Texas Instruments CY74FCT821BTPC

Overview

CY74FCT821BTPC from Texas Instruments is a 10-bit positive-edge-triggered D-type 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, I_off partial-power-down support, and 7.5-ns propagation delay (t_PLH/t_PHL) at 50-pF load - ideal for address/data bus buffering in industrial control backplanes.

For engineers reviewing the CY74FCT821BTPC datasheet, CY74FCT821BTPC pinout, CY74FCT821BTPC application, or CY74FCT821BTPC equivalent, key selection criteria include its 24-pin PDIP package, guaranteed 3.3-V typical V_OH, matched rise/fall times, edge-rate-controlled noise immunity, and compatibility with FCT/F/AM29821 logic families.

Technical Context

This device implements ten independent D-type flip-flops synchronized to the rising edge of CP, with output enable (OE) controlling simultaneous 3-state output assertion or high-impedance disable. Its I_off circuitry actively blocks current backflow when V_CC = 0 V, enabling safe partial-power-down operation in mixed-voltage systems.

The register uses FCT-family silicon with edge-rate control to suppress simultaneous switching noise, achieves TTL-level input thresholds (V_IL = 0.8 V, V_VIH = 2.0 V), and maintains full 5-V supply compatibility (V_CC = 4.75–5.25 V) while delivering reduced-noise output transitions and 10-pF typical input capacitance.

Key Specifications

Pinout & Package

24-pin plastic dual in-line package (PDIP), 0.600-inch body width, through-hole mounting. Pin 1 marked by notch or dot; pin 12 = GND, pin 24 = V_CC.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY74FCT821BTPC, the SOIC alternative offers better thermal dissipation and automated assembly compatibility, while the TSSOP version reduces board area by >60% but demands precision placement - all three share identical functional behavior, timing, and I/O electrical characteristics.

Availability

CY74FCT821BTPC is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus expansion, automated test equipment stimulus generation, and programmable logic controller I/O modules requiring stable component supply across extended temperature ranges.

Supply support for CY74FCT821BTPC 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 decades of experience in industrial-grade interface ICs.

CY74FCT821BTPC belongs to the FCT logic family - engineered for robust 5-V bus interfacing in electrically noisy, thermally demanding environments where signal integrity and power sequencing resilience are critical.

FAQ

What is the maximum clock frequency supported by CY74FCT821BTPC?

CY74FCT821BTPC supports a maximum operating clock frequency of approximately 133 MHz, derived from its 7.5-ns maximum propagation delay (t_PLH/t_PHL) under 50-pF load conditions. This assumes setup/hold time margins are met and system-level timing closure accounts for board trace delays and jitter. The device does not specify a minimum clock pulse width beyond the 6-ns minimum t_w requirement.

Does CY74FCT821BTPC support partial-power-down operation?

Yes, CY74FCT821BTPC includes I_off circuitry that disables outputs and limits current to ±1 µA when V_CC = 0 V, enabling safe partial-power-down operation. This feature prevents damaging back-current flow when CY74FCT821BTPC is powered off while other devices on the same bus remain active - a key requirement in modular industrial systems.

What is the purpose of the edge-rate control in CY74FCT821BTPC?

The edge-rate control in CY74FCT821BTPC intentionally slows output voltage transitions to reduce simultaneous switching noise (SSN) and electromagnetic interference (EMI). This design feature improves signal integrity on shared buses and mitigates ground bounce in high-pin-count PDIP packages, making CY74FCT821BTPC especially suitable for dense backplane and industrial control applications.

Can CY74FCT821BTPC be used with 3.3-V logic systems?

CY74FCT821BTPC is a 5-V-only device (V_CC = 4.75–5.25 V) and is not 3.3-V tolerant on inputs or outputs. While it accepts TTL-level inputs (V_IL ≤ 0.8 V, V_VIH ≥ 2.0 V), direct connection to 3.3-V CMOS outputs risks overvoltage damage. For mixed-voltage systems, level-shifting or translation buffers must be used between CY74FCT821BTPC and 3.3-V logic domains.

How does the 3-state output control work on CY74FCT821BTPC?

CY74FCT821BTPC uses an active-low output enable (OE) signal: when OE is low, registered data appears on Y0–Y9 outputs; when OE is high, all ten outputs enter high-impedance state regardless of CP or D inputs. This allows multiple CY74FCT821BTPC devices to share a common bus without contention, with OE coordinated via system-level control logic or address decoders.