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Home > Products > Integrated Circuits (ICs) > Logic > FIFOs Memory

Texas Instruments SN74ACT3631-15PQ

Name: SN74ACT3631-15PQ
Brand: Texas Instruments
SKU: SN74ACT3631-15PQ
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74ACT3631-15PQ

Manufacturer:: Texas Instruments

Category:: FIFOs Memory

Package:: 132-BQFP Bumpered

Datasheet:: SN74ACT3631-15PQ.pdf

Description:: IC FIFO SYNC 512X36 132BQFP

Quantity:: RFQ Add To RFQ list

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Product details

Overview

SN74ACT3631-15PQ from Texas Instruments is a 512 × 36-bit clocked FIFO memory IC with dual asynchronous ports, supporting up to 67 MHz clock frequency, 11 ns read access time, and synchronous retransmit capability. It operates in industrial temperature range (0°C to 70°C) and implements two 36-bit mailbox registers for inter-port control messaging - used in high-speed data buffering between mismatched bus domains in telecom line cards and DSP interface subsystems.

For engineers reviewing the SN74ACT3631-15PQ datasheet, SN74ACT3631-15PQ pinout, SN74ACT3631-15PQ application, or SN74ACT3631-15PQ equivalent, key selection considerations include programmable almost-full/empty flag offsets, CLKA/CLKB metastability-hardened flag synchronization, mailbox register flag handshaking, and compatibility with microprocessor bus timing constraints in real-time embedded systems.

Technical Context

The SN74ACT3631-15PQ employs a dual-clock synchronous architecture with independent CLKA and CLKB domains, each driving separate write/read pointer logic and status flag generation. Its 512 × 36 SRAM core supports concurrent port-A writes and port-B reads without arbitration, enabled by two-stage synchronized flags (IR/AF on CLKA; OR/AE on CLKB) to suppress metastability during clock domain crossing.

It integrates programmable offset registers for AF and AE flags (1–508 words), selectable via parallel load from port A, serial load over FS0/SD, or preset values (8 or 64). Retransmit mode uses shadow read pointer logic triggered by RTM/RFM to enable repeatable FIR filter coefficient streaming, while mailbox registers (Mail1/Mail2) provide non-blocking command channel handshaking with MBF1/MBF2 flag signaling.

Key Specifications

Parameter	Value and Actual Design Meaning
Memory Depth × Width	512 × 36 bits - provides 18,432-bit buffer capacity for burst-mode data alignment between dissimilar clock domains.
Max Clock Frequency	67 MHz - enables real-time buffering of high-throughput digital streams such as T3/E3 framers or PCI-to-PCI bridge interfaces.
Read Access Time	11 ns - guarantees sub-15 ns latency from CLKB edge to valid output data, critical for deterministic DSP pipeline staging.
Operating Temperature	0°C to 70°C - qualified for commercial-grade industrial control and communications equipment without derating.
Supply Voltage	5 V ± 5% - compatible with legacy TTL/CMOS bus systems and requires no level-shifting for 5-V microprocessor interfacing.
Technology Node	0.8-µm Advanced CMOS - delivers low static power (< 100 mW typical) while maintaining TTL-compatible input thresholds and output drive strength.
Flag Synchronization	Two-stage flip-flop sync per flag - reduces metastability failure probability below 10⁻¹² per operation when CLKA and CLKB are fully asynchronous.

Pinout & Package

SN74ACT3631-15PQ is housed in a 132-pin Plastic Quad Flat (PQ) package with 0.65 mm lead pitch, compliant with JEDEC MS-026. Pin numbering follows standard PQ top-view convention with corner pin 1 marked.

Pin/Terminal	Circuit Role	Design Meaning
A0–A35	Port-A bidirectional data bus	36-bit parallel interface for writing to or reading from FIFO/mailbox; high-impedance when CSA or W/RA inactive.
B0–B35	Port-B bidirectional data bus	36-bit parallel interface for reading from or writing to FIFO/mailbox; active only when CSB = L and W/RB = H.
CLKA, CLKB	Free-running synchronous clocks	Independent continuous clocks; all port operations gated on low-to-high transitions; support asynchronous or coincident timing.
IR, OR, AF, AE	Synchronized status flags	IR/AF tied to CLKA domain; OR/AE tied to CLKB domain; two-stage sync ensures reliable handshake across clock boundaries.
MBA, MBB	Mailbox select controls	Select mail1/mail2 register instead of FIFO for port-A/port-B transfers; enable non-blocking control message exchange.
RTM, RFM	Retransmit mode controls	RTM initiates retransmit loop at current output word; RFM resets read pointer to retransmit start point on next CLKB edge.
RST	Asynchronous reset input	Requires four CLKA + four CLKB rising edges while low; initializes pointers, clears flags, and loads AF/AE offset defaults.

