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

Texas Instruments SN74ACT3638-30PCB

Name: SN74ACT3638-30PCB
Brand: Texas Instruments
SKU: SN74ACT3638-30PCB
Price: 2.40 USD
Availability: InStock
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Part No.:: SN74ACT3638-30PCB

Manufacturer:: Texas Instruments

Category:: FIFOs Memory

Package:: -

Datasheet:: SN74ACT3638-30PCB.pdf

Description:: IC FIFO 512X32 BI-DIRECTIONAL

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Product details

Overview

SN74ACT3638-30PCB from Texas Instruments is a clocked bidirectional FIFO memory IC with two independent 512 × 32 dual-port SRAM buffers, supporting asynchronous or coincident 67 MHz clocks (CLKA/CLKB), 11 ns read access time, and retransmit capability on FIFO1. It enables high-speed data buffering between mismatched or isolated synchronous domains in industrial control backplanes.

For engineers reviewing the SN74ACT3638-30PCB datasheet, SN74ACT3638-30PCB pinout, SN74ACT3638-30PCB application, or SN74ACT3638-30PCB equivalent, key selection criteria include dual-clock domain isolation, programmable almost-full/empty flag offsets (1–508), mailbox-bypass register support, synchronized flag timing, and 120-pin TQFP (PCB) package compatibility with legacy TI FIFO designs.

Technical Context

The SN74ACT3638-30PCB implements two independent clocked FIFOs (FIFO1 and FIFO2), each with 512 × 32-bit depth, using low-power 0.8-µm Advanced CMOS. CLKA synchronizes all port-A operations-including IRA, ORA, AFA, AEA-and CLKB synchronizes port-B signals including IRB, ORB, AFB, AEB.

It supports synchronous retransmit mode via RTM/RFM controls on FIFO1, and uses two-stage synchronization for all flags to mitigate metastability across asynchronous clock domains. Flag offset registers (X1/Y1 for FIFO1; X2/Y2 for FIFO2) are programmable from port A or loaded via FS0/FS1 during reset.

Key Specifications

Parameter	Value and Actual Design Meaning
Memory Depth × Width × Ports	512 × 32 × 2 - Two independent dual-port FIFOs, enabling full-duplex buffering without external arbitration.
Max Clock Frequency	67 MHz - Supports high-throughput inter-processor or bus-to-bus bridging at sub-15 ns cycle time.
Read Access Time	11 ns - Enables direct interface with fast microprocessors (e.g., TMS320Cxx, SHARC) without wait states.
Flag Synchronization	Two-stage flip-flop sync - Reduces metastability risk when CLKA and CLKB operate asynchronously.
Programmable Flag Offsets	1–508 words - Allows precise tuning of almost-full/almost-empty thresholds for custom flow-control latency budgets.
Operating Temperature	0°C to +70°C - Qualified for commercial-grade embedded systems, not extended industrial or automotive.
Technology Node	0.8 µm Advanced CMOS - Delivers low static power and TTL-compatible I/O levels (V_OH ≥ 2.4 V, V_OL ≤ 0.5 V).

Pinout & Package

SN74ACT3638-30PCB 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 (not electrically connected). Pin numbering follows standard counter-clockwise top-view layout starting at pin 1 (RSTA).

