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Texas Instruments SN74ACT3638-20PCB
- Part No.:
- SN74ACT3638-20PCB
- Manufacturer:
- Texas Instruments
- Category:
- FIFOs Memory
- Package:
- -
- Datasheet:
-
SN74ACT3638-20PCB.pdf
- Description:
- IC FIFO 512X32 BI-DIRECTIONAL
- Quantity:
- Payment:
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Product details
Overview
SN74ACT3638-20PCB from Texas Instruments is a clocked bidirectional FIFO memory IC with two independent 512 × 32 dual-port SRAM buffers, supporting asynchronous or coincident free-running clocks (CLKA/CLKB), 67 MHz max clock frequency, 11 ns read access time, and mailbox-bypass registers for inter-processor communication in embedded data-path bridging applications.
For engineers reviewing the SN74ACT3638-20PCB datasheet, SN74ACT3638-20PCB pinout, SN74ACT3638-20PCB application, or SN74ACT3638-20PCB equivalent, key selection considerations include bidirectional clock domain isolation, programmable almost-full/empty flag offsets, retransmit capability on FIFO1, synchronized status flags, and 120-pin thin quad flat package compatibility with microprocessor bus interfaces.
Technical Context
The SN74ACT3638-20PCB integrates two independent 512 × 32 clocked FIFOs-FIFO1 (A→B) and FIFO2 (B→A)-with fully synchronous, edge-triggered port control logic. Each port uses separate continuous clocks (CLKA/CLKB), chip selects (CSA/CSB), enable signals (ENA/ENB), and write/read direction controls (W/RA/W/RB).
Status flags-including IRA/ORA/AEA/AFA (CLKA-synchronized) and IRB/ORB/AEB/AFB (CLKB-synchronized)-are two-stage metastability-hardened. Flag offset registers (X1/Y1 for FIFO1; X2/Y2 for FIFO2) are programmable via port A or preset during reset using FS0/FS1, enabling precise flow-control tuning across clock domains.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Depth × Width × Ports | 512 × 32 × 2 - Two independent dual-port FIFOs, each buffering 16,384 bits bidirectionally between asynchronous clock domains. |
| Max Clock Frequency | 67 MHz - Enables high-throughput data transfer in real-time bridge and protocol translation systems without external clock division. |
| Read Access Time | 11 ns - Guarantees sub-15 ns latency from clock edge to valid output data, critical for tight-timing microprocessor bus handshaking. |
| Flag Synchronization | Two-stage flip-flop sync - Reduces metastability risk when CLKA and CLKB operate asynchronously; ensures reliable flag assertion timing. |
| Programmable Flag Offsets | X1/X2/Y1/Y2 registers - Allow runtime configuration of almost-empty (1–508 words) and almost-full (1–508 empty slots) thresholds per FIFO. |
| Retransmit Capability | FIFO1 only - Enables repeat reads from a user-marked location via RTM/RFM controls, supporting packet retransmission or debug replay. |
| Mailbox Registers | Two 32-bit bypass registers (Mail1/Mail2) - Provide atomic inter-processor messaging without FIFO queuing delay or pointer management. |
Pinout & Package
SN74ACT3638-20PCB 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 top-view layout with corner pin 1 marked.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CLKA / CLKB | Free-running input clocks | Independent, asynchronous or coincident clocks driving port-A and port-B synchronous transfers; low-to-high edges gate all data and flag updates. |
| CSA / CSB | Chip select inputs | Enable port-A/B operation; high disables data I/O and forces A0–A31/B0–B31 into high-impedance state regardless of W/RA/W/RB. |
| W/RA / W/RB | Port direction controls | W/RA high = port-A write; W/RB low = port-B write - inverted logic accommodates standard microprocessor bus polarity conventions. |
| A0–A31 / B0–B31 | 32-bit bidirectional data buses | Shared I/O lines per port; direction and drive strength controlled by CSA/CSB + W/RA/W/RB + ENA/ENB logic states. |
| IRA / ORA / AEA / AFA | CLKA-synchronized status flags | Indicate FIFO2 fill status (input-ready/output-ready/almost-empty/almost-full); used for handshaking with port-A controller. |
| IRB / ORB / AEB / AFB | CLKB-synchronized status flags | Indicate FIFO1 fill status; enable deterministic flow control from port-B side without cross-clock-domain sampling hazards. |
| RST1 / RST2 | Independent FIFO reset inputs | Asynchronous active-high resets requiring four CLKA+CLKB transitions; initialize pointers, flags, and mailbox flags separately per FIFO. |
| MBF1 / MBF2 | Mailbox full flags | Open-drain outputs signaling mail1/mail2 register occupancy; asserted low after write, cleared by corresponding port read. |
