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Texas Instruments SN74ACT3641-20PQ
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- Part No.:
- SN74ACT3641-20PQ
- Manufacturer:
- Texas Instruments
- Category:
- FIFOs Memory
- Package:
- 132-BQFP Bumpered
- Datasheet:
-
SN74ACT3641-20PQ.pdf
- Description:
- IC FIFO SYNC 1KX36 13NS 132BQFP
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
SN74ACT3641-20PQ from Texas Instruments is a 1024 × 36-bit clocked FIFO memory IC with dual asynchronous ports (A/B), synchronous retransmit capability, programmable almost-full/almost-empty flags, and mailbox registers. It operates up to 67 MHz with 11 ns access time and supports microprocessor interfacing via CLKA/CLKB-synchronized control logic in industrial temperature range (0°C to 70°C).
For engineers reviewing the SN74ACT3641-20PQ datasheet, SN74ACT3641-20PQ pinout, SN74ACT3641-20PQ application, or SN74ACT3641-20PQ equivalent, key selection criteria include dual-clock domain synchronization, 36-bit bidirectional data width, retransmit mode timing behavior, flag offset programming methods (serial/parallel/preset), and PQ-package thermal and routing constraints.
Technical Context
The SN74ACT3641-20PQ implements a dual-port SRAM-based FIFO with independent CLKA and CLKB domains, each supporting free-running clocks that may be asynchronous or coincident. Its functional block includes write/read pointers, two-stage synchronized status flags (IR/AF on CLKA; OR/AE on CLKB), and dedicated mailbox registers (Mail1/Mail2) with flag signaling (MBF1/MBF2).
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 via FS0/SD and FS1/SEN-and directly govern FIFO fill-level thresholds. Retransmit mode uses shadow read pointer logic triggered by RTM/RFM to enable repeatable data streaming without disrupting ongoing writes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 1024 × 36 bits - provides 1024 words of 36-bit depth for high-bandwidth buffering between mismatched clock domains. |
| Max Clock Frequency | 67 MHz - defines maximum sustained throughput per port; determines minimum cycle time for reliable CLKA/CLKB operation. |
| Access Time | 11 ns - specifies worst-case delay from clock edge to valid output data, critical for timing closure in high-speed interfaces. |
| Operating Temperature | 0°C to 70°C - qualifies for commercial/industrial ambient environments; no extended temp grade support. |
| Supply Voltage | 5 V ± 5% - requires stable 5 V rail; compatible with TTL/CMOS logic families and legacy microprocessor buses. |
| Technology | Advanced CMOS (0.8 µm) - enables low power consumption while maintaining high speed and noise immunity. |
| Flag Synchronization | Two-stage flip-flop sync - reduces metastability risk when CLKA and CLKB operate asynchronously. |
Pinout & Package
SN74ACT3641-20PQ is housed in a 132-pin Plastic Quad Flat (PQ) package with 0.65 mm lead pitch, designed for surface-mount assembly and thermal dissipation in dense PCB layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A35 | Port-A bidirectional data bus | 36-bit interface for writing/reading FIFO or Mail1 register; high-impedance when CSA or W/RA inactive. |
| B0–B35 | Port-B bidirectional data bus | 36-bit interface for reading/writing FIFO or Mail2 register; outputs active only when CSB = L and W/RB = H. |
| CLKA, CLKB | Free-running port clocks | Independent synchronous timing references; all transfers gated to rising edge; support asynchronous or coincident operation. |
| ENA, ENB | Port master enables | Enable/disable port activity independently; required HIGH to allow CLKA/CLKB transitions to trigger reads/writes. |
| CSA, CSB | Port chip selects | Assert LOW to activate respective port; place data lines in high-Z state when HIGH. |
| W/RA, W/RB | Port write/read direction controls | W/RA = H → write; W/RB = L → write; both define active transfer direction per clock edge. |
| IR, OR, AF, AE | Status flags | IR/AF synchronized to CLKA; OR/AE 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; control data path routing at port level. |