Key Features

Feature	Design Value
Synchronous retransmit mode	Enables repeatable streaming of FIR coefficients or protocol headers without CPU intervention; initiated by RTM/RFM with shadow read pointer.
Programmable flag offsets	AF/AE thresholds set to 1–508 words via serial load, parallel load from port A, or preset (8 or 64); eliminates fixed-threshold design constraints.
Dual 36-bit mailbox registers	Mail1 (port-A → port-B) and Mail2 (port-B → port-A) provide dedicated non-FIFO channels for control/status messages with MBF1/MBF2 handshaking.
Metastability-hardened flag sync	IR/AF synchronized to CLKA; OR/AE synchronized to CLKB using dual flip-flop stages - validated per SCZA004 for <10⁻¹² failure rate.
Microprocessor interface logic	Integrated CSA/CSB, ENA/ENB, W/RA/W/RB decoding eliminates external glue logic; supports standard 80Cxx/68K-style bus timing.

Applications

Telecom Line Card Buffering	DSP Interface Coefficient Streaming
Use Scenario: Bridging T1/E1 framer outputs to ATM segmentation engines with clock domain isolation. IC Role / Device Role / Timing Role: Clocked FIFO providing elastic store between 1.544 MHz and 125 MHz domains while absorbing jitter and burst gaps. Use Value: Eliminates external synchronizers and reduces PCB area by integrating dual-mailbox handshaking for frame alignment commands.	Use Scenario: Streaming FIR filter coefficients from host processor to fixed-point DSP with repeatable access pattern. IC Role / Device Role / Timing Role: Retransmit-capable FIFO acting as coefficient cache with programmable depth to match filter tap count. Use Value: Enables zero-overhead coefficient reuse during multi-pass filtering without DMA reload or CPU polling.
Industrial PLC I/O Data Aggregation	Legacy Bus Protocol Translation
Use Scenario: Consolidating sensor data from multiple RS-485 Modbus slaves into a single Ethernet controller stream. IC Role / Device Role / Timing Role: Dual-port FIFO buffering variable-length Modbus responses while decoupling slave response timing from master polling rate. Use Value: Prevents data loss during bus contention and allows deterministic scheduling of Ethernet packet assembly.	Use Scenario: Interfacing ISA-bus microcontrollers to modern PCIe-based host controllers via FPGA bridge. IC Role / Device Role / Timing Role: Clock-domain crossing FIFO with mailbox registers handling configuration register writes and interrupt status reads. Use Value: Removes need for custom FIFO IP in FPGA; simplifies timing closure with guaranteed 11 ns access and 67 MHz throughput.

Telecom Line Card Buffering

DSP Interface Coefficient Streaming

Use Scenario: Bridging T1/E1 framer outputs to ATM segmentation engines with clock domain isolation.

IC Role / Device Role / Timing Role: Clocked FIFO providing elastic store between 1.544 MHz and 125 MHz domains while absorbing jitter and burst gaps.

Use Value: Eliminates external synchronizers and reduces PCB area by integrating dual-mailbox handshaking for frame alignment commands.

Use Scenario: Streaming FIR filter coefficients from host processor to fixed-point DSP with repeatable access pattern.

IC Role / Device Role / Timing Role: Retransmit-capable FIFO acting as coefficient cache with programmable depth to match filter tap count.

Use Value: Enables zero-overhead coefficient reuse during multi-pass filtering without DMA reload or CPU polling.

Industrial PLC I/O Data Aggregation

Legacy Bus Protocol Translation

Use Scenario: Consolidating sensor data from multiple RS-485 Modbus slaves into a single Ethernet controller stream.

IC Role / Device Role / Timing Role: Dual-port FIFO buffering variable-length Modbus responses while decoupling slave response timing from master polling rate.

Use Value: Prevents data loss during bus contention and allows deterministic scheduling of Ethernet packet assembly.

Use Scenario: Interfacing ISA-bus microcontrollers to modern PCIe-based host controllers via FPGA bridge.

IC Role / Device Role / Timing Role: Clock-domain crossing FIFO with mailbox registers handling configuration register writes and interrupt status reads.

Use Value: Removes need for custom FIFO IP in FPGA; simplifies timing closure with guaranteed 11 ns access and 67 MHz throughput.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74ACT3641-15PQ	Same 512 × 36 architecture but lacks mailbox registers and retransmit logic; no MBF1/MBF2 or RTM/RFM pins.	Used where only basic FIFO buffering is needed; unsuitable for control-message coexistence or coefficient replay.	Select when cost reduction is prioritized and mailbox/retransmit features are unused.
SN74ACT3651-15PQ	Includes mailbox registers but omits retransmit mode; no RTM/RFM inputs or shadow pointer logic.	Supports command/data separation but cannot perform repeated streaming; limited to one-time coefficient load scenarios.	Choose when mailbox handshaking is required but retransmit loops are unnecessary.

