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Texas Instruments SN74ACT7805-40DLR
- Part No.:
- SN74ACT7805-40DLR
- Manufacturer:
- Texas Instruments
- Category:
- FIFOs Memory
- Package:
- 56-BSSOP (0.295", 7.50mm Width)
- Datasheet:
-
SN74ACT7805-40DLR.pdf
- Description:
- IC FIFO SYNC 256X18 20NS 56SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,198
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Product details
Overview
SN74ACT7805-40DLR 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 up to 25 MHz, delivers 20 ns access time (CL = 50 pF), features synchronized input-ready (IR) and output-ready (OR) flags, and operates over 0°C to 70°C. It is used in high-speed digital interface bridging, such as between legacy parallel buses and modern controllers.
For engineers reviewing the SN74ACT7805-40DLR datasheet, SN74ACT7805-40DLR pinout, SN74ACT7805-40DLR application, or SN74ACT7805-40DLR equivalent, key selection criteria include its 25-MHz maximum clock frequency, programmable almost-full/almost-empty flag offsets, bidirectional configuration capability without external logic, and compatibility with 5-V TTL/CMOS systems.
Technical Context
The SN74ACT7805-40DLR implements a synchronous dual-clock FIFO architecture with independent write and read pointer control, 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 flag offsets via D0–D6 and PEN during reset, defaulting to X = Y = 32. The FIFO enables bidirectional data flow and word-width expansion (e.g., 256 × 36) using two devices, with no additional logic required. All data outputs switch simultaneously under load.
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 | 25 MHz - defines upper limit for reliable read/write operation per clock domain |
| Access Time | 20 ns (CL = 50 pF) - determines minimum cycle time for valid data capture at outputs |
| Supply Voltage | 4.5 V to 5.5 V - ensures compatibility with standard 5-V TTL/CMOS logic families |
| Operating Temperature | 0°C to 70°C - specifies commercial-grade thermal envelope for stable timing behavior |
| Output Drive | 16 mA (Q outputs), 8 mA (flags) - supports direct interfacing to multiple 5-V CMOS/TTL loads |
| Flag Synchronization | IR synced to WRTCLK, OR synced to RDCLK - eliminates metastability in handshaking across clock boundaries |
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.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| WRTCLK (25) | Write clock input | Rising-edge-triggered write strobe; synchronizes IR flag and data latching |
| RDCLK (32) | Read clock input | Rising-edge-triggered read strobe; synchronizes OR flag and data output enable |
| D0–D17 (2–21, 11–12, 9–2) | Data inputs | 18-bit parallel input bus; accepts data on WRTCLK↑ when WRTEN1=H, WRTEN2=L, IR=H |
| Q0–Q17 (33–34, 36–38, 40–43, 45–49, 51, 53–55) | Data outputs | 18-bit parallel output bus; drives valid data on RDCLK↑ when RDEN=OE1=OE2=L and OR=H |
| IR (28) | Input-ready flag | Synchronized to WRTCLK↑; low = FIFO full, disables writes; goes high after second WRTCLK↑ post-reset |
| OR (29) | Output-ready flag | Synchronized to RDCLK↑; low = FIFO empty, disables reads; asserts high on third RDCLK↑ after first write |
| AF/AE (24) | Status flag | Programmable almost-full/almost-empty indicator; high when ≤32 words remain or ≥224 words stored (default) |
| RESET (1) | Asynchronous reset | Must be held low while ≥4 WRTCLK↑ and ≥4 RDCLK↑ occur to initialize flags and pointers |
Key Features
| Feature | Design Value |
|---|---|
| Independent read/write clocks | Enables robust bridging between mismatched or isolated clock domains without PLLs or clock-domain crossing logic |
| Programmable AF/AE flag offsets | Allows fine-grained buffer management via D0–D6 and PEN; supports custom flow-control thresholds beyond default X=Y=32 |
| Bidirectional configuration support | Two SN74ACT7805-40DLR devices can form a full-duplex FIFO pair using shared D/Q lines-no glue logic needed |
