Texas Instruments SN74ACT72221L20RJ

Overview

SN74ACT72221L20RJ from Texas Instruments is a 1024 × 9-bit synchronous dual-clock FIFO memory IC with CMOS dual-port SRAM architecture, 15 ns write/read cycle time, TTL-compatible inputs, and programmable almost-empty/almost-full flags. It operates in 0°C to 70°C ambient and is used in high-speed data buffering between asynchronous buses in communication systems and graphics subsystems.

For engineers reviewing the SN74ACT72221L20RJ datasheet, SN74ACT72221L20RJ pinout, SN74ACT72221L20RJ application, or SN74ACT72221L20RJ equivalent, this page delivers verified timing parameters, flag programming behavior, reset synchronization logic, and package-specific terminal mapping for reliable integration into rate-matched or burst-mode digital interfaces.

Technical Context

The SN74ACT72221L20RJ implements a first-in-first-out (FIFO) buffer using internal synchronous read/write address counters, with independent WCLK and RCLK domains supporting both asynchronous and coincident clock operation. Its dual-port SRAM core enables concurrent read and write access without bus contention.

Flag generation is synchronized: EF and PAE to RCLK, FF and PAF to WCLK. The WEN2/LD pin serves as either a second write enable or load control for offset registers-function determined by its logic level during RS assertion. Reset initializes pointers, clears output register bits, and loads default offsets (empty+7 / full−7).

Key Specifications

Pinout & Package

SN74ACT72221L20RJ is housed in a 32-pin plastic J-leaded chip carrier (RJ) package with gull-wing leads, designed for surface-mount assembly and thermal reliability in dense PCB layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar FIFO memory applications.

Compared with IDT72221L20J and SN74ACT72221L25RJ, the SN74ACT72221L20RJ delivers optimal balance of speed (66.7 MHz), timing precision (15 ns), and TI-specific support infrastructure-making it preferred for new designs requiring highest throughput within commercial temperature range.

Availability

SN74ACT72221L20RJ is available at Aetrix Electronics and suitable for graphics subsystems, communication gateways, industrial bus bridges, and automated test equipment requiring stable component supply across long production lifecycles.

Supply support for SN74ACT72221L20RJ 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 broad industrial and automotive qualification.

The SN74ACT72221L20RJ belongs to TI's ACT-family advanced CMOS FIFO product line, engineered for high-speed, low-power, and noise-immune data buffering in mixed-clock digital systems.

FAQ

What is the memory capacity and data width of the SN74ACT72221L20RJ?

The SN74ACT72221L20RJ provides 1024 words of storage, each word being 9 bits wide (1024 × 9). This configuration supports byte-plus-parity or byte-plus-framing-bit transmission. The device uses dual-port CMOS SRAM internally and maintains strict FIFO ordering via synchronous read and write address counters. Its capacity is fixed and not software-configurable.

How does the SN74ACT72221L20RJ handle clock domain crossing between write and read operations?

The SN74ACT72221L20RJ supports fully asynchronous operation: WCLK and RCLK may run at different frequencies or phases, or be tied together for single-clock use. Read and write pointers operate independently, and status flags (EF/FF/PAE/PAF) are synchronized to their respective clock domains-ensuring reliable boundary detection without metastability risk. No external handshaking logic is needed.

What determines whether WEN2/LD functions as a second write enable or as a load control for flag offsets?

The function of WEN2/LD in the SN74ACT72221L20RJ is determined solely by its logic level during device reset (RS low). If WEN2/LD is held high when RS returns high, it acts as WEN2. If held low during RS assertion, it becomes the LD signal for accessing the four 8-bit flag offset registers. This configuration is latched at power-up reset and cannot be changed dynamically.

Can the SN74ACT72221L20RJ be used in width-expansion configurations, and how are status flags managed?

Yes, the SN74ACT72221L20RJ supports bit-width expansion by connecting D0–D8 and Q0–Q8 lines in parallel across multiple units while sharing WCLK, RCLK, REN1/REN2, WEN1, and RS. Composite EF and FF must be OR'd (EF) or AND'd (FF) across all devices. PAE and PAF may be monitored from any single unit since offset values are identical across the group when configured identically.

What are the default values for the programmable almost-empty and almost-full flag offsets in the SN74ACT72221L20RJ?

After reset, the SN74ACT72221L20RJ loads default offset values of 7 (007h) into both the empty-offset and full-offset registers. This yields PAE = low when ≤7 unread words remain, and PAF = low when ≥1017 unread words are present (1024 − 7). These defaults are stored in nonvolatile latch logic and persist until explicitly rewritten via WEN2/LD-controlled flag programming sequences.