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Texas Instruments SN74ABT7820-30PH
- Part No.:
- SN74ABT7820-30PH
- Manufacturer:
- Texas Instruments
- Category:
- FIFOs Memory
- Package:
- 80-BQFP
- Datasheet:
-
SN74ABT7820-30PH.pdf
- Description:
- IC FIFO ASYNC 512X18X2 80QFP
- Quantity:
- Payment:
- Shipping:
Inventory:3,400
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Product details
Overview
SN74ABT7820-30PH from Texas Instruments is a strobed bidirectional FIFO memory IC with two independent 512 × 18-bit asynchronous FIFO buffers, 12 ns access time at 50-pF load, 67 MHz max clock rate, and programmable almost-full/almost-empty flags. It enables high-speed data buffering between mismatched bus domains in telecom backplanes and industrial protocol gateways.
For engineers reviewing the SN74ABT7820-30PH datasheet, SN74ABT7820-30PH pinout, SN74ABT7820-30PH application, or SN74ABT7820-30PH equivalent, key selection considerations include dual-FIFO depth matching, strobe-synchronized read/write control, programmable flag offsets, and 80-pin PH package compatibility with legacy Widebus™ system designs.
Technical Context
The SN74ABT7820-30PH integrates two fully independent 512-word × 18-bit FIFOs with separate load clocks (LDCKA/LDCKB), unload clocks (UNCKA/UNCKB), and reset controls (RSTA/RSTB), enabling simultaneous bidirectional data flow without arbitration. Each FIFO supports real-time bypass via SAB/SBA select logic and output enable gating via GAB/GBA.
Flag generation is hardware-based and configurable: AF/AEA and AF/AEB support programmable almost-empty (X) and almost-full (Y) thresholds (default 128), while FULLA/FULLB, EMPTYA/EMPTYB, and HFA/HFB provide fixed-depth status signals. All timing parameters are specified for VCC = 4.5–5.5 V and TA = 0°C to 70°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Depth × Width × Banks | 512 × 18 × 2 - Two independent FIFOs, each storing up to 512 words of 18-bit parallel data, enabling full-duplex buffering without shared memory contention. |
| Access Time | 12 ns at 50-pF load - Enables reliable operation at 67 MHz clock rates with sufficient setup/hold margin for synchronous bus interfaces. |
| Max Clock Frequency | 67 MHz - Supports high-throughput data streaming in packetized communication links and real-time DSP interconnects. |
| Supply Voltage Range | 4.5 V to 5.5 V - Compatible with standard 5-V TTL/CMOS logic families and industrial power rails. |
| Operating Temperature | 0°C to 70°C - Qualified for commercial and industrial embedded systems where ambient thermal management is constrained. |
| Programmable Flag Offsets | X/Y = 0–255 (default 128) - Allows fine-grained buffer-level monitoring for adaptive flow control in variable-latency protocols. |
| Output Drive Strength | IOL = 24 mA, IOH = –12 mA - Sustains signal integrity across 18-bit wide buses with moderate trace capacitance and fanout. |
Pinout & Package
SN74ABT7820-30PH uses an 80-pin plastic quad flat (PH) package with 0.65 mm lead pitch and exposed thermal pad. Pin numbering follows standard top-view layout per TI SCAS206D datasheet.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A17 | Port-A bidirectional data I/O | 18-bit parallel interface for side A; connects directly to host processor or peripheral bus; supports real-time pass-through or FIFO read/write. |
| B0–B17 | Port-B bidirectional data I/O | 18-bit parallel interface for side B; independently controlled; enables full-duplex data transfer between asymmetric subsystems. |
| LDCKA / LDCKB | FIFO write strobe inputs | Low-to-high transition loads data into FIFO A or B only when respective FULL flag is high; ensures no overflow during write. |
| UNCKA / UNCKB | FIFO read strobe inputs | Low-to-high transition unloads data from FIFO A or B only when respective EMPTY flag is high; prevents underflow reads. |
| RSTA / RSTB | Asynchronous FIFO reset inputs | Active-low reset clears FIFO contents and initializes all flags (FULL high, EMPTY low, HFA/HFB low, AF high). |
| PENA / PENB | Flag offset programming enable | Used post-reset to latch A0–A7/B0–B7 as X/Y values for AF/AEA/AF/AEB; enables runtime configuration of flow-control thresholds. |
| SAB / SBA | Bus select controls | Select source for B-port/A-port outputs: low = real-time data from opposite port, high = FIFO output - eliminates multiplexer glitches. |
| GAB / GBA | Output enable controls | High enables A0–A17/B0–B17 drivers; low places outputs in high-impedance state for bus sharing or isolation. |
| AF/AEA / AF/AEB | Programmable almost-full/almost-empty flags | Open-drain outputs active high when FIFO contains ≤X words or ≥(512−Y) words; default X=Y=128 triggers at 25% and 75% fill level. |