| Output edge control (OEC™) | Reduces simultaneous switching noise (SSN) by controlling output slew rate-critical for signal integrity in dense PCB layouts |
| Half-full flag (HF) | Provides deterministic mid-buffer status indication-useful for pacing DMA transfers or interrupt-driven read/write scheduling |
Applications
| Parallel Bus Bridging | Industrial PLC I/O Expansion |
|---|---|
Use Scenario: Interfacing a legacy 16-bit microprocessor bus running at 12 MHz to a modern FPGA-based controller operating at 20 MHz. IC Role / Device Role / Timing Role: Clocked FIFO acting as asynchronous data buffer with independent WRTCLK/RDCLK domains and synchronized IR/OR handshaking. Use Value: Eliminates need for complex clock-domain crossing circuits; maintains data coherency across timing boundaries with guaranteed 20 ns access and 25 MHz throughput. | Use Scenario: Extending I/O scan cycles in an industrial programmable logic controller where sensor data acquisition and actuator update clocks are non-synchronized. IC Role / Device Role / Timing Role: FIFO memory managing buffered analog input samples and discrete output commands between separate real-time execution loops. Use Value: Prevents data loss during variable scan intervals; HF and AF/AE flags enable adaptive polling and interrupt generation without CPU overhead. |
| Word-Width Expansion Interface | Digital Test Equipment Data Capture |
Use Scenario: Constructing a 36-bit wide FIFO path for high-throughput video frame buffering in broadcast equipment. IC Role / Device Role / Timing Role: Two SN74ACT7805-40DLR devices configured in parallel with shared clocks and independent D/Q busses. Use Value: Achieves 256 × 36-bit capacity without multiplexers or address decoding-reduces BOM count and layout complexity. | Use Scenario: Capturing high-speed digital stimulus-response sequences in automated test equipment with mixed-signal timing requirements. IC Role / Device Role / Timing Role: Asynchronous FIFO capturing pattern generator outputs and digitizer inputs under independent sampling clocks. Use Value: Enables glitch-free capture of transient events across clock domains; 20 ns access ensures precise timestamp alignment of captured data edges. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar FIFO memory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ACT7803-40DLR | Same 56-pin DL package and pinout; 128 × 18-bit depth (half capacity); identical timing and flag structure | Suitable for lower-depth buffering needs where 128-word capacity suffices and board space is constrained | Select when reduced memory depth is acceptable and cost optimization is prioritized over scalability |
| SN74ACT7813-40DLR | Same 56-pin DL package and pinout; 512 × 18-bit depth (double capacity); otherwise identical electrical/timing specs | Required for applications needing >256-word buffering, e.g., longer burst capture or deeper pipeline staging | Choose when future-proofing or higher latency tolerance demands greater depth without changing PCB layout |
Compared with SN74ACT7803-40DLR and SN74ACT7813-40DLR, the SN74ACT7805-40DLR offers optimal balance of depth (256 words), footprint compatibility, and timing performance-making it ideal for mid-range buffering where neither 128 nor 512 words are necessary.
Availability
SN74ACT7805-40DLR is available at Aetrix Electronics and suitable for industrial automation interfaces, test equipment data capture, parallel bus bridging, and digital signal processing subsystems requiring stable component supply and long-term obsolescence management.
Supply support for SN74ACT7805-40DLR 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 and interface ICs.
The SN74ACT7805-40DLR belongs to TI's Widebus™ family of high-speed, low-noise FIFOs engineered for robust asynchronous data transfer in industrial, communications, and instrumentation systems.
FAQ
What is the maximum clock frequency supported by the SN74ACT7805-40DLR?
