Texas Instruments SN74ACT7881-30FN

Overview

SN74ACT7881-30FN from Texas Instruments is a clocked 1024 × 18-bit asynchronous FIFO memory IC with independent read/write clocks, programmable almost-full/almost-empty flag (AF/AE), 11 ns access time at 50-pF load, and 68-pin plastic leaded chip carrier (FN) package. It enables data rate bridging between mismatched clock domains in high-speed digital systems such as telecom line cards and video frame buffers.

For engineers reviewing the SN74ACT7881-30FN datasheet, SN74ACT7881-30FN pinout, SN74ACT7881-30FN application, or SN74ACT7881-30FN equivalent, key selection considerations include its 33.4 MHz maximum clock frequency (–30 speed grade), dual enable control per port (WRTEN1/WRTEN2, RDEN1/RDEN2), input-ready/output-ready flag timing synchronization to respective clocks, and pin-to-pin compatibility with SN74ACT7882/SN74ACT7884.

Technical Context

The SN74ACT7881-30FN implements a synchronous write control path driven by WRTCLK and asynchronous read control synchronized to RDCLK, with internal pointers tracking fill level. Its status-flag logic generates HF (half-full), IR (input-ready), OR (output-ready), and programmable AF/AE flags using either user-defined offset (X = D8–D0) or default X = 256.

It features independent 18-bit parallel data paths (D0–D17 inputs, Q0–Q17 outputs), tri-state output drivers controlled by OE, and reset-initiated pointer initialization requiring ≥4 cycles of both WRTCLK and RDCLK. The device operates across 0°C to 70°C with VCC = 4.5 V to 5.5 V and supports word-width and word-depth expansion via cascaded flag signaling.

Key Specifications

Pinout & Package

SN74ACT7881-30FN uses a 68-pin plastic leaded chip carrier (PLCC-FN) package with J-lead geometry, designed for surface-mount assembly and thermal dissipation up to 39°C/W (θJA).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ACT7882-30FN and SN74ACT7884-30FN, the SN74ACT7881-30FN delivers native 18-bit width in single-package form-eliminating inter-device skew and routing complexity-while retaining full pin compatibility and identical speed grading for drop-in replacement in width-constrained layouts.

Availability

SN74ACT7881-30FN is available at Aetrix Electronics and suitable for telecom infrastructure, industrial automation, test equipment, and video processing applications requiring stable component supply and long-term obsolescence management.

Supply support for SN74ACT7881-30FN 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 logic families including Widebus™.

The SN74ACT7881-30FN belongs to TI's Widebus™ family of high-speed FIFO memories, engineered specifically for clock-domain isolation and data-rate matching in demanding digital systems where deterministic latency and robust flag signaling are critical.

FAQ

What is the maximum operating frequency of the SN74ACT7881-30FN?

The SN74ACT7881-30FN supports a maximum clock frequency of 33.4 MHz for both WRTCLK and RDCLK inputs, as specified in the –30 speed grade timing table. This rating assumes VCC = 4.5 V to 5.5 V and operation within 0°C to 70°C ambient temperature. The device achieves this performance with 11 ns access time at 50-pF load, making it suitable for high-throughput data buffering in industrial and communications systems.

How does the AF/AE flag programming work on the SN74ACT7881-30FN?

The AF/AE flag on the SN74ACT7881-30FN is programmed during reset using the DAF pin and D0–D8 inputs. To set a custom offset X, assert DAF low, then apply the 9-bit value to D0–D8 before taking RESET high. Holding DAF high during reset selects the default X = 256. The programmed value determines the FIFO fill-level thresholds at which AF/AE transitions-enabling precise flow-control tuning without firmware intervention.

Is the SN74ACT7881-30FN pin-compatible with other members of the ACT788x family?

Yes, the SN74ACT7881-30FN is explicitly pin-to-pin compatible with SN74ACT7882, SN74ACT7884, and SN74ACT7811 in the 68-pin FN package. This allows direct substitution in existing PCB layouts when changing depth/width configurations-e.g., replacing SN74ACT7882 (1024×9) with SN74ACT7881-30FN (1024×18) eliminates need for parallel device routing while maintaining identical control pin mapping and timing behavior.

What are the key timing requirements for reliable reset of the SN74ACT7881-30FN?

A valid reset of the SN74ACT7881-30FN requires RESET to be held low for at least four complete cycles of both WRTCLK and RDCLK. During this period, internal read/write pointers initialize to zero, and status flags (OR, HF, IR) settle to defined states (OR/HF/IR low, AF/AE high). The reset sequence must occur at power-up; failure to meet the four-cycle minimum may result in undefined pointer states and unreliable flag behavior in subsequent operation.

Can the SN74ACT7881-30FN be used in word-width expansion configurations?

Yes, the SN74ACT7881-30FN supports word-width expansion by connecting multiple devices in parallel with shared WRTCLK, RDCLK, and control signals (WRTEN1/WRTEN2, RDEN1/RDEN2, OE, RESET, DAF). Data buses (D0–D17, Q0–Q17) are concatenated to form wider paths (e.g., two devices yield 1024 × 36), while IR and OR flags are OR'd externally. This configuration preserves full timing compliance and leverages the device's native 18-bit width without additional glue logic.