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Texas Instruments SN74ACT3651-15PCB
- Part No.:
- SN74ACT3651-15PCB
- Manufacturer:
- Texas Instruments
- Category:
- FIFOs Memory
- Package:
- 120-LQFP
- Datasheet:
-
SN74ACT3651-15PCB.pdf
- Description:
- IC FIFO SYNC 2KX36 120HLQFP
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
SN74ACT3651-15PCB from Texas Instruments is a 2048 × 36-bit clocked FIFO memory IC with dual asynchronous ports (A/B), 67 MHz max clock frequency, 11 ns read access time, and synchronous retransmit capability - used for high-speed data buffering between mismatched bus domains in telecom line cards and DSP-based signal processing systems.
For engineers reviewing the SN74ACT3651-15PCB datasheet, SN74ACT3651-15PCB pinout, SN74ACT3651-15PCB application, or SN74ACT3651-15PCB equivalent, key selection criteria include programmable almost-full/empty flag offsets, mailbox register support for control-message handshaking, metastability-hardened flag synchronization, and pin-to-pin compatibility with SN74ACT3631/SN74ACT3641 for drop-in upgrades.
Technical Context
The SN74ACT3651-15PCB implements a dual-clock, dual-port SRAM-based FIFO with independent CLKA and CLKB domains that may operate asynchronously or coincidently. Its functional core includes write/read pointer logic, two-stage synchronized status flags (IR/AF on CLKA; OR/AE on CLKB), and shadow-pointer retransmit architecture enabling repeat reads from a user-defined starting address.
It integrates two 36-bit mailbox registers (Mail1/Mail2) with dedicated MBA/MBB select inputs and MBF1/MBF2 flags for inter-port command exchange, plus serial/parallel/programmable offset loading for AF/AE thresholds - all implemented in low-power 0.8-µm Advanced CMOS technology rated for 0°C to 70°C operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Depth × Width | 2048 × 36 bits - supports up to 2048 words of 36-bit data storage per FIFO channel. |
| Max Clock Frequency | 67 MHz - enables real-time buffering of high-throughput digital streams such as T3/E3 framers or JESD204B link interfaces. |
| Read Access Time | 11 ns - guarantees deterministic latency for time-critical read operations in synchronous control loops. |
| Flag Synchronization | Two-stage flip-flop sync - reduces metastability risk when CLKA and CLKB operate asynchronously. |
| Operating Temperature | 0°C to 70°C - validated for commercial-grade embedded systems including industrial controllers and network edge devices. |
| Technology Node | 0.8-µm Advanced CMOS - delivers low static power consumption while maintaining high-speed performance. |
| Retransmit Capability | Synchronous retransmit mode - allows repeated reads from a programmable start address without disturbing ongoing write operations. |
Pinout & Package
SN74ACT3651-15PCB uses a 120-pin Thin Quad Flat Package (TQFP), designated PCB in TI documentation, with 0.4 mm lead pitch and exposed thermal pad. Pin numbering follows standard TQFP top-view convention (pin 1 at top-left corner).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A35 | Port-A bidirectional data bus | 36-bit parallel interface for writing/reading FIFO or Mail1 register under CLKA control. |
| B0–B35 | Port-B bidirectional data bus | 36-bit parallel interface for writing/reading FIFO or Mail2 register under CLKB control. |
| CLKA / CLKB | Free-running port clocks | Independent synchronous timing references; IR/AF tied to CLKA edge, OR/AE to CLKB edge. |
| ENA / ENB | Port-A/B master enable | Global gate for port activity - must be high to allow CLKA/CLKB-triggered transfers. |
| CSA / CSB | Port-A/B chip select | Active-low enables port data drivers and internal logic; high = high-Z outputs. |
| W/RA / W/RB | Port-A/B write/read direction | W/RA high = write to FIFO/Mail1; W/RB low = write to FIFO/Mail2 (inverted logic). |
| IR / OR | Status flags | IR low = FIFO full (write disabled); OR high = valid data ready in output register. |
| AF / AE | Programmable threshold flags | AF low = ≤ Y empty locations remain; AE low = ≤ X words stored - both synchronized to respective clocks. |
| MBA / MBB | Mailbox select | High selects mailbox register (Mail1 for A, Mail2 for B); low selects FIFO path. |
| MBF1 / MBF2 | Mailbox full flags | Low indicates new mail written to Mail1/Mail2; reset by corresponding port read. |
