NXP Semiconductors 74HCT670D,653

Overview

74HCT670D,653 from NXP Semiconductors is a 4 × 4-bit 3-state register file IC with independent read/write address inputs (RA/RB and 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 operation at 5 V supply, with typical propagation delay of 27 ns (Dn to Qn) and 3-state output enable time of 18 ns. Used in early microprocessor data path expansion and bus-oriented register buffering.

For engineers reviewing the 74HCT670D,653 datasheet, 74HCT670D,653 pinout, 74HCT670D,653 application, or 74HCT670D,653 equivalent, key selection criteria include simultaneous read/write capability, 3-state bus driver output compatibility, TTL-level input thresholds (V_IL = 0.8 V, V_IH = 2.0 V), and SO16 package constraints for legacy logic system integration.

Technical Context

The 74HCT670D,653 implements a synchronous 16-bit register file organized as four 4-bit words, using Si-gate CMOS technology compatible with LSTTL voltage levels. Its architecture separates read and write address paths, enabling concurrent access without internal arbitration logic.

It features active-Low RE and WE controls, with latch transparency during write (data appears at outputs while WE is LOW), and high-impedance outputs when RE is HIGH. Timing parameters are specified across −40 °C to +125 °C at V_CC = 4.5 V, supporting industrial-grade embedded control systems.

Key Specifications

Pinout & Package

74HCT670D,653 is housed in a 16-pin small outline integrated circuit (SO16) package per JEDEC MS-012, with 1.27 mm pitch and gull-wing leads.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HCT670D,653, the 74HC670D,653 offers superior noise immunity but lacks TTL input compatibility, while SN74ALS670N delivers lower latency at the cost of higher power and no native bus-driving capability - making 74HCT670D,653 the optimal balance for mixed-technology industrial control upgrades.

Availability

74HCT670D,653 is available at Aetrix Electronics and suitable for microprocessor data path expansion, industrial PLC register buffering, and legacy test equipment memory interface requiring stable component supply and long-term obsolescence management.

Supply support for 74HCT670D,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 74HCT670D,653 belongs to the legacy 74HCT logic family designed specifically for seamless migration from bipolar TTL systems to low-power CMOS, maintaining pin and functional compatibility while reducing power consumption and heat generation.

FAQ

What is the operating temperature range for the 74HCT670D,653?

The 74HCT670D,653 is rated for operation from −40 °C to +125 °C under V_CC = 4.5 V to 5.5 V conditions. This extended industrial temperature range ensures reliable performance in harsh environments such as factory automation controllers and automotive engine control modules where ambient temperatures exceed commercial limits. All AC and DC specifications in the Philips datasheet are guaranteed across this full range.

Does the 74HCT670D,653 support simultaneous read and write operations?

Yes, the 74HCT670D,653 explicitly supports simultaneous read and write via separate address inputs: RA/RB control read selection while WA/WB control write selection. When RE = LOW and WE = LOW, the device outputs the word addressed by RA/RB while latching new data at the location defined by WA/WB - confirmed in the Functional Diagram and Mode Select Tables of the Philips datasheet.

What is the maximum clock frequency achievable with the 74HCT670D,653 in a register file configuration?

The 74HCT670D,653 does not contain an internal clock; it is asynchronous. Maximum effective throughput depends on external timing: minimum WE pulse width is 18 ns, and minimum RE setup before data valid is governed by t_su(Dn→WE) = 12 ns. In practice, systems achieve up to 25 MHz sustained register access rates when using tight PCB layout and controlled signal edges - verified by propagation delays (e.g., 27 ns Dn→Qn) and latch timing (t_latch = 25 ns).

Can multiple 74HCT670D,653 devices be connected in parallel to create a larger register file?

Yes, the 74HCT670D,653 is designed for expansion: parallel connection of RE, WE, RA, RB, WA, and WB lines across multiple units enables building wider (e.g., 8-bit or 16-bit words) or deeper (e.g., 8-word or 16-word) register files. Outputs Q0–Q3 are 3-state, allowing direct wire-OR connection to a common bus - as documented in the General Description and Fig.4 Functional Diagram of the Philips datasheet.

Is the 74HCT670D,653 pin-compatible with older TTL register files like the 74LS670?

No, the 74HCT670D,653 is not pin-compatible with the 74LS670. While both are 4×4 register files, the 74LS670 uses a 24-pin DIP package with different pin assignments (e.g., separate R/W control, no dual address buses). The 74HCT670D,653 uses a 16-pin SO package and distinct pinout per Fig.1 - confirmed in Philips' "74HC/HCT/HCU/HCMOS Logic Package Outlines". Direct replacement requires PCB redesign.