Texas Instruments SN74LVC821APWR

Overview

SN74LVC821APWR from Texas Instruments is a 10-bit bus-interface D-type flip-flop with 3-state outputs, designed for 1.65 V to 3.6 V operation. It features edge-triggered clocking on the positive CLK transition, buffered OE control for high-impedance output states, and mixed-mode I/O compatibility (5-V-tolerant inputs with 3.3-V VCC). It is used in bidirectional bus drivers with parity and wide buffer register implementations.

For engineers reviewing the SN74LVC821APWR datasheet, SN74LVC821APWR pinout, SN74LVC821APWR application, or SN74LVC821APWR equivalent, key selection considerations include its 10-bit synchronous latch function, 3.3-V supply compatibility, 5.5-V input tolerance, 7.3 ns max propagation delay at 3.3 V, and TSSOP-24 package footprint for space-constrained digital interface designs.

Technical Context

This device implements ten independent edge-triggered D-type flip-flops sharing a common clock (CLK) and output-enable (OE) signal. Each flip-flop captures data on the rising edge of CLK and drives true logic levels to its Q output unless OE asserts high-impedance state.

The Ioff partial-power-down feature disables outputs when VCC = 0 V, preventing current backflow in powered-down systems. Inputs accept up to 5.5 V regardless of VCC level, enabling direct interfacing between 3.3-V logic domains and legacy 5-V peripherals without level shifters.

Key Specifications

Pinout & Package

TSSOP-24 (PW) package: 4.4 mm × 5.1 mm body, 0.65 mm pitch, 1.2 mm max height, lead-free NIPDAU finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC821ADWR and SN74LVC821ADGVR, the SN74LVC821APWR offers the optimal balance of compact size (TSSOP), manufacturability (standard 0.65 mm pitch), and thermal performance for surface-mount production, making it the default choice for new 3.3-V digital interface designs.

Availability

SN74LVC821APWR is available at Aetrix Electronics and suitable for industrial PLC backplane interfaces, automotive body control module I/O expansion, and medical imaging data acquisition buffers requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for SN74LVC821APWR 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 high-reliability industrial and automotive-grade components.

The SN74LVC821A product line delivers scalable, voltage-flexible bus-interface logic for system-level interconnect - engineered specifically for robust mixed-voltage operation and seamless integration into 3.3-V digital subsystems.

FAQ

What is the maximum clock frequency supported by the SN74LVC821APWR?

The SN74LVC821APWR supports a maximum clock frequency of 150 MHz under recommended operating conditions (VCC = 3.3 V, TA = 25°C), verified by timing parameter fmax in the official TI datasheet SCAS304J. This rating assumes proper signal integrity, load capacitance ≤50 pF, and clean power delivery. At lower VCC (e.g., 1.8 V), the usable frequency decreases due to increased propagation delay.

Does the SN74LVC821APWR support 5-V input signals while operating at 3.3-V VCC?

Yes, the SN74LVC821APWR accepts input voltages up to 5.5 V regardless of VCC level (1.65–3.6 V), enabling direct interfacing with 5-V logic families without external level shifters. This mixed-mode capability is explicitly documented in the "Features" and "Recommended Operating Conditions" sections of the TI datasheet, and applies to all data (D) and control (CLK, OE) inputs.

How does the Ioff feature function in the SN74LVC821APWR?

The Ioff feature in the SN74LVC821APWR disables all outputs when VCC = 0 V, blocking current flow from live inputs into the unpowered device. This prevents damaging back-current during partial power-down scenarios - a requirement for hot-swap and modular system architectures. The specification confirms Ioff leakage ≤ ±10 µA when VI or VO = 5.5 V and VCC = 0 V.

What is the recommended pull-up resistor value for OE on the SN74LVC821APWR during power-up?

TI recommends tying OE to VCC through a pull-up resistor to ensure high-impedance outputs during power-up or power-down transients. The minimum resistor value depends on the driver's current-sinking capability; for standard CMOS drivers, 4.7 kΩ to 10 kΩ is typical. This ensures OE remains asserted (high) until system firmware actively drives it low, preventing bus contention.

Is the SN74LVC821APWR pin-compatible with other members of the SN74LVC821A family?

Yes, all SN74LVC821A variants - including SN74LVC821APWR, SN74LVC821ADWR, SN74LVC821ADGVR, and SN74LVC821ADBR - share identical pinouts and electrical functionality. Differences are limited to package type (TSSOP, SOIC, TVSOP, SSOP), thermal characteristics, and packaging format; no PCB layout changes are needed when substituting within the same package family.