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Texas Instruments SN74ACT7881-20PN
- Part No.:
- SN74ACT7881-20PN
- Manufacturer:
- Texas Instruments
- Category:
- FIFOs Memory
- Package:
- 80-LQFP
- Datasheet:
-
SN74ACT7881-20PN.pdf
- Description:
- IC FIFO SYNC 1KX18 13NS 80LQFP
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
SN74ACT7881-20PN from Texas Instruments is a clocked first-in, first-out (FIFO) memory IC with 1024 × 18-bit organization, 50-pF load access time of 11 ns, asynchronous read/write synchronization to independent clocks, and programmable almost-full/almost-empty flag. It serves as a data buffering interface between mismatched-speed digital subsystems in high-throughput communication and control systems.
For engineers reviewing the SN74ACT7881-20PN datasheet, SN74ACT7881-20PN pinout, SN74ACT7881-20PN application, or SN74ACT7881-20PN equivalent, key selection criteria include its 18-bit parallel I/O width, dual-clock domain support (WRTCLK/RDCLK), status flag architecture (AF/AE, HF, IR, OR), 5-V operation, and 80-pin shrink quad flat (PN) package compatibility with system-level timing and bus-loading requirements.
Technical Context
The SN74ACT7881-20PN implements a synchronous FIFO core with independent write and read pointer logic, RAM array (1024 × 18), and status-flag generation circuitry. Its dual-clock architecture allows WRTCLK and RDCLK to operate at different frequencies up to 50 MHz (–20 speed grade), with flags (IR, OR, HF, AF/AE) synchronized to their respective clock domains.
Status flag behavior is defined by precise timing relationships: IR asserts on the second WRTCLK edge after RESET release; OR asserts on the third RDCLK edge after first valid write; AF/AE boundary is programmable via DAF/D0–D8 during reset, supporting configurable buffer thresholds (e.g., X = 256 default → AF active ≤257 or ≥769 words).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Depth × Width | 1024 × 18 bits - supports 18-bit parallel data streams with full-depth buffering for burst-mode transfers. |
| Access Time | 11 ns at 50-pF load - enables reliable 50-MHz operation with margin for PCB trace delays and fanout. |
| Max Clock Frequency | 50 MHz - maximum supported WRTCLK or RDCLK frequency for –20 speed grade, verified under CL = 50 pF. |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5-V TTL/CMOS logic rails and noise-tolerant industrial power supplies. |
| Output Drive | –8 mA / +16 mA - sufficient to directly drive 50-pF loads and multiple TTL inputs without external buffers. |
| Operating Temperature | 0°C to 70°C - rated for commercial and industrial ambient environments without derating. |
| Flag Programmability | AF/AE offset programmable via DAF/D0–D8 - allows dynamic adjustment of buffer threshold for application-specific flow control. |
Pinout & Package
SN74ACT7881-20PN uses an 80-pin shrink quad flat (PN) package with 0.5-mm lead pitch, optimized for high-density PCB layouts and thermal performance (θJA = 62°C/W). Pin functions are validated per TI SCAS227E datasheet Figures 1–2 and Terminal Functions table.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| WRTCLK (Pin 29) | Write clock input | Synchronizes all write operations; rising edge latches D0–D17 when IR, WRTEN1, WRTEN2 are high. |
| RDCLK (Pin 5) | Read clock input | Synchronizes all read operations; rising edge outputs Q0–Q17 when OR, OE, RDEN1, RDEN2 are high. |
| AF/AE (Pin 33) | Status output | Programmable flag indicating FIFO occupancy ≤(X+1) or ≥(1025–X) words; used for throttle signaling. |
| IR (Pin 35) | Status output | Input-ready flag: high when FIFO has space for at least one word; drives write-enable logic in upstream systems. |
| OR (Pin 66) | Status output | Output-ready flag: high when FIFO contains ≥1 word; enables downstream read arbitration and data consumption. |
| D0–D17 (Pins 1–4, 6–9, 11–15, 17, 19–26) | Data inputs | 18-bit parallel input bus; D0–D8 also carry AF/AE offset value during DAF-driven programming sequence. |
| Q0–Q17 (Pins 38–39, 41–42, 44, 46–47, 49–50, 52–53, 55–56, 58–59, 61, 63–64) | Data outputs | 18-bit noninverting parallel output bus; outputs enabled only when OE is high and RDCLK edge occurs. |
