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Texas Instruments CY74FCT646TQCT
- Part No.:
- CY74FCT646TQCT
- Manufacturer:
- Texas Instruments
- Package:
- 24-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
CY74FCT646TQCT.pdf
- Description:
- IC TXRX NON-INVERT 5.25V 24SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,331
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Product details
Overview
CY74FCT646TQCT from Texas Instruments is an 8-bit registered transceiver with 3-state outputs, designed for bidirectional data routing between A and B buses in high-speed TTL/CMOS mixed-signal systems. It features independent A/B registers, dual clock inputs (CPAB/CPBA), direction control (DIR), output-enable (G), and data-source select (SAB/SBA). With 64-mA sink and 32-mA source drive strength, it supports robust bus interfacing in industrial control backplanes.
For engineers reviewing the CY74FCT646TQCT datasheet, CY74FCT646TQCT pinout, CY74FCT646TQCT application, or CY74FCT646TQCT equivalent, key selection criteria include its 9 ns propagation delay (tPLH/tPHL), Ioff partial-power-down capability, matched rise/fall times, edge-rate controlled noise immunity, and compatibility with TTL input/output logic levels.
Technical Context
This device implements a dual-bus registered transceiver architecture with separate D-type flip-flop registers for A and B data paths, enabling synchronous storage and multiplexed forwarding of real-time or registered data. Control logic decodes DIR, G, SAB, and SBA to determine whether data flows transparently or from internal registers - supporting isolation, store-and-forward, and bidirectional transfer modes.
Its Ioff circuitry disables outputs when VCC = 0 V (±1 µA leakage), allowing safe hot-insertion and partial-power-down operation. Edge-rate control circuitry limits dV/dt to reduce simultaneous switching noise, while matched rise/fall times (typ. 3.5 ns) minimize skew across all 8 bits under 5-V supply conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.75 V to 5.25 V - ensures stable operation within commercial-grade 5-V rail tolerances |
| Max Propagation Delay | 9 ns (A↔B) - enables reliable timing in ≤110 MHz bus cycles with setup/hold margin |
| Output Drive Strength | 64 mA sink / 32 mA source - drives heavy capacitive loads (≤50 pF) without signal degradation |
| Ioff Leakage Current | ±1 µA at VCC = 0 V - prevents backfeed current during power sequencing or hot-swap events |
| Input Logic Compatibility | TTL-level VIH ≥ 2 V, VIL ≤ 0.8 V - interoperates directly with legacy 74LS/ALS logic without level shifters |
| ESD Protection | 2000-V HBM, 200-V MM, 1000-V CDM - meets industrial handling and board-level ESD requirements |
| Operating Temperature | –40°C to +85°C - qualified for extended-temperature commercial and industrial environments |
Pinout & Package
CY74FCT646TQCT is packaged in a 24-pin QSOP (DBQ) with 0.65 mm pitch, 3.9 mm body width, and moisture sensitivity level 2 (260°C peak reflow). The package supports automated assembly and offers improved thermal resistance (θJA = 61°C/W) versus SOIC.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A1–A8 | Data register A inputs / B register outputs | Connects to upstream A-bus; latched data appears on B-bus when DIR = high and G = low |
| B1–B8 | Data register B inputs / A register outputs | Connects to downstream B-bus; registered A-data drives these pins in transmit mode |
| CPAB | Low-to-high clock pulse for A→B register load | Triggers capture of A-bus data into B-side register on rising edge |
| CPBA | Low-to-high clock pulse for B→A register load | Triggers capture of B-bus data into A-side register on rising edge |
| DIR | Direction control input | When low: B→A data flow; when high: A→B data flow (active only if G = low) |
| G | Output-enable input | High = 3-state (high-impedance) outputs; low = enabled transceiver operation |
| SAB | Source-select for A-bus outputs | Low = real-time B-bus data; high = stored B-register data routed to A-bus |
| SBA | Source-select for B-bus outputs | Low = real-time A-bus data; high = stored A-register data routed to B-bus |
| VCC | Positive supply | 5-V nominal supply; must be decoupled locally with 0.1 µF ceramic capacitor |
