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STMicroelectronics M74HCT646RM13TR
- Part No.:
- M74HCT646RM13TR
- Manufacturer:
- STMicroelectronics
- Package:
- 24-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
M74HCT646RM13TR.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 24SO
- Quantity:
- Payment:
- Shipping:
Inventory:4,753
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Product details
Overview
M74HCT646RM13TR from STMicroelectronics is an octal bus transceiver and register with 3-state outputs, implementing bidirectional data flow between A and B buses via edge-triggered clocking (CLOCK AB/BA), direction control (DIR), and output enable (G). It features TTL-compatible inputs (VIH ≥ 2.0 V, VIL ≤ 0.8 V), symmetrical drive strength (|IOH| = IOL = 6 mA min), balanced propagation delays (tPLH ≅ tPHL), and operates at up to 60 MHz (typ.) at VCC = 4.5 V in industrial temperature range (–55 °C to +125 °C).
For engineers reviewing the M74HCT646RM13TR datasheet, M74HCT646RM13TR pinout, M74HCT646RM13TR application, or M74HCT646RM13TR equivalent, key selection criteria include its dual-register architecture for time-multiplexed A/B bus storage, 3-state isolation during G high, and TSSOP-24 package suitability for space-constrained board-level data routing in legacy-compatible digital systems.
Technical Context
The device integrates eight D-type flip-flops per bus path, enabling synchronous latching of A→B or B→A data on low-to-high clock transitions. Control logic decouples register loading from transceiver direction: SELECT AB/BA chooses between real-time (transparent) or registered data output, while DIR determines active bus direction only when G is low.
Its C2MOS silicon gate process delivers low quiescent current (ICC ≤ 4 µA at TA = 25 °C) and robust ESD protection on all inputs. The symmetrical output impedance ensures matched rise/fall times (tTLH/tTHL ≤ 19 ns) and supports clean signal integrity in mixed-signal backplane or memory interface applications requiring deterministic timing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures stable operation across standard 5 V TTL/CMOS rails with ±10% tolerance. |
| fMAX | 60 MHz (typ.) at VCC = 4.5 V - Supports high-speed data transfer in legacy bus architectures without timing closure issues. |
| tPLH / tPHL | 20–48 ns (CL = 50 pF) - Balanced propagation ensures minimal skew between register-loaded and transparent-mode outputs. |
| IOL / IOH | 6 mA (min) - Drives standard TTL loads directly without external buffers in point-to-point or lightly loaded stubs. |
| VIH / VIL | 2.0 V (min) / 0.8 V (max) - Guarantees interoperability with 5 V TTL output stages without level-shifting. |
| ICC (Quiescent) | 4 µA (max) at TA = 25 °C - Enables low-static-power operation in always-on control logic or standby modes. |
| Operating Temp | –55 °C to +125 °C - Qualified for extended-temperature industrial and automotive under-hood environments. |
Pinout & Package
TSSOP-24 package: 4.4 mm × 6.5 mm body, 0.65 mm pitch, 1.1 mm max height, lead-free, RoHS-compliant.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 23 | CLOCK AB / CLOCK BA | Edge-triggered clock inputs controlling synchronous latch of A→B or B→A data into internal D-flip-flops. |
| 2, 22 | SELECT AB / SELECT BA | Multiplex control selecting registered vs. transparent data output on respective bus paths. |
| 3, 21 | GAB / G | Direction and global output enable: GAB sets A→B direction; G (active-low) enables/disables all 3-state outputs. |
| 4–11 | A1–A8 | Bidirectional A-bus terminals supporting input, output, or high-impedance states depending on G and DIR status. |
| 13–20 | B1–B8 | Bidirectional B-bus terminals with identical 3-state behavior as A-bus, isolated when G is high. |
| 12 | GND | Reference ground plane for noise immunity and stable logic thresholds across full temperature range. |
| 24 | VCC | Primary power supply connection; decoupling required within 1 cm for AC performance compliance. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent register banks | Enables concurrent capture of A and B bus data on separate clock edges, supporting ping-pong buffering in DMA controllers. |
| Pin- and function-compatible with 74 series 646 | Direct drop-in replacement for legacy 74LS646/74ALS646 in existing PCB layouts without redesign. |
| Symmetrical output drive (6 mA) | Eliminates need for external pull-ups/pull-downs in open-drain or wired-OR configurations. |
| High-impedance output disable (G high) | Allows safe bus sharing among multiple transceivers on same net without contention or shoot-through current. |
| ESD-protected inputs | Withstands ≥2 kV HBM per IEC 61000-4-2, reducing susceptibility to handling damage in manufacturing and field service. |
Applications
| Industrial PLC Backplane Interface | Legacy Memory Expansion Module |
|---|---|
Use Scenario: Bidirectional data exchange between CPU module and I/O expansion cards over a shared 8-bit parallel bus with strict timing constraints. IC Role / Device Role / Timing Role: Acts as a direction-controlled, register-buffered bus transceiver synchronizing data transfers to system clock edges while isolating modules during reconfiguration. Use Value: Prevents bus contention during hot-swap events and enables deterministic latency via registered mode, meeting IEC 61131-3 cycle-time requirements. | Use Scenario: Extending address/data bus width between microcontroller and external SRAM or EPROM in retro-computing or instrumentation designs. IC Role / Device Role / Timing Role: Provides 3-state isolation and clocked data latching to resolve timing mismatches between fast MCU and slower memory access cycles. Use Value: Eliminates need for discrete glue logic and reduces PCB layer count by integrating register + transceiver + direction control in one TSSOP-24 package. |
| Automotive Engine Control Unit (ECU) Diagnostics Port | Test Equipment Data Acquisition Interface |