| FULLA / FULLB | Full status flags | Active-high when FIFO is completely filled (512 words); used to halt writes until space becomes available. |
| EMPTYA / EMPTYB | Empty status flags | Active-high when FIFO contains zero words; used to prevent invalid reads and synchronize consumer readiness. |
| HFA / HFB | Half-full status flags | Active-high when FIFO contains ≥256 words; provides coarse buffer occupancy feedback for interrupt-driven or polling-based software control. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent FIFO architecture | Enables concurrent bidirectional data flow without arbitration logic or shared memory conflicts - critical for full-duplex serial protocol bridges. |
| Strobed load/unload control | LDCK/UNCK edge-triggered operation decouples timing from system clock domain, supporting asynchronous interfacing between disparate clock domains. |
| Programmable AF/AE flag offsets | Allows dynamic tuning of flow-control thresholds (X/Y = 0–255) to match application-specific latency and burst-length requirements. |
| Real-time bypass mode | SAB/SBA select logic routes data directly between ports without FIFO delay - essential for low-latency debug paths or initialization sequences. |
| Glitch-free bus management | Hardware-select circuitry eliminates metastability and decoding spikes during transitions between real-time and stored data modes. |
Applications
| Telecom Line Card Buffering | Industrial Protocol Gateway |
|---|---|
Use Scenario: Buffering packetized TDM data between framer ASIC and backplane switch fabric operating at different clock domains. IC Role / Device Role / Timing Role: Dual-FIFO acts as elastic store to absorb clock skew and jitter; LDCKA/UNCKB synchronized to line clock, LDCKB/UNCKA to switch clock. Use Value: Eliminates packet loss due to frequency mismatch; 512-word depth accommodates worst-case burst latency; 12 ns access ensures sub-cycle alignment. |
Use Scenario: Bridging Modbus RTU over RS-485 to EtherNet/IP on a PLC controller with isolated power domains. IC Role / Device Role / Timing Role: SN74ABT7820-30PH isolates UART and Ethernet MAC timing; FIFO A handles RS-485 receive, FIFO B handles Ethernet transmit. Use Value: Prevents UART overrun during Ethernet congestion; programmable AF flags trigger DMA reload before buffer starvation; GAB/GBA enable safe bus isolation during hot-swap events. |
| Test Equipment Data Capture | Automated Test System (ATE) Interface |
Use Scenario: Capturing high-speed digital stimulus-response waveforms from DUTs using parallel pattern generators and digitizers. IC Role / Device Role / Timing Role: Acts as acquisition FIFO: LDCKA captures generator output, UNCKB streams to host memory; SAB/SBA enables real-time loopback verification. Use Value: 67 MHz clock support matches 100+ Mbps pattern rates; 18-bit width covers multi-channel DIO; half-full flag triggers DMA fetch to minimize CPU overhead. |
Use Scenario: Interfacing multiple instrument modules (DMM, SMU, scope) to central controller via shared 18-bit backplane. IC Role / Device Role / Timing Role: Provides per-module FIFO buffering to decouple module timing from controller scheduling; RSTA/RSTB allow individual module reset without system reboot. Use Value: Enables hot-plug instrumentation; programmable AF/AEB allows per-module flow control granularity; 80-pin PH package fits dense ATE chassis layouts. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bidirectional FIFO memory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| IDT72V251L15PF | 3.3-V only supply; 512 × 18 depth; 15 ns access; LVDS-compatible I/O; no real-time bypass mode. | Requires level-shifting for 5-V systems; lacks SAB/SBA select logic - cannot emulate direct bus pass-through. | Choose for new 3.3-V designs prioritizing lower power and EMI; avoid when backward compatibility with 5-V Widebus™ infrastructure is required. |
| SN74ACT7820-30PH | Same pinout and function but ACT logic family; 4.5–5.5 V supply; 10 ns access; higher drive strength (IOL = 48 mA); no programmable AF offsets. | Fixed 128-word AF threshold only; faster timing but less flexible flow control; higher ICC at 67 MHz. | Choose when maximum speed and noise immunity are critical and flag programmability is unnecessary; verify thermal design due to higher power dissipation. |
Compared with IDT72V251L15PF and SN74ACT7820-30PH, the SN74ABT7820-30PH uniquely balances 5-V compatibility, real-time bypass capability, and field-programmable flag thresholds - making it the optimal choice for maintaining legacy Widebus™ system interoperability while supporting adaptive buffer management.
