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NXP Semiconductors 74HC646N,652
- Part No.:
- 74HC646N,652
- Manufacturer:
- NXP Semiconductors
- Package:
- 24-DIP (0.600", 15.24mm)
- Datasheet:
-
74HC646N,652.pdf
- Description:
- IC TXRX NON-INVERT 6V 24DIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,762
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Product details
Overview
74HC646N,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 selection (SAB/SBA). Typical propagation delay is 11 ns at 5 V, max 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 74HC646N,652 datasheet, 74HC646N,652 pinout, 74HC646N,652 application, or 74HC646N,652 equivalent, key selection considerations include real-time vs. registered data multiplexing, 3-state isolation timing (tPZH/tPHZ ≤ 44 ns), DIR/OE logic polarity, and HC-level CMOS compatibility with TTL systems.
Technical Context
The 74HC646N,652 integrates dual 8-bit D-type flip-flop registers with a configurable transceiver core. Data on either A or B bus is edge-triggered into its respective register on LOW-to-HIGH transitions of CPAB or CPBA. The DIR input determines data direction during active OE (LOW), while SAB/SBA select between transparent (real-time) or registered data paths.
It supports simultaneous storage and transmission: when OE = HIGH (isolation mode), A data may be latched into B register and B data into A register. Input functions remain enabled regardless of OE state, enabling asynchronous capture - critical for handshake-based bus arbitration in legacy 8-bit systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | 74HC high-speed CMOS, TTL-compatible input thresholds |
| Propagation Delay | 11 ns typical (A↔B, CL = 15 pF, VCC = 5 V) - enables ≤90 MHz bus handshaking |
| Max Clock Frequency | 69 MHz (HC, VCC = 5 V) - supports fast register loading in synchronous bus bridges |
| Supply Voltage Range | 2.0 V to 6.0 V - allows operation in 3.3 V and 5 V mixed-voltage systems |
| 3-State Enable/Disable Time | tPZH ≤ 44 ns (VCC = 6 V) - ensures clean bus release before next cycle |
| Input Capacitance | 3.5 pF - minimizes capacitive loading on driving bus lines |
| Operating Temperature | −40 °C to +125 °C - qualified for under-hood automotive and industrial control environments |
Pinout & Package
74HC646N,652 uses a 24-pin dual in-line package (DIP) with 0.600-inch body width and standard through-hole mounting. Pin 12 is GND; pin 24 is VCC. All A-side I/Os (A0–A7) occupy pins 4–11; B-side I/Os (B0–B7) occupy pins 13–20 in mirrored order.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CPAB (pin 1) | A-to-B register clock | LOW-to-HIGH edge triggers A-bus data capture into B register |
| SAB (pin 2) | A-to-B source select | Chooses real-time A data or stored A data for B-bus output |
| DIR (pin 3) | Direction control | When OE = LOW: DIR = LOW → A→B; DIR = HIGH → B→A |
| A0–A7 (pins 4–11) | A-bus I/O terminals | Bidirectional 3-state ports; inputs always active for register capture |
| GND (pin 12) | Ground reference | 0 V return path for all internal logic and I/O stages |
| B0–B7 (pins 13–20) | B-bus I/O terminals | Bidirectional 3-state ports; function mirrors A0–A7 |
| OE (pin 21) | Output enable | Active LOW: enables transceiver outputs; HIGH forces all I/Os to high-impedance |
| SBA (pin 22) | B-to-A source select | Chooses real-time B data or stored B data for A-bus output |
| CPBA (pin 23) | B-to-A register clock | LOW-to-HIGH edge triggers B-bus data capture into A register |
| VCC (pin 24) | Positive supply | 2.0–6.0 V power rail; powers logic core and output drivers |
Key Features
| Feature | Design Value |
|---|---|
| Independent A/B registers | Enables concurrent storage of data from both buses without conflict or arbitration delay |
| Multiplexed real-time & stored data | SAB/SBA inputs allow dynamic switching between live bus traffic and latched values per direction |
| Always-enabled input capture | Data at A/B pins is sampled on every CPAB/CPBA rising edge - even when outputs are disabled |
| Bus-driver output capability | Drives standard 50-pF loads at full speed without external buffers - reduces BOM count |
| Wide voltage and temperature range | Operates from 2.0 V to 6.0 V and −40 °C to +125 °C - suitable for harsh industrial deployments |
Applications
| Industrial PLC Backplane Interface | Legacy Microcontroller Bus Expansion |
|---|---|
Use Scenario: Interfacing multiple 8-bit microcontrollers to a shared I/O backplane with isolated address/data lanes. IC Role / Device Role / Timing Role: Bidirectional bus transceiver with register hold capability to decouple master/slave timing skew and prevent bus contention. Use Value: Enables deterministic data transfer using CPAB/CPBA clocks while DIR/OE manage direction and isolation - eliminating need for external glue logic. | Use Scenario: Expanding the data bus of an 8051 or Z80-based system to support additional peripherals or memory banks. IC Role / Device Role / Timing Role: Octal register-controlled transceiver that synchronizes peripheral access with CPU clock domain via CPAB/CPBA edges. Use Value: Provides registered handshaking (tsu = 10 ns min, th = 6 ns min at VCC = 6 V) ensuring setup/hold compliance in marginal timing designs. |
| Automotive Body Control Module | Test Equipment Signal Routing |
Use Scenario: Isolating and routing sensor data between CAN-linked ECUs and local ADC/DAC subsystems in engine bay modules. IC Role / Device Role / Timing Role: High-temperature-rated bus interface that stores sensor snapshots (via CPAB/CPBA) and forwards them on demand via DIR/OE control. Use Value: −40 °C to +125 °C rating and 6 V tolerance ensure reliable operation near heat sources without derating or cooling. | Use Scenario: Configurable signal path selection in automated test fixtures where DUT I/O must be dynamically connected to stimulus or measurement channels. IC Role / Device Role / Timing Role: Reconfigurable 8-bit bidirectional switch with latch capability to capture DUT responses and replay stimuli. Use Value: SAB/SBA multiplexing allows real-time pass-through or stored pattern replay - reducing fixture FPGA resource usage. |
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 |
|---|---|---|---|
| 74HCT646N,652 | TTL-compatible inputs (VIH = 2.0 V min); slightly slower propagation (13 ns typ) but better noise immunity in noisy 5 V systems | Better suited for mixed-logic systems with legacy TTL drivers or long PCB traces | Select when interfacing with 74LS or other TTL-family devices requiring guaranteed VIH/VIL thresholds |
| SN74LVTH16646DLR | 16-bit, 3.3 V only, LVCMOS level; higher drive strength (±24 mA), no CPAB/CPBA clock inputs - purely transceiver mode | Lacks register functionality; requires external clocking logic for storage use cases | Choose only if 16-bit width and 3.3 V operation are mandatory and register capability is handled elsewhere |
Compared with 74HC646N,652, the 74HCT646N,652 offers superior noise margin in electrically noisy 5 V environments but trades 2 ns propagation delay; the SN74LVTH16646DLR provides double width and higher drive at 3.3 V but eliminates integrated clocked storage - making it unsuitable for applications requiring on-chip data latching.
