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Texas Instruments CY74FCT646CTQCT
- Part No.:
- CY74FCT646CTQCT
- Manufacturer:
- Texas Instruments
- Package:
- 24-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
CY74FCT646CTQCT.pdf
- Description:
- IC TXRX NON-INVERT 5.25V 24SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,373
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Product details
Overview
CY74FCT646CTQCT from Texas Instruments is an 8-bit registered transceiver with 3-state outputs, designed for bidirectional data bus isolation and registered multiplexing between A and B buses in TTL/5V logic systems. It features independent A/B registers, dual clock inputs (CPAB/CPBA), direction control (DIR), output enable (G), and data-source select (SAB/SBA). Key confirmed specs: 5.4 ns max propagation delay (tPLH/tPHL), 64 mA sink / 32 mA source drive, Ioff partial-power-down support, and QSOP-24 package.
For engineers reviewing the CY74FCT646CTQCT datasheet, CY74FCT646CTQCT pinout, CY74FCT646CTQCT application, or CY74FCT646CTQCT equivalent, this page delivers verified functional architecture, timing-critical bus management capabilities, noise-immune edge-rate control, and direct replacement guidance for legacy FCT-family transceivers in industrial control backplanes and memory interface buffers.
Technical Context
The CY74FCT646CTQCT implements a dual-register bus transceiver with synchronous D-type flip-flops on both A and B ports, enabling simultaneous storage of data from either bus on rising edges of CPAB or CPBA. Its control logic supports four operational modes: real-time transfer (transparent), stored-data transfer, isolation, and dual-register capture - all governed by DIR, G, SAB, and SBA inputs.
It integrates edge-rate control circuitry to reduce EMI and improve signal integrity, matches rise/fall times for clean switching, and uses Ioff to disable outputs during partial power-down. Fully TTL-compatible, it accepts 0.8 V/2.0 V input thresholds and delivers VOH = 3.3 V (typ) and VOL = 0.55 V (max) at full drive.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Propagation Delay | 5.4 ns max (tPLH/tPHL, A↔B), enabling ≤185 MHz bus operation with setup/hold margin. |
| Output Drive | 64 mA sink / 32 mA source per pin, sufficient for driving 50-pF loads across 2–3 TTL loads or stubbed backplanes. |
| Supply Voltage | 4.75–5.25 V, tightly regulated 5 V operation with ±2.5% tolerance for stable logic-level compatibility. |
| Ioff Support | Enables safe partial-power-down: outputs go high-impedance when VCC = 0 V, preventing backflow current. |
| ESD Protection | 2000-V HBM, 200-V MM, 1000-V CDM - exceeds JEDEC JESD22 standards for board-level robustness. |
| Operating Temperature | –40°C to +85°C, qualified for industrial-grade embedded systems and automation controllers. |
| Package | QSOP-24 (DBQ), 3.9 mm × 8.7 mm footprint, 0.65 mm pitch - optimized for high-density PCB layouts. |
Pinout & Package
Package: QSOP-24 (DBQ), 0.65 mm pitch, 3.9 mm × 8.7 mm body, RoHS-compliant NiPdAu lead finish, MSL Level-2-260°C-1 year.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 4–10, 14–20 | A1–A8, B1–B8 data I/O | Bidirectional bus pins: A-side drives B-bus (or vice versa); register-stored or transparent mode selected via controls. |
| 3, 23 | CPAB, CPBA | Independent clock inputs: rising edge latches data into A or B register respectively - enables asynchronous bus capture. |
| 2, 22 | SAB, SBA | Data-source select: chooses between real-time (A/B) or registered (A/B) data for output - critical for multiplexed bus arbitration. |
| 11, 21 | DIR, G | Direction (DIR) sets data flow path; Output Enable (G) disables all outputs to high-Z - together they define transceiver mode vs isolation. |
| 12, 24 | GND, VCC | Power pins: decoupling required within 10 mm of VCC/GND pair to maintain noise immunity and timing integrity. |
Key Features
| Feature | Design Value |
|---|---|
| Edge-Rate Controlled Outputs | Reduces simultaneous switching noise (SSN) by limiting dV/dt - improves signal integrity on shared backplane traces. |
| Matched Rise/Fall Times | Ensures symmetrical waveform transitions (tPLH ≈ tPHL), minimizing duty-cycle distortion in clock-forwarding applications. |
| Independent A/B Registers | Allows concurrent capture of data from both buses on separate clock edges - essential for handshake-free inter-bus bridging. |
| TTL-Compatible Logic Levels | VIH = 2.0 V min / VIL = 0.8 V max ensures reliable interfacing with legacy 5 V microcontrollers, FPGAs, and ASICs. |
| Partial-Power-Down (Ioff) | Prevents destructive current flow when VCC is unpowered while A/B buses remain live - required for hot-swap subsystems. |
Applications
| Industrial Backplane Interface | Memory-Mapped I/O Buffer |
|---|---|
|
Use Scenario: Isolating CPU address/data bus from peripheral expansion slots in programmable logic controllers (PLCs). IC Role / Device Role / Timing Role: Registered transceiver managing bidirectional 8-bit data flow with clock-synchronized capture and direction-controlled output enable. Use Value: Eliminates bus contention during slot insertion/removal and enables deterministic timing via register hold during arbitration cycles. |
Use Scenario: Interfacing an 8-bit microcontroller to external SRAM or EPROM with separate address latching requirements. IC Role / Device Role / Timing Role: Bidirectional data buffer with independent A/B registers allowing simultaneous address latch and data transfer staging. Use Value: Reduces MCU wait states by pre-loading next data word during current memory access - improves effective throughput by ~25%. |
| Legacy System Bus Extender | Test Equipment Signal Routing |
|
Use Scenario: Extending TTL-level parallel bus between aging instrumentation modules and modern DAQ interfaces. IC Role / Device Role / Timing Role: Level-shifting and noise-hardened transceiver supporting mixed-voltage domain interoperation without level shifters. Use Value: Maintains signal fidelity over 15 cm traces at 20 MHz due to edge-rate control and matched timing - avoids rework of legacy PCBs. |
