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onsemi MC74LCX646DWR2
- Part No.:
- MC74LCX646DWR2
- Manufacturer:
- onsemi
- Package:
- -
- Datasheet:
-
MC74LCX646DWR2.pdf
- Description:
- REGISTERED BUS TRANSCEIVER
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Inventory:1,000
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Product details
Overview
MC74LCX646DWR2 from ON Semiconductor is a low-voltage CMOS octal transceiver/registered transceiver operating from 2.3 V to 3.6 V, featuring 5 V-tolerant inputs/outputs, 24 mA balanced output drive, and real-time or registered bidirectional data transfer between A and B buses. It serves as a bus interface IC in memory address driving and TTL-level bus systems.
For engineers reviewing the MC74LCX646DWR2 datasheet, pinout, applications, or equivalent options, key selection criteria include 5 V tolerance for mixed-voltage interconnects, register-controlled data staging, OE/DIR/SAB/SBA mode flexibility, and SOIC-24 packaging with verified 3-state timing behavior.
Technical Context
The MC74LCX646DWR2 implements dual 8-bit bidirectional data paths with independent clocked storage registers per bus (QA/QB), controlled by CAB/CBA clock inputs and DIR/OE logic. Its operation supports transparent (real-time) transfer, isolated storage, and clocked registration - all under single-supply 2.3–3.6 V bias.
It integrates LVTTL/LVCMOS compatibility, IOFF protection at VCC = 0 V, and 5.5 V absolute input voltage rating. Propagation delays are specified down to 1.5 ns (typical) for clock-to-output and select-to-output paths, with skew ≤1.0 ns across outputs.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 2.3 V to 3.6 V - Enables direct interfacing with 2.5 V and 3.3 V logic domains without level shifters. |
| VI Absolute Max | −0.5 V to +7.0 V - Supports safe connection to 5 V TTL sources without external clamping. |
| IOL / IOH | ±24 mA at VCC ≥ 3.0 V - Drives standard TTL loads and sustains signal integrity on stubbed or moderately loaded buses. |
| tPLH / tPHL | 1.5 ns min, 9.5 ns max (VCC = 2.7 V) - Ensures sub-10 ns propagation for high-speed bus arbitration and synchronous transfers. |
| ICC Quiescent | 10 μA - Reduces static power draw in battery-backed or low-power standby modes. |
| IOFF Leakage | 10 μA at VCC = 0 V - Guarantees high-impedance isolation during hot-swap or power sequencing events. |
| ESD HBM | >2000 V - Meets industrial I/O robustness requirements without external protection diodes. |
Pinout & Package
DW suffix indicates 24-lead plastic SOIC package (Case 751E), 7.8 mm × 4.4 mm body, 1.27 mm pitch, gull-wing leads, JEDEC MS-013 compliant.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A7 | Side A bidirectional I/O | Connects to local bus segment; driven or sensed depending on DIR/OE state and register mode. |
| B0–B7 | Side B bidirectional I/O | Interfaces to remote bus segment; supports real-time or stored data routing to/from A side. |
| CAB, CBA | Register clock inputs | Edge-triggered clocks: CAB latches A-port data into QB register; CBA latches B-port data into QA register. |
| SAB, SBA | Select control inputs | Configure multiplexing: SAB = L enables real-time A→B transfer; SBA = L enables real-time B→A transfer. |
| DIR | Direction control | DIR = H enables A→B data flow; DIR = L enables B→A data flow - active only when OE = L. |
| OE | Output enable | OE = L activates transceiver outputs; OE = H forces all A/B pins to high-impedance 3-state mode. |
| VCC, GND | Power supply terminals | Single 2.3–3.6 V supply; decoupling required within 1 cm of VCC/GND pins for AC noise suppression. |
Key Features
| Feature | Design Value |
|---|---|
| 5 V-tolerant I/O | Enables seamless integration with legacy 5 V peripherals while powered from 2.5 V/3.3 V rails - no external level translators needed. |
| Register + transparent modes | Supports both immediate bus coupling and synchronized data staging - critical for burst-mode memory access and pipeline alignment. |