Pin/Terminal	Circuit Role	Design Meaning
A0–A31	Port-A bidirectional data bus	32-bit parallel interface for FIFO2 read/write and Mail2 register access; high-impedance when CSA or W/RA high.
B0–B31	Port-B bidirectional data bus	32-bit parallel interface for FIFO1 read/write and Mail1 register access; high-impedance when CSB or W/RB low.
CLKA / CLKB	Free-running port clocks	Independent synchronous timing sources; all port-A flags and transfers sync to CLKA edge; all port-B sync to CLKB edge.
CSA / CSB	Port chip select inputs	Active-low enables; disable data bus drivers and block clock-gated transfers when deasserted.
W/RA / W/RB	Port write/read direction control	W/RA high = port-A write; W/RB low = port-B write; polarity inversion ensures consistent active-high logic for both ports.
IRA / IRB	Input-ready flags (synchronized)	Indicate FIFO readiness to accept writes: IRA low = FIFO1 full; IRB low = FIFO2 full; both two-stage synced to respective clocks.
ORA / ORB	Output-ready flags (synchronized)	Indicate valid data available for reads: ORA low = FIFO2 empty; ORB low = FIFO1 empty; both synced to read-clock domains.
MBF1 / MBF2	Mailbox full flags	MBF1 low = Mail1 register occupied; MBF2 low = Mail2 register occupied; used for handshaking in mailbox-bypass mode.
RST1 / RST2	Independent FIFO reset inputs	Asynchronous active-high resets requiring four CLKA+CLKB transitions; initialize pointers, flags, and offset registers.
RTM / RFM	Retransmit control inputs	RTM high + CLKB↑ selects retransmit start point; RFM high + CLKB↑ restarts retransmit sequence from marked location.

Key Features

Feature	Design Value
Dual independent clock domains	Enables seamless data transfer between systems with unrelated clocks (e.g., DSP core @ 60 MHz ↔ FPGA fabric @ 50 MHz) without external clock domain crossing logic.
Retransmit capability on FIFO1	Allows repeated reading of a fixed data vector (≥3 words) from a user-marked position-critical for firmware bootloading or configuration replay over slow buses.
Mailbox-bypass registers (Mail1/Mail2)	Provide dedicated 32-bit registers for urgent control messages or initialization data, decoupled from FIFO flow control and accessible without disturbing FIFO state.
Programmable almost-full/empty offsets	Permits dynamic adjustment of flow-control thresholds (1–508 words) via port-A writes or hardware FS0/FS1 pins-enabling adaptive buffer management in real-time systems.
Synchronized status flags with metastability hardening	All eight status flags (IRA/ORA/AFA/AEA/IRB/ORB/AFB/AEB) use dual-register sync chains, meeting TI's published MTBF > 10⁹ hours for asynchronous clock operation.

Applications

Industrial Backplane Bridge	Multi-Processor Communication Hub
Use Scenario: Isolating CPU and FPGA subsystems on a shared VME or CompactPCI backplane where clock domains differ and deterministic latency is required. IC Role / Device Role / Timing Role: SN74ACT3638-30PCB acts as a dual-clock-domain FIFO bridge, absorbing burst writes from CPU and feeding steady reads to FPGA logic, with mailbox registers handling interrupt acknowledgments. Use Value: Eliminates need for custom CDC logic or dual-port RAM; 11 ns access time ensures no pipeline stalls in 67 MHz CPU-to-FPGA data streaming.	Use Scenario: Coordinating data exchange between two ARM-based controllers running independent real-time OS instances with non-synchronized system clocks. IC Role / Device Role / Timing Role: SN74ACT3638-30PCB serves as a bidirectional message queue, with FIFO1 buffering CPU1→CPU2 traffic and FIFO2 handling CPU2→CPU1 replies, while mailboxes pass priority commands. Use Value: Programmable almost-full/empty flags allow per-link flow control tuning; retransmit mode enables reliable firmware update packet replay without host CPU intervention.
DSP-FPGA Data Pipeline	Legacy Bus Protocol Translator
Use Scenario: Streaming sensor data from a TI C6000 DSP (CLKA domain) into an Xilinx Kintex FPGA (CLKB domain) for real-time filtering and compression. IC Role / Device Role / Timing Role: SN74ACT3638-30PCB functions as a clock-domain-crossing FIFO, with CLKA driven by DSP clock and CLKB derived from FPGA fabric clock; RDYA/RDYB provide ready signals to both masters. Use Value: Two-stage synchronized flags prevent metastability-induced data loss; 512-word depth absorbs jitter between DSP DMA bursts and FPGA processing cycles.	Use Scenario: Interfacing a modern microcontroller (SPI/I²C) to a legacy 32-bit parallel bus (e.g., ISA-style) in test equipment, requiring protocol conversion and buffering. IC Role / Device Role / Timing Role: SN74ACT3638-30PCB operates as a protocol-agnostic data shifter-microcontroller writes to Mail2, then triggers FIFO2→FIFO1 transfer; FPGA logic reads B0–B31 and formats for legacy bus timing. Use Value: Mailbox-bypass register allows immediate command injection (e.g., "reset peripheral") without waiting for FIFO fill level; 120-pin PCB package matches footprint of obsolete FIFOs in field-replaceable modules.

