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NXP Semiconductors 74HC646D,652
- Part No.:
- 74HC646D,652
- Manufacturer:
- NXP Semiconductors
- Package:
- 24-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
74HC646D,652.pdf
- Description:
- IC TXRX NON-INVERT 6V 24SO
- Quantity:
- Payment:
- Shipping:
Inventory:2,881
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Product details
Overview
74HC646D,652 from Nexperia is an octal bus transceiver/register with 3-state outputs, designed for bidirectional data flow control between two 8-bit buses. It features independent A/B registers, clocked storage (CPAB/CPBA), direction control (DIR), output enable (OE), and source select (SAB/SBA). Typical propagation delay is 11 ns at 5 V, maximum clock frequency is 69 MHz, and it operates across −40 °C to +125 °C - used in industrial microcontroller bus interfacing and memory-mapped I/O expansion.
For engineers reviewing the 74HC646D,652 datasheet, 74HC646D,652 pinout, 74HC646D,652 application, or 74HC646D,652 equivalent, key selection criteria include real-time vs. registered data multiplexing, 3-state isolation timing (tPZH/tPHZ ≤ 44 ns), DIR/OE logic polarity, and compatibility with 5 V CMOS/TTL systems.
Technical Context
The 74HC646D,652 integrates dual 8-bit D-type flip-flop registers with a bidirectional transceiver core, enabling simultaneous storage and transparent transfer of data between A and B buses. Its control architecture uses edge-triggered clocks (CPAB/CPBA), active-low OE, and DIR-driven bus direction - all operating under standard 74HC voltage thresholds (VI = GND to VCC).
It supports three functional modes: isolation (OE = HIGH), real-time transfer (SAB/SBA = LOW), and registered transfer (SAB/SBA = HIGH), with input functions always enabled regardless of OE state. The device is specified per JEDEC 7A and exhibits typical power dissipation capacitance of 30 pF per channel.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | 74HC high-speed CMOS - compatible with TTL input levels and low-power operation at 2–6 V supply |
| Bus Width | 8-bit bidirectional A and B ports - supports full byte-level data routing without external gating |
| Propagation Delay | 11 ns (typ.) An/Bn to Bn/An at VCC = 5 V, CL = 15 pF - enables reliable timing in 69 MHz clock domains |
| 3-State Enable/Disable Time | tPZH = 44 ns max (VCC = 6 V) - ensures clean bus arbitration during mode switching |
| Operating Temperature | −40 °C to +125 °C - qualified for industrial and automotive under-hood applications |
| Input Capacitance | 3.5 pF - minimizes loading on driving logic and preserves signal integrity in dense PCB layouts |
| Power Dissipation Cap. | 30 pF per channel - used to calculate dynamic power: PD = CPD × VCC² × fi + Σ(CL × VCC² × fo) |
Pinout & Package
74HC646D,652 is housed in a 24-pin SOIC (Small Outline Integrated Circuit) package with 300 mil body width and standard 1.27 mm pitch - compliant with JEDEC MS-013AC and "74HC/HCT Logic Package Outlines".