Key Features
| Feature | Design Value |
|---|---|
| Independent dual-clock FIFO architecture | Enables robust bridging between non-synchronized subsystems (e.g., DSP ↔ FPGA, CPU ↔ peripheral bus) without external arbitration logic. |
| Programmable almost-full/empty flag offsets | Allows dynamic adjustment of buffer watermark thresholds (1–508 words) via port-A writes or hardware-selectable presets, optimizing latency vs. overflow safety. |
| Synchronous retransmit mode (FIFO1) | Supports repeat-read of up to 512-word sequences from a marked starting address using RTM/RFM controls-ideal for packet resend or diagnostic trace replay. |
| Dual 32-bit mailbox-bypass registers | Provides zero-latency, non-queued inter-processor messaging with dedicated MBF1/MBF2 flags, eliminating FIFO pointer management overhead. |
| Metastability-hardened flag synchronization | Two-stage synchronizers on all status flags reduce failure probability below 10⁻⁹ per hour under worst-case clock skew, meeting industrial reliability requirements. |
Applications
| High-Speed Protocol Bridge | Multi-CPU Interconnect |
|---|---|
|
Use Scenario: Bridging between a 67 MHz PCI Express endpoint and a 50 MHz legacy parallel bus in industrial motion controllers. IC Role / Device Role / Timing Role: SN74ACT3638-20PCB acts as a clock-domain crossing FIFO, absorbing bursty PCIe traffic on port-A (CLKA) and smoothing delivery to the slower bus on port-B (CLKB). Use Value: Eliminates need for custom ASIC glue logic; 11 ns access time ensures minimal pipeline stall on the fast side, while programmable AFA/AEB flags prevent overflow under variable load. |
Use Scenario: Coordinating real-time sensor fusion between ARM Cortex-A9 and TI C66x DSP in an autonomous vehicle ECU. IC Role / Device Role / Timing Role: SN74ACT3638-20PCB serves as a dual-directional data conduit-passing raw ADC streams from DSP to ARM (FIFO1), and control commands from ARM to DSP (FIFO2). Use Value: Mailbox registers enable immediate command injection without FIFO queuing delay; retransmit mode allows DSP to replay critical sensor frames during fault recovery. |
| Embedded Debug Trace Buffer | Legacy Bus Upgrader |
|
Use Scenario: Capturing instruction traces from a microcontroller core running at 40 MHz for off-chip analysis via USB 2.0 interface. IC Role / Device Role / Timing Role: SN74ACT3638-20PCB buffers trace data on port-A (CLKA), then streams it out on port-B (CLKB) synchronized to USB packet timing. Use Value: Almost-full flag (AFA) triggers trace compression before overflow; retransmit mode enables replay of last N instructions upon breakpoint hit. |
Use Scenario: Modernizing a 1990s PLC backplane by inserting FPGA-based I/O modules while retaining original 80C188 CPU and ISA-style bus. IC Role / Device Role / Timing Role: SN74ACT3638-20PCB decouples CPU bus cycles (port-A) from FPGA DMA bursts (port-B), acting as a timing-isolated data staging buffer. Use Value: 120-pin TQFP footprint matches legacy socket layouts; mailbox registers allow CPU to send configuration updates to FPGA without disturbing ongoing FIFO data flow. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar clocked bidirectional FIFO applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| IDT72V2115L15PF | Single 512 × 18 FIFO with LVDS I/O; no mailbox registers; supports 133 MHz clock; different flag architecture (no programmable offsets). | Targeted at high-speed serial link buffering, not dual-processor bridging; lacks retransmit and mailbox features required for SN74ACT3638-20PCB use cases. | Select only if LVDS signaling and higher clock rate outweigh loss of bidirectional flexibility and mailbox functionality. |
| ON Semiconductor NB3N502DR2G | 3.3 V, 2 × 256 × 18 clocked FIFO; no retransmit; no mailbox; smaller depth; supports 100 MHz; different pinout and flag naming. | Designed for video/audio stream buffering-not microprocessor bus bridging; insufficient depth and missing SN74ACT3638-20PCB's dual-clock handshake features. | Consider only for cost-sensitive, lower-bandwidth applications where 512-word depth and mailbox registers are unnecessary. |
Compared with IDT72V2115L15PF and NB3N502DR2G, SN74ACT3638-20PCB uniquely delivers dual 512×32 FIFOs with mailbox bypass, retransmit, and fully programmable flag offsets in a single 120-pin package-making it irreplaceable for deterministic multi-processor data exchange where timing isolation and feature parity are mandatory.
