STMicroelectronics M74HC670B1R

Overview

M74HC670B1R from STMicroelectronics is a high-speed CMOS 4-word × 4-bit register file with 3-state outputs, fabricated in silicon gate C²MOS technology. It supports simultaneous read/write via independent address and enable inputs, delivers 22 ns typical propagation delay at 6 V, draws ≤4 µA quiescent current, and operates across 2–6 V supply. It is used in digital logic systems requiring compact, low-power data storage with bus-sharing capability.

For engineers reviewing the M74HC670B1R datasheet, M74HC670B1R pinout, M74HC670B1R application, or M74HC670B1R equivalent, key selection criteria include its 4×4 register architecture, separate read/write address control, 3-state output enable timing (tPZL/tPLZ), symmetrical drive strength (±4 mA), and compatibility with standard 74-series register file logic interfaces.

Technical Context

The M74HC670B1R implements a synchronous, dual-port register file with fully independent read and write paths: RA/RB select one of four 4-bit words for readout, while WA/WB select the target word for write operations. All address and control inputs (RE, WE) are edge-triggered and internally synchronized to avoid metastability during concurrent access.

Its 3-state outputs are controlled by RE (active-low read enable) and inherently tri-stated when WE is high; output impedance exceeds 10⁶ Ω in high-impedance mode. The device uses Schmitt-trigger input buffers for noise immunity (VNIH/VNIL ≥28% VCC) and includes ESD protection on all pins per IEC 61000-4-2 Level 2.

Key Specifications

Pinout & Package

Package: Plastic DIP-16 (0.300 inch width), JEDEC MS-001, body dimensions 20.0 × 8.5 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 4×4 register file applications.

Compared with the M74HC670B1R, the 74HC670N offers identical functionality with minor leakage improvements for automotive use, while the SN74LV670ADW trades 6 V operation for speed and 3.3 V optimization-making it unsuitable for legacy 5 V or mixed-rail systems.

Availability

M74HC670B1R is available at Aetrix Electronics and suitable for microcontroller peripheral interface, digital signal processing buffer, and industrial PLC I/O mapping requiring stable component supply and long-term obsolescence management.

Supply support for M74HC670B1R 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, specializing in automotive, industrial, and power discrete solutions with over 40 years of analog and digital IC innovation.

The M74HC670B1R belongs to ST's legacy HC logic family, designed specifically for high-reliability, low-power register file applications in industrial control, test equipment, and retro-computing system upgrades.

FAQ

What is the maximum clock frequency supported by the M74HC670B1R?

The M74HC670B1R does not use a clock signal; it is an asynchronous register file. Its maximum operating frequency is determined by the minimum pulse width of WE (3 ns min at 6 V) and setup/hold times (3 ns setup, 5 ns hold). In practice, this supports reliable operation up to ~45 MHz for tightly controlled address/data/enable timing sequences.

Can M74HC670B1R outputs drive multiple 74HC inputs directly?

Yes. With IOL/IOH ≥ ±4 mA and 74HC input current ≤1 µA, each output can drive at least 2000 74HC loads. However, capacitive loading (CL > 50 pF) increases propagation delay and transition time; for >10 loads, add series termination or buffer amplification to maintain timing margins.

Is the M74HC670B1R still in active production?

No. STMicroelectronics has marked the M74HC670B1R as obsolete (as noted in the datasheet footer). Aetrix Electronics maintains legacy inventory and provides last-time-buy support, including full traceability, extended warranty, and cross-reference assistance for functional replacements like the 74HC670N or SN74LV670ADW.

How does the 3-state output behavior interact with RE and WE signals?

Outputs Q1–Q4 go high-impedance when RE = H, regardless of WE state. When RE = L, outputs reflect the selected word's contents - unless WE = L and a write is active, in which case outputs remain stable (not updated) until the next RE assertion. This allows clean bus sharing without output contention during writes.