Texas Instruments SN74ACT72221L25RJ

Overview

SN74ACT72221L25RJ 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 controllers.

For engineers reviewing the SN74ACT72221L25RJ datasheet, SN74ACT72221L25RJ pinout, SN74ACT72221L25RJ application, or SN74ACT72221L25RJ equivalent, key selection criteria include its 1024-word depth, 9-bit data path with parity support, independent RCLK/WCLK timing, flag synchronization methodology, and RJ-package thermal/mechanical constraints.

Technical Context

This device implements a first-in, first-out (FIFO) buffer using internal write and read address counters synchronized to separate clocks (WCLK and RCLK), enabling fully asynchronous or coincident operation. Its dual-port SRAM core supports concurrent read/write access with boundary control via EF/FF flags and programmable PAE/PAF flags.

Flag logic is clock-synchronized: EF and PAE are edge-triggered on RCLK, while FF and PAF are edge-triggered on WCLK. The WEN2/LD pin serves as either a second write enable or load control for offset registers, determined by its logic level during reset - a hardware-configurable mode that defines whether programmable flag offsets are active.

Key Specifications

Pinout & Package

SN74ACT72221L25RJ is housed in a 32-pin plastic J-leaded chip carrier (RJ package), surface-mountable with gull-wing leads, rated for reflow soldering per JEDEC J-STD-020, and optimized for low-inductance signal routing in dense PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT72221L15JI and SN74ACT72221L20RJ, SN74ACT72221L25RJ delivers optimal balance of speed (66.7 MHz), compatibility (TTL inputs, RJ package), and power (160 mA max), making it preferred for new 5 V high-throughput FIFO designs where timing margin and drop-in manufacturability are critical.

Availability

SN74ACT72221L25RJ is available at Aetrix Electronics and suitable for graphics frame buffering, serial communication bridging, industrial PLC data queuing, and video capture preprocessing requiring stable component supply across multi-year production cycles.

Supply support for SN74ACT72221L25RJ 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 over 50 years of innovation in high-reliability interface and memory products.

The SN74ACT72221L25RJ belongs to TI's ACT-family advanced CMOS FIFO product line, designed specifically for high-speed, low-latency data buffering in mixed-clock-domain systems such as telecom infrastructure, industrial automation, and digital imaging.

FAQ

What is the memory organization of the SN74ACT72221L25RJ?

The SN74ACT72221L25RJ is organized as 1024 words × 9 bits, implemented using CMOS dual-port SRAM. This provides 9216 bits of total storage, supporting byte-wide data plus parity or framing information. The 1024-word depth enables buffering of large data bursts, such as full video scanlines or Ethernet packets, without overflow under proper flag management.

How does the SN74ACT72221L25RJ handle asynchronous clock domains?

The SN74ACT72221L25RJ natively supports asynchronous operation via independent WCLK and RCLK inputs. EF and PAE flags are synchronized to RCLK, while FF and PAF flags are synchronized to WCLK - eliminating metastability without external synchronizer circuits. This allows safe data transfer between buses running at unrelated frequencies, such as UART and PCI Express domains.

What is the function of the WEN2/LD pin on the SN74ACT72221L25RJ?

The WEN2/LD pin on the SN74ACT72221L25RJ is a dual-function terminal whose role is determined at reset: held high → acts as second write enable (WEN2); held low → becomes load (LD) control for programming flag offset registers. This hardware-selectable mode defines whether programmable PAE/PAF offsets are active, and cannot be changed dynamically during operation.

Can the SN74ACT72221L25RJ be used in width-expansion configurations?

Yes, the SN74ACT72221L25RJ supports bit-width expansion by connecting multiple units in parallel. Input controls (WCLK, RCLK, WEN1, REN1, etc.) are shared across devices, while D0–D8 and Q0–Q8 are concatenated. Composite EF/FF signals require wired-OR logic; PAE/PAF may be monitored from any single device. Figure 12 in the datasheet shows an 18-bit expansion example.

What are the default flag offset values for the SN74ACT72221L25RJ?

After reset, the SN74ACT72221L25RJ loads default flag offsets: programmable almost-empty (PAE) = empty + 7, and programmable almost-full (PAF) = full − 7. These 8-bit offset registers can be reprogrammed via WEN2/LD and WCLK sequences to customize trigger points - for example, setting PAE = empty + 2 for aggressive DMA triggering in low-latency systems.