Texas Instruments SN74ACT7811-15PN

Overview

SN74ACT7811-15PN from Texas Instruments is a 1024 × 18-bit clocked first-in, first-out (FIFO) memory IC with independent asynchronous read/write clocks, 15 ns access time at 50-pF load, programmable almost-full/almost-empty flag, and 80-pin LQFP (PN) package. It enables high-speed data buffering between mismatched clock domains in digital communication interfaces.

For engineers reviewing the SN74ACT7811-15PN datasheet, SN74ACT7811-15PN pinout, SN74ACT7811-15PN application, or SN74ACT7811-15PN equivalent, this page delivers verified timing parameters, flag behavior, cascading capability, and real-world FIFO integration guidance for synchronous/asynchronous bridging designs.

Technical Context

The SN74ACT7811-15PN implements dual-clock FIFO architecture with separate WRTCLK/RDCLK inputs, enabling independent write and read operations synchronized to distinct system clocks. Its internal pointer logic tracks fill level and drives status flags-IR, OR, HF, AF/AE-synchronously to respective clocks.

It supports bit-parallel 18-bit data transfer at up to 40 MHz (−15 speed grade), features programmable AF/AE offset (default X = 256), and allows expansion in word width (via DAF/AF-AE configuration) and depth (cascadable with timing compensation). All I/Os are ACT-family CMOS compatible with 4.5–5.5 V supply.

Key Specifications

Pinout & Package

SN74ACT7811-15PN is housed in an 80-pin Thin Quad Flat Package (LQFP, PN), measuring 14.0 mm × 14.0 mm × 1.4 mm, with 0.5-mm lead pitch and exposed thermal pad (JEDEC MS-026 compliant).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ACT7881-15PN, SN74ACT7811-15PN adds programmable AF/AE for adaptive flow control; compared with IDT7203LA15TPG, it delivers native 18-bit width and simpler layout at the cost of slightly higher access time and no JTAG support.

Availability

SN74ACT7811-15PN is available at Aetrix Electronics and suitable for telecom line interface, digital signal processing interface, and industrial fieldbus gateway applications requiring stable component supply despite its obsolete status-inventory is secured through authorized legacy channel partners.

Supply support for SN74ACT7811-15PN 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 data-path components.

The SN74ACT7811-15PN belongs to TI's Widebus™ family of high-speed FIFO memories, designed specifically for clock-domain bridging in industrial, communications, and instrumentation systems demanding deterministic latency and robust flag signaling.

FAQ

What is the maximum operating frequency of the SN74ACT7811-15PN?

The SN74ACT7811-15PN supports a maximum clock frequency of 40 MHz for both WRTCLK and RDCLK inputs, as confirmed by its −15 speed grade designation and timing specifications in the SCAS151C datasheet. This rating applies across the full 0°C to 70°C temperature range with VCC = 4.5 V to 5.5 V and CL = 50 pF. The 40 MHz limit ensures reliable setup/hold timing compliance for all control and data paths within the SN74ACT7811-15PN.

How does the AF/AE flag behave during reset on the SN74ACT7811-15PN?

During reset, the AF/AE flag behavior of the SN74ACT7811-15PN depends on the DAF pin state: if DAF is held high, the default offset X = 256 is used, making AF/AE high when FIFO contains ≤257 or ≥768 words; if DAF transitions low before RESET goes high, the binary value on D0–D8 is latched as the custom X value. This programming occurs on every reset cycle and defines the boundary for the SN74ACT7811-15PN's programmable status flag.

Can the SN74ACT7811-15PN be used in word-width expansion configurations?

Yes, the SN74ACT7811-15PN supports word-width expansion-for example, two devices can implement a 1024 × 36-bit FIFO. In such configurations, D18–D35 and Q18–Q35 connect to the second device while sharing common WRTCLK, RDCLK, RESET, and flag lines. The SN74ACT7811-15PN's dedicated DAF and AF/AE pins retain full programmability per device, enabling independent buffer management in wide-bus systems.

What are the key timing requirements for OE assertion relative to RDCLK on the SN74ACT7811-15PN?

For reliable read operation, OE must be asserted high at least 5 ns before the rising edge of RDCLK, as specified in the setup time (tsu) table of the SN74ACT7811-15PN datasheet. Failure to meet this requirement risks invalid data on Q outputs. Additionally, OE hold time is 1 ns after RDCLK↑, and output enable/disable delays (ten/tdis) are 2–11 ns and 2–14 ns respectively-critical for bus-sharing timing budgets in multiplexed systems using the SN74ACT7811-15PN.

Is the SN74ACT7811-15PN pin-compatible with other members of the SN74ACT78xx family?

Yes, the SN74ACT7811-15PN is pin-to-pin compatible with SN74ACT7881, SN74ACT7882, and SN74ACT7884 in the same 80-pin LQFP (PN) package, as explicitly stated in the datasheet. This compatibility extends to all signal, power, and ground pin assignments-including identical D/Q bus mapping, clock/enable locations, and flag pin positions-allowing drop-in replacement where functional differences (e.g., flag sets or depth) are acceptable for the SN74ACT7811-15PN's target application.