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Texas Instruments SN74ACT7811-20FN
- Part No.:
- SN74ACT7811-20FN
- Manufacturer:
- Texas Instruments
- Category:
- FIFOs Memory
- Package:
- 68-LCC (J-Lead)
- Datasheet:
-
SN74ACT7811-20FN.pdf
- Description:
- IC FIFO SYNC 1KX18 20NS 68PLCC
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
SN74ACT7811-20FN from Texas Instruments is a 1024 × 18-bit clocked first-in, first-out (FIFO) memory IC with independent asynchronous read/write clocks, 15 ns access time at 50-pF load, programmable almost-full/almost-empty flag, and 68-pin PLCC (FN) package. It enables high-speed data buffering between mismatched clock domains in communication controllers and digital signal processing systems.
For engineers reviewing the SN74ACT7811-20FN datasheet, SN74ACT7811-20FN pinout, SN74ACT7811-20FN application, or SN74ACT7811-20FN equivalent, key selection considerations include its dual-clock synchronization capability, 28.5 MHz maximum RDCLK/WRTCLK frequency, 18-bit parallel I/O width, and support for cascading in word depth or width without external logic.
Technical Context
The SN74ACT7811-20FN implements a synchronous FIFO architecture with separate write-pointer and read-pointer control logic, each synchronized to its respective clock domain (WRTCLK and RDCLK). Its status flags-IR, OR, HF, AF/AE, and DAF-are generated synchronously to their associated clocks, enabling deterministic timing across clock boundaries.
It supports programmable AF/AE offset via DAF-controlled reset sequence, allowing user-defined thresholds (e.g., X = 256 default) for flow control signaling. The device uses ACT-family CMOS technology, delivering TTL-compatible input thresholds (VIH = 2 V, VIL = 0.8 V), ±8 mA/16 mA output drive, and operates over 0°C to 70°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Depth × Width | 1024 words × 18 bits - provides 18.4 kbit buffer capacity for burst-mode data alignment |
| Access Time | 15 ns at 50-pF load - enables reliable operation up to 28.5 MHz clock rate per timing spec |
| Max Clock Frequency | 28.5 MHz (RDCLK/WRTCLK) - defines upper limit for sustained read/write throughput |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5-V TTL/CMOS system rails |
| I/O Drive Strength | –8 mA (IOH), 16 mA (IOL) - sufficient for direct bus interface without external buffers |
| Operating Temperature | 0°C to 70°C - rated for commercial-grade industrial equipment environments |
| Power Dissipation Cap. | 65 pF per 1K bits - used to calculate dynamic power consumption at 5 MHz |
Pinout & Package
SN74ACT7811-20FN is housed in a 68-pin Plastic Leaded Chip Carrier (PLCC) package (FN), with J-lead geometry conforming to JEDEC MS-018. Pin 1 is located at the index corner; leads are arranged in a square perimeter with 0.05-inch pitch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (RESET) | Asynchronous reset input | Initiates pointer reset and flag initialization; requires ≥4 WRTCLK/RDCLK cycles for full synchronization |
| 2 (OE) | Output enable control | Places Q0–Q17 outputs in high-impedance state when low; must be high before RDCLK rising edge to enable read |
| 3–4 (RDEN2, RDEN1) | Read enable inputs | Both must be high before RDCLK rising edge to gate valid read transfers; not required for first-word read |
| 5 (RDCLK) | Read clock input | Free-running clock that synchronizes all read operations and OR/HF/AF-AE flag updates |
| 26–19,17,15–7 (D0–D17) | Data inputs | 18-bit parallel input bus; D0–D8 also carry AF/AE offset value during DAF-controlled reset |
| 27 (DAF) | Define AF/AE input | High-to-low transition latches D0–D8 as programmable AF/AE offset; held high for default X = 256 |
| 29 (WRTCLK) | Write clock input | Free-running clock that synchronizes all write operations and IR flag updates |
| 30–31 (WRTEN2, WRTEN1) | Write enable inputs | Both must be high before WRTCLK rising edge to gate valid write transfers |
| 33 (AF/AE) | Status flag output | Open-drain output indicating FIFO fill level relative to programmed threshold (X+1 or 1025−X) |
| 35 (IR) | Input-ready flag | Indicates FIFO not full; driven low on second WRTCLK after RESET, high on second WRTCLK after first write |
| 36 (HF) | Half-full flag | Asserts high when ≥513 words stored; used for coarse flow control in depth-expanded configurations |
| 38–39,41–42,44,46–47,49–50,52–53,55–56,58–59,61,63–64 (Q0–Q17) | Data outputs | Noninverting 18-bit parallel output bus; first word appears on third RDCLK after first valid write |