| GND | Ground reference | Common return path for all I/O and internal logic; requires low-inductance PCB connection |
Key Features
| Feature | Design Value |
|---|---|
| Independent A/B register staging | Enables asynchronous buffering - e.g., A-bus can sample sensor data while B-bus concurrently transmits prior frame to host MCU |
| Edge-rate controlled outputs | Reduces simultaneous switching noise (SSN) by limiting slew rate, improving signal integrity on dense PCBs |
| Ioff partial-power-down support | Allows one side of a dual-voltage system to power down while preserving isolation and preventing latch-up |
| Matched rise/fall times | Ensures <100 ps skew across all 8 bits, critical for parallel bus timing closure in high-speed control applications |
| 3.3-V compatible VOH (typ. 3.3 V) | Interoperates with 3.3-V logic families when VCC = 5 V, simplifying mixed-voltage interface design |
Applications
| Industrial Backplane Interface | Legacy System Bus Extension |
|---|---|
Use Scenario: Interfacing a modern microcontroller unit (MCU) to a legacy 8-bit ISA-style backplane carrying parallel address/data/control signals. IC Role / Device Role / Timing Role: Registered transceiver providing synchronized, noise-immune bidirectional data transfer between MCU and backplane peripherals. Use Value: Eliminates timing violations caused by long trace lengths via register staging, while Ioff protects powered-down modules during hot-swap maintenance. |
Use Scenario: Extending a 1980s-era industrial PLC's I/O expansion slot with new sensor modules using updated 5-V CMOS logic. IC Role / Device Role / Timing Role: Level-shifting and bus-isolation transceiver ensuring TTL-compatible signaling between legacy and new subsystems. Use Value: Matches TTL input thresholds and provides 64-mA drive to overcome aging backplane capacitance, maintaining signal fidelity over 20+ years of service life. |
| Test Equipment Data Capture | Programmable Logic Controller (PLC) I/O Module |
Use Scenario: Capturing parallel digital waveforms from DUTs in automated test equipment (ATE), where precise sampling alignment and bus contention avoidance are mandatory. IC Role / Device Role / Timing Role: Registered buffer capturing real-time bus states on CPAB/CPBA edges, then forwarding to FPGA-based acquisition logic. Use Value: 9 ns max delay and sub-ns skew enable deterministic timestamping of 100+ MHz parallel signals without external synchronization logic. |
Use Scenario: Isolating field I/O signals (e.g., 24-V sensors/actuators) from the PLC's internal 5-V logic bus using optocoupler interfaces and local bus repeaters. IC Role / Device Role / Timing Role: Registered repeater managing data flow between isolated I/O banks and central processor bus with glitch-free handshaking. Use Value: DIR/G-controlled directionality and SAB/SBA multiplexing allow dynamic reconfiguration of I/O mapping without firmware changes or hardware rewiring. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar registered transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| CY74FCT646TSOCT | Same core logic, but in SOIC-24 (DW) package with 46°C/W θJA and tube/reel packaging | Preferred for through-hole prototyping or legacy SOIC-based production lines requiring manual inspection | Select when board layout uses SOIC footprints or when lower thermal resistance is prioritized over space-constrained designs |
| SN74FCT646ATQCT | 6.3 ns max propagation delay (vs. 9 ns), 48-mA sink / 12-mA source drive, same QSOP-24 package | Better suited for higher-speed backplanes (>120 MHz) where tighter timing margins are required | Choose when system clock rates exceed 100 MHz and reduced drive strength is acceptable for lighter loads |
Compared with CY74FCT646TSOCT, CY74FCT646TQCT saves board area and improves high-frequency signal integrity via QSOP's shorter lead inductance; compared with SN74FCT646ATQCT, it trades speed for higher drive strength and noise immunity - making it optimal for noisy industrial environments with moderate timing demands.
Availability
CY74FCT646TQCT is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus extensions, ATE data capture subsystems, and programmable logic controller I/O modules requiring stable component supply across multi-year production cycles.
