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Texas Instruments SN74ACT3641-20PCB
- Part No.:
- SN74ACT3641-20PCB
- Manufacturer:
- Texas Instruments
- Category:
- FIFOs Memory
- Package:
- 120-LQFP
- Datasheet:
-
SN74ACT3641-20PCB.pdf
- Description:
- IC FIFO SYNC 1KX36 120HLQFP
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
SN74ACT3641-20PCB 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 and mailbox-based inter-processor communication.
For engineers reviewing the SN74ACT3641-20PCB datasheet, SN74ACT3641-20PCB pinout, SN74ACT3641-20PCB application, or SN74ACT3641-20PCB equivalent, key selection criteria include its 120-pin thin quad flat (PCB) package, programmable almost-full/almost-empty flags synchronized to independent clocks CLKA/CLKB, dual 36-bit mailbox registers, and pin-to-pin compatibility with SN74ACT3631 and SN74ACT3651 for scalable FIFO depth or width expansion.
Technical Context
The SN74ACT3641-20PCB implements a dual-clock, synchronous FIFO architecture using 1024 × 36-bit SRAM with two-stage metastability-hardened flag synchronization. Its port-A interface (CLKA, CSA, W/RA, ENA) and port-B interface (CLKB, CSB, W/RB, ENB) operate independently-clocks may be asynchronous or coincident-and each supports write/read, mailbox access, and retransmit mode control via RTM and RFM inputs.
Flag logic includes IR and AF synchronized to CLKA, OR and AE synchronized to CLKB, and programmable offset registers (X for AE, Y for AF) loaded via parallel (Port A), serial (FS0/SD, FS1/SEN), or preset (8 or 64) methods. Retransmit mode enables repeat reads from a user-marked location without disrupting ongoing writes, while mailbox registers (Mail1/Mail2) provide dedicated command-passing channels between ports.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 1024 × 36-bit SRAM FIFO buffer - supports 36-bit wide data paths with 1K depth for burst buffering. |
| Max Clock Frequency | 67 MHz - enables real-time streaming at up to 2.4 Gbps aggregate throughput (36 bits × 67 MHz). |
| Access Time | 11 ns - guarantees deterministic read latency for time-critical control loops and DSP interfaces. |
| Flag Synchronization | Two-stage flip-flop sync for IR/AF (to CLKA) and OR/AE (to CLKB) - reduces metastability risk in asynchronous clock domain crossings. |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade embedded systems and industrial controller applications. |
| Technology | Low-power 0.8-µm Advanced CMOS - delivers TTL-compatible drive strength with reduced static power vs. bipolar FIFOs. |
| Retransmit Capability | Synchronous retransmit with shadow read pointer - allows repeat playback of FIR filter coefficients or protocol headers without host CPU intervention. |
Pinout & Package
SN74ACT3641-20PCB is housed in a 120-pin thin quad flat package (TQFP), designated "PCB" in TI documentation, with 0.4 mm lead pitch and exposed thermal pad. Pin numbering follows standard TQFP top-view convention (pin 1 at top-left corner, counterclockwise).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A35 | Port-A bidirectional data bus | 36-bit parallel interface for writing to or reading from FIFO or Mail1 register under CLKA control. |
| B0–B35 | Port-B bidirectional data bus | 36-bit parallel interface for reading from or writing to FIFO or Mail2 register under CLKB control. |
| CLKA, CLKB | Free-running port clocks | Independent synchronous timing references; all transfers gated on low-to-high transitions; support asynchronous or coincident operation. |
| ENA, ENB | Port-A/B master enable inputs | Enable/disable port activity; must be high for valid CLKA/CLKB-triggered transfers. |
| CSA, CSB | Port-A/B chip select inputs | Assert low to activate port data drivers; place A0–A35/B0–B35 in high-Z when deasserted. |
| W/RA, W/RB | Port-A/B write/read select | W/RA high = write to FIFO/Mail1; W/RB low = write to FIFO/Mail2 - defines directionality per port. |
| IR, OR, AF, AE | Status flags | IR/AF synchronized to CLKA; OR/AE synchronized to CLKB; indicate FIFO fill level and readiness with programmable thresholds. |
| MBA, MBB | Mailbox select inputs | Select Mail1 (A-side) or Mail2 (B-side) for read/write instead of FIFO array - enables sideband command channel. |
| RTM, RFM | Retransmit control | RTM high + OR high initiates retransmit mode; RFM high + CLKB rising edge resets read pointer to marked location. |
