Texas Instruments SN74ACT7805-25DL

Overview

SN74ACT7805-25DL from Texas Instruments is a 256 × 18-bit clocked FIFO memory IC designed for asynchronous data buffering between independent clock domains. It supports free-running, asynchronous or coincident read/write clocks, delivers 12 ns access time with 50-pF load, operates up to 40 MHz (–25 speed grade), and features synchronized input-ready (IR) and output-ready (OR) flags. It is used in high-speed digital interface bridging, such as between microprocessor buses and peripheral controllers.

For engineers reviewing the SN74ACT7805-25DL datasheet, SN74ACT7805-25DL pinout, SN74ACT7805-25DL application, or SN74ACT7805-25DL equivalent, key selection considerations include its 40-MHz maximum clock frequency, 18-bit bidirectional width expansion capability, programmable almost-full/almost-empty flag offsets, low-power Advanced CMOS process, and compatibility with SN74ACT7803/SN74ACT7813 for footprint reuse.

Technical Context

The SN74ACT7805-25DL implements a synchronous dual-clock FIFO architecture with independent write and read pointer logic, status-flag synchronization to respective clocks, and reset-initiated initialization of IR, OR, and HF flags. Its internal 256 × 18 RAM block uses distributed VCC/GND pins and TI's patented Output Edge Control (OEC™) to suppress simultaneous switching noise.

Write operations occur on the rising edge of WRTCLK when WRTEN1 is high, WRTEN2 is low, and IR is high; reads occur on the rising edge of RDCLK when RDEN, OE1, and OE2 are low and OR is high. The AF/AE flag supports programmable depth offsets (X/Y) via D0–D6 during reset, defaulting to X = Y = 32.

Key Specifications

Pinout & Package

Packaged in a 56-pin Shrink Small-Outline (DL) package with 300-mil body width and 25-mil center-to-center lead pitch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ACT7803-25DL and SN74ACT7813-25DL, the SN74ACT7805-25DL uniquely balances programmable flow control, minimal external logic requirements, and proven interoperability in bidirectional and width-expanded configurations-making it optimal for deterministic, low-latency inter-processor buffering where flexibility and layout reuse are critical.

Availability

SN74ACT7805-25DL is available at Aetrix Electronics and suitable for high-speed bus bridging, DSP interface buffering, multi-processor communication links, and industrial PLC I/O modules requiring stable component supply and long-term obsolescence management.

Supply support for SN74ACT7805-25DL 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 heritage in high-reliability interface and memory products.

The SN74ACT7805-25DL belongs to TI's Widebus™ family of advanced CMOS FIFOs, engineered specifically for robust clock-domain crossing in commercial and industrial digital systems demanding predictable latency and noise immunity.

FAQ

What is the maximum supported clock frequency for SN74ACT7805-25DL?

The SN74ACT7805-25DL is rated for a maximum clock frequency of 40 MHz, corresponding to its –25 speed grade designation. This applies independently to both WRTCLK and RDCLK inputs under recommended operating conditions (VCC = 4.5 V to 5.5 V, TA = 0°C to 70°C). Timing parameters such as setup/hold and propagation delays are guaranteed within this limit.

How does the AF/AE flag programming work on SN74ACT7805-25DL?

After reset and before the first write, the SN74ACT7805-25DL allows programming of separate almost-empty (X) and almost-full (Y) offsets via D0–D6. When PEN is pulsed low during WRTCLK high, the D0–D6 value latches as X; a second PEN pulse latches Y. Default values are X = Y = 32 if PEN remains high. Both offsets range from 0 to 127.

Is SN74ACT7805-25DL pin-compatible with other FIFOs in the same family?

Yes, the SN74ACT7805-25DL is pin-to-pin compatible with SN74ACT7803-25DL and SN74ACT7813-25DL in the DL package. All share identical pin assignments, electrical characteristics, and timing behavior, enabling drop-in substitution where functional differences (e.g., AF/AE programmability or status register) are acceptable or accounted for in firmware.

What happens to the output data bus (Q0–Q17) when OR is low on SN74ACT7805-25DL?

When OR is low, indicating the FIFO is empty, the SN74ACT7805-25DL holds the last valid word previously read on Q0–Q17. The outputs remain stable and do not float or change unless a new read occurs. This behavior simplifies downstream logic design by eliminating the need for external hold registers or bus-keeper circuits.

Does SN74ACT7805-25DL require power-on reset sequencing?

Yes, the SN74ACT7805-25DL must be reset upon power-up. RESET must be asserted low while at least four rising edges occur on both WRTCLK and RDCLK to properly initialize internal pointers and flags (IR, OR, HF low; AF/AE high). Failure to meet this requirement may result in undefined flag states or corrupted data transfer.