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Texas Instruments SN74ACT7805-20DL
- Part No.:
- SN74ACT7805-20DL
- Manufacturer:
- Texas Instruments
- Category:
- FIFOs Memory
- Package:
- 56-BSSOP (0.295", 7.50mm Width)
- Datasheet:
-
SN74ACT7805-20DL.pdf
- Description:
- IC FIFO SYNC 256X18 13NS 56SSOP
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
SN74ACT7805-20DL from Texas Instruments is a 256 × 18-bit clocked FIFO memory IC designed for asynchronous data buffering between independent clock domains. It supports free-running, asynchronous or coincident read/write clocks, delivers 12 ns access time with 50-pF load, operates up to 50 MHz (–20 speed grade), and features synchronized input-ready (IR) and output-ready (OR) flags. It is used in high-speed digital interface bridging, such as between microprocessor buses and peripheral controllers.
For engineers reviewing the SN74ACT7805-20DL datasheet, SN74ACT7805-20DL pinout, SN74ACT7805-20DL application, or SN74ACT7805-20DL equivalent, key selection criteria include its 50-MHz maximum clock frequency, dual-synchronized flag architecture, programmable almost-full/empty thresholds, bidirectional configuration capability, and compatibility with other Widebus™ FIFOs in system-level timing isolation designs.
Technical Context
The SN74ACT7805-20DL implements a synchronous dual-clock FIFO architecture with independent write and read pointer control logic, status-flag synchronization to respective clocks (IR to WRTCLK, OR to RDCLK), and reset-initiated initialization of all flags. Its internal 256 × 18-bit RAM uses low-power advanced CMOS technology with patented output edge control (OEC™) to suppress simultaneous switching noise.
It supports programmable AF/AE offsets via D0–D6 and PEN during reset, enabling configurable depth thresholds (X/Y = 0–127); default values are X = Y = 32. The FIFO requires four rising edges on both WRTCLK and RDCLK under RESET assertion to fully initialize internal synchronizers and flags.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Depth × Width | 256 words × 18 bits - provides 4.6-kbit buffer capacity for burst-mode data alignment across clock domains |
| Max Clock Frequency | 50 MHz - defines maximum sustained data throughput per clock domain (WRTCLK or RDCLK) |
| Access Time | 12 ns - guarantees valid Q-output data within 12 ns after RDCLK rising edge under 50-pF load |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5-V TTL/CMOS logic rails and industrial power margins |
| Operating Temperature | 0°C to 70°C - rated for commercial-grade embedded systems and board-level interconnect applications |
| Output Drive | 16 mA (Q outputs), 8 mA (flags) - ensures robust signal integrity driving multiple TTL loads or PCB traces |
| Flag Synchronization | IR synced to WRTCLK, OR synced to RDCLK - eliminates metastability in handshake signaling between clock domains |
Pinout & Package
Packaged in a 56-pin Shrink Small-Outline (DL) package with 300-mil body width and 25-mil center-to-center lead pitch, optimized for high-density PCB layouts and thermal dissipation in multi-FIFO systems.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| WRTCLK (25) | Write clock input | Low-to-high transition writes data when WRTEN1=H, WRTEN2=L, IR=H; IR flag is synchronized to this edge |
| RDCLK (32) | Read clock input | Low-to-high transition reads data when RDEN=OE1=OE2=L and OR=H; OR flag is synchronized to this edge |
| D0–D17 (2–21, 11–12, 9–2) | Data inputs | 18-bit parallel input bus; D0–D6 also serve as AF/AE offset programming latch during PEN cycle |
| Q0–Q17 (33–34, 36–38, 40–43, 45–49, 51, 53–55) | Data outputs | 18-bit parallel output bus; first written word appears on Q0–Q17 on third RDCLK edge after initial write |
| IR (28) | Input-ready flag output | High indicates FIFO not full; synchronized to WRTCLK rising edge; disabled during reset |
| OR (29) | Output-ready flag output | High indicates valid data present on Q0–Q17; synchronized to RDCLK rising edge; asserted after first word loaded |
| AF/AE (24) | Status flag output | High when FIFO contains ≤X words (almost-empty) or ≥(256−Y) words (almost-full); defaults to X=Y=32 |
| RESET (1) | Asynchronous reset input | Active-low; must be held low while at least four WRTCLK and four RDCLK rising edges occur to clear sync registers |
| PEN (23) | Program enable input | Low during WRTCLK rise latches D0–D6 as AF/AE offset; disables writes while active |
