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STMicroelectronics M74HCT640B1R
- Part No.:
- M74HCT640B1R
- Manufacturer:
- STMicroelectronics
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
M74HCT640B1R.pdf
- Description:
- IC TRANSCEIVER INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,844
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Product details
Overview
M74HCT640B1R from STMicroelectronics is an octal bus transceiver with 3-state inverted outputs, designed for bidirectional asynchronous data bus interfacing. It features directional control (DIR), output enable (G), symmetrical drive strength (±6 mA), 13 ns typical propagation delay at 4.5 V, and TTL-compatible input thresholds - deployed in industrial backplane interface and legacy system bus isolation.
For engineers reviewing the M74HCT640B1R datasheet, M74HCT640B1R pinout, M74HCT640B1R application, or M74HCT640B1R equivalent, key selection criteria include bidirectional 3-state bus control timing, high-impedance isolation behavior, VIH/VIL compatibility with TTL logic families, and DIP-20 mechanical fit for through-hole board upgrades.
Technical Context
The M74HCT640B1R implements dual-bus bidirectional data flow controlled by DIR and G inputs: when G = L, data passes either A→B (DIR = L) or B→A (DIR = H); when G = H, both A and B ports enter high-impedance state. Its C2MOS silicon gate process enables low ICC (4 µA max) while maintaining rail-to-rail CMOS output swing.
Propagation delays are balanced (tPLH ≅ tPHL), and output transition times (7–12 ns typ.) support reliable operation up to ~30 MHz under CL = 50 pF. Input protection diodes and static discharge safeguards ensure robustness in noisy industrial environments without external clamping.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Propagation Delay | 13 ns typical at VCC = 4.5 V, CL = 50 pF - enables sub-40 MHz synchronous bus handshaking |
| Output Drive | ±6 mA min. - sufficient to drive 50 pF loads across 15 cm PCB traces without signal degradation |
| Input Thresholds | VIH ≥ 2.0 V, VIL ≤ 0.8 V - ensures interoperability with standard TTL logic outputs |
| Quiescent Current | 4 µA max. at TA = 25°C - supports low-power standby in always-on industrial controllers |
| Supply Range | 4.5–5.5 V - compatible with regulated +5 V rails and tolerant of ±10% line variation |
| Operating Temp | −55°C to +125°C - qualified for extended-temperature industrial and automotive under-hood use |
| High-Z Leakage | ±10 µA max. at −55°C to +125°C - prevents unintended bus contention during isolation |
Pinout & Package
Package: Plastic DIP-20 (0.300" wide), 20-pin through-hole, JEDEC MS-001 compliant. Pin pitch: 2.54 mm.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | DIR | Direction control: L = A→B, H = B→A; referenced to VCC/GND, not floating |
| 2–9 | A1–A8 | Port A bidirectional I/O: driven or high-Z depending on G and DIR state |
| 11–18 | B1–B8 | Port B bidirectional I/O: complementary to A port per DIR setting |
| 19 | G | Active-low output enable: L = functional, H = both ports high-Z |
| 10 | GND | Reference ground for all logic and power terminals |
| 20 | VCC | +4.5 V to +5.5 V supply; decoupling capacitor required at pin |
Key Features
| Feature | Design Value |
|---|---|
| Inverted 3-state outputs | Ensures deterministic bus release: outputs go high-Z only when G = H, eliminating metastable states |
| Symmetrical output impedance | |IOH| = |IOL| ≥ 6 mA - minimizes skew between rising/falling edges on shared bus lines |
| TTL-compatible inputs | VIH ≥ 2.0 V / VIL ≤ 0.8 V - eliminates need for level-shifting when interfacing with 74LS/74F families |
| Low quiescent power | ICC ≤ 4 µA at 25°C - reduces thermal load in dense backplane modules with dozens of transceivers |
| Extended temperature range | Operates from −55°C to +125°C - validated for deployment in unheated outdoor enclosures and engine-control bays |
Applications
| Industrial Backplane Interface | Legacy System Bus Isolation |
|---|---|
Use Scenario: Interfacing a microcontroller bus to a multi-slot ISA-style backplane with mixed-vendor peripheral cards. IC Role / Device Role / Timing Role: Bidirectional bus transceiver enabling CPU-initiated reads/writes to expansion cards while isolating noise between slots. Use Value: 13 ns propagation delay and ±6 mA drive maintain signal integrity across 20 cm backplane traces at 8 MHz clock rates. | Use Scenario: Upgrading aging PLC I/O modules where original 74LS640 parts are obsolete and no longer available. IC Role / Device Role / Timing Role: Pin- and function-compatible replacement providing identical A↔B directionality and 3-state control. Use Value: TTL-compatible inputs and DIP-20 footprint allow direct drop-in replacement without PCB redesign or firmware changes. |
| Automotive ECU Subsystem Bridge | Test Equipment Signal Conditioning |
