Texas Instruments SN74LVC821ADWR

Overview

SN74LVC821ADWR 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, Ioff partial-power-down support, 5.5 V-tolerant inputs, 7.3 ns max propagation delay at 3.3 V, and is used in bidirectional bus drivers and I/O port buffering in mixed-voltage systems.

For engineers reviewing the SN74LVC821ADWR datasheet, SN74LVC821ADWR pinout, SN74LVC821ADWR application, or SN74LVC821ADWR equivalent, this page delivers verified electrical specs, SOIC-24 package mapping, functional role in bus isolation, and validated alternative options for 10-bit latch-based interface design.

Technical Context

This device implements ten independent positive-edge-triggered D-type flip-flops with a shared clock (CLK) and buffered output-enable (OE) control. All ten Q outputs enter high-impedance state when OE is high, enabling bus sharing without pull-ups or interface components.

It supports mixed-mode signal operation: inputs accept up to 5.5 V while operating from 1.65–3.6 V VCC, allowing direct interfacing between 3.3-V logic and legacy 5-V peripherals. Ioff circuitry prevents backflow current during partial power-down, meeting JESD 78 latch-up and JESD 22 ESD requirements.

Key Specifications

Pinout & Package

SN74LVC821ADWR is housed in a 24-pin SOIC (DW) package, 7.5 mm × 15.4 mm body size, 1.27 mm pitch, with gull-wing leads and RoHS-compliant NiPdAu finish. MSL Level-1 rating enables standard reflow without dry-pack handling.

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, SN74LVC821APWR saves >40% board area with identical timing and drive strength, while 74LVC821ADB provides greater inter-pin clearance for reinforced insulation-both retain full functional and pinout compatibility but differ in thermal performance and layout fit.

Availability

SN74LVC821ADWR is available at Aetrix Electronics and suitable for industrial automation backplanes, automotive body control modules, test equipment pattern generation, and network switch management interfaces requiring stable component supply and long-term manufacturability.

Supply support for SN74LVC821ADWR 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 connectivity solutions with over 50 years of process and reliability expertise.

The SN74LVC821ADWR belongs to TI's LVC logic family, engineered specifically for low-voltage, high-speed bus interface applications in mixed-signal systems requiring robust voltage translation and power-aware operation.

FAQ

What is the maximum clock frequency supported by SN74LVC821ADWR?

The SN74LVC821ADWR supports a maximum clock frequency of 150 MHz under recommended operating conditions at VCC = 3.3 V. This value is derived from the minimum pulse width requirement (tw ≥ 3.3 ns) and confirmed in the Switching Characteristics table. At lower supply voltages like 1.8 V, the achievable frequency remains 150 MHz per published timing data, though actual system margin depends on load capacitance and signal integrity.

Does SN74LVC821ADWR support 5-V input signals while operating at 1.8 V VCC?

Yes, SN74LVC821ADWR accepts input voltages up to 5.5 V regardless of VCC level, including at 1.8 V operation. This is explicitly specified in the Recommended Operating Conditions table under "VI Input voltage" (0 to 5.5 V). The feature enables direct interfacing with legacy 5-V logic without external level shifters, making SN74LVC821ADWR ideal for voltage-domain bridging in mixed-supply systems.

What is the purpose of the Ioff specification for SN74LVC821ADWR?

The Ioff specification (±10 µA max at VI or VO = 5.5 V) ensures that SN74LVC821ADWR disables its output buffers when VCC = 0 V, preventing damaging current backflow from live I/O lines into the unpowered device. This supports safe partial-power-down operation in modular systems, such as hot-swappable cards or subsystems with independent power rails, and is verified per JESD 78 latch-up and JESD 22 ESD standards.

Can SN74LVC821ADWR replace SN74LVC821ADW in existing designs?

Yes, SN74LVC821ADWR is a direct tape-and-reel variant of SN74LVC821ADW, sharing identical SOIC-24 (DW) package, pinout, electrical specifications, and thermal characteristics. The only difference is packaging format: SN74LVC821ADW ships in tubes of 25, while SN74LVC821ADWR ships in reels of 2000. No PCB or schematic changes are required when substituting SN74LVC821ADWR for SN74LVC821ADW.

How does the OE pin behave during power-up of SN74LVC821ADWR?

During power-up, OE should be tied to VCC through a pullup resistor to ensure the outputs remain in high-impedance state until the system controller asserts valid logic levels. The minimum resistor value depends on the driver's current-sinking capability, as stated in the datasheet. Leaving OE floating risks undefined output states and potential bus contention; SN74LVC821ADWR does not include internal pullups on OE, so external biasing is mandatory for robust power sequencing.