Texas Instruments SN74LVC821ADWE4

Overview

SN74LVC821ADWE4 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 V_CC operation. It features edge-triggered clocking on the positive CLK transition, buffered output-enable (OE) control, and supports mixed-mode signal operation with 5-V-tolerant inputs. It is used in I/O port expansion, bidirectional bus driving with parity, and wide buffer register applications.

For engineers reviewing the SN74LVC821ADWE4 datasheet, SN74LVC821ADWE4 pinout, SN74LVC821ADWE4 application, or SN74LVC821ADWE4 equivalent, key selection considerations include its 10-bit synchronous latch function, 3-state drive capability (±24 mA at 3 V), 7.3 ns max propagation delay at 3.3 V, I_off partial-power-down support, and compatibility with both 3.3-V and 5-V input systems.

Technical Context

This device implements ten independent edge-triggered D-type flip-flops sharing a common clock (CLK) and output-enable (OE) control. Each flip-flop captures data on the rising edge of CLK and presents true outputs at Q pins. OE operates asynchronously to place all ten Q outputs simultaneously into high-impedance or active logic states without affecting internal latch operation.

The SN74LVC821ADWE4 uses LVC-series CMOS technology with 5-V-tolerant inputs, enabling direct interfacing between 3.3-V logic domains and legacy 5-V peripherals. Its I_off circuitry actively disables outputs during power-down to prevent backflow current, and its low ground bounce (<0.8 V) and undershoot (>2 V) ensure signal integrity in high-speed, capacitive bus environments.

Key Specifications

Pinout & Package

TSSOP-24 (PW) package: 4.4 mm × 5.0 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 SN74LVC821APWR, SN74LVC821ADWE4 offers identical functionality in tube packaging for flexibility in evaluation and small-batch integration; compared with SN74LVCH162374ADGGR, it provides verified 5-V-tolerant operation and simpler single-supply control, making it preferable for cost-sensitive, mixed-voltage 10-bit bus applications.

Availability

SN74LVC821ADWE4 is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, automotive body control module interfaces, and server backplane data buffering requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for SN74LVC821ADWE4 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 interface and timing products.

The SN74LVC821ADWE4 belongs to TI's LVC logic family, engineered for low-voltage, high-speed bus interface applications where mixed-voltage compatibility, low power, and robust noise immunity are essential in industrial and automotive systems.

FAQ

What is the maximum clock frequency supported by the SN74LVC821ADWE4?

The SN74LVC821ADWE4 supports a maximum clock frequency of 150 MHz under recommended operating conditions (V_CC = 3.3 V, T_A = 25°C). This is derived from its minimum clock pulse width (3.3 ns) and verified timing characteristics in the official datasheet. The SN74LVC821ADWE4 achieves this performance while maintaining setup (1.9 ns) and hold (1.5 ns) timing margins essential for reliable synchronous operation.

Does the SN74LVC821ADWE4 support 5-V input signals while operating at 3.3-V V_CC?

Yes, the SN74LVC821ADWE4 supports 5-V-tolerant inputs - its VI rating extends to 5.5 V regardless of V_CC level. This allows direct connection to 5-V drivers in mixed-voltage systems without external level shifters. The SN74LVC821ADWE4 maintains full logic functionality and timing specifications when V_CC is 3.3 V and inputs swing from 0 V to 5 V, as confirmed in the "Recommended Operating Conditions" table.

How does the I_off feature work in the SN74LVC821ADWE4?

The I_off circuitry in the SN74LVC821ADWE4 automatically disables all outputs when V_CC = 0 V, limiting input/output leakage to ±10 µA even if signals up to 5.5 V remain present. This prevents damaging backflow current during partial power-down or hot-swap events. The SN74LVC821ADWE4 retains this protection across its full –40°C to 85°C operating range, making it suitable for systems requiring graceful power sequencing.

What is the output drive strength of the SN74LVC821ADWE4 at 3.3-V V_CC?

At V_CC = 3.3 V, the SN74LVC821ADWE4 delivers ±24 mA output drive strength (I_OH/I_OL). Specifically, it sources –24 mA with V_OH ≥ 2.2 V and sinks 24 mA with V_OL ≤ 0.55 V. This high drive capability enables direct interfacing with high-capacitance buses or multiple TTL loads without external buffers, a key design advantage confirmed in the Electrical Characteristics table.

Is the SN74LVC821ADWE4 pin-compatible with other packages in the same family?

Yes, the SN74LVC821ADWE4 (TSSOP-24) shares identical pinout and functionality with other SN74LVC821A variants including SOIC-24 (DW), SSOP-24 (DB), and TVSOP-24 (DGV) packages. All variants use the same 24-pin assignment: pins 1–10 = D inputs, pin 11 = OE, pin 12 = GND, pin 13 = V_CC, pins 14–23 = Q outputs, pin 24 = CLK. This uniformity allows direct PCB footprint substitution across package types without redesign.