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Texas Instruments SN74ACT3631-20PQ
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- Part No.:
- SN74ACT3631-20PQ
- Manufacturer:
- Texas Instruments
- Category:
- FIFOs Memory
- Package:
- 132-BQFP Bumpered
- Datasheet:
-
SN74ACT3631-20PQ.pdf
- Description:
- IC FIFO SYNC 512X36 132BQFP
- Quantity:
- Payment:
- Shipping:
Inventory:2,865
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Product details
Overview
SN74ACT3631-20PQ 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 programmable almost-full/empty flags synchronized to CLKA and CLKB respectively. It enables high-speed data buffering between mismatched bus domains in telecom line cards and DSP-based signal processing systems.
For engineers reviewing the SN74ACT3631-20PQ datasheet, SN74ACT3631-20PQ pinout, SN74ACT3631-20PQ application, or SN74ACT3631-20PQ equivalent, key selection criteria include dual-port clock domain isolation, synchronous retransmit capability for FIR filter coefficient replay, mailbox register support for control-message handshaking, and 132-pin PQ package compatibility with legacy TI FIFO designs.
Technical Context
The SN74ACT3631-20PQ implements a 512-word × 36-bit dual-port SRAM FIFO with independent CLKA and CLKB clocks that may operate asynchronously or coincidently. Its status-flag logic uses two-stage synchronization to suppress metastability, with IR/AF tied to CLKA and OR/AE tied to CLKB.
It integrates two 36-bit mailbox registers (Mail1/Mail2), each with dedicated flag outputs (MBF1/MBF2), and supports three offset programming modes-preset (8 or 64), parallel load via Port A, or serial load via FS0/SD-enabling precise almost-empty (X) and almost-full (Y) thresholds from 1 to 508 words.
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-X interface bridges. |
| Read Access Time | 11 ns: Guarantees sub-15 ns latency for output data availability after CLKB edge, critical for deterministic timing in control loops. |
| Flag Synchronization | Two-stage flip-flop sync: Reduces metastability risk when CLKA and CLKB are fully asynchronous, ensuring reliable flag assertion timing. |
| Operating Temperature | 0°C to 70°C: Qualified for commercial-grade embedded systems including network edge routers and industrial PLC I/O modules. |
| Technology Node | 0.8-µm Advanced CMOS: Delivers low static power consumption while maintaining TTL-compatible input thresholds and 36-bit drive strength. |
| Retransmit Capability | Synchronous retransmit mode: Allows repeat reads from a user-marked location without disrupting ongoing writes-essential for FIR coefficient replay in DSP pipelines. |
Pinout & Package
SN74ACT3631-20PQ is housed in a 132-pin Plastic Quad Flat (PQ) package with 0.65 mm lead pitch, compatible with Yamaichi socket IC51-1324-828. Pin functions are validated per TI SCAS246G datasheet Rev. April 1998.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A35 | Port-A bidirectional data bus | 36-bit parallel interface for write/read operations gated by CLKA, CSA, W/RA, and ENA. |
| B0–B35 | Port-B bidirectional data bus | 36-bit parallel interface for write/read operations gated by CLKB, CSB, W/RB, and ENB; inverted W/RB polarity vs. W/RA. |
| CLKA, CLKB | Free-running port clocks | Independent continuous clocks; IR/AF synchronized to CLKA edges, OR/AE to CLKB edges. |
| ENA, ENB | Port master enable inputs | High-active enables for respective port operations; required alongside chip select and direction control. |
| CSA, CSB | Port chip select inputs | Low-active enables for port A/B data bus drivers; places A0–A35/B0–B35 in high-Z when deasserted. |
| W/RA, W/RB | Port write/read select | W/RA high = write on CLKA; W/RB high = read on CLKB (inverse logic for B-side). |
| IR, OR, AF, AE | Status flag outputs | IR/AF synchronized to CLKA; OR/AE to CLKB; all active-low; programmable thresholds via FS0/FS1. |
| MBA, MBB | Mailbox select inputs | Selects Mail1 (A-side) or Mail2 (B-side) for read/write instead of FIFO; controls MBF1/MBF2 flag behavior. |
| RTM, RFM | Retransmit control inputs | RTM high initiates retransmit mode; RFM high triggers read-from-mark during retransmit. |