Use Scenario: Isolating diagnostic CAN controller bus from proprietary sensor acquisition subsystem operating at different voltage domains. IC Role / Device Role / Timing Role: Direction-controlled data bridge that prevents ground loop currents while allowing firmware-triggered data forwarding. Use Value: −55°C to +125°C rating and 4 µA ICC support operation in engine bay-mounted ECUs with minimal self-heating. | Use Scenario: Buffering and isolating digital stimulus signals between arbitrary waveform generator and DUT during production test. IC Role / Device Role / Timing Role: High-Z-enabled bus separator preventing signal reflection and crosstalk during test vector transitions. Use Value: Balanced tPLH/tPHL and 7 ns output transition time ensure <1 ns edge jitter in 25 MHz test patterns. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HCT640N | Same logic function, identical AC/DC specs, TI-manufactured DIP-20 package | No difference in bus isolation or timing behavior; same pinout and drive capability | Select when TI-sourced parts preferred for supply chain diversification |
| 74HCT640D | NXP SO-16 package (not pin-compatible); lacks two ground pins and has different pin mapping | Requires PCB redesign; unsuitable for DIP-20 socket replacement | Consider only for new designs targeting surface-mount assembly and space-constrained layouts |
Compared with SN74HCT640N, M74HCT640B1R offers identical electrical performance but differs in manufacturer qualification and traceability; versus 74HCT640D, it provides direct DIP-20 mechanical compatibility essential for legacy board repair without layout modification.
Availability
M74HCT640B1R is available at Aetrix Electronics and suitable for industrial backplane interface, legacy system bus isolation, and automotive ECU subsystem bridging requiring stable component supply over extended product lifecycles.
Supply support for M74HCT640B1R 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, designing and manufacturing analog, MCU, power, and discrete devices for industrial, automotive, and consumer markets.
The M74HCT640B1R belongs to the HCT logic family - engineered for TTL-compatible CMOS operation with low power and high noise immunity in harsh industrial environments.
FAQ
What is the maximum recommended capacitive load for M74HCT640B1R outputs?
The datasheet specifies AC characteristics at CL = 50 pF and CL = 150 pF. For guaranteed timing compliance, keep total load (including trace and stub capacitance) ≤150 pF. Exceeding this increases propagation delay nonlinearly and may cause setup/hold violations in synchronous systems.
Can M74HCT640B1R operate reliably at VCC = 4.2 V?
No. The recommended operating supply is strictly 4.5 V to 5.5 V. At 4.2 V, VOH drops below 4.0 V and VIH margin erodes - violating TTL compatibility and risking false logic interpretation in cascaded systems.
Is DIR pin allowed to float during operation?
No. Floating DIR causes undefined directionality and potential bus contention. The datasheet mandates DIR be actively driven to VCC or GND. Internal pull-ups/downs are absent; external biasing is required if control logic is inactive.
Does M74HCT640B1R support hot insertion?
No. It lacks hot-swap protection circuitry such as slew-rate limiting or current limiting on I/O pins. Insertion while powered risks latch-up due to transient voltage overshoot on A/B pins, especially when buses are pre-driven.
M74HCT640B1R Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- 74HCT
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Logic Type:
- Transceiver, 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:
- Through Hole
- Supplier Device Package:
- 20-DIP
M74HCT640B1R FAQ
1.How can I place an order for M74HCT640B1R through Aetrix?
Please submit a Request for Quotation (RFQ) for M74HCT640B1R 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 M74HCT640B1R reliable?
The price and inventory of M74HCT640B1R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for M74HCT640B1R is usually 5 days.
3.What payment methods are accepted for M74HCT640B1R?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for M74HCT640B1R transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for M74HCT640B1R?
M74HCT640B1R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your M74HCT640B1R 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 M74HCT640B1R?
For technical support, including M74HCT640B1R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your M74HCT640B1R requirements.
6.How does Aetrix verify that M74HCT640B1R is sourced from the original manufacturer or authorized distributors?
All M74HCT640B1R 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 M74HCT640B1R meets industry standards.
7.What is the process for return or replacement of M74HCT640B1R?
All M74HCT640B1R units undergo pre-shipment inspection (PSI). If there is an issue with M74HCT640B1R, 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 M74HCT640B1R part is unused and in its original packaging.
Return procedure for M74HCT640B1R:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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