Use Scenario: Isolating and conditioning diagnostic data lines between ECU main processor and OBD-II connector under harsh EMI and temperature conditions. IC Role / Device Role / Timing Role: Serves as a ruggedized, temperature-rated bus interface managing bidirectional UART or custom protocol signals with glitch-free state transitions. Use Value: Maintains signal integrity across –40 °C to +125 °C ambient while suppressing ground bounce through controlled slew rates and low ICC. | Use Scenario: Interfacing FPGA-based acquisition logic with legacy 8-bit parallel ADC/DAC modules requiring precise setup/hold timing and bus contention avoidance. IC Role / Device Role / Timing Role: Functions as a programmable bus repeater with selectable register bypass, enabling both real-time sampling and buffered burst reads. Use Value: Reduces FPGA I/O resource usage by offloading bus arbitration and timing-critical latching to dedicated hardware. |
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 |
|---|---|---|---|
| SN74HCT646N | DIP-24 package; higher ICC (≤ 80 µA); same AC specs but wider tPLH/tPHL max (48 ns vs. 44 ns at –55 °C to +125 °C). | Limited to through-hole prototyping or legacy repair; unsuitable for automated SMT assembly or high-density layouts. | Select when mechanical compatibility with socketed DIP footprints is mandatory and thermal derating is acceptable. |
| 74VHC646M | Higher VCC range (2 V to 5.5 V); lower drive (IOL = 8 mA typ.); faster fMAX (80 MHz typ. at 5 V); different pinout (no separate SELECT pins). | Requires PCB redesign due to functional differences in select logic and voltage scaling; not pin-compatible. | Choose only for new designs needing wider supply range and higher speed, accepting layout changes and validation effort. |
Compared with SN74HCT646N and 74VHC646M, M74HCT646RM13TR uniquely combines TSSOP-24 compactness, guaranteed –55 °C to +125 °C operation, and full 74-series 646 functional equivalence-making it optimal for volume-manufactured industrial and automotive boards where footprint, reliability, and drop-in compatibility are jointly critical.
Availability
M74HCT646RM13TR is available at Aetrix Electronics and suitable for industrial PLC backplanes, automotive ECU diagnostics ports, and legacy memory expansion modules requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for M74HCT646RM13TR 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, digital, and mixed-signal ICs for industrial, automotive, and consumer markets.
This device belongs to the M74HCT high-speed CMOS logic family, engineered for TTL-compatible operation with low power consumption and robust noise immunity in mission-critical control and interface applications.
FAQ
What is the maximum clock frequency supported by M74HCT646RM13TR?
The device supports a typical maximum clock frequency of 60 MHz at VCC = 4.5 V and CL = 50 pF, with a minimum guaranteed value of 20 MHz across the full operating temperature range (–55 °C to +125 °C), as specified in the AC Electrical Characteristics table.
Does M74HCT646RM13TR support hot insertion or live bus swapping?
No-while the device provides high-impedance isolation when G is high, it lacks built-in hot-swap protection circuitry such as slew-rate limiting or undervoltage lockout. Safe insertion requires power and signal sequencing per STMicroelectronics Application Note AN2012.
Can SELECT AB and SELECT BA be tied together for simplified control?
Yes-tying SELECT AB and SELECT BA together enables simultaneous selection of registered or transparent mode for both A→B and B→A paths, reducing GPIO usage; however, this eliminates independent multiplexing capability and must be verified against timing margins in the target system.
Is M74HCT646RM13TR compliant with modern RoHS and REACH requirements?
Yes-the TSSOP-24 package is lead-free and RoHS 2011/65/EU compliant, with full material declarations available in STMicroelectronics' Product Change Notification PCN-2022-017 and REACH SVHC screening confirming absence of substances above threshold levels.
M74HCT646RM13TR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- 74HCT
- Package/Case:
- 24-SOIC (0.295", 7.50mm 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:
- 6mA, 6mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -55°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-SO
M74HCT646RM13TR FAQ
1.How can I place an order for M74HCT646RM13TR through Aetrix?
Please submit a Request for Quotation (RFQ) for M74HCT646RM13TR 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 M74HCT646RM13TR reliable?
The price and inventory of M74HCT646RM13TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for M74HCT646RM13TR is usually 5 days.
3.What payment methods are accepted for M74HCT646RM13TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for M74HCT646RM13TR transactions.
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4.How is shipping managed for M74HCT646RM13TR?
M74HCT646RM13TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your M74HCT646RM13TR 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 M74HCT646RM13TR?
For technical support, including M74HCT646RM13TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your M74HCT646RM13TR requirements.
6.How does Aetrix verify that M74HCT646RM13TR is sourced from the original manufacturer or authorized distributors?
All M74HCT646RM13TR 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 M74HCT646RM13TR meets industry standards.
7.What is the process for return or replacement of M74HCT646RM13TR?
All M74HCT646RM13TR units undergo pre-shipment inspection (PSI). If there is an issue with M74HCT646RM13TR, 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 M74HCT646RM13TR part is unused and in its original packaging.
Return procedure for M74HCT646RM13TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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