Supply support for CY74FCT646TQCT 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 industrial and automotive ICs.
CY74FCT646TQCT belongs to TI's FCT logic family, engineered for noise-immune, mixed-voltage system interfacing in harsh industrial environments where signal integrity and power sequencing robustness are critical.
FAQ
What is the maximum clock frequency supported by CY74FCT646TQCT for reliable register operation?
CY74FCT646TQCT does not specify a maximum clock frequency in its datasheet; instead, it defines minimum pulse width (tw ≥ 6 ns) and setup/hold times (tsu = 4 ns, th = 2 ns). For reliable operation, the maximum usable clock frequency is constrained by the sum of tsu + th + tPLH, yielding ~110 MHz as a practical upper limit for clean register capture under worst-case conditions. CY74FCT646TQCT maintains this margin across –40°C to +85°C.
Does CY74FCT646TQCT support hot-swap or live-insertion in powered-backplane systems?
Yes - CY74FCT646TQCT supports hot-swap via its Ioff circuitry, which disables outputs and limits leakage to ±1 µA when VCC = 0 V. This prevents damaging back-current flow from live backplane traces into the unpowered device. However, external series resistors and TVS protection on A/B bus lines are still recommended per TI application guidelines for full hot-swap robustness.
Can CY74FCT646TQCT operate with a 3.3-V supply voltage?
No - CY74FCT646TQCT is specified only for 4.75 V to 5.25 V operation per its recommended operating conditions. Applying 3.3 V violates absolute maximum ratings and will result in undefined logic behavior, insufficient output drive, and potential damage due to improper internal biasing. For 3.3-V systems, consider TI's ALVC or LVT logic families instead of CY74FCT646TQCT.
How does the SAB and SBA control logic affect data routing in CY74FCT646TQCT?
In CY74FCT646TQCT, SAB selects the source for A-bus outputs: low = real-time B-bus data, high = stored B-register data. SBA similarly selects B-bus output source: low = real-time A-bus data, high = stored A-register data. These controls operate independently of DIR and G, enabling flexible multiplexing - e.g., real-time A→B transfer while simultaneously forwarding stored B-data to A-bus for diagnostics.
Is CY74FCT646TQCT pin-compatible with older 74FCT646 variants like CY54FCT646T?
Yes - CY74FCT646TQCT shares identical pinout, function mapping, and electrical behavior with CY54FCT646T in Q/SO packages, including CPAB/CPBA, DIR, G, SAB, SBA, and A/B bus assignments. The primary differences are wider commercial temperature range (–40°C to +85°C vs. –55°C to +125°C) and higher drive strength (64/32 mA vs. 48/12 mA), but pin-for-pin compatibility is maintained for drop-in replacement in existing designs.
CY74FCT646TQCT Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74FCT
- Package/Case:
- 24-SSOP (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Logic Type:
- Transceiver, Non-Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 32mA, 64mA
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-SSOP
CY74FCT646TQCT FAQ
1.How can I place an order for CY74FCT646TQCT through Aetrix?
Please submit a Request for Quotation (RFQ) for CY74FCT646TQCT 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 CY74FCT646TQCT reliable?
The price and inventory of CY74FCT646TQCT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CY74FCT646TQCT is usually 5 days.
3.What payment methods are accepted for CY74FCT646TQCT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CY74FCT646TQCT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CY74FCT646TQCT?
CY74FCT646TQCT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CY74FCT646TQCT 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 CY74FCT646TQCT?
For technical support, including CY74FCT646TQCT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CY74FCT646TQCT requirements.
6.How does Aetrix verify that CY74FCT646TQCT is sourced from the original manufacturer or authorized distributors?
All CY74FCT646TQCT 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 CY74FCT646TQCT meets industry standards.
7.What is the process for return or replacement of CY74FCT646TQCT?
All CY74FCT646TQCT units undergo pre-shipment inspection (PSI). If there is an issue with CY74FCT646TQCT, 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 CY74FCT646TQCT part is unused and in its original packaging.
Return procedure for CY74FCT646TQCT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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