Texas Instruments SN74ALVCH16821DLR

Overview

SN74ALVCH16821DLR from Texas Instruments is a 3.3-V, 20-bit bus-interface D-type flip-flop with 3-state outputs, designed for 1.65-V to 3.6-V V_CC operation. It functions as two independent 10-bit flip-flops or one unified 20-bit register, edge-triggered on the positive clock transition, and features bus-hold circuitry eliminating external pullup/pulldown resistors - used in high-density memory address/data bus buffering and hot-swap I/O expansion.

For engineers reviewing the SN74ALVCH16821DLR datasheet, SN74ALVCH16821DLR pinout, SN74ALVCH16821DLR application, or SN74ALVCH16821DLR equivalent, key selection criteria include its 56-pin TSSOP (DGG) package, ±24-mA output drive at 3 V, 150-MHz maximum clock frequency, bus-hold input retention, and dual 10-bit configurable operation mode.

Technical Context

This device implements two synchronized 10-bit D-type flip-flop banks sharing independent clock (1CLK/2CLK) and output-enable (1OE/2OE) controls, enabling flexible partitioning of data paths. Each bank supports true-level latching on CLK↑ with simultaneous 10-bit parallel capture and 3-state output control.

Its bus-hold circuitry actively maintains valid logic states on undriven inputs without external components, while the 3-state outputs support high-impedance bus isolation with t_dis = 4.6 ns (V_CC = 3.3 V) and t_en = 5.1 ns, ensuring clean bus contention management in multi-drop systems.

Key Specifications

Pinout & Package

TSSOP-56 (DGG) package: 13.9 mm × 6.1 mm × 1.2 mm body, 0.5-mm lead pitch, gull-wing leads, RoHS-compliant NiPdAu finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 20-bit bus-interface flip-flop applications.

Compared with SN74ALVCH16821DLR, SN74LVC16374DGGR requires two packages and external biasing for 20-bit operation, while 74AVC16835DGGR offers higher clock rate but removes bus-hold - making SN74ALVCH16821DLR the optimal balance of integration, robustness, and compatibility in mixed-voltage industrial bus designs.

Availability

SN74ALVCH16821DLR is available at Aetrix Electronics and suitable for memory interface buffering, hot-swap I/O expansion, and industrial fieldbus multiplexing requiring stable component supply across extended temperature ranges.

Supply support for SN74ALVCH16821DLR 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 innovation in high-reliability logic and interface ICs.

The SN74ALVCH16821DLR belongs to TI's Widebus™ family - engineered specifically for high-speed, low-voltage bus interface applications in computing, communications, and industrial automation where signal integrity and power efficiency are critical.

FAQ

What is the recommended power-up sequence for SN74ALVCH16821DLR?

TI specifies that OE should be tied to V_CC through a pullup resistor during power-up/down to ensure outputs remain in high-impedance state until supply stabilizes. For SN74ALVCH16821DLR, this prevents bus contention on powered-down systems. The minimum resistor value depends on the driver's current-sinking capability, and TI recommends verifying stability across the full -40°C to 85°C operating range using the absolute maximum ratings table in the SCES037F datasheet.

Does SN74ALVCH16821DLR support mixed-voltage operation between data and control pins?

Yes - SN74ALVCH16821DLR supports 1.65-V to 3.6-V V_CC, and its VIH/VIL thresholds scale with V_CC (e.g., VIH = 0.65×V_CC at 1.65 V). All inputs - including 1CLK, 2CLK, 1OE, 2OE, and D pins - are fully 5-V tolerant per absolute maximum ratings (VI up to 4.6 V), enabling safe interfacing with legacy 5-V logic while powered from 3.3-V or 2.5-V rails.

How does the bus-hold feature function on SN74ALVCH16821DLR inputs?

The bus-hold circuitry on SN74ALVCH16821DLR actively maintains the last valid logic state on each D input when undriven, using ±75 µA hold current at 3 V. This eliminates external pullup/pulldown resistors and prevents floating inputs from drifting into undefined states - critical during power sequencing or partial system resets. TI explicitly warns against combining bus-hold with external resistors, as it may cause contention or excessive current draw.

Can SN74ALVCH16821DLR operate reliably at 150 MHz across its full temperature range?

Yes - SN74ALVCH16821DLR guarantees 150-MHz maximum clock frequency across the full -40°C to 85°C operating range, as confirmed in the TIMING REQUIREMENTS table of SCES037F. This rating applies under worst-case V_CC = 1.65 V and includes margin for process variation; actual performance at 3.3 V typically exceeds 180 MHz in typical conditions.

What is the thermal resistance (θ_JA) of the SN74ALVCH16821DLR package?

The SN74ALVCH16821DLR uses the TSSOP-56 (DGG) package with a specified junction-to-ambient thermal resistance (θ_JA) of 48°C/W, per TI's PACKAGE OPTION ADDENDUM. This value assumes standard JEDEC 2-layer board conditions; actual thermal performance improves with added copper pour and thermal vias. The DL variant (SSOP) has higher θ_JA = 56°C/W, confirming DGG's superior thermal efficiency for high-duty-cycle applications.