Compared with SN74ACT3631-15PQ, SN74ACT3641-15PQ removes mailbox and retransmit functionality to reduce pin count and cost, while SN74ACT3651-15PQ retains mailboxes but excludes retransmit logic - making SN74ACT3631-15PQ the only option supporting both concurrent control messaging and repeatable data streaming in a single device.

Availability

SN74ACT3631-15PQ is available at Aetrix Electronics and suitable for telecom infrastructure, DSP interface subsystems, industrial PLC I/O modules, and legacy bus translation requiring stable component supply across long production lifecycles.

Supply support for SN74ACT3631-15PQ 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-reliability interface and memory products.

The SN74ACT3631-15PQ belongs to TI's ACT-family clocked FIFO product line, designed specifically for deterministic, low-latency data buffering between asynchronous digital subsystems in communications and industrial control applications.

FAQ

What is the maximum supported clock frequency for SN74ACT3631-15PQ?

The SN74ACT3631-15PQ supports clock frequencies up to 67 MHz on both CLKA and CLKB inputs, as specified in the SCAS246G datasheet. This rating applies across the full 0°C to 70°C operating temperature range and assumes proper signal integrity, termination, and power supply decoupling per TI layout guidelines.

How does the retransmit mode function in SN74ACT3631-15PQ?

In SN74ACT3631-15PQ, retransmit mode is activated by a rising edge on CLKB while RTM = high and OR = high, which latches the current output word as the retransmit start point. Subsequent rising edges on CLKB with RFM = high reload that same word into the output register, enabling repeatable streaming without CPU involvement or external memory.

Can SN74ACT3631-15PQ operate with fully asynchronous CLKA and CLKB clocks?

Yes, SN74ACT3631-15PQ is explicitly designed for asynchronous CLKA and CLKB operation. Its IR/AF flags are synchronized to CLKA and OR/AE to CLKB using two-stage flip-flop chains, reducing metastability risk to less than 10⁻¹² per operation - validated in TI application report SCZA004.

What are the programming methods for the almost-full and almost-empty flag offsets in SN74ACT3631-15PQ?

SN74ACT3631-15PQ supports three AF/AE offset programming methods: (1) preset values (8 or 64) selected via FS1/FS0 at reset, (2) parallel load from port A (two writes to Y then X registers using A8–A0), or (3) serial load via FS0/SD with 18-bit sequence synchronized to CLKA edges while FS1/SEN is low.

Is SN74ACT3631-15PQ pin-compatible with other devices in the same family?

Yes, SN74ACT3631-15PQ is pin-to-pin compatible with SN74ACT3641-15PQ and SN74ACT3651-15PQ in the 132-pin PQ package, sharing identical pin assignments for clocks, data buses, chip selects, enables, and flags - allowing drop-in replacement where functional differences (mailbox/retransmit) are not required.

SN74ACT3631-15PQ Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74ACT

Package/Case:: 132-BQFP Bumpered

Packaging:: Tray

Product Status:: Obsolete

Programmable:: Not Verified

Memory Size:: 18K (512 x 36)

Function:: Synchronous

Data Rate:: 66.7MHz

Access Time:: 11ns

Voltage - Supply:: 4.5 V ~ 5.5 V

Current - Supply (Max):: 400µA

Bus Directional:: Bi-Directional

Expansion Type:: Depth, Width

Programmable Flags Support:: Yes

Retransmit Capability:: Yes

FWFT Support:: No

Operating Temperature:: 0°C ~ 70°C

Mounting Type:: Surface Mount

Supplier Device Package:: 132-BQFP (24.13x24.13)

SN74ACT3631-15PQ FAQ

1.How can I place an order for SN74ACT3631-15PQ through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74ACT3631-15PQ on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for SN74ACT3631-15PQ reliable?

The price and inventory of SN74ACT3631-15PQ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ACT3631-15PQ is usually 5 days.

3.What payment methods are accepted for SN74ACT3631-15PQ?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ACT3631-15PQ transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74ACT3631-15PQ?

SN74ACT3631-15PQ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74ACT3631-15PQ order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for SN74ACT3631-15PQ?

For technical support, including SN74ACT3631-15PQ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ACT3631-15PQ requirements.

6.How does Aetrix verify that SN74ACT3631-15PQ is sourced from the original manufacturer or authorized distributors?

All SN74ACT3631-15PQ products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SN74ACT3631-15PQ meets industry standards.

7.What is the process for return or replacement of SN74ACT3631-15PQ?

All SN74ACT3631-15PQ units undergo pre-shipment inspection (PSI). If there is an issue with SN74ACT3631-15PQ, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The SN74ACT3631-15PQ part is unused and in its original packaging.

Return procedure for SN74ACT3631-15PQ:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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