Texas Instruments SN74ACT7811-25FN

Overview

SN74ACT7811-25FN from Texas Instruments is a 1024 × 18-bit clocked first-in, first-out (FIFO) memory IC with independent asynchronous read/write ports, 15 ns access time at 50-pF load, programmable almost-full/almost-empty flag, and 68-pin PLCC (FN) package. It enables high-speed data buffering between mismatched clock domains in telecom line cards and industrial protocol gateways.

For engineers reviewing the SN74ACT7811-25FN datasheet, SN74ACT7811-25FN pinout, SN74ACT7811-25FN application, or SN74ACT7811-25FN equivalent, key selection criteria include its 16.7 MHz maximum clock frequency, dual-clock synchronization capability, 18-bit parallel I/O, status flag timing behavior, and compatibility with SN74ACT7881/7882/7884 for drop-in upgrades.

Technical Context

The SN74ACT7811-25FN implements a synchronous FIFO architecture with separate write clock (WRTCLK) and read clock (RDCLK) domains, each driving independent pointer logic. Its internal 1024-word × 18-bit RAM array supports concurrent write and read operations without bus contention.

Status flags-including IR (input-ready), OR (output-ready), HF (half-full), and programmable AF/AE-are synchronized to their respective clocks and driven with guaranteed setup/hold timing relative to WRTCLK↑ or RDCLK↑ edges. The DAF input allows dynamic configuration of the AF/AE offset during reset cycles.

Key Specifications

Pinout & Package

SN74ACT7811-25FN uses a 68-pin plastic J-leaded chip carrier (PLCC) package (FN), measuring 24.2 mm × 24.2 mm with 1.27-mm lead pitch. Pin 1 is located at the index corner adjacent to the notch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ACT7881-25FN, the SN74ACT7811-25FN adds runtime AF/AE boundary adjustment via DAF, enabling adaptive buffer management; versus IDT7203L15TPG, it delivers native 18-bit width and 5-V-only operation with lower component count but less voltage flexibility.

Availability

SN74ACT7811-25FN is available at Aetrix Electronics and suitable for telecom infrastructure, industrial protocol conversion, test instrumentation, and digital acquisition systems requiring stable component supply across extended production lifecycles.

Supply support for SN74ACT7811-25FN 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 company headquartered in Dallas, Texas, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74ACT7811-25FN belongs to TI's Widebus™ family of high-speed interface ICs, designed specifically for clock-domain isolation and data rate translation in real-time communication and control systems.

FAQ

What is the maximum clock frequency supported by the SN74ACT7811-25FN?

The SN74ACT7811-25FN supports a maximum clock frequency of 16.7 MHz for both WRTCLK and RDCLK inputs. This rating is verified under recommended operating conditions (VCC = 4.5 V to 5.5 V, CL = 50 pF, TA = 0°C to 70°C) and corresponds to the -25 speed grade. Exceeding this frequency may result in timing violations affecting IR, OR, or AF/AE flag accuracy and data integrity in the SN74ACT7811-25FN.

How does the AF/AE flag programming work on the SN74ACT7811-25FN?

The AF/AE flag on the SN74ACT7811-25FN is programmed during reset by controlling the DAF input and D0–D8 data lines. With DAF held low, a low pulse on RESET stores the binary value on D0–D8 as the AF/AE offset X. With DAF held high, RESET uses the default X = 256. The SN74ACT7811-25FN then asserts AF/AE high when FIFO occupancy is ≤(X+1) or ≥(1025−X) words, enabling precise flow control tailored to system needs.

Is the SN74ACT7811-25FN pin-compatible with other FIFO devices in the same family?

Yes, the SN74ACT7811-25FN is pin-to-pin compatible with SN74ACT7881, SN74ACT7882, and SN74ACT7884 in the same FN package. All share identical pin assignments for power, clocks, enables, data I/O, and status flags. However, functional differences exist: SN74ACT7881 lacks DAF-controlled AF/AE programming, while SN74ACT7882/7884 offer different depth/width configurations. The SN74ACT7811-25FN retains full electrical and mechanical interchangeability.

What are the key timing parameters that define read and write operation in the SN74ACT7811-25FN?

Key timing parameters for the SN74ACT7811-25FN include: OE, RDEN1, and RDEN2 must be high ≥5 ns before RDCLK↑ to enable read; IR and OR flags respond within 2–16 ns after WRTCLK↑ or RDCLK↑ respectively; AF/AE changes occur 6–26 ns after RDCLK↑ or RESET↓; and data appears on Q0–Q17 4–25 ns after RDCLK↑. These values are specified for the -25 speed grade and ensure deterministic behavior in synchronous FIFO control loops.

Can the SN74ACT7811-25FN be used in cascaded configurations for increased memory depth or width?

Yes, the SN74ACT7811-25FN supports both word-width and word-depth expansion. For width expansion (e.g., 1024×36), connect multiple devices in parallel with shared clocks/enables and separate D/Q buses. For depth expansion (e.g., 2048×18), daisy-chain RDCLK and WRTCLK while routing OR→IR and IR→OR between stages. Timing delays scale linearly: OR goes high after (N×3) RDCLK cycles post-first-write, and IR recovers after (N×2) WRTCLK cycles post-fill in an N-device depth chain. The SN74ACT7811-25FN's architecture guarantees correct sequencing without external glue logic.