| RST | Asynchronous reset input | Requires four low-to-high transitions on both CLKA and CLKB while RST is low to initialize pointers and flags. |
| VCC, GND | Power supply terminals | Multiple VCC (pins 3, 13, 22, 33, 44, 55, 66, 77, 88, 99, 110, 121, 132) and GND (pins 4, 14, 23, 34, 45, 56, 67, 78, 89, 100, 111, 122) pins ensure low-noise operation across wide bus. |
Key Features
| Feature | Design Value |
|---|---|
| Dual asynchronous clock domains | Enables seamless bridging between independent system clocks (e.g., 66 MHz PCI and 48 MHz USB PHY) without external synchronization logic. |
| Synchronous retransmit mode | Supports deterministic replay of up to 512 words from any marked location-used for coefficient streaming in FIR filters without CPU intervention. |
| Programmable almost-full/empty flags | Configurable X/Y offsets (1–508) allow fine-grained flow control tuning to match specific burst-length requirements in packet buffering applications. |
| Integrated mailbox registers | Two 36-bit bypass registers (Mail1/Mail2) with dedicated flags (MBF1/MBF2) simplify inter-processor command exchange in dual-CPU architectures. |
| Metastability-hardened flag outputs | Two-stage synchronization on all status flags ensures robust operation under worst-case clock skew conditions in multi-board systems. |
Applications
| Telecom Line Card Buffering | DSP-Based Signal Processing |
|---|---|
Use Scenario: Buffering variable-length ATM cells between OC-3 framer and backplane switch fabric operating at different clock rates. IC Role / Device Role / Timing Role: Clocked FIFO providing elastic storage with independent CLKA (framer clock) and CLKB (switch clock) domains. Use Value: Eliminates need for external clock-domain crossing logic while maintaining cell-order integrity and enabling jitter-tolerant cell scheduling. |
Use Scenario: Streaming FIR filter coefficients from host processor to DSP core during real-time audio processing. IC Role / Device Role / Timing Role: Retransmit-capable FIFO acting as coefficient replay buffer synchronized to DSP sample clock. Use Value: Enables zero-overhead coefficient reuse across multiple filter taps without DMA reload or CPU polling overhead. |
| Industrial PLC I/O Interface | Legacy Bus Bridging |
Use Scenario: Isolating Modbus RTU master (9.6 kbps) from high-speed EtherCAT slave interface (100 Mbps) in distributed I/O modules. IC Role / Device Role / Timing Role: Dual-port FIFO with mailbox registers handling command/response handshaking and data staging. Use Value: Prevents protocol collision and guarantees deterministic response latency by decoupling slow serial and fast Ethernet timing domains. |
Use Scenario: Interfacing 16-bit ISA bus peripherals to modern 32-bit microcontroller subsystems with mismatched data widths and timing. IC Role / Device Role / Timing Role: Width-expansible FIFO (two SN74ACT3631-20PQ in parallel) converting 16-bit bursts to 36-bit aligned transfers. Use Value: Maintains backward compatibility without custom ASIC design; leverages pin-to-pin compatibility with SN74ACT3641/SN74ACT3651 for drop-in upgrades. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar clocked FIFO applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ACT3641-20PQ | Same 512 × 36 architecture but lacks mailbox registers and synchronous retransmit logic; no MBF1/MBF2, RTM, or RFM pins. | Suitable only for basic FIFO buffering where command-channel handshaking and coefficient replay are unnecessary. | Select when cost reduction is prioritized over advanced control features and board space allows separate mailbox logic. |
| SN74ACT3651-20PQ | Identical pinout and feature set but rated for extended temperature range (–40°C to 85°C); otherwise functionally identical to SN74ACT3631-20PQ. | Required for automotive or outdoor industrial deployments where ambient temperature exceeds 70°C. | Choose for harsh-environment applications; direct replacement if thermal qualification is mandatory. |
Compared with SN74ACT3641-20PQ, SN74ACT3631-20PQ adds mailbox registers and retransmit capability essential for control-plane/data-plane separation; versus SN74ACT3651-20PQ, it trades extended temperature rating for lower cost in commercial environments.
