Texas Instruments SN74LVC821ANSR

Overview

SN74LVC821ANSR 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 VCC 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 SN74LVC821ANSR datasheet, SN74LVC821ANSR pinout, SN74LVC821ANSR application, or SN74LVC821ANSR equivalent, key selection criteria include 3-state drive capability, 10-bit synchronous latching, 5.5-V input tolerance, Ioff partial-power-down support, and SSOP-24 package compatibility for space-constrained board layouts.

Technical Context

This device implements ten independent D-type flip-flops sharing a common clock (CLK) and output-enable (OE) control. Each flip-flop captures data at the rising edge of CLK and presents true logic at Q outputs, while OE independently places all ten outputs into high-impedance state without affecting internal latch operation.

It supports mixed-voltage system interfacing: inputs accept up to 5.5 V regardless of VCC (1.65–3.6 V), enabling direct connection to 5-V logic while powered from 3.3-V or lower rails. The Ioff feature disables outputs during power-down to prevent backflow current, satisfying JESD 78 Class II latch-up and JESD 22 ESD requirements.

Key Specifications

Pinout & Package

SN74LVC821ANSR is housed in a 24-pin Shrink Small Outline Package (SSOP-DB), measuring 7.9 mm × 4.9 mm with 0.65 mm lead pitch and 1.2 mm max height. The package is RoHS-compliant, moisture-sensitivity Level-1 rated, and suitable for automated assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC821ADBR, SN74LVC821ANSR offers identical functionality and performance; compared with SN74ALVC821APW, it trades 2.1 ns of speed for broader voltage flexibility and 5-V tolerance - critical for legacy interface bridging.

Availability

SN74LVC821ANSR is available at Aetrix Electronics and suitable for industrial I/O expansion, memory interface buffering, and communications backplane interface applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.

Supply support for SN74LVC821ANSR 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, automotive, and communications IC design.

The SN74LVC821ANSR belongs to TI's LVC logic family - engineered for low-voltage, high-speed, mixed-signal interfacing in space- and power-constrained systems where reliability and voltage translation are essential.

FAQ

What is the maximum clock frequency supported by SN74LVC821ANSR?

The SN74LVC821ANSR supports a maximum clock frequency of 150 MHz under recommended operating conditions (VCC = 3.3 V, TA = 25°C). This is derived from its minimum clock pulse width (tw) specification of 3.3 ns and verified timing analysis in the official datasheet. At lower VCC voltages, the achievable frequency decreases due to increased propagation delay.

Does SN74LVC821ANSR support partial power-down operation?

Yes, SN74LVC821ANSR supports partial power-down via its Ioff feature. When VCC = 0 V, the Ioff circuitry limits input/output leakage to ±10 µA even with VI or VO at 5.5 V, preventing damaging current backflow between powered and unpowered system domains - a requirement for hot-swap and multi-rail architectures.

Can SN74LVC821ANSR be used as a level translator between 5-V and 3.3-V logic?

Yes, SN74LVC821ANSR functions as a unidirectional level translator: its inputs accept up to 5.5 V regardless of VCC (1.65–3.6 V), allowing 5-V signals to safely drive the D and OE inputs while the device operates from a 3.3-V supply. Outputs swing rail-to-rail (0 V to VCC), so output-side translation requires external circuitry.

What is the thermal resistance (θJA) of the SSOP-24 package used in SN74LVC821ANSR?

The SSOP-24 (DB) package of SN74LVC821ANSR has a junction-to-ambient thermal resistance (θJA) of 63°C/W, measured under standard JEDEC conditions. This value assumes a two-layer PCB with minimal copper area; actual thermal performance improves with enhanced layout practices such as thermal vias and copper pour under the exposed pad (if present) - though DB lacks an exposed pad.

How does the output-enable (OE) pin behave during power-up or power-down sequences?

To ensure outputs remain in high-impedance during power transitions, OE should be tied to VCC through a pullup resistor. The minimum resistor value depends on the driver's sink capability; TI recommends ≥10 kΩ for typical microcontroller GPIOs. This prevents bus contention or undefined states before VCC stabilizes, as OE is active-low and internally undriven during power sequencing.