| RESET (Pin 1) | Asynchronous reset | Clears internal pointers and flags; requires ≥4 WRTCLK/RDCLK cycles to guarantee full initialization. |
Key Features
| Feature | Design Value |
|---|---|
| Independent asynchronous clocks | Enables seamless bridging between systems operating at different clock domains (e.g., DSP ↔ microcontroller). |
| Programmable AF/AE flag | Allows runtime-configurable buffer thresholds (X = 0–511) to match real-time flow-control policies without hardware change. |
| Expandable architecture | Supports word-width expansion (parallel stacking) and word-depth expansion (daisy-chained FIFOs) for custom memory configurations. |
| Direct bus interface capability | High-output-drive ACT logic eliminates need for external line drivers when interfacing to 5-V TTL/CMOS buses. |
| Comprehensive status signaling | Four dedicated flags (IR, OR, HF, AF/AE) provide granular visibility into FIFO state for deterministic software/hardware flow management. |
Applications
| Network Packet Buffering | DSP Data Streaming |
|---|---|
Use Scenario: Temporarily stores Ethernet frames or ATM cells between MAC layer and protocol stack where ingress/egress rates differ. IC Role / Device Role / Timing Role: Asynchronous FIFO buffer decoupling PHY and MAC clock domains while maintaining packet integrity and low latency. Use Value: Prevents packet loss during traffic bursts using programmable AF/AE to trigger backpressure before overflow, leveraging 11-ns access for line-rate throughput. | Use Scenario: Buffers sensor samples between high-speed ADC and slower DSP processing pipeline in real-time signal analysis. IC Role / Device Role / Timing Role: Clock-domain translator synchronizing 50-MHz sampling clock to 25-MHz DSP core clock with deterministic latency. Use Value: Enables continuous acquisition without gaps via IR/OR handshaking, while HF flag triggers DMA prefetch to minimize CPU overhead. |
| Industrial PLC I/O Expansion | Video Frame Synchronization |
Use Scenario: Aggregates digital I/O status updates from distributed fieldbus nodes into centralized controller with variable scan cycle times. IC Role / Device Role / Timing Role: Data staging buffer isolating deterministic control loop timing from asynchronous field device response jitter. Use Value: Guarantees deterministic worst-case latency (≤13 ns tpd) for safety-critical I/O updates, with AF/AE preventing overrun during transient overload. | Use Scenario: Aligns pixel data streams from multiple camera sensors operating at slightly different frame rates into unified video processing pipeline. IC Role / Device Role / Timing Role: Dual-clock FIFO absorbing timing skew between camera clock domains and display controller clock domain. Use Value: Eliminates frame tearing using HF flag to schedule double-buffered frame swaps, while 18-bit width supports RGB565 or YUV422 formats. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar FIFO memory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ACT7882-20PN | Same 1024 × 18 architecture and pinout; differs only in factory-programmed AF/AE offset (X = 128 vs. SN74ACT7881's user-programmable X). | Fixed-threshold flow control; no DAF programming required but lacks runtime configurability. | Select SN74ACT7882-20PN if AF/AE threshold is static and board space must avoid DAF routing. |
| SN74ACT7884-20PN | Same 1024 × 18 organization and timing; includes additional status register accessible via serial interface (not present in SN74ACT7881-20PN). | Enables software-read flag states and extended diagnostics; requires extra serial control lines. | Choose SN74ACT7884-20PN when host MCU needs real-time flag monitoring beyond discrete pin reads. |
Compared with SN74ACT7881-20PN, SN74ACT7882-20PN offers simplified fixed-threshold operation, while SN74ACT7884-20PN adds diagnostic visibility at the cost of interface complexity-neither is pin-compatible replacement without verifying DAF and serial interface usage.
Availability
SN74ACT7881-20PN is available at Aetrix Electronics and suitable for network packet buffering, DSP data streaming, industrial PLC I/O expansion, and video frame synchronization requiring stable component supply across long-lifecycle embedded programs.
Supply support for SN74ACT7881-20PN 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 logic families.
