Texas Instruments SN74ACT7811-18PN

Overview

SN74ACT7811-18PN 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 telecom line cards and industrial protocol gateways.

For engineers reviewing the SN74ACT7811-18PN datasheet, SN74ACT7811-18PN pinout, SN74ACT7811-18PN application, or SN74ACT7811-18PN equivalent, key selection criteria include independent RDCLK/WRTCLK synchronization, 40 MHz max clock frequency, 18-bit parallel I/O, programmable AF/AE offset, and cascading support for word-width/depth expansion.

Technical Context

The SN74ACT7811-18PN implements dual-clock FIFO architecture with separate write-control logic synchronized to WRTCLK and read-control logic synchronized to RDCLK. Its internal 1024-word × 18-bit RAM array supports concurrent write and read operations without bus contention.

Flag generation is fully synchronous: IR and OR are updated on the second or third rising edge of WRTCLK/RDCLK respectively; HF, AF/AE, and DAF-programmed status flags align precisely with clock edges and reset timing sequences defined in Figures 1–4.

Key Specifications

Pinout & Package

SN74ACT7811-18PN uses an 80-pin thin quad flat package (PN), measuring 12.2 mm × 12.2 mm × 1.4 mm (JEDEC MS-026 compliant). Pin numbering follows standard counter-clockwise orientation with Pin 1 marked by corner notch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ACT7881-18PN and SN74ACT7882-18PN, the SN74ACT7811-18PN uniquely delivers user-definable AF/AE thresholds and native 18-bit width in a single package-reducing component count and enabling adaptive buffer management in real-time systems.

Availability

SN74ACT7811-18PN is available at Aetrix Electronics and suitable for telecom infrastructure, industrial protocol conversion, test instrumentation, and video synchronization applications requiring stable component supply across extended production lifecycles.

Supply support for SN74ACT7811-18PN 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 SN74ACT7811-18PN belongs to TI's Widebus™ family of high-speed FIFO memories, designed specifically for clock-domain isolation and burst-mode data buffering in communications and industrial control systems.

FAQ

What is the maximum operating frequency of the SN74ACT7811-18PN?

The SN74ACT7811-18PN supports a maximum clock frequency of 35 MHz for both RDCLK and WRTCLK inputs under recommended operating conditions (VCC = 4.5 V to 5.5 V, TA = 0°C to 70°C, CL = 50 pF). This rating is verified in the timing requirements table (page 11) and corresponds to the -18 speed grade designation in the part number.

How is the almost-full/almost-empty (AF/AE) flag programmed on the SN74ACT7811-18PN?

The AF/AE flag on the SN74ACT7811-18PN is programmed during reset using the DAF pin. To set a custom offset X, assert DAF low before RESET, then pulse RESET low-to-high; D0–D8 values at DAF transition define X. To use the default X = 256, hold DAF high during RESET. This procedure is detailed in Terminal Functions (page 5) and Figure 1.

Does the SN74ACT7811-18PN support cascading for increased memory depth or width?

Yes, the SN74ACT7811-18PN is explicitly designed for cascading. Word-width expansion to 36 bits uses parallel D/Q connections and shared clocks (Figure 8); word-depth expansion to 2048 words uses daisy-chained IR/OR flags and staggered clock timing (Figure 7). Both methods preserve full flag functionality and timing integrity.

What are the key timing parameters for read and write operations on the SN74ACT7811-18PN?

Key timing parameters include: tpd(RDCLK↑ → Q) = 15 ns max (page 12), tsu(D0–D17 before WRTCLK↑) = 5 ns, th(D0–D17 after WRTCLK↑) = 1 ns, and tw(WRTCLK pulse) = 14 ns min (page 11). These ensure reliable operation at 35 MHz with standard 50-pF loads and define critical setup/hold margins for synchronous interface design.

Is the SN74ACT7811-18PN pin-compatible with other devices in the SN74ACT78xx family?

Yes, the SN74ACT7811-18PN is pin-to-pin compatible with SN74ACT7881, SN74ACT7882, and SN74ACT7884 in the same PN package, as confirmed in the device description (page 1). This allows drop-in replacement for functional variants while retaining identical PCB layout and interconnects.