Texas Instruments SN74ACT3641-30PQ

Overview

SN74ACT3641-30PQ from Texas Instruments is a 1024 × 36-bit clocked FIFO memory IC with dual asynchronous ports, supporting up to 67 MHz clock frequency, 11 ns access time, and synchronous retransmit capability. It buffers data between port A and port B in high-speed digital systems requiring deterministic latency, such as DSP interfacing and DMA-controlled data pipelines.

For engineers reviewing the SN74ACT3641-30PQ datasheet, SN74ACT3641-30PQ pinout, SN74ACT3641-30PQ application, or SN74ACT3641-30PQ equivalent, key selection considerations include programmable almost-full/empty flag offsets, mailbox register support for control-message passing, dual-clock synchronization architecture, and PQ-package pin compatibility with SN74ACT3631/SN74ACT3651 for drop-in upgrades.

Technical Context

The SN74ACT3641-30PQ implements a dual-port SRAM-based FIFO with independent CLKA and CLKB clocks, enabling fully asynchronous operation between ports while maintaining metastability-hardened flag synchronization via two-stage flip-flop chains. Its retransmit logic uses shadow read pointer tracking to enable repeat reads from user-defined start addresses without disrupting ongoing writes.

Flag offset registers (X for AE, Y for AF) are programmable via three methods-preset (8 or 64), parallel load from port A (A9–A0), or serial load through FS0/SD-and directly govern FIFO status signaling behavior. Mailbox registers (mail1/mail2) operate independently of FIFO storage and provide dedicated 36-bit command channels synchronized to their respective port clocks.

Key Specifications

Pinout & Package

SN74ACT3641-30PQ is housed in a 132-pin Plastic Quad Flat (PQ) package with 0.65 mm lead pitch, compliant with JEDEC MS-026 standard. Pin assignments follow TI's standardized PQ footprint for clocked FIFOs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ACT3641-30PQ, SN74ACT3631-30PQ omits mailbox and retransmit logic - reducing gate count and power but eliminating sideband control and repeat-read capability; SN74ACT3651-30PQ retains full FIFO function but modifies flag behavior and removes mailbox flag outputs, affecting interrupt-driven mailbox monitoring.

Availability

SN74ACT3641-30PQ is available at Aetrix Electronics and suitable for high-speed digital interface design, DSP subsystem integration, and industrial protocol bridging requiring stable component supply and long-term obsolescence management.

Supply support for SN74ACT3641-30PQ 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 leadership in high-performance timing and interface ICs.

The SN74ACT3641-30PQ belongs to TI's advanced clocked FIFO product line, designed specifically for deterministic, low-latency data buffering across asynchronous clock domains in communications, computing, and industrial automation systems.

FAQ

What is the maximum supported clock frequency for SN74ACT3641-30PQ?

The SN74ACT3641-30PQ supports clock frequencies up to 67 MHz on both CLKA and CLKB inputs, as confirmed in the SCAS338C datasheet revision October 1997. This rating applies across the full 0°C to 70°C operating temperature range and is validated for both read and write operations under worst-case voltage and process corners.

Does SN74ACT3641-30PQ support truly asynchronous clock domains between port A and port B?

Yes, SN74ACT3641-30PQ supports fully asynchronous operation: CLKA and CLKB may run at different frequencies, phases, or even be stopped independently. Its IR/AF flags are synchronized to CLKA, OR/AE to CLKB, and internal pointer logic uses metastability-hardened registers to ensure reliable cross-domain status reporting without external synchronizers.

How is the almost-empty (AE) flag programmed on SN74ACT3641-30PQ?

The AE flag offset (X register) on SN74ACT3641-30PQ is programmed during device reset using FS0/FS1 inputs to select preset (8 or 64), parallel load from port A (A9–A0), or serial load via FS0/SD. All methods write to the same X register used to define the threshold at which AE goes low - values are programmable from 1 to 1020.

Can SN74ACT3641-30PQ perform repeated reads from a specific FIFO location?

Yes, SN74ACT3641-30PQ supports synchronous retransmit mode: when RTM is asserted high with OR high, a rising CLKB edge marks the current output register content as the first retransmit word. Subsequent reads loop from that point until RTM is deasserted, enabling repeat playback without CPU intervention or external address tracking.

What is the function of the mailbox registers in SN74ACT3641-30PQ?

SN74ACT3641-30PQ includes two independent 36-bit mailbox registers (mail1 and mail2) with dedicated flags MBF1 and MBF2. They operate in parallel with the main FIFO, allowing sideband control messages (e.g., configuration commands or status updates) to be exchanged between port A and port B without consuming FIFO storage or affecting data flow timing.