The SN74ACT7881-20PN belongs to TI's Widebus™ family of high-speed FIFO memories, engineered specifically for robust asynchronous data buffering in mixed-clock-domain digital systems.
FAQ
What is the maximum operating frequency of the SN74ACT7881-20PN?
The SN74ACT7881-20PN supports a maximum clock frequency of 50 MHz for both WRTCLK and RDCLK inputs, as specified for the –20 speed grade under recommended conditions (VCC = 4.5 V to 5.5 V, TA = 0°C to 70°C, CL = 50 pF). This rating is confirmed by timing parameter fmax in the SCAS227E datasheet, with 11-ns access time providing design margin for signal integrity and layout-induced delays.
How is the AF/AE flag programmed on the SN74ACT7881-20PN?
The AF/AE flag on the SN74ACT7881-20PN is programmed during reset by controlling DAF (Pin 27) and D0–D8 (Pins 19–26, 17, 15–7). To set a custom offset X, drive DAF low before RESET, then pulse RESET low-to-high while DAF remains low-the binary value on D0–D8 becomes X. For default X = 256, hold DAF high during RESET. The SN74ACT7881-20PN executes this procedure on every power-on or active-low RESET assertion.
Does the SN74ACT7881-20PN support word-width expansion, and how is it implemented?
Yes, the SN74ACT7881-20PN supports word-width expansion to increase data bus size beyond 18 bits. This is implemented by connecting identical devices in parallel: tie all control signals (WRTCLK, RDCLK, WRTEN1/2, RDEN1/2, OE, RESET) together, route D0–D17 to first device and D18–D35 to second, and combine Q0–Q17 and Q18–Q35 outputs. IR and OR signals are OR'd externally; AF/AE and HF may be sampled from either device. The SN74ACT7881-20PN's pinout and timing ensure deterministic coherency across expanded buses.
What are the voltage and current specifications for the SN74ACT7881-20PN outputs?
The SN74ACT7881-20PN outputs meet ACT-family specifications: VOH ≥ 2.4 V at IOH = –8 mA and VOL ≤ 0.5 V at IOL = 16 mA, with VCC = 4.5 V. Input thresholds are VIH ≥ 2.0 V and VIL ≤ 0.8 V. These values ensure robust noise margins in 5-V TTL/CMOS systems and allow direct connection to standard logic families without level-shifting. The SN74ACT7881-20PN maintains these specs across its full operating temperature range (0°C to 70°C).
Is the SN74ACT7881-20PN pin-compatible with other members of the SN74ACT788x family?
Yes, the SN74ACT7881-20PN is pin-to-pin compatible with SN74ACT7882-20PN and SN74ACT7884-20PN in the same PN package, sharing identical pin assignments for power, clocks, data, enables, flags, and reset. Functional differences exist in AF/AE programming (user-defined vs. fixed vs. register-accessible) and optional features (serial interface on SN74ACT7884), but PCB layout and interconnect remain unchanged. This compatibility simplifies design reuse and migration across the SN74ACT788x family.
SN74ACT7881-20PN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ACT
- Package/Case:
- 80-LQFP
- Packaging:
- Tray
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Memory Size:
- 18K (1K 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:
- 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:
- 80-LQFP (12x12)
SN74ACT7881-20PN FAQ
1.How can I place an order for SN74ACT7881-20PN through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ACT7881-20PN 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 SN74ACT7881-20PN reliable?
The price and inventory of SN74ACT7881-20PN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ACT7881-20PN is usually 5 days.
3.What payment methods are accepted for SN74ACT7881-20PN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ACT7881-20PN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ACT7881-20PN?
SN74ACT7881-20PN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ACT7881-20PN 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 SN74ACT7881-20PN?
For technical support, including SN74ACT7881-20PN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ACT7881-20PN requirements.
6.How does Aetrix verify that SN74ACT7881-20PN is sourced from the original manufacturer or authorized distributors?
All SN74ACT7881-20PN 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 SN74ACT7881-20PN meets industry standards.
7.What is the process for return or replacement of SN74ACT7881-20PN?
All SN74ACT7881-20PN units undergo pre-shipment inspection (PSI). If there is an issue with SN74ACT7881-20PN, 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 SN74ACT7881-20PN part is unused and in its original packaging.
Return procedure for SN74ACT7881-20PN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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