Availability
74HC646N,652 is available at Aetrix Electronics and suitable for industrial PLC backplane interfaces, legacy microcontroller bus expansions, and automotive body control modules requiring stable component supply over extended product lifecycles.
Supply support for 74HC646N,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 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 74HC646N,652 belongs to Nexperia's 74HC logic family - engineered for high-speed, low-power, pin-compatible replacement of legacy TTL bus interfaces while supporting modern mixed-voltage system design.
FAQ
What is the maximum operating voltage for the 74HC646N,652?
The 74HC646N,652 supports a supply voltage range of 2.0 V to 6.0 V. Its absolute maximum rating is 7.0 V, but sustained operation above 6.0 V is not recommended. At 6.0 V, propagation delays improve (e.g., tPHL/tPLH drops to 11 ns typical), and the device remains fully functional across its full −40 °C to +125 °C temperature range - critical for industrial and automotive applications where voltage rails may fluctuate.
Does the 74HC646N,652 support true bidirectional data flow with independent clocking?
Yes, the 74HC646N,652 supports true bidirectional data flow with independent clocking: CPAB (pin 1) captures A-bus data into the B register on its rising edge, while CPBA (pin 23) captures B-bus data into the A register on its rising edge. This allows concurrent registration of data from both buses - essential for handshake protocols where A and B sides operate on different timing domains. The DIR and OE inputs then control which registered or real-time data appears on the opposing bus.
How does the 74HC646N,652 handle bus isolation when OE is HIGH?
When OE is HIGH, all A0–A7 and B0–B7 outputs enter high-impedance state, isolating both buses. Crucially, input functionality remains fully active: data present on either bus continues to be sampled on every CPAB or CPBA rising edge. This enables background data capture (e.g., logging sensor values on B bus) while the main data path is isolated - a key capability for fault-tolerant and diagnostic modes in industrial controllers using the 74HC646N,652.
What is the purpose of the SAB and SBA inputs on the 74HC646N,652?
The SAB (pin 2) and SBA (pin 22) inputs on the 74HC646N,652 select the data source for each transceiver direction: SAB chooses between real-time A-bus data or stored A-bus data for output onto the B bus; SBA selects real-time B-bus data or stored B-bus data for output onto the A bus. This multiplexing enables flexible data routing - for example, forwarding live sensor readings (transparent mode) while simultaneously replaying previously captured calibration data (registered mode) - all within a single 74HC646N,652 device.
Is the 74HC646N,652 pin-compatible with the 74HC648N,652?
Yes, the 74HC646N,652 is pin-compatible with the 74HC648N,652, as confirmed in the datasheet: "The '646' is functionally identical to the '648', but has non-inverting data paths." Both share identical pin configuration, electrical characteristics, and register/transceiver architecture. The sole difference is signal polarity: the 74HC646N,652 passes data without inversion, whereas the 74HC648N,652 inverts data on both A→B and B→A paths. This makes direct substitution possible when inversion is not required - verified across all 24 pins including CPAB, CPBA, DIR, OE, SAB, SBA, and I/Os.
74HC646N,652 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- NXP Semiconductors
- Series:
- 74HC
- Package/Case:
- 24-DIP (0.600", 15.24mm)
- 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:
- Through Hole
- Supplier Device Package:
- 24-DIP
74HC646N,652 FAQ
1.How can I place an order for 74HC646N,652 through Aetrix?
Please submit a Request for Quotation (RFQ) for 74HC646N,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 74HC646N,652 reliable?
The price and inventory of 74HC646N,652 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 74HC646N,652 is usually 5 days.
3.What payment methods are accepted for 74HC646N,652?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 74HC646N,652 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 74HC646N,652?
74HC646N,652 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 74HC646N,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 74HC646N,652?
For technical support, including 74HC646N,652 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 74HC646N,652 requirements.
6.How does Aetrix verify that 74HC646N,652 is sourced from the original manufacturer or authorized distributors?
All 74HC646N,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 74HC646N,652 meets industry standards.
7.What is the process for return or replacement of 74HC646N,652?
All 74HC646N,652 units undergo pre-shipment inspection (PSI). If there is an issue with 74HC646N,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 74HC646N,652 part is unused and in its original packaging.
Return procedure for 74HC646N,652:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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