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (CPAB) | A-to-B clock input | LOW-to-HIGH edge-triggered - latches A-bus data into B-register; controls real-time/registered path selection |
| 2 (SAB) | A-to-B source select | Selects between real-time A data (SAB = LOW) or stored A data (SAB = HIGH) routed to B bus |
| 3 (DIR) | Direction control | Determines active bus direction when OE = LOW: DIR = LOW → A→B; DIR = HIGH → B→A |
| 4–11 (A0–A7) | A-bus I/O terminals | Bidirectional 8-bit port - inputs when receiving from B, outputs when driving B (3-state controlled by OE/DIR) |
| 12 (GND) | Ground reference | 0 V return path for all internal logic and I/O - must be low-impedance for noise immunity |
| 13–20 (B0–B7) | B-bus I/O terminals | Bidirectional 8-bit port - symmetric function to A0–A7; driven only when OE = LOW and DIR matches direction |
| 21 (OE) | Output enable | Active-LOW - disables all A/B outputs to high-impedance; input functions remain fully operational |
| 22 (SBA) | B-to-A source select | Selects between real-time B data (SBA = LOW) or stored B data (SBA = HIGH) routed to A bus |
| 23 (CPBA) | B-to-A clock input | LOW-to-HIGH edge-triggered - latches B-bus data into A-register; enables synchronized B→A capture |
| 24 (VCC) | Positive supply | 2.0–6.0 V operation - powers internal registers, transceiver logic, and output drivers |
Key Features
| Feature | Design Value |
|---|---|
| Independent A/B register storage | Enables concurrent capture of data from both buses - critical for handshake-free dual-bus buffering |
| Multiplexed real-time and stored data paths | SAB/SBA pins allow dynamic selection between live bus signals and registered values - eliminates need for external MUX logic |
| Always-enabled input functionality | Data latching continues even when outputs are disabled (OE = HIGH) - supports background register updates during bus contention |
| Non-inverting data paths | Unlike 74HC648, 74HC646D,652 preserves signal polarity end-to-end - simplifies timing analysis and avoids inversion logic overhead |
| Bus-driver output capability | Drives standard CMOS/TTL loads directly - no external buffers required for point-to-point or short-bus interconnects |
Applications
| Microcontroller Bus Expansion | Industrial PLC Backplane Interface |
|---|---|
Use Scenario: Expanding limited GPIO or address/data bus lines of an MCU (e.g., ARM Cortex-M0+) to interface with multiple peripheral ICs. IC Role / Device Role / Timing Role: Bidirectional bus transceiver with register hold - isolates MCU from peripheral timing skew while enabling burst-mode data transfers. Use Value: Reduces firmware overhead by offloading byte-wide data staging; 11 ns propagation delay ensures setup/hold compliance with 24 MHz APB bus timing. |
Use Scenario: Interfacing modular I/O cards to a central controller over a shared 8-bit parallel backplane in programmable logic controllers. IC Role / Device Role / Timing Role: Registered bus isolator - stores sensor/actuator data during backplane arbitration cycles and releases it synchronously upon command. Use Value: Eliminates metastability risk during hot-swap events; −40 °C to +125 °C rating supports operation in uncooled control cabinets. |
| Memory-Mapped I/O Bridge | Legacy Parallel Port Adapter |
Use Scenario: Connecting legacy parallel-interface peripherals (e.g., ADCs, DACs, LCD controllers) to modern SoCs lacking native parallel interfaces. IC Role / Device Role / Timing Role: Synchronized data bridge - captures peripheral status/data on CPAB/CPBA edges and presents it via memory-mapped A-bus reads/writes. Use Value: Enables deterministic latency (≤44 ns 3-state disable) for time-critical sampling; non-inverting path preserves bit-order alignment with software drivers. |
Use Scenario: Adapting vintage parallel printer or scanner modules to embedded Linux systems using GPIO-based bit-banging parallel ports. IC Role / Device Role / Timing Role: Level-shifting and drive-strengthening transceiver - translates 3.3 V SoC GPIO to 5 V tolerant signals while sourcing/sinking ≥4 mA per line. Use Value: Replaces discrete transistor arrays; 3.5 pF input capacitance prevents signal degradation at 2 MHz handshaking rates. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver/register applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 74HCT646D,653 | TTL-compatible inputs (VIH = 2.0 V min); identical pinout and register logic | Required where host system uses mixed 5 V TTL and CMOS logic families | Select when interfacing with legacy 74LS or 74F devices - maintains same timing and control behavior |
| SN74LVTH16646DGGR | 16-bit, dual-supply (1.65–3.6 V core / 3.3 V I/O), different pin count (56-pin TSSOP) | Used in low-voltage, high-density applications where 8-bit width is insufficient | Choose only if 16-bit width and LVCMOS compatibility are mandatory - not pin-compatible or drop-in |
Compared with 74HC646D,652, the 74HCT646D,653 offers identical functionality with TTL-input thresholds for legacy compatibility, while the SN74LVTH16646DGGR provides double the bus width and lower voltage operation but requires PCB redesign and firmware adaptation.
