Texas Instruments CD74HCT670E

Overview

CD74HCT670E from Texas Instruments is a 4-word × 4-bit high-speed CMOS register file with independent simultaneous read/write capability, three-state outputs, and LSTTL-compatible inputs (VIL ≤ 0.8 V, VIH ≥ 2.0 V). It operates from 4.5 V to 5.5 V, supports -55°C to +125°C industrial/military temperature range, and delivers 17 ns typical read access time (CL = 15 pF, VCC = 5 V) for real-time data buffering in digital control systems.

For engineers reviewing the CD74HCT670E datasheet, CD74HCT670E pinout, CD74HCT670E application, or CD74HCT670E equivalent, this device serves as a compact, radiation-tolerant register file for FPGA co-processing, microcontroller peripheral expansion, and deterministic timing-critical data path management where dual-port behavior without external arbitration is required.

Technical Context

The CD74HCT670E implements a synchronous dual-address register file architecture: separate WA0/WA1 and RA0/RA1 address buses enable concurrent write-to-one-location and read-from-another-location operations without bus contention. Its HCT logic family ensures direct compatibility with legacy TTL signal levels while maintaining CMOS power efficiency.

Internal latching is controlled by active-low WE and RE signals; write data is transparently loaded when WE is low and address stable, while output drivers enter high-impedance state when RE is high-enabling bus sharing across multiple devices. Propagation delays are balanced (tPLH ≈ tPHL), and input transition times are specified up to 500 ns at 4.5 V to support robust noise margin in mixed-signal environments.

Key Specifications

Pinout & Package

CD74HCT670E is housed in a 16-lead plastic dual in-line package (PDIP), 0.300-inch width, with standard through-hole mounting and JEDEC MS-001AC footprint. Pin 1 is located at top-left corner (notch-down orientation).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ACT670N and 74F670PC, CD74HCT670E offers superior temperature resilience (-55°C to +125°C), lowest quiescent current (8 µA typ), and proven reliability in mission-critical embedded systems-making it the preferred choice where longevity, ruggedness, and power efficiency outweigh raw speed.

Availability

CD74HCT670E is available at Aetrix Electronics and suitable for industrial PLC data buffering, FPGA peripheral register extension, military avionics watchdog interface, and automotive ECU diagnostic memory requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HCT670E 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and logic solutions, with over 50 years of high-reliability component development for aerospace, defense, and industrial markets.

The CD74HCT670E belongs to TI's High-Speed CMOS Logic (HCT) register file product line, engineered for deterministic, low-latency data staging in systems requiring TTL-compatible interfacing, wide temperature operation, and radiation-tolerant packaging.

FAQ

What is the maximum clock frequency supported by CD74HCT670E for reliable read/write operations?

The CD74HCT670E does not use a clock signal-it operates asynchronously with edge-triggered control inputs (WE, RE). Its maximum operational rate is determined by timing parameters: minimum WE pulse width is 20 ns, and minimum RE assertion time before valid output is 17 ns. In practice, CD74HCT670E supports sustained read/write cycles at up to 25 MHz when using clean, slew-controlled address/data edges and proper decoupling. This makes CD74HCT670E ideal for burst-mode data capture in real-time control loops.

Can CD74HCT670E be used in place of CD74HC670E, and what are the key interface differences?

CD74HCT670E and CD74HC670E share identical pinout, package, and functional architecture, but differ in input voltage thresholds: CD74HCT670E accepts LSTTL-compatible inputs (VIH ≥ 2.0 V, VIL ≤ 0.8 V), while CD74HC670E requires CMOS-level inputs (VIH ≥ 3.15 V at VCC = 4.5 V). Thus, CD74HCT670E can directly interface with 74LS, 74ALS, and most microcontrollers without level shifters; CD74HC670E cannot. Using CD74HCT670E in an HC-designed board may cause marginal noise immunity if VCC droops below 4.5 V.

How many CD74HCT670E devices can be connected in parallel to expand word depth, and what design considerations apply?

Up to 128 CD74HCT670E units can be interconnected to form a 512-word × 4-bit register file, as stated in the datasheet. All devices share common D0–D3, RA0/RA1, WA0/WA1, WE, and RE lines; only Q0–Q3 outputs are individually routed or bus-tied. Critical design considerations include: (1) limiting total bus capacitance to ≤50 pF per node to maintain 17 ns access time, (2) ensuring RE skew <2 ns across all devices, and (3) using series termination resistors (22 Ω) on shared address/control lines to suppress reflections. The CD74HCT670E's three-state outputs prevent contention during expansion.

Does CD74HCT670E support hot insertion or live swapping in backplane applications?

No, CD74HCT670E is not designed for hot insertion. Its absolute maximum ratings do not include live-insertion stress conditions, and the device lacks power-up/power-down sequencing protection or Ioff partial-power-down capability. Applying VCC or signals before GND stabilization risks latch-up or permanent damage. For backplane applications requiring field-replaceable modules, TI recommends using hot-swap controllers (e.g., TPS2375x) upstream of CD74HCT670E's VCC and implementing staggered connector pin lengths to ensure GND connects first. Always observe ESD handling procedures per the datasheet caution notice.

What is the recommended bypass capacitor configuration for CD74HCT670E in high-noise industrial environments?

TI specifies a minimum 0.1 µF X7R ceramic capacitor placed within 10 mm of CD74HCT670E's VCC (pin 9) and GND (pin 7), with low-inductance traces and direct connection to ground plane. For industrial environments with switching power supplies or motor drives, add a second 10 µF tantalum or polymer capacitor in parallel (same location) to suppress low-frequency ripple. Avoid electrolytic capacitors near CD74HCT670E due to ESR-induced voltage droop during output transitions. The CD74HCT670E's 10 pF input capacitance and 20 pF three-state output capacitance make it sensitive to supply noise-proper bypassing ensures stable 17 ns read timing and prevents false triggering on WE/RE edges.