| IOFF protection | Prevents back-driving and current leakage when VCC is off - essential for live insertion in modular backplane systems. |
| 24 mA balanced drive | Delivers symmetrical rise/fall times and consistent edge rates across all 16 I/Os, minimizing ground bounce and crosstalk. |
| Sub-10 ns propagation | Meets timing budgets for 100 MHz+ parallel bus systems with setup/hold margins preserved across temperature and voltage corners. |
Applications
| Memory Address Buffering | Backplane Bus Interface |
|---|---|
|
Use Scenario: Driving 8-bit or 16-bit address lines from a low-voltage microcontroller to multiple 5 V SRAM or EPROM devices. IC Role / Device Role / Timing Role: Bidirectional address transceiver with register hold capability to synchronize address valid windows across asynchronous memory chips. Use Value: Eliminates need for discrete level shifters and reduces board space; 5 V tolerance prevents damage during hot-plug of memory modules. |
Use Scenario: Interfacing a 3.3 V FPGA control plane to a 5 V legacy backplane carrying ISA-style I/O expansion slots. IC Role / Device Role / Timing Role: Registered transceiver providing glitch-free bus handoff between clock domains and enabling safe hot-swap detection via OE control. Use Value: IOFF ensures no current injection during partial power-up; ±24 mA drive maintains signal integrity over 15 cm backplane traces. |
| Industrial PLC I/O Module | Test Equipment Data Capture |
|
Use Scenario: Isolating and buffering digital I/O signals between a 2.5 V ARM-based controller and 5 V field sensors/actuators in noisy factory environments. IC Role / Device Role / Timing Role: Dual-bus transceiver with selectable real-time or registered transfer to decouple sensor sampling from actuator update cycles. Use Value: ESD >2000 V HBM withstands EMI-induced transients; 10 μA quiescent current extends battery life in portable diagnostic units. |
Use Scenario: Capturing parallel data streams from DUTs running at mixed voltage levels (e.g., 5 V logic analyzers feeding 3.3 V pattern generators). IC Role / Device Role / Timing Role: Clock-synchronized data latch (via CAB/CBA) used to align asynchronous test vectors before loading into FIFO buffers. Use Value: Sub-10 ns skew ensures deterministic capture timing across all 8 bits; 3-state outputs prevent bus contention during vector reconfiguration. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal registered transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LVC646A | Same 2.3–3.6 V VCC range and 5 V-tolerant I/O, but lacks CAB/CBA clock inputs - only supports transparent mode and 3-state control. | Cannot perform registered data capture; limited to simple bus buffering without staging capability. | Choose SN74LVC646A only if clocked registration is unnecessary and cost reduction is prioritized over functional flexibility. |
| 74ALVC646 | Higher speed (fmax = 200 MHz), same pinout and voltage specs, but IOFF not guaranteed and ESD rating unspecified. | Better suited for high-frequency test equipment where propagation delay dominates over hot-swap safety. | Select 74ALVC646 when system timing margin is tight and live-insertion is not required - verify IOFF behavior separately. |
Compared with SN74LVC646A and 74ALVC646, the MC74LCX646DWR2 uniquely combines clocked register functionality, guaranteed IOFF, and industrial-grade ESD in a single SOIC-24 package - making it the only option supporting both real-time and staged bus transfers with full power-cycle robustness.
Availability
MC74LCX646DWR2 is available at Aetrix Electronics and suitable for memory address driving, backplane bus interfacing, and industrial I/O module design requiring stable component supply, long-term lifecycle support, and verified 5 V-tolerant operation.
Supply support for MC74LCX646DWR2 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
ON Semiconductor is a global semiconductor manufacturer specializing in energy-efficient power management, analog, logic, and custom devices for automotive, industrial, and cloud infrastructure markets.