Availability
SN74ACT3638-20PCB is available at Aetrix Electronics and suitable for high-reliability embedded communications, industrial protocol bridging, and legacy bus modernization requiring stable component supply and long-term lifecycle support.
Supply support for SN74ACT3638-20PCB 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-performance interface and memory products.
The SN74ACT3638-20PCB belongs to TI's advanced CMOS clocked FIFO family, designed specifically for deterministic, low-latency data buffering across asynchronous clock domains in industrial, telecom, and computing infrastructure.
FAQ
What is the maximum supported clock frequency for SN74ACT3638-20PCB?
The SN74ACT3638-20PCB supports clock frequencies up to 67 MHz on both CLKA and CLKB inputs. This specification is guaranteed across the commercial temperature range (0°C to 70°C) and reflects the device's optimized 0.8-µm Advanced CMOS process. Operation beyond 67 MHz is not characterized and may result in timing violations or metastability in flag outputs.
Does SN74ACT3638-20PCB support true bidirectional data flow on a single port?
No-SN74ACT3638-20PCB implements two unidirectional FIFO paths: FIFO1 moves data from port-A to port-B, and FIFO2 moves data from port-B to port-A. Each port (A/B) has dedicated 32-bit I/O lines and independent control logic, enabling simultaneous full-duplex operation but not shared-line bidirectional transfer like a transceiver.
How is the retransmit function implemented in SN74ACT3638-20PCB?
The retransmit function applies exclusively to FIFO1 and is activated by asserting RTM high while ORB is high, followed by a rising edge on CLKB to mark the current output register content as the retransmit start point. Subsequent reads (with RFM high) cycle through the same sequence from that point. SN74ACT3638-20PCB does not support retransmit on FIFO2.
Can SN74ACT3638-20PCB's almost-full and almost-empty flag offsets be changed dynamically during operation?
Yes-SN74ACT3638-20PCB allows runtime programming of all four offset registers (X1, Y1, X2, Y2) via port-A writes after simultaneous FIFO reset with FS0=FS1=low. Each offset value can be set between 1 and 508 words, enabling adaptive flow control without hardware changes or power cycling.
What is the purpose of the mailbox-bypass registers in SN74ACT3638-20PCB?
SN74ACT3638-20PCB includes two independent 32-bit mailbox registers (Mail1 and Mail2) that operate outside the FIFO queues. They provide instantaneous, non-queued inter-processor messaging-e.g., Mail1 accepts writes from port-B and is readable from port-A, flagged by MBF1. This avoids FIFO latency and pointer management overhead for urgent control signals.
SN74ACT3638-20PCB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Programmable:
- Not Verified
- Memory Size:
- -
- Function:
- -
- Data Rate:
- -
- Access Time:
- -
- Voltage - Supply:
- -
- Current - Supply (Max):
- -
- Bus Directional:
- -
- Expansion Type:
- -
- Programmable Flags Support:
- -
- Retransmit Capability:
- -
- FWFT Support:
- -
- Operating Temperature:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
SN74ACT3638-20PCB FAQ
1.How can I place an order for SN74ACT3638-20PCB through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ACT3638-20PCB 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 SN74ACT3638-20PCB reliable?
The price and inventory of SN74ACT3638-20PCB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ACT3638-20PCB is usually 5 days.
3.What payment methods are accepted for SN74ACT3638-20PCB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ACT3638-20PCB transactions.
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4.How is shipping managed for SN74ACT3638-20PCB?
SN74ACT3638-20PCB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ACT3638-20PCB 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 SN74ACT3638-20PCB?
For technical support, including SN74ACT3638-20PCB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ACT3638-20PCB requirements.
6.How does Aetrix verify that SN74ACT3638-20PCB is sourced from the original manufacturer or authorized distributors?
All SN74ACT3638-20PCB 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 SN74ACT3638-20PCB meets industry standards.
7.What is the process for return or replacement of SN74ACT3638-20PCB?
All SN74ACT3638-20PCB units undergo pre-shipment inspection (PSI). If there is an issue with SN74ACT3638-20PCB, 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 SN74ACT3638-20PCB part is unused and in its original packaging.
Return procedure for SN74ACT3638-20PCB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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