| WRTEN1/WRTEN2 (27/26) | Write enable inputs | Enable write only when WRTEN1=H and WRTEN2=L; prevents partial-word writes |
| RDEN/OE1/OE2 (31/56/30) | Read and output enable inputs | Enable read and output drive only when all three are low and OR=H; OE1/OE2 control 3-state output drivers |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional configuration support | Two SN74ACT7805-20DL devices can be interconnected without external logic to implement full-duplex data flow between two clock domains |
| Programmable AF/AE thresholds | Allows dynamic tuning of almost-full/almost-empty warning points (X/Y = 0–127) via D0–D6 and PEN, improving buffer management flexibility |
| Synchronized status flags | IR and OR flags are edge-synchronized to WRTCLK and RDCLK respectively, eliminating metastability in handshaking protocols |
| Width expansion capability | Multiple devices can be cascaded to form wider FIFOs (e.g., 256 × 36) using shared clocks and coordinated enables-no glue logic required |
| OEC™ noise suppression | Texas Instruments' patented Output Edge Control circuit dampens simultaneous switching noise across all 18 outputs, enhancing signal integrity in dense layouts |
Applications
| Microprocessor Bus Bridging | Digital Signal Processor Interface |
|---|---|
Use Scenario: Isolating a 50-MHz CPU bus from a slower 25-MHz peripheral controller while maintaining burst transfer integrity. IC Role / Device Role / Timing Role: SN74ACT7805-20DL acts as a clock-domain crossing FIFO, absorbing timing skew and preventing data loss during bus arbitration transitions. Use Value: Enables deterministic latency with 12-ns access time and eliminates need for complex handshake logic or software polling. | Use Scenario: Buffering real-time audio sample streams between an ADC running at 48 kHz and a DSP core operating at 100 MHz. IC Role / Device Role / Timing Role: SN74ACT7805-20DL serves as a decoupling FIFO, accepting samples on one clock and delivering them on another with synchronized OR/IR flags. Use Value: Prevents underrun/overrun errors by leveraging programmable AF/AE thresholds to trigger DMA reloads before buffer exhaustion. |
| Network Packet Assembler | Industrial PLC I/O Module |
Use Scenario: Aggregating fragmented Ethernet frames from multiple PHYs into a unified MAC interface with variable-length packet alignment. IC Role / Device Role / Timing Role: SN74ACT7805-20DL functions as a depth-flexible frame buffer, using HF and AF/AE flags to manage packet assembly windows. Use Value: Supports jitter-tolerant packet reassembly with 256-word depth and precise flag timing-critical for deterministic network latency. | Use Scenario: Interfacing fieldbus sensors (e.g., Profibus DP) running at 12 Mbps with a 50-MHz ARM-based controller in modular I/O racks. IC Role / Device Role / Timing Role: SN74ACT7805-20DL provides isolated, noise-immune data staging between asynchronous fieldbus timing and deterministic controller scheduling. Use Value: OEC™ circuitry reduces EMI in electrically noisy industrial environments, while dual-clock operation avoids timing lockstep failures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar FIFO memory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ACT7803-20DL | Same pinout, identical timing and flag behavior, but 128 × 18 capacity (half depth) | Suitable where smaller buffer depth suffices and board space or cost optimization is prioritized | Select when 128-word depth meets system latency budget and footprint constraints |
| SN74ACT7813-20DL | Same pinout and timing, but 512 × 18 capacity (double depth); higher ICC and slightly longer tpd (13 ns vs. 12 ns) | Preferred for applications requiring extended buffering, e.g., video line buffers or high-jitter serial links | Choose when deeper buffering justifies marginally higher power and propagation delay |
Compared with SN74ACT7803-20DL and SN74ACT7813-20DL, the SN74ACT7805-20DL offers optimal balance of depth (256 words), speed (50 MHz), and power efficiency for mid-range asynchronous interface buffering-making it the default choice for general-purpose clock-domain isolation where neither minimal nor maximal depth is required.
Availability
SN74ACT7805-20DL is available at Aetrix Electronics and suitable for microprocessor bus bridging, digital signal processor interfacing, network packet assembly, and industrial PLC I/O modules requiring stable component supply and long-term obsolescence management.
Supply support for SN74ACT7805-20DL 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 timing components.