Availability
SN74ACT3631-20PQ is available at Aetrix Electronics and suitable for telecom infrastructure, DSP acceleration, industrial PLC I/O, and legacy bus bridging applications requiring stable component supply and long-term obsolescence management.
Supply support for SN74ACT3631-20PQ 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 FIFO and interface ICs.
The SN74ACT3631-20PQ belongs to TI's ACT-family clocked FIFO product line, designed specifically for deterministic, low-latency data buffering across asynchronous clock domains in communications and real-time control systems.
FAQ
What is the maximum supported clock frequency for SN74ACT3631-20PQ?
The SN74ACT3631-20PQ supports clock frequencies up to 67 MHz on both CLKA and CLKB inputs, as specified in the SCAS246G datasheet Rev. April 1998. 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 synchronous retransmit feature work in SN74ACT3631-20PQ?
The SN74ACT3631-20PQ enters retransmit mode when RTM is high and OR is high on a rising CLKB edge, marking the current output register content as the first retransmit word. Subsequent reads with RFM high cause the shadow read pointer to reload, enabling repeat playback-critical for FIR coefficient streaming without CPU involvement.
Can SN74ACT3631-20PQ be used with only one clock domain?
Yes, SN74ACT3631-20PQ supports single-clock operation: CLKA and CLKB may be tied together or driven coincidentally. All port-A signals remain synchronized to CLKA, and all port-B signals to CLKB-even when clocks are identical-preserving functional integrity and flag timing relationships.
What are the valid programming methods for the almost-empty and almost-full offset registers in SN74ACT3631-20PQ?
SN74ACT3631-20PQ supports three offset programming modes selected via FS0/FS1 during RST assertion: preset values (8 or 64), parallel load from Port A (A8–A0), or serial load via FS0/SD with 18-bit sequence. Each method sets independent X (AE) and Y (AF) thresholds from 1 to 508 words.
Is SN74ACT3631-20PQ pin-compatible with other devices in the same family?
Yes, SN74ACT3631-20PQ is pin-to-pin compatible with SN74ACT3641-20PQ and SN74ACT3651-20PQ in the 132-pin PQ package. Shared pinout enables hardware reuse across variants differing only in feature set (e.g., mailbox presence) or temperature grade (commercial vs. extended).
SN74ACT3631-20PQ 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:
- 50MHz
- Access Time:
- 13ns
- 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)
SN74ACT3631-20PQ FAQ
1.How can I place an order for SN74ACT3631-20PQ through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ACT3631-20PQ 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 SN74ACT3631-20PQ reliable?
The price and inventory of SN74ACT3631-20PQ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ACT3631-20PQ is usually 5 days.
3.What payment methods are accepted for SN74ACT3631-20PQ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ACT3631-20PQ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ACT3631-20PQ?
SN74ACT3631-20PQ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ACT3631-20PQ 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 SN74ACT3631-20PQ?
For technical support, including SN74ACT3631-20PQ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ACT3631-20PQ requirements.
6.How does Aetrix verify that SN74ACT3631-20PQ is sourced from the original manufacturer or authorized distributors?
All SN74ACT3631-20PQ 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 SN74ACT3631-20PQ meets industry standards.
7.What is the process for return or replacement of SN74ACT3631-20PQ?
All SN74ACT3631-20PQ units undergo pre-shipment inspection (PSI). If there is an issue with SN74ACT3631-20PQ, 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 SN74ACT3631-20PQ part is unused and in its original packaging.
Return procedure for SN74ACT3631-20PQ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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