Availability
74HC646D,652 is available at Aetrix Electronics and suitable for industrial microcontroller bus expansion, PLC backplane interfacing, and memory-mapped I/O bridging requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for 74HC646D,652 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
Nexperia is a global leader in high-performance discrete, logic, and PowerMOS semiconductors, spun off from NXP's Standard Products division in 2017 and focused on automotive, industrial, computing, and consumer markets.
The 74HC646D,652 belongs to Nexperia's 74HC logic family - engineered for robustness, low power, and pin compatibility with legacy TTL systems in space-constrained industrial control and instrumentation designs.
FAQ
What is the supply voltage range supported by the 74HC646D,652?
The 74HC646D,652 operates from 2.0 V to 6.0 V, with full AC/DC specifications guaranteed across this range. At 2.0 V, maximum clock frequency drops to 21 MHz; at 6.0 V, propagation delay improves to 11 ns (typ.) and output drive strength increases. This wide range allows direct integration with both 3.3 V and 5 V systems without level shifters.
How does the 74HC646D,652 handle simultaneous data capture on both A and B buses?
The 74HC646D,652 supports concurrent capture: CPAB edge latches A-bus data into the B-register, while CPBA edge latches B-bus data into the A-register - both operations occur independently. Input functions remain active regardless of OE state, enabling background registration while outputs are isolated - essential for glitch-free bus arbitration.
Is the 74HC646D,652 pin-compatible with the 74HC648?
No - although functionally similar, the 74HC646D,652 has non-inverting data paths, whereas the 74HC648 uses inverting paths. Pinout is identical, but signal polarity differs. Substituting one for the other without inverting logic elsewhere will cause functional failure. Always verify polarity requirements before replacement.
What is the meaning of "SAB = HIGH" in the 74HC646D,652 function table?
When SAB = HIGH, the 74HC646D,652 routes stored (registered) A-bus data - captured on the last CPAB rising edge - to the B bus instead of real-time A-bus data. This enables deterministic, clock-synchronized transfers independent of A-bus signal stability, critical for interfacing with asynchronous peripherals.
Does the 74HC646D,652 support hot insertion or live bus swapping?
The 74HC646D,652 is not explicitly rated for hot insertion, but its 3-state outputs (with tPHZ ≤ 44 ns) and always-enabled inputs allow safe bus disconnection during OE = HIGH. For true hot-swap compliance, external series resistors and slew-rate limiting are recommended - consult Nexperia Application Note AN10312 for implementation guidance.
74HC646D,652 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- NXP Semiconductors
- Series:
- 74HC
- Package/Case:
- 24-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- 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:
- 7.8mA, 7.8mA
- Voltage - Supply:
- 2V ~ 6V
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-SO
74HC646D,652 FAQ
1.How can I place an order for 74HC646D,652 through Aetrix?
Please submit a Request for Quotation (RFQ) for 74HC646D,652 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 74HC646D,652 reliable?
The price and inventory of 74HC646D,652 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 74HC646D,652 is usually 5 days.
3.What payment methods are accepted for 74HC646D,652?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 74HC646D,652 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 74HC646D,652?
74HC646D,652 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 74HC646D,652 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 74HC646D,652?
For technical support, including 74HC646D,652 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 74HC646D,652 requirements.
6.How does Aetrix verify that 74HC646D,652 is sourced from the original manufacturer or authorized distributors?
All 74HC646D,652 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 74HC646D,652 meets industry standards.
7.What is the process for return or replacement of 74HC646D,652?
All 74HC646D,652 units undergo pre-shipment inspection (PSI). If there is an issue with 74HC646D,652, 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 74HC646D,652 part is unused and in its original packaging.
Return procedure for 74HC646D,652:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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