| 66 (OR) | Output-ready flag | Indicates FIFO not empty; set low on third RDCLK after RESET, high on third RDCLK after first write |
Key Features
| Feature | Design Value |
|---|---|
| Independent asynchronous clocks | Enables seamless bridging between dissimilar clock domains (e.g., 25 MHz processor ↔ 40 MHz peripheral) without handshake logic |
| Programmable AF/AE flag | Allows custom flow-control thresholds via DAF-controlled reset, supporting adaptive buffer management in variable-rate systems |
| Cascadable architecture | Supports expansion to >1024-word depth or >18-bit width using only shared clocks and flag chaining-no glue logic required |
| Fast 15 ns access time | Meets timing closure requirements for 28.5 MHz sustained data transfer rates with 50-pF load, reducing inter-stage latency |
| ACT-family drive strength | ±8 mA/16 mA output current eliminates need for bus transceivers in point-to-point 5-V backplane interfaces |
Applications
| Telecom Line Card Buffering | Digital Signal Processor Interface |
|---|---|
|
Use Scenario: Buffering ATM cell payloads between line-side framer and switch fabric with mismatched clock domains. IC Role / Device Role / Timing Role: Asynchronous FIFO providing elastic storage to absorb jitter and phase differences between OC-3 (155.52 MHz) and internal bus clocks. Use Value: Eliminates external handshaking logic while maintaining deterministic latency via IR/OR flag-driven flow control. |
Use Scenario: Interfacing a TI C6000 DSP with an ADC operating at 50 MSPS and a DAC running at 48 MSPS. IC Role / Device Role / Timing Role: Clock-domain crossing FIFO decoupling sample acquisition and playback paths to prevent underrun/overrun. Use Value: Enables real-time audio/video streaming with programmable AF/AE thresholds to adapt to variable processing loads. |
| Industrial PLC Communication Module | Test Equipment Data Capture |
|
Use Scenario: Isolating Modbus RTU serial interface (9.6 kbps) from high-speed Ethernet controller (100 Mbps) in programmable logic controllers. IC Role / Device Role / Timing Role: Synchronizing low-speed fieldbus data into high-speed packetized network stream using dual-clock FIFO architecture. Use Value: Prevents data loss during burst transmissions by leveraging HF and IR flags for hardware-triggered DMA transfers. |
Use Scenario: Capturing transient waveforms from multi-channel oscilloscopes where analog front-end sampling and digital analysis run on separate clocks. IC Role / Device Role / Timing Role: High-reliability buffer storing pre-trigger samples until trigger event, then streaming to host via PCIe. Use Value: Delivers 18-bit resolution capture with 15 ns access time, ensuring no sample misalignment across clock boundaries. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar FIFO memory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ACT7881-20FN | Same 1024 × 18 architecture and pinout, but lacks programmable AF/AE flag and DAF input; uses fixed 256-word threshold. | Suitable for simpler flow control where fixed almost-full/empty points suffice; no DAF reset sequence needed. | Select when AF/AE programmability is unnecessary and cost reduction is prioritized over configuration flexibility. |
| SN74ACT7884-20FN | 1024 × 9-bit depth (half width); shares same FN package and timing, but requires two devices for 18-bit width. | Used in narrower data path designs or where board space allows dual-device width expansion. | Choose when system data width is ≤9 bits or when modular width scaling is preferred over monolithic 18-bit solution. |
Compared with SN74ACT7881-20FN and SN74ACT7884-20FN, the SN74ACT7811-20FN uniquely delivers programmable AF/AE thresholding and full 18-bit width in a single 68-pin PLCC, reducing component count and eliminating inter-device skew in depth-expanded systems.
Availability
SN74ACT7811-20FN is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, test instrumentation, and digital signal processing systems requiring stable component supply and long-term obsolescence management.
Supply support for SN74ACT7811-20FN 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 experience in high-reliability timing and interface ICs.
The SN74ACT7811-20FN belongs to TI's Widebus™ family of high-speed FIFO memories, designed specifically for clock-domain bridging in communications, computing, and industrial control systems demanding deterministic latency and robust flag signaling.
FAQ
What is the maximum operating frequency for SN74ACT7811-20FN?
