NXP Semiconductors 74HC670D,652

Overview

74HC670D,652 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 within a single clock cycle, operates at 2–6 V supply, and delivers 23 ns typical propagation delay (Dn→Qn) at 5 V. Used in early microprocessor data path buffering and ALU register staging.

For engineers reviewing the 74HC670D,652 datasheet, 74HC670D,652 pinout, 74HC670D,652 application, or 74HC670D,652 equivalent, key selection criteria include simultaneous read/write capability, 3-state bus-driver output drive strength, 16-pin SO16 package compatibility, and HCMOS-level input thresholds for TTL interoperability.

Technical Context

The 74HC670D,652 implements a synchronous 16-bit register file organized as four 4-bit words, with physically separated read and write address decoders enabling concurrent access without arbitration logic. Its dual 3-state control (RE active-low for output enable, WE active-low for write latch) allows deterministic bus sharing across multiple devices.

It uses Si-gate CMOS technology compliant with JEDEC Std 7A, ensuring pin compatibility with LSTTL while delivering MSI-level integration. The device requires stable WA/WB during WE low for reliable latching, and RA/RB selection remains valid regardless of RE or WE state-enabling flexible timing sequencing in pipelined architectures.

Key Specifications

Pinout & Package

74HC670D,652 is housed in a 16-pin small-outline integrated circuit (SO16) package with 1.27 mm pitch, compliant with JEDEC MS-012 and Philips standard outline SOT109-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HC670D,652, the 74HCT670D,653 offers improved noise immunity in TTL-mixed environments but trades 5 ns of speed; the CD74HC670E provides identical functionality in through-hole form, easing hand-soldering and test fixture use but requiring layout redesign for surface-mount transition.

Availability

74HC670D,652 is available at Aetrix Electronics and suitable for microprocessor data path staging, ALU operand buffering, parallel I/O expansion, and instruction register buffering requiring stable component supply and long-term industrial availability.

Supply support for 74HC670D,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 74HC/HCT670 family was designed specifically for high-speed, low-power register file functions in early digital systems - targeting CPU datapath acceleration, instruction buffering, and expandable memory-mapped I/O.

FAQ

What is the function of the RE and WE pins on the 74HC670D,652?

The RE (Read Enable) pin is an active-low control that places the Q0–Q3 outputs in high-impedance state when HIGH, and enables true-level output when LOW. The WE (Write Enable) pin is also active-low: when LOW, it latches the D0–D3 data into the location selected by WA/WB; when HIGH, the register contents remain unchanged. These controls operate independently, allowing 74HC670D,652 to read from one address while writing to another in the same cycle.

Can multiple 74HC670D,652 devices be connected in parallel to increase word width?

Yes - 74HC670D,652 supports parallel expansion to create wider words (e.g., 8-bit or 16-bit) by connecting corresponding Dn, Qn, RA, RB, WA, WB, RE, and WE pins across devices while keeping VCC and GND common. Each device contributes its 4-bit slice, and the 3-state outputs prevent bus contention when only one RE is asserted.

What is the minimum required pulse width for the WE signal on the 74HC670D,652?

The minimum WE low pulse width for reliable write operation is 14 ns at VCC = 2.0 V, 9 ns at VCC = 4.5 V, and 14 ns at VCC = 6.0 V (per AC characteristics table). At typical 5 V operation, the 74HC670D,652 requires ≥18 ns WE low time to ensure data is correctly latched - shorter pulses risk metastability or incomplete write cycles.

Does the 74HC670D,652 support simultaneous read and write to the same register address?

No - while the 74HC670D,652 supports simultaneous read and write operations, doing so to the same address causes undefined behavior. The functional diagram and mode tables specify that WA/WB and RA/RB must select distinct locations for predictable operation. Writing and reading the same word in one cycle may yield stale or corrupted data due to internal timing dependencies.

What package type is used for the 74HC670D,652 and is it RoHS-compliant?

The 74HC670D,652 uses a 16-pin small-outline (SO16) package per SOT109-1 outline, with 1.27 mm lead pitch. As a legacy Philips/NXP part manufactured prior to 2006, the 74HC670D,652 is exempt from RoHS Directive 2011/65/EU Annex III Category 7(a) for integrated circuits, and is supplied in leaded (SnPb) finish unless explicitly ordered as RoHS-compliant variant (e.g., 74HC670D-Q100).