The SN74ACT7805-20DL belongs to TI's Widebus™ family of high-speed FIFOs, engineered specifically for robust, low-noise clock-domain crossing in commercial and industrial digital systems.
FAQ
What is the maximum clock frequency supported by the SN74ACT7805-20DL?
The SN74ACT7805-20DL supports a maximum clock frequency of 50 MHz for both WRTCLK and RDCLK, as specified for the –20 speed grade. This rating assumes operation within recommended conditions (VCC = 4.5 V to 5.5 V, TA = 0°C to 70°C) and accounts for worst-case timing margins including setup/hold and propagation delays. The SN74ACT7805-20DL achieves this performance while maintaining 12 ns access time with a 50-pF load.
How does the SN74ACT7805-20DL handle reset initialization?
The SN74ACT7805-20DL requires an asynchronous active-low RESET signal held low while at least four rising edges occur on both WRTCLK and RDCLK to fully initialize internal synchronizers. Upon completion, IR, OR, and HF flags are set low, and AF/AE is set high. The SN74ACT7805-20DL must be reset at power-up to ensure deterministic flag states and prevent undefined FIFO behavior during early operation.
Can the SN74ACT7805-20DL be configured for bidirectional data flow?
Yes-the SN74ACT7805-20DL supports bidirectional configuration without additional logic. Two devices can be interconnected using shared clocks and cross-wired enables (e.g., WRTCLK of Device A tied to RDCLK of Device B) to create full-duplex buffering. This capability is explicitly documented in the application section of the SN74ACT7805-20DL datasheet and leverages its independent read/write clock architecture and flag synchronization.
What is the function of the PEN pin on the SN74ACT7805-20DL?
The PEN (Program Enable) pin on the SN74ACT7805-20DL controls programming of the almost-full/almost-empty (AF/AE) offset values. When PEN is low during a WRTCLK rising edge, the binary value on D0–D6 is latched as the AF/AE threshold (X for almost-empty, Y for almost-full). PEN must remain high to retain default X = Y = 32. Writes are disabled while PEN is active, ensuring safe reconfiguration without data corruption in the SN74ACT7805-20DL.
Is the SN74ACT7805-20DL pin-compatible with other Widebus™ FIFOs?
Yes-the SN74ACT7805-20DL is pin-to-pin compatible with SN74ACT7803-20DL (128 × 18) and SN74ACT7813-20DL (512 × 18), sharing identical DL-package pinout, timing behavior, and flag signaling. This allows direct substitution based on depth requirements without PCB redesign. All three parts use the same 56-pin shrink small-outline package and maintain consistent electrical characteristics across the speed grade, simplifying design reuse for the SN74ACT7805-20DL and its alternatives.
SN74ACT7805-20DL Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ACT
- Package/Case:
- 56-BSSOP (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Memory Size:
- 4.5K (256 x 18)
- Function:
- Synchronous
- Data Rate:
- 50MHz
- Access Time:
- 13ns
- Voltage - Supply:
- 4.5 V ~ 5.5 V
- Current - Supply (Max):
- 400µA
- Bus Directional:
- Uni-Directional
- Expansion Type:
- Width
- Programmable Flags Support:
- Yes
- Retransmit Capability:
- No
- FWFT Support:
- No
- Operating Temperature:
- 0°C ~ 70°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 56-SSOP
SN74ACT7805-20DL FAQ
1.How can I place an order for SN74ACT7805-20DL through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ACT7805-20DL 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 SN74ACT7805-20DL reliable?
The price and inventory of SN74ACT7805-20DL are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ACT7805-20DL is usually 5 days.
3.What payment methods are accepted for SN74ACT7805-20DL?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ACT7805-20DL transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ACT7805-20DL?
SN74ACT7805-20DL orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ACT7805-20DL 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 SN74ACT7805-20DL?
For technical support, including SN74ACT7805-20DL datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ACT7805-20DL requirements.
6.How does Aetrix verify that SN74ACT7805-20DL is sourced from the original manufacturer or authorized distributors?
All SN74ACT7805-20DL 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 SN74ACT7805-20DL meets industry standards.
7.What is the process for return or replacement of SN74ACT7805-20DL?
All SN74ACT7805-20DL units undergo pre-shipment inspection (PSI). If there is an issue with SN74ACT7805-20DL, 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 SN74ACT7805-20DL part is unused and in its original packaging.
Return procedure for SN74ACT7805-20DL:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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