| RST | Asynchronous reset | Requires ≥4 CLKA + ≥4 CLKB rising edges low-to-high while RST held low. |
| RTM / RFM | Retransmit controls | RTM high + OR high initiates retransmit; RFM high + CLKB rising edge restarts loop from mark. |
| FS0/SD / FS1/SEN | Flag offset programming | Dual-function pins for serial/parallel/preset loading of AF/AE offset registers X and Y. |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous retransmit mode | Enables repeat reads from any FIFO location without halting writes - critical for FIR filter coefficient replay or protocol retry sequences. |
| Dual 36-bit mailbox registers | Provides non-blocking command/data exchange between ports A and B using dedicated MBA/MBB and MBF1/MBF2 handshake signals. |
| Programmable AF/AE offsets | Three configuration methods (preset 8/64, parallel load via A0–A10, or 22-bit serial load) allow precise tuning of buffer occupancy thresholds. |
| Metastability-hardened flag sync | Two-stage synchronizers on IR/AF (CLKA domain) and OR/AE (CLKB domain) ensure reliable flag assertion across asynchronous clock boundaries. |
| Pin-to-pin compatibility | Direct replacement for SN74ACT3631 and SN74ACT3641 - simplifies design reuse and migration within same family. |
Applications
| Telecom Line Interface Cards | DSP-Based Signal Processing |
|---|---|
Use Scenario: Buffering between T3 framer ASIC (25.6 MHz) and backplane switch fabric (62.5 MHz). IC Role / Device Role / Timing Role: Clocked FIFO bridging asynchronous clock domains while preserving packet integrity and minimizing jitter-induced slip. Use Value: 2048-word depth absorbs burst traffic; 11 ns access ensures minimal latency penalty; AF/AE flags trigger DMA pre-fetch before underflow/overflow. | Use Scenario: Feeding coefficient data to a fixed-point DSP executing real-time FIR filtering on sensor inputs. IC Role / Device Role / Timing Role: Re-transmittable FIFO delivering identical filter taps repeatedly during multiple convolution passes. Use Value: Synchronous retransmit mode eliminates external address counters; mailbox registers pass new tap sets without interrupting active filtering. |
| Industrial Motion Control Systems | Automated Test Equipment (ATE) |
Use Scenario: Isolating microcontroller command stream (16 MHz) from servo drive PWM generator (40 MHz). IC Role / Device Role / Timing Role: Dual-port FIFO decoupling control-plane commands from time-critical motion execution. Use Value: MBA/MBB-selectable mailboxes shuttle configuration updates; IR/AF flags prevent command loss during rapid acceleration profiles. | Use Scenario: Capturing high-speed digital stimulus/response patterns between pattern generator and DUT interface. IC Role / Device Role / Timing Role: High-bandwidth data capture FIFO with deterministic read latency for real-time pass/fail analysis. Use Value: 67 MHz clock support matches 100+ Mbps test vectors; OR flag enables immediate post-capture processing without polling delay. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar clocked FIFO applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ACT3631-15PCB | Same 2048 × 36 capacity, identical pinout and timing, but lacks mailbox registers and retransmit capability. | Suitable only where basic FIFO buffering suffices - no command handshaking or repeat-read requirements. | Select when cost reduction is prioritized and mailbox/retransmit features are unused. |
| IDT72V2115L15PF | 36-bit × 2048 depth, 15 ns access, LVCMOS I/O, but uses single clock domain and lacks dual-mailbox architecture. | Requires external logic for cross-domain handshaking; no native retransmit mode - limits use in DSP coefficient replay. | Choose if system already uses IDT timing ecosystem and can accommodate simplified flag logic. |
Compared with SN74ACT3631-15PCB and IDT72V2115L15PF, SN74ACT3651-15PCB uniquely combines mailbox registers, synchronous retransmit, and dual-clock metastability hardening - making it the only option for applications requiring concurrent command/data transfer and repeat-read functionality without external state machines.
Availability
SN74ACT3651-15PCB is available at Aetrix Electronics and suitable for telecom infrastructure, DSP subsystems, industrial motion controllers, and automated test equipment requiring stable component supply and long-term obsolescence management.