The SN74ACT7811-20FN supports a maximum clock frequency of 28.5 MHz for both RDCLK and WRTCLK, as specified in the timing table for the -20 speed grade. This corresponds to a 15 ns access time under 50-pF load conditions, enabling reliable high-throughput data buffering in systems with tight timing budgets. The SN74ACT7811-20FN achieves this performance using ACT-family CMOS technology with optimized internal pointer logic.
How does the programmable AF/AE flag work on SN74ACT7811-20FN?
The SN74ACT7811-20FN implements programmable AF/AE via the DAF input and RESET sequence: a high-to-low DAF transition latches D0–D8 as the offset value X, and a subsequent RESET pulse configures the flag to assert when FIFO contains ≤(X+1) or ≥(1025−X) words. Holding DAF high selects the default X = 256. This mechanism allows runtime adaptation of flow-control thresholds without firmware intervention, making the SN74ACT7811-20FN suitable for variable-bandwidth applications.
Is SN74ACT7811-20FN pin-compatible with other members of the SN74ACT78xx family?
Yes, the SN74ACT7811-20FN is pin-to-pin compatible with SN74ACT7881, SN74ACT7882, and SN74ACT7884 in the same FN package, sharing identical pin assignments for clocks, enables, data I/O, flags, and power. This compatibility allows drop-in replacement for functional variants-such as substituting SN74ACT7881-20FN when programmable AF/AE is not required-without PCB redesign. The SN74ACT7811-20FN maintains full electrical and timing interoperability within this footprint.
What are the key timing parameters for read and write operations on SN74ACT7811-20FN?
For read operations, SN74ACT7811-20FN requires OE, RDEN1, and RDEN2 to be high before the RDCLK rising edge, with setup/hold times of 5 ns/1 ns respectively. Write operations require IR, WRTEN1, and WRTEN2 high before WRTCLK↑, with identical timing margins. Propagation delays include tpd(RDCLK↑→Q) = 4–20 ns and tpd(WRTCLK↑→IR) = 2–16 ns, ensuring predictable flag assertion and data visibility. These values are validated across 0°C to 70°C and 4.5–5.5 V supply range for the SN74ACT7811-20FN.
Can SN74ACT7811-20FN be used in depth-expanded configurations?
Yes, the SN74ACT7811-20FN supports depth expansion by cascading multiple devices: after the first word is loaded, OR goes high after (N × 3) RDCLK cycles, and IR recovers after (N × 2) WRTCLK cycles, where N is the number of cascaded units. This behavior is built into the flag logic and requires no external control logic. The SN74ACT7811-20FN's consistent timing and shared clock distribution make it ideal for building 2048×18 or larger FIFOs while preserving deterministic latency-verified in TI Application Report SCAS151C.
SN74ACT7811-20FN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ACT
- Package/Case:
- 68-LCC (J-Lead)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Memory Size:
- 18K (1K x 18)
- Function:
- Synchronous
- Data Rate:
- 28.5MHz
- Access Time:
- 20ns
- Voltage - Supply:
- 4.5 V ~ 5.5 V
- Current - Supply (Max):
- 1mA
- Bus Directional:
- Uni-Directional
- Expansion Type:
- Depth, Width
- Programmable Flags Support:
- Yes
- Retransmit Capability:
- No
- FWFT Support:
- No
- Operating Temperature:
- 0°C ~ 70°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 68-PLCC (24.23x24.23)
SN74ACT7811-20FN FAQ
1.How can I place an order for SN74ACT7811-20FN through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ACT7811-20FN 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 SN74ACT7811-20FN reliable?
The price and inventory of SN74ACT7811-20FN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ACT7811-20FN is usually 5 days.
3.What payment methods are accepted for SN74ACT7811-20FN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ACT7811-20FN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ACT7811-20FN?
SN74ACT7811-20FN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ACT7811-20FN 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 SN74ACT7811-20FN?
For technical support, including SN74ACT7811-20FN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ACT7811-20FN requirements.
6.How does Aetrix verify that SN74ACT7811-20FN is sourced from the original manufacturer or authorized distributors?
All SN74ACT7811-20FN 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 SN74ACT7811-20FN meets industry standards.
7.What is the process for return or replacement of SN74ACT7811-20FN?
All SN74ACT7811-20FN units undergo pre-shipment inspection (PSI). If there is an issue with SN74ACT7811-20FN, 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 SN74ACT7811-20FN part is unused and in its original packaging.
Return procedure for SN74ACT7811-20FN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74ACT7811-20FN Tags
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7201LA15JGI
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7204L12JG
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72V2105L10PFG
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72V2111L15PFGI
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72V2113L6PFG
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72V36110L6PFG
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7202LA25JGI
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