| RTM, RFM | Retransmit control | RTM = H + OR = H initiates retransmit mode; RFM = H triggers re-read from marked location during retransmit. |
| RST | Asynchronous reset | Requires ≥4 rising edges on both CLKA and CLKB while LOW; initializes pointers, flags, and mailbox states. |
| FS0/SD, FS1/SEN | Flag offset programming | Dual-function pins: configure X/Y register loading method (preset/parallel/serial) on RST rising edge. |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous retransmit capability | Enables repeatable streaming of user-selected FIFO segments using shadow read pointer, preserving integrity during concurrent writes. |
| Programmable almost-full/almost-empty flags | Offset values (X/Y) configurable via serial, parallel, or preset methods-enables adaptive flow control for variable-rate systems. |
| Dual 36-bit mailbox registers | Mail1 and Mail2 provide sideband command/control channel between ports, decoupled from main FIFO data path and flagged for handshake. |
| Two-stage synchronized status flags | IR/AF tied to CLKA; OR/AE tied to CLKB-reduces metastability failure probability in asynchronous clock domain crossings. |
| Microprocessor interface logic | Integrated CSA/CSB, W/RA/W/RB, ENA/ENB decoding simplifies connection to 80x86, Motorola 68k, or custom bus controllers. |
Applications
| Telecom Line Card Buffering | DSP Data Pipeline Interface |
|---|---|
Use Scenario: Bridging data streams between TDM framer and DSP core operating at different clock rates. IC Role / Device Role / Timing Role: Clocked FIFO buffering with independent CLKA (framer clock) and CLKB (DSP clock) domains. Use Value: Eliminates data loss during rate mismatches; programmable AF/AE flags enable dynamic buffer watermarking for jitter tolerance. |
Use Scenario: Feeding FIR filter coefficients and sample data into a fixed-point DSP with bursty I/O scheduling. IC Role / Device Role / Timing Role: Dual-port FIFO with synchronous retransmit for coefficient reuse across multiple filter taps. Use Value: Reduces external memory accesses; retransmit mode allows repeated coefficient reads without CPU intervention. |
| Industrial PLC Communication Gateway | Legacy Bus-to-PCIe Bridge Controller |
Use Scenario: Aggregating sensor data from multiple RS-485 Modbus slaves onto a real-time Ethernet backbone. IC Role / Device Role / Timing Role: High-throughput 36-bit FIFO with mailbox registers for command handshaking between protocol stacks. Use Value: Mailbox flags (MBF1/MBF2) provide hardware-level interlock for configuration updates; 67 MHz clock headroom supports oversampling. |
Use Scenario: Adapting wide parallel address/data bus (e.g., ISA or VME) to PCIe endpoint with packetized transaction layer. IC Role / Device Role / Timing Role: Depth-scalable FIFO buffer with pin-compatible expansion (multiple SN74ACT3641-20PQ in parallel). Use Value: 1024-word depth accommodates PCIe TLP payload bursts; PQ package supports compact adapter board layout. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar clocked FIFO applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ACT3631-20PQ | Same 1024 × 36 architecture but lacks mailbox registers and synchronous retransmit logic. | Suitable for basic buffering where sideband control or repeated data streaming is unnecessary. | Choose when cost reduction is prioritized and mailbox/retransmit features are unused. |
| SN74ACT3651-20PQ | Includes identical mailbox and retransmit functionality but adds programmable reset polarity and enhanced flag timing margins. | Better suited for systems requiring deterministic reset behavior or tighter setup/hold compliance under marginal signal integrity. | Select when operating near timing limits or requiring configurable RST assertion polarity. |
Compared with SN74ACT3631-20PQ, SN74ACT3641-20PQ adds mailbox registers and retransmit capability-critical for command/data coexistence and coefficient reuse-while SN74ACT3651-20PQ extends reliability with configurable reset and improved flag timing, making it preferable in margin-constrained designs.