Industrial Backplane Bridge

Multi-Processor Communication Hub

Use Scenario: Isolating CPU and FPGA subsystems on a shared VME or CompactPCI backplane where clock domains differ and deterministic latency is required.

IC Role / Device Role / Timing Role: SN74ACT3638-30PCB acts as a dual-clock-domain FIFO bridge, absorbing burst writes from CPU and feeding steady reads to FPGA logic, with mailbox registers handling interrupt acknowledgments.

Use Value: Eliminates need for custom CDC logic or dual-port RAM; 11 ns access time ensures no pipeline stalls in 67 MHz CPU-to-FPGA data streaming.

Use Scenario: Coordinating data exchange between two ARM-based controllers running independent real-time OS instances with non-synchronized system clocks.

IC Role / Device Role / Timing Role: SN74ACT3638-30PCB serves as a bidirectional message queue, with FIFO1 buffering CPU1→CPU2 traffic and FIFO2 handling CPU2→CPU1 replies, while mailboxes pass priority commands.

Use Value: Programmable almost-full/empty flags allow per-link flow control tuning; retransmit mode enables reliable firmware update packet replay without host CPU intervention.

DSP-FPGA Data Pipeline

Legacy Bus Protocol Translator

Use Scenario: Streaming sensor data from a TI C6000 DSP (CLKA domain) into an Xilinx Kintex FPGA (CLKB domain) for real-time filtering and compression.

IC Role / Device Role / Timing Role: SN74ACT3638-30PCB functions as a clock-domain-crossing FIFO, with CLKA driven by DSP clock and CLKB derived from FPGA fabric clock; RDYA/RDYB provide ready signals to both masters.

Use Value: Two-stage synchronized flags prevent metastability-induced data loss; 512-word depth absorbs jitter between DSP DMA bursts and FPGA processing cycles.

Use Scenario: Interfacing a modern microcontroller (SPI/I²C) to a legacy 32-bit parallel bus (e.g., ISA-style) in test equipment, requiring protocol conversion and buffering.

IC Role / Device Role / Timing Role: SN74ACT3638-30PCB operates as a protocol-agnostic data shifter-microcontroller writes to Mail2, then triggers FIFO2→FIFO1 transfer; FPGA logic reads B0–B31 and formats for legacy bus timing.

Use Value: Mailbox-bypass register allows immediate command injection (e.g., "reset peripheral") without waiting for FIFO fill level; 120-pin PCB package matches footprint of obsolete FIFOs in field-replaceable modules.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
IDT72V2115L15PF	3.3 V only; 1024 × 18 depth; 15 ns access; LVCMOS I/O; no mailbox registers or retransmit mode.	Targeted at telecom/datacom line cards with narrower bus widths and strict 3.3 V compliance; lacks mailbox bypass and retransmit features.	Choose IDT72V2115L15PF only if 3.3 V supply, smaller word width, and higher density outweigh loss of mailbox/retransmit functionality.
ON Semiconductor NB3N502DR2G	Single 256 × 16 FIFO; 100 MHz max; 3.3 V; integrated PLL clock multiplier; no dual-clock independence or mailbox registers.	Designed for PCIe endpoint buffering with clock multiplication; unsuitable for true asynchronous domain bridging or mailbox-based control messaging.	Use NB3N502DR2G only for single-domain, high-frequency buffering where clock multiplication is needed and dual-clock isolation is unnecessary.

Compared with IDT72V2115L15PF and NB3N502DR2G, the SN74ACT3638-30PCB uniquely combines dual independent clock domains, mailbox-bypass registers, and retransmit capability in a 5 V-tolerant 120-pin TQFP-making it irreplaceable for legacy industrial systems requiring robust cross-domain messaging with fallback mechanisms.

