≤4µA), and fastest propagation (14ns typ.), making it optimal for ruggedized industrial and automotive control modules where reliability and timing precision are critical.

Availability

M74HC42B1R is available at Aetrix Electronics and suitable for industrial PLC I/O modules, legacy microcontroller address decoding, seven-segment display drivers, and test equipment front-panel logic requiring stable component supply across extended temperature ranges.

Supply support for M74HC42B1R 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 power applications.

The M74HC42B1R belongs to ST's high-speed CMOS logic family, engineered specifically for reliable, low-power decoding in harsh-environment control systems where timing accuracy and long-term stability are essential.

FAQ

What is the maximum clock frequency supported by M74HC42B1R?

The M74HC42B1R is a combinational logic device with no internal clock; its usable switching frequency depends on propagation delay and system timing margins. With 14ns typical tPD at 6V, it supports input transition rates up to approximately 35MHz in well-designed layouts with controlled trace lengths and proper decoupling.

Can M74HC42B1R drive LEDs directly?

Yes - each output can sink up to 4mA continuously (min), sufficient to drive low-current indicator LEDs with appropriate series resistors. For example, at VCC = 5V and VOL = 0.26V, a 1.2kΩ resistor yields ~3.9mA LED current while staying within absolute max ratings.

Is M74HC42B1R compatible with 3.3V microcontrollers?

Yes - its VIH threshold is 1.5V (min) at VCC = 2V and scales with supply, ensuring reliable recognition of 3.3V logic-high signals across its full 2–6V operating range. No level-shifting circuitry is required for interfacing with 3.3V MCUs.

Does M74HC42B1R have power-on reset or initialization behavior?

No - it is purely combinational logic with no internal state or reset function. Outputs reflect instantaneous input states after propagation delay. To ensure known initial states, external power-on reset circuitry or firmware-controlled input initialization is required.