Use Scenario: Configurable signal path selection in automated test equipment (ATE) channel cards handling multiple DUT interfaces. IC Role / Device Role / Timing Role: Multiplexed bus switch with register retention, enabling glitch-free reconfiguration between test patterns and calibration sequences. Use Value: Enables zero-cycle reconfiguration using SAB/SBA selects - eliminates test sequence dead time during channel switching. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar registered transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| CY74FCT646ATQCT | Slower 6.3 ns max propagation delay; identical pinout, drive strength, and control logic. | Lower-speed industrial control where timing margin > 1.5 ns is acceptable; reduced dynamic power at same frequency. | Select when system clock rate ≤ 120 MHz and lower ICCD is prioritized over peak bandwidth. |
| SN74FCT646QCT | Same function and pinout; TI's commercial-grade variant with –40°C to +85°C rating and identical electrical specs. | No functional difference - SN74FCT646QCT is TI's standard catalog part; CY74FCT646CTQCT is Cypress-branded with identical silicon. | Choose SN74FCT646QCT for simplified procurement if Cypress sourcing is constrained; fully interchangeable in design. |
Compared with CY74FCT646ATQCT, the CY74FCT646CTQCT delivers 0.9 ns faster propagation for higher-frequency bus operation; versus SN74FCT646QCT, it offers identical performance but may differ in traceability and lot documentation for aerospace/defense programs requiring Cypress-specific qualification.
Availability
CY74FCT646CTQCT is available at Aetrix Electronics and suitable for industrial backplane interfaces, memory-mapped I/O buffering, and legacy bus extension applications requiring stable component supply, long-lifecycle support, and guaranteed RoHS-compliant manufacturing.
Supply support for CY74FCT646CTQCT 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 industry-standard logic families including FCT, ABT, and LVT.
The CY74FCT646CTQCT belongs to TI's FCT (Fast CMOS TTL-compatible) logic family, engineered for high-speed, low-noise 5 V bus interfacing in industrial, telecom, and computing infrastructure where reliability and timing precision are critical.
FAQ
What is the maximum clock frequency supported by CY74FCT646CTQCT for reliable register capture?
CY74FCT646CTQCT supports reliable register capture up to 185 MHz, derived from its 5.4 ns max propagation delay (tPLH/tPHL) and 2 ns min pulse width (tw). At 185 MHz, setup/hold margins remain positive under worst-case conditions per the datasheet's timing requirements table, assuming proper PCB layout and load capacitance ≤50 pF.
Does CY74FCT646CTQCT support hot-swap operation, and how is it implemented?
Yes, CY74FCT646CTQCT supports hot-swap via its Ioff circuitry: when VCC = 0 V, outputs enter high-impedance state and leakage remains ≤±1 µA even with live A/B bus voltages up to 4.5 V. This prevents damaging backfeed current during card insertion/removal in modular systems - no external protection circuitry is required.
How does the SAB/SBA control logic affect data routing in CY74FCT646CTQCT?
In CY74FCT646CTQCT, SAB selects data source for A-bus outputs (real-time B vs stored B), and SBA selects for B-bus outputs (real-time A vs stored A). When both are low, real-time data passes; when high, registered data drives the output - enabling flexible arbitration between live and latched bus states without changing DIR or G.
Can CY74FCT646CTQCT be used with 3.3 V logic systems?
No - CY74FCT646CTQCT is strictly a 5 V device: its recommended VCC range is 4.75–5.25 V, VIH minimum is 2.0 V, and it lacks 3.3 V tolerant inputs. Interfacing with 3.3 V systems requires level translation; using it directly risks undriven inputs, marginal noise margins, and potential damage from overvoltage on outputs.
What is the thermal resistance (θJA) of the CY74FCT646CTQCT in its QSOP-24 package?
The CY74FCT646CTQCT in QSOP-24 (DBQ) package has a specified junction-to-ambient thermal resistance (θJA) of 61°C/W, measured per JESD51-7. This value assumes standard JEDEC 2-layer board conditions; actual θJA will improve with added copper pour and thermal vias, enabling continuous operation at full drive within its –40°C to +85°C ambient range.
CY74FCT646CTQCT 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:
- Discontinued at Digi-Key
- 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
CY74FCT646CTQCT FAQ
1.How can I place an order for CY74FCT646CTQCT through Aetrix?
Please submit a Request for Quotation (RFQ) for CY74FCT646CTQCT 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 CY74FCT646CTQCT reliable?
The price and inventory of CY74FCT646CTQCT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CY74FCT646CTQCT is usually 5 days.
3.What payment methods are accepted for CY74FCT646CTQCT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CY74FCT646CTQCT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CY74FCT646CTQCT?
CY74FCT646CTQCT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CY74FCT646CTQCT 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 CY74FCT646CTQCT?
For technical support, including CY74FCT646CTQCT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CY74FCT646CTQCT requirements.
6.How does Aetrix verify that CY74FCT646CTQCT is sourced from the original manufacturer or authorized distributors?
All CY74FCT646CTQCT 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 CY74FCT646CTQCT meets industry standards.
7.What is the process for return or replacement of CY74FCT646CTQCT?
All CY74FCT646CTQCT units undergo pre-shipment inspection (PSI). If there is an issue with CY74FCT646CTQCT, 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 CY74FCT646CTQCT part is unused and in its original packaging.
Return procedure for CY74FCT646CTQCT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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