Texas Instruments CY74FCT821BTSOC

Overview

CY74FCT821BTSOC from Texas Instruments is a 10-bit positive-edge-triggered bus-interface register with 3-state outputs, designed for high-capacitance load drive and low-bus-loading operation in 5-V TTL-compatible systems. It features 64-mA sink / 32-mA source drive, 7.5-ns propagation delay (tPLH/tPHL at CL = 50 pF), Ioff support for partial-power-down mode, and edge-rate control for improved noise immunity.

For engineers reviewing the CY74FCT821BTSOC datasheet, CY74FCT821BTSOC pinout, CY74FCT821BTSOC application, or CY74FCT821BTSOC equivalent, key selection criteria include 10-bit parallel data latching with output enable control, SOIC-24 package compatibility, TTL-level input/output interoperability, and industrial temperature range (–40°C to 85°C) suitability.

Technical Context

This device implements ten independent D-type flip-flops clocked on the low-to-high transition of CP, with synchronous 3-state output control via OE. Its Ioff circuitry actively disables outputs when VCC = 0 V, preventing backflow current during partial power-down.

Edge-rate control ensures matched rise/fall times and reduced switching noise, while input thresholds (VIH = 2 V min, VIL = 0.8 V max) and output voltage levels (VOH = 2.4 V min at –15 mA, VOL = 0.55 V max at 64 mA) guarantee full TTL logic compatibility and robust signal integrity across loaded buses.

Key Specifications

Pinout & Package

Package: SOIC-24 (DW), 7.5 mm × 15.4 mm body, 1.27 mm pitch, RoHS-compliant NIPDAU finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 10-bit bus-interface register applications.

Compared with CY74FCT821CTSOC (6 ns) and SN74FCT821ATSOC (10 ns), CY74FCT821BTSOC delivers a balanced trade-off of speed (7.5 ns), drive strength, and industrial temperature support-making it ideal for cost-sensitive, noise-immune bus interface applications where sub-6-ns timing is unnecessary.

Availability

CY74FCT821BTSOC is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, legacy bus buffering, automated test fixture control, and digital pattern generation requiring stable component supply and long-term lifecycle support.

Supply support for CY74FCT821BTSOC 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 delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

CY74FCT821BTSOC belongs to the FCT logic family, engineered specifically for high-drive, low-noise 5-V bus interfacing in industrial control and legacy system upgrades.

FAQ

What is the maximum clock frequency supported by CY74FCT821BTSOC?

CY74FCT821BTSOC does not specify a maximum clock frequency in its datasheet; instead, it defines minimum pulse width (tw = 6 ns) and setup/hold times (tsu = 3 ns, th = 1.5 ns). These parameters support reliable operation up to approximately 83 MHz in typical 50-pF load conditions, assuming proper PCB layout and signal integrity controls are applied to the CP net.

Does CY74FCT821BTSOC support hot insertion or live insertion?

CY74FCT821BTSOC supports partial-power-down via its Ioff feature, which disables outputs and limits current flow when VCC = 0 V. While this improves robustness during power sequencing, the device is not explicitly rated for hot insertion per IEEE 1394 or PCI standards. Safe live insertion requires external current-limiting and sequencing circuitry beyond CY74FCT821BTSOC's native capabilities.

What is the meaning of "FCT821B" marking on the CY74FCT821BTSOC package?

The top-side marking "FCT821B" on CY74FCT821BTSOC identifies the speed grade and family: "FCT" denotes the Fast CMOS Technology logic series, "821" is the base function number for 10-bit bus-interface registers, and "B" specifies the 7.5-ns propagation delay variant. This matches the ordering code CY74FCT821BTSOC and distinguishes it from "A" (10 ns) and "C" (6 ns) variants.

Can CY74FCT821BTSOC be used with 3.3-V microcontrollers?

CY74FCT821BTSOC operates exclusively from a 4.75–5.25-V supply and requires TTL-compatible input voltages (VIH ≥ 2 V, VIL ≤ 0.8 V). Direct connection to 3.3-V microcontrollers risks violating VIH min and may cause unreliable operation. A level-shifter or buffer such as SN74LVC245 is required to interface CY74FCT821BTSOC with 3.3-V logic domains.

Is CY74FCT821BTSOC pin-compatible with CY74FCT374-based designs?

Yes - CY74FCT821BTSOC is a 10-bit buffered extension of CY74FCT374 (8-bit), sharing identical pin functions for CP, OE, GND, and VCC. However, D/Y pin count differs (10 vs. 8), so direct replacement requires PCB layout modification. The functional interface (clock edge, 3-state control, TTL compatibility) remains consistent, easing migration in software and timing-critical logic design.