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Texas Instruments SN74BCT640DW
- Part No.:
- SN74BCT640DW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74BCT640DW.pdf
- Description:
- IC TXRX INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,086
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Product details
Overview
SN74BCT640DW from Texas Instruments is an 8-bit non-inverting bus transceiver with direction control (DIR) and output-enable (OE), designed for asynchronous bidirectional data transfer between A and B buses in TTL-level systems. It operates at 4.5 V to 5.5 V, supports ±64 mA B-port sink current, features undershoot-protection circuitry, and is rated for 0°C to 70°C industrial temperature range in a 20-pin SOIC (DW) package.
For engineers reviewing the SN74BCT640DW datasheet, SN74BCT640DW pinout, SN74BCT640DW application, or SN74BCT640DW equivalent, this device is selected for high-drive bidirectional bus isolation in legacy TTL-compatible backplanes, memory expansion interfaces, and industrial controller I/O expansion where robust ESD protection (>2000 V), power-up high-impedance state, and BiCMOS low standby current are critical.
Technical Context
The SN74BCT640DW implements dual 8-bit bidirectional data paths controlled by DIR (data flow direction) and OE (output enable). Its BiCMOS architecture combines bipolar output drivers for high current drive (64 mA sink on B port) with CMOS input stages for low DC loading and reduced standby current.
It features buffered control inputs (DIR, OE), undershoot-protection on all I/Os, and a power-up high-impedance state ensuring safe bus initialization. Absolute maximum ratings include −0.5 V to 5.5 V on I/O ports and −0.5 V to 7 V on supply and control pins.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage (VCC) | 4.5 V to 5.5 V - Ensures compatibility with standard 5 V TTL and mixed-voltage system rails. |
| B-port Low-Level Output Current (IOL) | 64 mA - Enables direct driving of multiple TTL loads or termination resistors without external buffers. |
| A-port High-Level Output Voltage (VOH) | 2.4 V min @ IOH = −3 mA - Guarantees TTL-compatible logic-high margin under full load. |
| Propagation Delay (tPLH/tPHL) | 0.5 ns min / 6.5 ns max - Supports high-speed bus handshaking up to ~150 MHz effective toggle rate. |
| ESD Protection | >2000 V per MIL-STD-883C, Method 3015 - Provides robust handling during board assembly and field service. |
| Operating Temperature | 0°C to 70°C - Qualified for commercial and industrial ambient environments without derating. |
| Package | SOIC-20 (DW) - Surface-mount footprint compatible with automated PCB assembly and IPC-7351 land patterns. |
Pinout & Package
SN74BCT640DW uses a 20-pin plastic small-outline integrated circuit (SOIC) package (DW), 7.5 mm wide, 12.8 mm long, 2.65 mm max height, RoHS-compliant NiPdAu lead finish, MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | DIR | Direction control input: L = B→A, H = A→B; buffered to reduce DC loading on upstream logic. |
| 2–9 | A1–A8 | A-side data I/O terminals - Bidirectional, TTL-compatible, with undershoot protection. |
| 10 | GND | Ground reference for all internal circuitry and I/O voltage thresholds. |
| 11–18 | B1–B8 | B-side data I/O terminals - Higher sink current capability (64 mA) than A-side (24 mA). |
| 19 | OE | Output-enable active-low input: L = enabled, H = high-impedance isolation; power-up default is high-Z. |
| 20 | VCC | Positive supply terminal - Must be decoupled locally; supports 4.5–5.5 V operation. |
Key Features
| Feature | Design Value |
|---|---|
| BiCMOS output stage | Delivers 64 mA sink current on B port while maintaining TTL VOH/VOL margins under load. |
| Undershoot-protection circuitry | Prevents negative transient excursions below −0.5 V on all I/O pins, protecting connected devices. |
| Power-up high-impedance state | Ensures bus isolation during power sequencing - no bus contention at startup or brownout. |
| Buffered control inputs | Reduces input loading to ≤0.1 µA (IIH) and ≤−0.65 mA (IIL), minimizing fanout burden on controllers. |
| State-of-the-art BiCMOS design | Reduces ICCZ (isolated-state supply current) to 4–11 mA - significantly lower than equivalent bipolar-only transceivers. |
Applications
| Industrial Backplane Interface | Legacy Memory Expansion |
|---|---|
|
Use Scenario: Isolating and translating address/data between CPU and peripheral modules across a 20-slot industrial backplane. IC Role / Device Role / Timing Role: Bidirectional bus transceiver enabling synchronous read/write cycles between master and slave cards using DIR and OE handshaking. Use Value: 64 mA B-port drive ensures signal integrity over 15 cm trace lengths with 50 Ω parallel termination; undershoot protection prevents latch-up in noisy factory environments. |