Availability
SN74ACT3641-20PQ is available at Aetrix Electronics and suitable for telecom line card buffering, DSP pipeline interfacing, industrial PLC gateways, and legacy bus-to-PCIe bridge controllers requiring stable component supply and long-term obsolescence management.
Supply support for SN74ACT3641-20PQ 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 heritage in high-reliability interface and memory products.
The SN74ACT3641-20PQ belongs to TI's advanced clocked FIFO family, engineered for deterministic data flow control in mixed-clock-domain systems such as communications infrastructure, industrial automation, and digital signal processing subsystems.
FAQ
What is the maximum supported clock frequency for SN74ACT3641-20PQ?
The SN74ACT3641-20PQ supports clock frequencies up to 67 MHz on both CLKA and CLKB inputs. This rating is validated across the full commercial temperature range (0°C to 70°C) and assumes proper signal integrity, termination, and power supply decoupling per TI's layout guidelines. Exceeding this frequency may result in timing violations or metastability in flag outputs.
How does the retransmit mode function in SN74ACT3641-20PQ?
In SN74ACT3641-20PQ, retransmit mode is activated by asserting RTM = HIGH while OR = HIGH, capturing the current FIFO output register content as the retransmit start point. Subsequent reads loop from that location until RTM is deasserted. RFM enables immediate re-triggering of the loop. The feature relies on shadow read pointer logic and preserves write capability during retransmission.
Can SN74ACT3641-20PQ operate with CLKA and CLKB running at different frequencies?
Yes, SN74ACT3641-20PQ is explicitly designed for asynchronous clock domains: CLKA and CLKB may run at different frequencies, phases, or duty cycles. Status flags (IR/AF and OR/AE) are two-stage synchronized to their respective clocks to mitigate metastability, and internal pointer logic handles independent read/write rates without data corruption.
What are the programming options for the almost-empty and almost-full flag offsets in SN74ACT3641-20PQ?
SN74ACT3641-20PQ supports three offset programming methods: (1) preset values (8 or 64) selected via FS1/FS0 at RST rising edge; (2) parallel load from Port-A using A9–A0 for Y then X registers; (3) serial load via FS0/SD with 20-bit sequence synchronized to CLKA edges while FS1/SEN is low. All methods set X (AE) and Y (AF) registers used for fill-level thresholding.
Is SN74ACT3641-20PQ pin-compatible with other devices in the same family?
Yes, SN74ACT3641-20PQ is pin-to-pin compatible with SN74ACT3631-20PQ and SN74ACT3651-20PQ in the 132-pin PQ package. This allows direct substitution where mailbox register usage or retransmit mode is not required (for SN74ACT3631-20PQ) or where enhanced reset timing is needed (for SN74ACT3651-20PQ), without PCB redesign.
SN74ACT3641-20PQ 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:
- 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:
- 132-BQFP (24.13x24.13)
SN74ACT3641-20PQ FAQ
1.How can I place an order for SN74ACT3641-20PQ through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ACT3641-20PQ 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 SN74ACT3641-20PQ reliable?
The price and inventory of SN74ACT3641-20PQ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ACT3641-20PQ is usually 5 days.
3.What payment methods are accepted for SN74ACT3641-20PQ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ACT3641-20PQ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ACT3641-20PQ?
SN74ACT3641-20PQ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ACT3641-20PQ 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 SN74ACT3641-20PQ?
For technical support, including SN74ACT3641-20PQ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ACT3641-20PQ requirements.
6.How does Aetrix verify that SN74ACT3641-20PQ is sourced from the original manufacturer or authorized distributors?
All SN74ACT3641-20PQ 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 SN74ACT3641-20PQ meets industry standards.
7.What is the process for return or replacement of SN74ACT3641-20PQ?
All SN74ACT3641-20PQ units undergo pre-shipment inspection (PSI). If there is an issue with SN74ACT3641-20PQ, 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 SN74ACT3641-20PQ part is unused and in its original packaging.
Return procedure for SN74ACT3641-20PQ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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