NXP Semiconductors 74HC670DB,112

Overview

74HC670DB,112 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 in a single clock cycle, operates at 5 V supply, and delivers 23 ns typical Dn→Qn propagation delay under 15 pF load.

For engineers reviewing the 74HC670DB,112 datasheet, 74HC670DB,112 pinout, 74HC670DB,112 application, or 74HC670DB,112 equivalent, this device serves as a compact, bus-compatible register buffer for early-generation microprocessor support logic, data path staging, and small-scale FIFO emulation where deterministic timing and output isolation are required.

Technical Context

The 74HC670DB,112 implements a synchronous 16-bit register file organized as four 4-bit words, using Si-gate CMOS technology compliant with JEDEC 7A. Its dual-address architecture enables concurrent access without internal arbitration, and its 3-state outputs permit direct bus connection without external drivers.

Read operations are controlled by RE (active LOW) and RA/RB address selection; write operations require WE (active LOW) and WA/WB addressing. Data latching occurs on WE falling edge, and output transparency during write is maintained only while WE is LOW - no metastability window is specified, and latch time (tlatch) is defined as 25 ns min at VCC = 4.5 V.

Key Specifications

Pinout & Package

74HC670DB,112 is housed in a 16-pin SOIC (Small Outline Integrated Circuit) package, 3.9 mm wide, with 1.27 mm pitch and gull-wing leads. Pin 1 is marked by a bevelled corner or notch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HC670DB,112, the 74HCT670DB,112 offers improved input compatibility with older TTL systems at nearly identical timing, while the SN74ALS670N delivers faster propagation but demands strict 5 V supply and lacks CMOS power efficiency - making it unsuitable for mixed-voltage or low-power deployments.

Availability

74HC670DB,112 is available at Aetrix Electronics and suitable for microprocessor support logic, data path staging, FIFO emulation, and bus interface isolation requiring stable component supply across industrial control, test equipment, and legacy system repair programs.

Supply support for 74HC670DB,112 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 specializing in secure connectivity solutions for automotive, industrial, and IoT applications, with roots in Philips' pioneering logic IC development.

The 74HC670DB,112 belongs to the 74HC/HCT family of high-speed CMOS logic devices designed for pin-compatible migration from LSTTL systems while delivering lower power, wider supply range, and enhanced noise immunity.

FAQ

What is the maximum operating frequency supported by the 74HC670DB,112?

The 74HC670DB,112 does not specify a maximum clock frequency, as it is an asynchronous register file. Its usable data rate is determined by timing parameters: minimum write pulse width (tW) is 14 ns at VCC = 2.0 V, and propagation delays (e.g., Dn→Qn = 23 ns typ. at 5 V) define the shortest safe cycle interval. For reliable operation, ensure setup/hold times (tsu = 12 ns, th = 5 ns at 4.5 V) are met between WE and address/data edges. The 74HC670DB,112 is intended for use in systems where control timing is managed externally, not by a global clock.

Can the 74HC670DB,112 operate at 3.3 V supply voltage?

Yes, the 74HC670DB,112 supports VCC from 2.0 V to 6.0 V, including 3.3 V nominal operation. At 3.3 V, AC characteristics scale predictably: propagation delays increase (e.g., Dn→Qn max ≈ 75 ns at −40 to +125 °C), and output drive strength decreases relative to 5 V. Input thresholds remain CMOS-compatible (VIH ≈ 2.1 V, VIL ≈ 1.2 V at 3.3 V), ensuring interoperability with 3.3 V logic families. The 74HC670DB,112 maintains full functionality across this range without derating or configuration changes.

How does the 74HC670DB,112 handle simultaneous read and write to the same register location?

The 74HC670DB,112 does not guarantee predictable behavior when reading from and writing to the same register location concurrently. The datasheet specifies that data presented at Dn inputs is latched on the falling edge of WE, and outputs reflect the *previously latched* value until the next RE assertion. If RA/RB and WA/WB select identical addresses while WE is active, the output may reflect either the old or newly latched data depending on internal race conditions - the 74HC670DB,112 is not designed for atomic read-modify-write. Use separate addresses or external synchronization to avoid ambiguity.

Is the 74HC670DB,112 pin-compatible with the 74LS670?

No, the 74HC670DB,112 is not pin-compatible with the 74LS670. While both are 4×4 register files with similar functional intent, the 74LS670 uses a 24-pin DIP package with different pin assignments (e.g., separate chip select, clock, and output enable signals), whereas the 74HC670DB,112 uses a 16-pin SOIC with consolidated RE/WE enables and shared address lines. The 74HC670DB,112 is pin-compatible only with other members of the 74HC/HCT670 family (e.g., 74HCT670DB,112), not with bipolar TTL predecessors.

What is the purpose of the tlatch parameter in the 74HC670DB,112 datasheet?

The tlatch parameter (25 ns min at VCC = 4.5 V) specifies the minimum time required after the falling edge of WE for internal latches to fully settle before RA/RB or RE can reliably access the newly written data. It ensures that a read operation initiated immediately after a write will retrieve the correct updated value - critical when implementing tight-loop register updates. This timing constraint applies only when reading from the same location just written; the 74HC670DB,112 does not require tlatch delay for reads from other locations. Failure to observe tlatch may result in metastable or incorrect output.