| RST | Asynchronous reset input | Requires ≥4 CLKA and ≥4 CLKB rising edges while low - initializes pointers, clears flags, and loads offset registers. |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous retransmit with shadow read pointer | Enables repeat reads from any FIFO location without host software overhead - critical for FIR filtering and protocol header replay. |
| Dual 36-bit mailbox registers (Mail1/Mail2) | Provides dedicated non-blocking command/data channels between Port A and Port B - eliminates FIFO contention for control messages. |
| Programmable almost-full/almost-empty offsets (X/Y) | Three programming modes (preset 8/64, parallel load from Port A, serial load via FS0/SD) allow runtime tuning of flow-control thresholds. |
| Metastability-hardened flag synchronization | Two-stage synchronizers on IR/AF (CLKA domain) and OR/AE (CLKB domain) ensure reliable flag assertion across asynchronous clock boundaries. |
| Pin-to-pin compatibility with SN74ACT3631/SN74ACT3651 | Enables drop-in replacement or width/depth scaling - e.g., parallel stacking for 72-bit width or cascading for >1K depth. |
Applications
| DSP Data Streaming | FPGA-to-Microprocessor Bridge |
|---|---|
Use Scenario: Real-time FIR filtering in telecom baseband processing where coefficient sets must be repeatedly accessed while new samples stream in. IC Role / Device Role / Timing Role: SN74ACT3641-20PCB acts as a retransmit-capable FIFO buffer between FPGA fabric and external memory, decoupling variable-latency memory reads from fixed-rate sample ingestion. Use Value: Synchronous retransmit eliminates DMA reload overhead; 11 ns access ensures coefficient fetches meet tight pipeline timing; dual mailboxes pass filter configuration updates without stalling data flow. |
Use Scenario: High-throughput command/data exchange between Xilinx Artix-7 FPGA and ARM Cortex-A9 processor in industrial motion controller. IC Role / Device Role / Timing Role: SN74ACT3641-20PCB serves as a dual-port, clock-domain-crossing FIFO with mailbox registers - isolating FPGA logic clock (100 MHz) from processor bus clock (50 MHz). Use Value: Asynchronous CLKA/CLKB operation prevents timing violations; programmable AF/AE flags enable adaptive backpressure; mailbox registers deliver real-time fault codes without FIFO occupancy interference. |
| Protocol Stack Offload | Test Equipment Data Capture |
Use Scenario: Ethernet MAC layer offload in network appliance, where packet headers require repeated parsing while payloads stream through DMA. IC Role / Device Role / Timing Role: SN74ACT3641-20PCB stores full packet buffers and provides retransmit access to header fields (e.g., VLAN tag, IP checksum) during hardware-assisted forwarding. Use Value: Retransmit mode avoids duplicate header storage; 1024-word depth accommodates jumbo frames; IR/AF flags coordinate with MAC TX/RX state machines to prevent overflow/underflow. |
Use Scenario: High-speed logic analyzer front-end capturing 36-bit parallel bus traces at 67 MHz for post-processing in PC-based analysis software. IC Role / Device Role / Timing Role: SN74ACT3641-20PCB functions as a deep, clocked capture buffer - accepting raw bus data on CLKA and releasing it over slower USB/PCIe interface via CLKB. Use Value: 67 MHz write clock matches source bus speed; OR/AE flags signal host when blocks are ready for transfer; mailbox registers pass trigger event timestamps alongside captured data. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar clocked FIFO memory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ACT3631-20PCB | Same 1024 × 36 size, identical PCB package, but lacks mailbox registers and retransmit capability. | Suitable only for basic FIFO buffering without sideband control or repeat-read requirements. | Select when cost reduction is prioritized and mailbox/retransmit features are unused. |
| SN74ACT3651-20PCB | Same footprint and pinout, but offers 2048 × 36 capacity and enhanced flag flexibility - no change to CLKA/CLKB interface logic. | Required when deeper buffering is needed for longer burst intervals or higher data rates. | Choose for future-proofing or applications demanding >1K word depth without PCB redesign. |
Compared with SN74ACT3631-20PCB, the SN74ACT3641-20PCB adds mailbox registers and retransmit mode at identical pinout and timing; versus SN74ACT3651-20PCB, it trades depth for integrated control features - making SN74ACT3641-20PCB optimal for balanced bandwidth, latency, and feature-rich inter-processor communication.