Availability
SN74ABT7820-30PH is available at Aetrix Electronics and suitable for telecom line cards, industrial protocol gateways, automated test equipment, and legacy 5-V embedded systems requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74ABT7820-30PH 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 industrial and communications ICs.
The SN74ABT7820-30PH belongs to TI's Widebus™ family of advanced BiCMOS bus-interface devices, designed specifically for high-speed, low-glitch data buffering in mixed-clock-domain systems requiring robust 5-V operation and field-configurable flow control.
FAQ
What is the primary function of the SN74ABT7820-30PH?
The SN74ABT7820-30PH is a dual 512 × 18-bit strobed bidirectional FIFO memory IC that buffers asynchronous data streams between mismatched clock domains. It provides independent load/unload strobes, programmable status flags, and real-time bypass capability - all implemented in a single 80-pin PH package. Its core function is elastic storage with deterministic timing control, not general-purpose RAM or register-based logic.
Does the SN74ABT7820-30PH support 3.3-V operation?
No, the SN74ABT7820-30PH is specified only for 4.5 V to 5.5 V operation per its recommended conditions and absolute maximum ratings. It is incompatible with 3.3-V logic families without level translation. The device uses ABT-series Advanced BiCMOS technology optimized for 5-V TTL compatibility, and applying 3.3 V to VCC will result in undefined behavior or failure to meet timing specifications.
How are the AF/AEA and AF/AEB flags programmed on the SN74ABT7820-30PH?
After asserting RSTA or RSTB, the SN74ABT7820-30PH latches the binary value on A0–A7 (for AF/AEA) or B0–B7 (for AF/AEB) as both the almost-empty (X) and almost-full (Y) offset values on the next LDCKA↑ or LDCKB↑ transition while PENA or PENB is low. A second LDCK pulse reprograms Y only. Default X=Y=128 is used if PENA/PENB remains high. Programming occurs before any data is written to the FIFO.
Can the SN74ABT7820-30PH operate with different clock frequencies on each FIFO?
Yes - the SN74ABT7820-30PH supports fully asynchronous operation: LDCKA and UNCKA can run at different frequencies than LDCKB and UNCKB, and each pair may be driven by independent clock sources. This enables true bidirectional bridging between subsystems with unrelated timing domains, such as a 67 MHz PCI Express link and a 25 MHz CAN controller interface.
What is the purpose of the SAB and SBA pins on the SN74ABT7820-30PH?
SAB and SBA are bus-select inputs that determine whether Port-B or Port-A outputs reflect real-time data from the opposite port (SAB=low/SBA=low) or stored FIFO data (SAB=high/SBA=high). This enables glitch-free real-time pass-through mode for initialization, diagnostics, or low-latency paths - a feature absent in basic FIFOs and critical for system-level debug and fail-safe operation.
SN74ABT7820-30PH Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ABT
- Package/Case:
- 80-BQFP
- Packaging:
- Tray
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Memory Size:
- 18K (512 x 18 x 2)
- Function:
- Asynchronous
- Data Rate:
- 33.3MHz
- Access Time:
- 17ns
- Voltage - Supply:
- 4.5 V ~ 5.5 V
- Current - Supply (Max):
- 95mA
- Bus Directional:
- Bi-Directional
- Expansion Type:
- -
- Programmable Flags Support:
- Yes
- Retransmit Capability:
- No
- FWFT Support:
- No
- Operating Temperature:
- 0°C ~ 70°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 80-QFP (14x20)
SN74ABT7820-30PH FAQ
1.How can I place an order for SN74ABT7820-30PH through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ABT7820-30PH 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 SN74ABT7820-30PH reliable?
The price and inventory of SN74ABT7820-30PH are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ABT7820-30PH is usually 5 days.
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SN74ABT7820-30PH orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ABT7820-30PH 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 SN74ABT7820-30PH?
For technical support, including SN74ABT7820-30PH datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ABT7820-30PH requirements.
6.How does Aetrix verify that SN74ABT7820-30PH is sourced from the original manufacturer or authorized distributors?
All SN74ABT7820-30PH 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 SN74ABT7820-30PH meets industry standards.
7.What is the process for return or replacement of SN74ABT7820-30PH?
All SN74ABT7820-30PH units undergo pre-shipment inspection (PSI). If there is an issue with SN74ABT7820-30PH, 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 SN74ABT7820-30PH part is unused and in its original packaging.
Return procedure for SN74ABT7820-30PH:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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