NXP Semiconductors 74HC670D,653

Overview

74HC670D,653 from NXP Semiconductors is a 4 × 4-bit 3-state register file IC with independent read/write address inputs (RA/RB, WA/WB), dual enable controls (RE/WE), and true non-inverting outputs (Q0–Q3). It supports simultaneous read-from-one-location and write-to-another in high-speed CMOS logic, operates at 2–6 V supply, and delivers 23 ns D→Q propagation delay at 5 V with 15 pF load.

For engineers reviewing the 74HC670D,653 datasheet, 74HC670D,653 pinout, 74HC670D,653 application, or 74HC670D,653 equivalent, this device serves as a compact, expandable memory buffer for bus-oriented digital systems requiring deterministic timing, low-power MSI logic, and multi-device stacking without contention.

Technical Context

The 74HC670D,653 implements a synchronous 16-bit register file organized as four 4-bit words, with physically separated read and write address paths enabling concurrent access. Its dual 3-state output control (RE-active-Low) and write-enable (WE-active-Low) allow precise bus arbitration and latch transparency during write cycles.

It uses Si-gate CMOS technology compliant with JEDEC 7A, pin-compatible with LSTTL, and supports expansion via parallel address enable distribution or cascaded word-length stacking. Output drive capability meets bus-driver specifications, and internal latching behavior is defined by stable WA/WB during WE LOW and RE-controlled output impedance.

Key Specifications

Pinout & Package

74HC670D,653 is housed in a 16-pin SO16 (Small Outline) package per JEDEC MS-012, with 1.27 mm pitch and standard surface-mount footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HC670D,653, the 74HCT670D,653 offers seamless integration into TTL-mixed environments without level shifters, while the SN74ALS670N trades power efficiency and 3-state capability for raw speed in legacy 5 V-only systems - neither is pin-compatible with HC variants beyond shared logic function.

Availability

74HC670D,653 is available at Aetrix Electronics and suitable for microprocessor bus interface, digital signal processing buffer, and programmable logic controller I/O mapping requiring stable component supply and long-term industrial availability.

Supply support for 74HC670D,653 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

NXP Semiconductors is a global semiconductor leader focused on secure connectivity solutions for automotive, industrial, and IoT applications, with roots in Philips' pioneering logic IC development.

The 74HC/HCT670 family was designed to deliver scalable, low-power register file functionality for bus-oriented digital systems where deterministic timing, expandability, and 3-state bus sharing are essential - targeting embedded control and instrumentation markets.

FAQ

What is the operating voltage range for the 74HC670D,653?

The 74HC670D,653 operates from 2.0 V to 6.0 V, supporting both 3.3 V and 5 V logic domains. Its CMOS input thresholds scale with VCC, and output drive strength varies accordingly - full specification compliance is guaranteed across this range per JEDEC 7A, with AC parameters tested at 2.0 V, 4.5 V, and 6.0 V.

Does the 74HC670D,653 support true dual-port operation?

The 74HC670D,653 supports *functional* dual-port behavior via independent RA/RB and WA/WB address inputs, enabling simultaneous read and write to different 4-bit registers. However, it lacks physically separate read/write ports - both operations share the same Q0–Q3 outputs, which are controlled exclusively by RE, not by read address alone.

How does the 3-state output control work on the 74HC670D,653?

The 74HC670D,653 uses active-LOW RE (pin 11) to control output impedance: when RE = LOW, Q0–Q3 drive true data; when RE = HIGH, all outputs enter high-impedance (Z) state regardless of RA/RB or RE timing. This allows safe connection of multiple 74HC670D,653 devices to a common bus without external bus transceivers.

Can the 74HC670D,653 be used in asynchronous systems?

Yes - the 74HC670D,653 has no internal clock; all operations are level- and edge-sensitive (WE and RE are active-LOW enables). Write latching occurs on WE transition from HIGH to LOW (with stable WA/WB/Dn), and read output is combinatorial from RA/RB when RE = LOW. Timing margins must respect setup/hold and propagation delays specified in the datasheet.

What is the maximum clock frequency supported by the 74HC670D,653?

The 74HC670D,653 does not have a clock input and is not a clocked sequential device. Its maximum usable frequency depends on system-level timing constraints: for reliable D→Q transfer, minimum WE pulse width is 14 ns (typical at 5 V), and minimum cycle time between successive writes is governed by tW, tsu, and th - limiting practical throughput to ≤35 MHz in tightly timed applications.