Texas Instruments SN74ACT72221L35RJ

Overview

SN74ACT72221L35RJ from Texas Instruments is a 1024 × 9-bit synchronous FIFO memory IC designed for high-speed data buffering between asynchronous or coincident clock domains. It features 15 ns write/read cycle times, TTL-compatible inputs, programmable almost-empty/almost-full flags (default offsets: empty+7 / full–7), and operates over 0°C to 70°C. Used in graphics rate buffers and communication system queues.

For engineers reviewing the SN74ACT72221L35RJ datasheet, SN74ACT72221L35RJ pinout, SN74ACT72221L35RJ application, or SN74ACT72221L35RJ equivalent, key selection criteria include its 1024-word depth, 9-bit bus width with parity support, dual-clock independence, flag synchronization logic, and RJ-package compatibility with IDT72221-family systems.

Technical Context

This device implements a CMOS dual-port SRAM-based FIFO with independent synchronous write and read control paths. Write operations are triggered on WCLK↑ when WEN1 is low and FF is high; reads occur on RCLK↑ when REN1/REN2 are low and EF is high. The internal address counters manage first-in, first-out data flow without external sequencing logic.

Flag generation uses synchronized flip-flop outputs: EF and PAE align to RCLK↑; FF and PAF align to WCLK↑. Programmable offset registers (accessed via WEN2/LD in load mode) allow runtime configuration of boundary thresholds, with default values stored in dedicated 8-bit LSB/MSB registers per flag.

Key Specifications

Pinout & Package

Package: 32-pin plastic J-leaded chip carrier (RJ), surface-mount compatible with standard reflow profiles.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT72221L15JG, SN74ACT72221L35RJ offers identical functionality but with Texas Instruments' qualification and support infrastructure; compared with SN74ACT72221L20RJ, it delivers 15 ns performance for high-throughput applications without layout changes.

Availability

SN74ACT72221L35RJ is available at Aetrix Electronics and suitable for graphics subsystems, industrial protocol bridges, high-speed serial interface queues, and legacy MCU memory expansion requiring stable component supply and long-lifecycle support.

Supply support for SN74ACT72221L35RJ 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 industrial and automotive qualification expertise.

The SN74ACT72221L35RJ belongs to TI's ACT-family advanced CMOS FIFO product line, engineered for reliable high-speed data buffering in mixed-clock-domain systems such as graphics pipelines and telecom infrastructure.

FAQ

What is the memory organization of the SN74ACT72221L35RJ?

The SN74ACT72221L35RJ implements a 1024 × 9-bit synchronous FIFO structure - meaning it stores 1024 discrete 9-bit words. This configuration supports byte-wide data plus parity or protocol framing bits, and is distinct from the 512×9 (SN74ACT72211L), 2048×9 (SN74ACT72231L), and 4096×9 (SN74ACT72241L) variants in the same family. The SN74ACT72221L35RJ uses dual-port SRAM for concurrent read/write access without external arbitration.

How does the programmable almost-full flag (PAF) operate in SN74ACT72221L35RJ?

In SN74ACT72221L35RJ, the PAF output goes low when unread words reach (1024 – m), where m is the value stored in the full-offset registers. At power-up, m defaults to 7, so PAF asserts at 1017 words. The offset is programmed via WEN2/LD in load mode using four consecutive WCLK↑ transitions to write LSB/MSB registers. PAF is synchronized to WCLK↑, ensuring deterministic timing relative to write operations.

Can SN74ACT72221L35RJ operate with a single clock for both read and write functions?

Yes, SN74ACT72221L35RJ supports single-clock operation: WCLK and RCLK may be tied together. Its architecture allows fully independent clocks but also accommodates coincident timing. When using one clock, WEN1 and REN1/REN2 control gating, and flag synchronization remains valid - EF/PAE still reference RCLK↑ edges, FF/PAF reference WCLK↑ edges, which are identical in this configuration.

What is the function of the WEN2/LD pin on SN74ACT72221L35RJ?

The WEN2/LD pin on SN74ACT72221L35RJ is a dual-function terminal whose role is determined at reset: if held high during RS deassertion, it acts as a second write enable (WEN2); if held low, it becomes the load (LD) signal for programming flag offset registers. This configuration is latched internally and persists until next reset - no runtime switching is supported.

Is SN74ACT72221L35RJ compatible with IDT72221L devices?

Yes, SN74ACT72221L35RJ is fully compatible with IDT72221L devices - including pinout, electrical characteristics, timing parameters, and functional behavior. Texas Instruments explicitly states "Fully Compatible With the IDT72211/72221/72231/72241" in the datasheet. This enables direct substitution in existing IDT-based designs without PCB or firmware modifications.