NXP Semiconductors 74HCT670N,652

Overview

74HCT670N,652 from NXP Semiconductors (formerly Philips) is a 4×4 3-state register file IC used for temporary data storage and parallel read/write operations in digital logic systems. It features independent read/write address inputs (RA/RB, WA/WB), dual 4-bit data paths (D0–D3, Q0–Q3), active-low RE/WE controls, and TTL-compatible input thresholds. It operates at 4.5 V to 5.5 V and supports simultaneous read-from-one-location/write-to-another in microcontroller peripheral interfaces and bus-oriented control logic.

For engineers reviewing the 74HCT670N,652 datasheet, 74HCT670N,652 pinout, 74HCT670N,652 application, or 74HCT670N,652 equivalent, key selection criteria include 3-state output timing (tPZH/tPHZ ≤ 53 ns at VCC = 4.5 V), write pulse width (tW ≥ 18 ns), set-up/hold times for Dn and WA/WB relative to WE, and compatibility with 74HCT logic families in bus-hold and multiplexed memory expansion designs.

Technical Context

The 74HCT670N,652 implements a 16-bit register file organized as four 4-bit words, enabling non-overlapping read and write cycles via separate address buses. Its dual-address architecture (RA/RB for read, WA/WB for write) allows concurrent access without internal arbitration logic.

It uses Si-gate CMOS technology with TTL-compatible input thresholds (VIH = 2.0 V min, VIL = 0.8 V max), 3-state outputs capable of bus driving, and operates across −40 °C to +125 °C. Propagation delays are specified at CL = 50 pF and VCC = 4.5 V, with tPHL/tPLH from RA/RB to Qn ≤ 50 ns (max) and from Dn to Qn ≤ 63 ns (max).

Key Specifications

Pinout & Package

74HCT670N,652 is supplied in a 16-pin plastic dual in-line package (DIP) with 0.3-inch body width and through-hole mounting. Pin spacing conforms to JEDEC MS-001.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HCT670N,652, the 74HC670N,652 offers wider supply range but reduced TTL interoperability, while SN74ALS670N delivers lower latency at the cost of power and bus-drive simplicity - making 74HCT670N,652 optimal for robust, mixed-logic bus interfaces requiring 3-state control and guaranteed 74LS compatibility.

Availability

74HCT670N,652 is available at Aetrix Electronics and suitable for industrial control panels, retro-computing hardware restoration, and embedded microcontroller peripheral interfaces requiring stable component supply over extended production lifecycles.

Supply support for 74HCT670N,652 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 74HCT670N,652 belongs to NXP's legacy 74HCT logic family, designed specifically for seamless integration with TTL-based systems while delivering CMOS power efficiency and noise immunity in industrial control and instrumentation.

FAQ

What is the operating temperature range for the 74HCT670N,652?

The 74HCT670N,652 is rated for operation from −40 °C to +125 °C. This extended industrial temperature range ensures reliable performance in demanding environments such as factory automation controllers, motor drives, and outdoor instrumentation where thermal cycling and ambient extremes are common. All AC and DC specifications in the Philips datasheet are validated across this full range.

Does the 74HCT670N,652 support simultaneous read and write to the same register location?

No, the 74HCT670N,652 does not guarantee correct behavior when reading from and writing to the same register location in the same cycle. The functional description explicitly states that the addressed location remains transparent to data while WE is LOW, and the latch time (tlatch) parameter defines the minimum delay required after WE goes HIGH before RA/RB may safely select that same location. Concurrent access to identical addresses must be avoided in system timing design.

What is the maximum capacitive load the 74HCT670N,652 outputs can drive?

The 74HCT670N,652 outputs are characterized for CL = 50 pF in AC testing, and its bus-driver capability supports standard TTL fan-out (up to 10 LSTTL loads). While not explicitly rated for higher capacitance, empirical use shows stable operation up to ~70 pF with acceptable timing margins at VCC = 4.5 V and Tamb = 25 °C. For loads exceeding 50 pF, verify setup/hold timing margins using the published tPZH/tPHZ and propagation delay specs.

Can the 74HCT670N,652 be used with a 3.3 V supply?

No, the 74HCT670N,652 is not specified for 3.3 V operation. Its absolute maximum VCC is 7.0 V, but the HCT family requires VCC ≥ 4.5 V to meet TTL-compatible input thresholds (VIH ≥ 2.0 V) and guaranteed output swing. At 3.3 V, input recognition fails and output VOH drops below 2.4 V, violating TTL interface requirements. Use 74LVC670 or similar 3.3 V logic for that voltage domain.

How is the 74HCT670N,652 pinout compatible with other 74-series logic devices?

The 74HCT670N,652 follows standard 16-pin DIP pinout conventions for register files and is pin compatible with the 74HC670 and 74HCT670 variants. Power (VCC, GND), data (D0–D3, Q0–Q3), and control (RE, WE, RA/RB, WA/WB) pins occupy identical positions across these parts, enabling direct substitution within the same family - provided voltage and timing constraints are met. No PCB layout change is needed for same-family upgrades.