Texas Instruments CY74FCT399CTSOC

Overview

CY74FCT399CTSOC from Texas Instruments is a high-speed quad 2-input register IC that selects four bits of data from either of two input sources (I0X/I1X) under control of a common select (S) input and latches them synchronously on the rising edge of clock (CP). It features noninverted outputs, 6.1 ns propagation delay (tPLH/tPHL), 64 mA sink / 32 mA source drive strength, Ioff partial-power-down support, and SOIC-16 packaging. It is used in bus multiplexing and data routing applications within industrial control logic systems.

For engineers reviewing the CY74FCT399CTSOC datasheet, CY74FCT399CTSOC pinout, CY74FCT399CTSOC application, or CY74FCT399CTSOC equivalent, this page provides verified functional identity, timing behavior, drive capability, power-down behavior, and validated alternative options for logic-level compatible register replacement in TTL/5V CMOS hybrid systems.

Technical Context

The CY74FCT399CTSOC implements four independent D-type flip-flops, each with dual-data inputs (I0X, I1X) and a shared select (S) line to choose between sources before clocked registration. Its output register is fully edge-triggered on CP's low-to-high transition, requiring only 3.5 ns setup time for data inputs and 8.5 ns for S relative to CP↑.

It integrates edge-rate control circuitry to reduce switching noise, supports TTL-compatible input thresholds (VIL = 0.8 V, VIH = 2.0 V), and delivers rail-aligned VOH (3.3 V typical at IOH = –15 mA) and VOL (0.55 V max at IOL = 64 mA) under 4.75–5.25 V supply. Ioff protection disables outputs when VCC = 0 V, limiting backflow current to ±1 µA.

Key Specifications

Pinout & Package

Package: SOIC-16 (DW), 7.5 mm × 10.3 mm body, 1.27 mm pitch, 2.65 mm max height, RoHS-compliant NIPDAU finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad 2-input register applications.

Compared with CY74FCT399CTSOC, SN74FCT399CTSO offers identical functionality and drop-in replacement capability, while 74AC399PC trades Ioff and TTL compatibility for broader voltage operation and marginal speed gain - making it unsuitable for industrial hot-swap or legacy TTL integration scenarios.

Availability

CY74FCT399CTSOC is available at Aetrix Electronics and suitable for industrial control logic, factory automation I/O hubs, and legacy system data routing requiring stable component supply, long-term lifecycle continuity, and guaranteed RoHS-compliant SOIC-16 sourcing.

Supply support for CY74FCT399CTSOC 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 innovation in industrial, automotive, and communications markets.

The CY74FCT399CTSOC belongs to TI's FCT logic family, designed specifically for high-speed, low-noise, TTL-compatible 5V digital interfacing in industrial and telecom infrastructure where reliability, noise immunity, and power-down safety are critical.

FAQ

What is the maximum clock frequency supported by the CY74FCT399CTSOC?

The CY74FCT399CTSOC has a maximum propagation delay of 6.1 ns (tPLH/tPHL), supporting reliable operation up to approximately 160 MHz in ideal conditions. However, actual maximum frequency depends on setup/hold timing margins, load capacitance, and PCB layout - TI recommends limiting clock rates to ≤125 MHz for robust margin in industrial environments with 50 pF loads.

Does the CY74FCT399CTSOC support partial power-down mode?

Yes, the CY74FCT399CTSOC supports partial power-down mode via its Ioff feature. When VCC = 0 V, the outputs are actively disabled, limiting backflow current to ±1 µA even if driven by external signals at up to 4.5 V - a key requirement for hot-swap and mixed-supply system designs.

Is the CY74FCT399CTSOC pin-compatible with standard 74FCT399 devices?

Yes, the CY74FCT399CTSOC is fully pin-compatible and functionally identical to other 74FCT399 variants including SN74FCT399CTSO and CY74FCT399ATSOC. All share the same SOIC-16 pinout, timing behavior, and DC specifications - differing only in speed grade (6.1 ns vs. 7 ns) and temperature range (-40°C to 85°C).

What are the input voltage thresholds for TTL compatibility in the CY74FCT399CTSOC?

The CY74FCT399CTSOC guarantees TTL-compatible input thresholds: VIH ≥ 2.0 V (minimum high-level input voltage) and VIL ≤ 0.8 V (maximum low-level input voltage) across the full operating temperature range. This allows direct interfacing with standard 74LS, 74ALS, and other TTL-family outputs without level-shifting circuitry.

Can the CY74FCT399CTSOC drive multiple TTL loads directly?

Yes, the CY74FCT399CTSOC can drive multiple TTL loads directly: its 64 mA sink and 32 mA source output drive strength meets or exceeds the fanout requirements of standard TTL (74LS) inputs. Each output can reliably drive up to 10 LS-TTL loads (20 µA IH, 0.4 mA IL) without external buffers.