Supply support for SN74ACT3651-15PCB 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 deep expertise in high-speed interface and memory products.
The SN74ACT3651-15PCB belongs to TI's ACT-family clocked FIFO product line, designed specifically for deterministic, low-latency data buffering across asynchronous clock domains in communications and real-time control systems.
FAQ
What is the maximum supported clock frequency for SN74ACT3651-15PCB?
The SN74ACT3651-15PCB 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 reflects the device's optimized 0.8-µm Advanced CMOS process. Operation beyond this frequency may result in timing violations or metastability in flag outputs.
How does the synchronous retransmit feature work in SN74ACT3651-15PCB?
The SN74ACT3651-15PCB enters retransmit mode when RTM is high and OR is high, capturing the current FIFO output register content as the first retransmit word. Subsequent reads cycle through FIFO contents from that point. RFM enables restarting the loop from the marked location. This occurs without disrupting ongoing writes or requiring external address tracking logic.
Can SN74ACT3651-15PCB operate with CLKA and CLKB running at different frequencies?
Yes - SN74ACT3651-15PCB is explicitly designed for asynchronous dual-clock operation. CLKA and CLKB may run at independent frequencies, phases, or even be stopped individually. Status flags (IR/AF synchronized to CLKA; OR/AE to CLKB) use two-stage synchronizers to maintain reliability across clock domain crossings.
What are the three methods to program the almost-full and almost-empty offset registers in SN74ACT3651-15PCB?
SN74ACT3651-15PCB supports preset (8 or 64), parallel load from port A (using A10–A0), or serial load via FS0/SD and FS1/SEN. The method is selected by FS0/FS1 states sampled during the rising edge of RST. All methods configure both X (AE offset) and Y (AF offset) registers, with values programmable from 1 to 2044.
Is SN74ACT3651-15PCB pin-compatible with other devices in the same family?
Yes - SN74ACT3651-15PCB is pin-to-pin compatible with SN74ACT3631 and SN74ACT3641 in the same 120-pin PCB package. This allows direct substitution where mailbox registers and retransmit functionality are not required, simplifying design reuse and second-source qualification.
SN74ACT3651-15PCB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ACT
- Package/Case:
- 120-LQFP
- Packaging:
- Tray
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Memory Size:
- 72K (2K x 36)
- Function:
- Synchronous
- Data Rate:
- 66.7MHz
- Access Time:
- 11ns
- Voltage - Supply:
- 4.5 V ~ 5.5 V
- Current - Supply (Max):
- 400µA
- Bus Directional:
- Bi-Directional
- Expansion Type:
- Depth, Width
- Programmable Flags Support:
- Yes
- Retransmit Capability:
- Yes
- FWFT Support:
- No
- Operating Temperature:
- 0°C ~ 70°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 120-HLQFP (14x14)
SN74ACT3651-15PCB FAQ
1.How can I place an order for SN74ACT3651-15PCB through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ACT3651-15PCB 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 SN74ACT3651-15PCB reliable?
The price and inventory of SN74ACT3651-15PCB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ACT3651-15PCB is usually 5 days.
3.What payment methods are accepted for SN74ACT3651-15PCB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ACT3651-15PCB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ACT3651-15PCB?
SN74ACT3651-15PCB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ACT3651-15PCB 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 SN74ACT3651-15PCB?
For technical support, including SN74ACT3651-15PCB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ACT3651-15PCB requirements.
6.How does Aetrix verify that SN74ACT3651-15PCB is sourced from the original manufacturer or authorized distributors?
All SN74ACT3651-15PCB 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 SN74ACT3651-15PCB meets industry standards.
7.What is the process for return or replacement of SN74ACT3651-15PCB?
All SN74ACT3651-15PCB units undergo pre-shipment inspection (PSI). If there is an issue with SN74ACT3651-15PCB, 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 SN74ACT3651-15PCB part is unused and in its original packaging.
Return procedure for SN74ACT3651-15PCB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74ACT3651-15PCB Tags
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7201LA15JGI
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7204L12JG
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72V82L15PAG8
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7205L15JGI
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7208L20JG
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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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SN74V245-15PAG
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