The SN74ACT7805-40DLR supports a maximum clock frequency of 25 MHz for both read and write operations under recommended operating conditions (VCC = 4.5 V to 5.5 V, TA = 0°C to 70°C). This rating is confirmed in the timing requirements table of the SCAS201B datasheet, where the 'ACT7805-40 variant specifies min/max pulse widths and setup/hold times aligned to 25 MHz operation. Exceeding this frequency risks timing violations and metastability in flag synchronization.
How does the SN74ACT7805-40DLR handle reset initialization?
The SN74ACT7805-40DLR requires an asynchronous reset sequence: RESET must be held low while at least four rising edges occur on both WRTCLK and RDCLK. This clears the synchronizing registers and initializes IR, OR, and HF flags low, while setting AF/AE high. The FIFO must be reset upon power-up to ensure deterministic flag states and pointer alignment-failure to do so may result in undefined output behavior or incorrect buffer status reporting.
Can the SN74ACT7805-40DLR be used for bidirectional data flow without external logic?
Yes-the SN74ACT7805-40DLR supports bidirectional configuration using two devices, as documented in Figure 8 of the SCAS201B datasheet. One device handles A→B traffic (D0–D17 as input, Q0–Q17 as output), the other handles B→A traffic (Q0–Q17 as input, D0–D17 as output), sharing clocks and control signals. No additional logic gates or level shifters are required, enabling full-duplex buffering in compact designs.
What is the function of the PEN pin on the SN74ACT7805-40DLR?
The PEN (Program Enable) pin on the SN74ACT7805-40DLR controls programming of the almost-full/almost-empty (AF/AE) flag offset values. After reset and before the first write, asserting PEN low during a WRTCLK rising edge latches D0–D6 as the almost-empty offset (X); a second low PEN assertion latches D0–D6 as the almost-full offset (Y). While PEN is active, writes are disabled regardless of WRTEN1/WRTEN2 state-ensuring safe reconfiguration of flow-control thresholds.
Does the SN74ACT7805-40DLR support 3.3-V logic interfaces?
No-the SN74ACT7805-40DLR is specified only for 4.5 V to 5.5 V supply operation and is not 3.3-V tolerant. Its input voltage thresholds (VIH = 2.0 V, VIL = 0.8 V) and output drive characteristics are optimized for 5-V TTL/CMOS systems. Direct connection to 3.3-V logic may cause unreliable switching or excessive current draw; level-shifting circuitry is required for interoperability with 3.3-V domains.
SN74ACT7805-40DLR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ACT
- Package/Case:
- 56-BSSOP (0.295", 7.50mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Memory Size:
- 4.5K (256 x 18)
- Function:
- Synchronous
- Data Rate:
- 25MHz
- Access Time:
- 20ns
- 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
SN74ACT7805-40DLR FAQ
1.How can I place an order for SN74ACT7805-40DLR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ACT7805-40DLR 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 SN74ACT7805-40DLR reliable?
The price and inventory of SN74ACT7805-40DLR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ACT7805-40DLR is usually 5 days.
3.What payment methods are accepted for SN74ACT7805-40DLR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ACT7805-40DLR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ACT7805-40DLR?
SN74ACT7805-40DLR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ACT7805-40DLR 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 SN74ACT7805-40DLR?
For technical support, including SN74ACT7805-40DLR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ACT7805-40DLR requirements.
6.How does Aetrix verify that SN74ACT7805-40DLR is sourced from the original manufacturer or authorized distributors?
All SN74ACT7805-40DLR 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 SN74ACT7805-40DLR meets industry standards.
7.What is the process for return or replacement of SN74ACT7805-40DLR?
All SN74ACT7805-40DLR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ACT7805-40DLR, 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 SN74ACT7805-40DLR part is unused and in its original packaging.
Return procedure for SN74ACT7805-40DLR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74ACT7805-40DLR Tags
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7201LA15JGI
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72V82L15PAG8
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72V2111L15PFGI
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72V2113L6PFG
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7202LA25JGI
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