Availability
SN74ACT3641-20PCB is available at Aetrix Electronics and suitable for DSP acceleration, FPGA-to-processor bridging, protocol stack offload, and test equipment data capture requiring stable component supply and long-term obsolescence management.
Supply support for SN74ACT3641-20PCB 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 interface and memory products.
The SN74ACT3641-20PCB belongs to TI's advanced clocked FIFO family designed for deterministic, low-latency data buffering across asynchronous clock domains in communications infrastructure, industrial automation, and test instrumentation.
FAQ
What is the maximum operating frequency supported by the SN74ACT3641-20PCB?
The SN74ACT3641-20PCB supports clock frequencies up to 67 MHz on both CLKA and CLKB inputs. This specification is validated across the full commercial temperature range (0°C to 70°C) and ensures reliable 11 ns access time and setup/hold margin compliance per the SCAS338C datasheet revision October 1997.
How does the retransmit functionality work in the SN74ACT3641-20PCB?
The SN74ACT3641-20PCB implements synchronous retransmit using a shadow read pointer that locks to the current location when RTM is asserted high and OR is high. Subsequent reads cycle through FIFO contents starting from that point. RFM enables immediate repositioning to the marked location on the next CLKB edge - a feature used in FIR filtering and protocol header replay without host CPU involvement.
Can the SN74ACT3641-20PCB be used with asynchronous clocks on Port A and Port B?
Yes, the SN74ACT3641-20PCB explicitly supports asynchronous operation of CLKA and CLKB - they may run at different frequencies or phases. Flag signals (IR/AF synchronized to CLKA; OR/AE to CLKB) use two-stage synchronizers to mitigate metastability, and the functional block diagram confirms independent clock domain handling for write and read paths.
What are the programming options for the almost-empty and almost-full offset registers in the SN74ACT3641-20PCB?
The SN74ACT3641-20PCB supports three offset register (X for AE, Y for AF) programming methods: preset values of 8 or 64 selected via FS1/FS0 at RST assertion; parallel load from Port A (two consecutive writes); or serial load via FS0/SD with 20-bit sequence synchronized to CLKA. All methods are documented in the SCAS338C datasheet Section "Almost-Empty Flag and Almost-Full Flag Offset Programming".
Is the SN74ACT3641-20PCB pin-compatible with other devices in the same family?
Yes, the SN74ACT3641-20PCB is pin-to-pin compatible with SN74ACT3631-20PCB and SN74ACT3651-20PCB in the 120-pin PCB package. This allows direct substitution or system scalability - for example, replacing SN74ACT3631-20PCB to add mailbox/retransmit features, or upgrading to SN74ACT3651-20PCB for doubled depth - without PCB layout changes.
SN74ACT3641-20PCB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ACT
- Package/Case:
- 120-LQFP
- Packaging:
- Tray
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Memory Size:
- 36K (1K 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:
- 120-HLQFP (14x14)
SN74ACT3641-20PCB FAQ
1.How can I place an order for SN74ACT3641-20PCB through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ACT3641-20PCB 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 SN74ACT3641-20PCB reliable?
The price and inventory of SN74ACT3641-20PCB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ACT3641-20PCB is usually 5 days.
3.What payment methods are accepted for SN74ACT3641-20PCB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ACT3641-20PCB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ACT3641-20PCB?
SN74ACT3641-20PCB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ACT3641-20PCB 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 SN74ACT3641-20PCB?
For technical support, including SN74ACT3641-20PCB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ACT3641-20PCB requirements.
6.How does Aetrix verify that SN74ACT3641-20PCB is sourced from the original manufacturer or authorized distributors?
All SN74ACT3641-20PCB 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 SN74ACT3641-20PCB meets industry standards.
7.What is the process for return or replacement of SN74ACT3641-20PCB?
All SN74ACT3641-20PCB units undergo pre-shipment inspection (PSI). If there is an issue with SN74ACT3641-20PCB, 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 SN74ACT3641-20PCB part is unused and in its original packaging.
Return procedure for SN74ACT3641-20PCB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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