The MC74LCX646DWR2 belongs to the LCX low-voltage CMOS logic family, designed specifically for mixed-voltage system interfacing where 2.5 V/3.3 V core logic must reliably communicate with legacy 5 V peripherals.
FAQ
What is the maximum clock frequency supported by the MC74LCX646DWR2?
The MC74LCX646DWR2 supports a maximum clock pulse frequency (fmax) of 150 MHz at VCC = 3.0–3.6 V and 100 MHz at VCC = 2.7 V, as specified in the AC Characteristics table. This applies to CAB and CBA inputs controlling register latching - real-time transfer has no clock dependency but follows propagation delay limits.
Does the MC74LCX646DWR2 support hot-swap or live insertion?
Yes, the MC74LCX646DWR2 supports live insertion and withdrawal per its datasheet. The IOFF specification guarantees high-impedance I/O states when VCC = 0 V, preventing back-current flow and protecting upstream drivers during partial power cycling - a key requirement for modular backplane systems.
Can the MC74LCX646DWR2 operate with a 2.5 V supply?
Yes, the MC74LCX646DWR2 is fully specified for operation from 2.3 V to 3.6 V, including 2.5 V. At 2.5 V, DC parameters such as VIH (2.0 V min), VOL (0.55 V max at 24 mA), and ICC (10 μA) remain valid, and AC performance meets fmax = 100 MHz with propagation delays up to 9.5 ns.
What is the function of the SAB and SBA pins on the MC74LCX646DWR2?
The SAB and SBA pins are select control inputs that determine whether real-time (transparent) or registered data appears on the respective bus outputs. When SAB = L, real-time A-port data passes to B; when SBA = L, real-time B-port data passes to A. Both can be asserted simultaneously for bidirectional transparent mode - independent of DIR/OE state.
Is the MC74LCX646DWR2 pin-compatible with other 24-pin SOIC transceivers like the 74LCX16245?
No, the MC74LCX646DWR2 is not pin-compatible with the 74LCX16245 or other octal transceivers. Its 24-pin SOIC pinout (Case 751E) is unique: it includes dedicated CAB/CBA clock inputs, SAB/SBA select controls, and dual-direction register architecture - unlike the simpler DIR/OE-only layout of 74LCX16245, which has different pin assignments and no clocked register capability.
MC74LCX646DWR2 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Logic Type:
- -
- Number of Elements:
- -
- Number of Bits per Element:
- -
- Input Type:
- -
- Output Type:
- -
- Current - Output High, Low:
- -
- Voltage - Supply:
- -
- Operating Temperature:
- -
- Grade:
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- Qualification:
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- Mounting Type:
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MC74LCX646DWR2 FAQ
1.How can I place an order for MC74LCX646DWR2 through Aetrix?
Please submit a Request for Quotation (RFQ) for MC74LCX646DWR2 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 MC74LCX646DWR2 reliable?
The price and inventory of MC74LCX646DWR2 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC74LCX646DWR2 is usually 5 days.
3.What payment methods are accepted for MC74LCX646DWR2?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC74LCX646DWR2 transactions.
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4.How is shipping managed for MC74LCX646DWR2?
MC74LCX646DWR2 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC74LCX646DWR2 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 MC74LCX646DWR2?
For technical support, including MC74LCX646DWR2 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC74LCX646DWR2 requirements.
6.How does Aetrix verify that MC74LCX646DWR2 is sourced from the original manufacturer or authorized distributors?
All MC74LCX646DWR2 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 MC74LCX646DWR2 meets industry standards.
7.What is the process for return or replacement of MC74LCX646DWR2?
All MC74LCX646DWR2 units undergo pre-shipment inspection (PSI). If there is an issue with MC74LCX646DWR2, 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 MC74LCX646DWR2 part is unused and in its original packaging.
Return procedure for MC74LCX646DWR2:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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