Availability

SN74ACT3638-30PCB is available at Aetrix Electronics and suitable for industrial backplane bridges, multi-processor communication hubs, DSP-FPGA pipelines, legacy bus protocol translators, and real-time control systems requiring stable component supply across long-lifecycle deployments.

Supply support for SN74ACT3638-30PCB 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 industrial and communications ICs.

The SN74ACT3638-30PCB belongs to TI's ACT-family advanced CMOS logic portfolio, designed specifically for high-speed, low-power clocked FIFO applications in commercial-grade embedded systems requiring deterministic latency and dual-clock domain isolation.

FAQ

What is the maximum supported clock frequency for SN74ACT3638-30PCB?

The SN74ACT3638-30PCB supports clock frequencies up to 67 MHz on both CLKA and CLKB inputs. This specification is guaranteed across the full commercial temperature range (0°C to +70°C) and defines the upper limit for reliable synchronous data transfer through either port. Exceeding 67 MHz may result in timing violations, flag metastability, or data corruption, as confirmed in the SCAS228D datasheet revision April 1998.

Does SN74ACT3638-30PCB support true asynchronous operation between CLKA and CLKB?

Yes, SN74ACT3638-30PCB explicitly supports asynchronous operation between CLKA and CLKB - they may run at different frequencies, phases, or even be stopped independently. All status flags (IRA, ORA, AFA, AEA, IRB, ORB, AFB, AEB) are two-stage synchronized to their respective clock domains to suppress metastability, as documented in the functional description and flag timing sections of the SCAS228D datasheet.

How is the retransmit function implemented in SN74ACT3638-30PCB?

The SN74ACT3638-30PCB implements retransmit exclusively on FIFO1 using RTM and RFM control inputs. A rising edge on CLKB with RTM high marks the current output register content as the first retransmit word. Subsequent rising edges on CLKB with RFM high restart the sequence from that marked location. This enables repeatable delivery of fixed-length vectors (≥3 words) without host CPU involvement.

Can SN74ACT3638-30PCB be used with 3.3 V logic interfaces?

No - SN74ACT3638-30PCB is a 5 V-only device built on TI's ACT-family Advanced CMOS process. Its input thresholds and output drive levels (V_OH ≥ 2.4 V, V_OL ≤ 0.5 V at V_CC = 5 V) are specified for 5 V TTL/CMOS compatibility. Direct connection to 3.3 V logic requires level-shifting circuitry; the device does not support mixed-voltage I/O or 3.3 V supply operation.

What package type does SN74ACT3638-30PCB use, and is it RoHS compliant?

SN74ACT3638-30PCB uses a 120-pin Thin Quad Flat Package (TQFP) designated "PCB" in TI documentation, with 0.4 mm lead pitch and JEDEC MO-220 standard footprint. As a 1998-production device, it predates RoHS legislation and is not RoHS compliant; leaded solder assembly is required. No lead-free variant was released under this part number.

SN74ACT3638-30PCB 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:: -

SN74ACT3638-30PCB FAQ

1.How can I place an order for SN74ACT3638-30PCB through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74ACT3638-30PCB 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 SN74ACT3638-30PCB reliable?

The price and inventory of SN74ACT3638-30PCB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ACT3638-30PCB is usually 5 days.

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SN74ACT3638-30PCB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74ACT3638-30PCB 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 SN74ACT3638-30PCB?

For technical support, including SN74ACT3638-30PCB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ACT3638-30PCB requirements.

6.How does Aetrix verify that SN74ACT3638-30PCB is sourced from the original manufacturer or authorized distributors?

All SN74ACT3638-30PCB 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 SN74ACT3638-30PCB meets industry standards.

7.What is the process for return or replacement of SN74ACT3638-30PCB?

All SN74ACT3638-30PCB units undergo pre-shipment inspection (PSI). If there is an issue with SN74ACT3638-30PCB, 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 SN74ACT3638-30PCB part is unused and in its original packaging.

Return procedure for SN74ACT3638-30PCB:

1.Submit a request within 90 days.

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

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