Use Scenario: Expanding 8-bit data bus between microcontroller and external SRAM/ROM in retro-computing or instrumentation designs. IC Role / Device Role / Timing Role: Direction-controlled data path that switches automatically during memory read (A→B) and write (B→A) phases. Use Value: Sub-7 ns propagation delay enables 120 ns minimum memory access cycles; power-up high-Z prevents bus contention during reset assertion. |
| Programmable Logic I/O Bridge | TTL-to-TTL Bus Isolation |
|
Use Scenario: Interfacing FPGA I/O banks to legacy TTL peripherals requiring level-shifted, isolated data paths. IC Role / Device Role / Timing Role: Level-consistent bidirectional buffer with independent OE control per transceiver bank for partial bus gating. Use Value: Buffered DIR/OE inputs tolerate slow-rising FPGA control signals; 2000 V ESD rating protects FPGA I/O from field-induced discharge events. |
Use Scenario: Electrically isolating two independent 8-bit TTL subsystems (e.g., sensor interface and display driver) sharing common ground but requiring fault containment. IC Role / Device Role / Timing Role: Active-isolation device disabling both A and B ports simultaneously via OE, eliminating leakage paths. Use Value: ICCZ of 4–11 mA in isolation mode minimizes standby power in battery-backed systems; undervoltage lockout inherent in VCC threshold prevents metastability. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS245N | Bipolar TTL only; 24 mA max sink; no undershoot protection; higher ICC (40 mA typical); slower (12 ns max tPLH). | Limited to lower-speed, low-noise environments; unsuitable for long traces or electrically harsh settings. | Choose only if cost sensitivity outweighs noise immunity and drive strength requirements. |
| SN74LVC245APW | 3.3 V only; CMOS I/O; 24 mA sink; no BiCMOS drive; supports 1.65–3.6 V; no MIL-STD-883 ESD rating. | Requires level-shifting for 5 V systems; lacks robustness for industrial backplane use. | Select when migrating to 3.3 V logic families and board space is constrained (TSSOP-20). |
Compared with SN74LS245N and SN74LVC245APW, the SN74BCT640DW uniquely delivers 5 V TTL compatibility, 64 mA drive, built-in undershoot protection, and military-grade ESD tolerance - making it the only choice for ruggedized 5 V bus bridging where signal integrity and reliability are non-negotiable.
Availability
SN74BCT640DW is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy memory expansion, programmable logic I/O bridging, and TTL-to-TTL bus isolation requiring stable component supply across extended production lifecycles.
Supply support for SN74BCT640DW 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
Texas Instruments is a global semiconductor leader founded in 1930, specializing in analog, embedded processing, and logic solutions with broad industrial, automotive, and communications reach.
The SN74BCT640DW belongs to TI's legacy BCT (Bipolar-CMOS Transceiver) logic family, engineered specifically for high-drive, noise-tolerant 5 V bus interfacing in mission-critical industrial and military-grade systems.
FAQ
What is the maximum sink current supported by the B-port outputs of the SN74BCT640DW?
The SN74BCT640DW B-port outputs support up to 64 mA sink current per pin under recommended operating conditions (VCC = 4.5 V, TA = 0°C to 70°C). This value is specified in the electrical characteristics table for IOL (B port) and enables direct interface with multiple TTL inputs or 50 Ω terminated lines without external buffering. Exceeding this current risks VOL degradation or thermal stress.
Does the SN74BCT640DW have built-in ESD protection, and what standard does it meet?
Yes, the SN74BCT640DW provides ESD protection exceeding 2000 V per MIL-STD-883C, Method 3015. This is confirmed in the "Features" section of the datasheet and verified in absolute maximum ratings. The protection applies to all I/O and control pins, making the SN74BCT640DW suitable for environments with frequent handling or electrical noise exposure.
Can the SN74BCT640DW operate with a 3.3 V supply voltage?
No, the SN74BCT640DW is not rated for 3.3 V operation. Its recommended VCC range is strictly 4.5 V to 5.5 V, and absolute maximum supply is 7 V. Operation below 4.5 V may result in undefined logic thresholds, marginal VOH/VOL, or failure to meet timing specifications. For 3.3 V systems, consider SN74LVC245A instead - but note it is not a drop-in replacement for SN74BCT640DW.
What happens to the outputs of the SN74BCT640DW during power-up?
During power-up, the SN74BCT640DW enters a high-impedance state on all A and B port outputs regardless of DIR or OE logic levels. This power-up high-Z behavior is explicitly documented in the features list and prevents bus contention or unintended data corruption at system startup - a critical safety feature for reliable industrial system initialization.
Is the SN74BCT640DW pin-compatible with other packages in the same family, such as SN74BCT640N?
Yes, the SN74BCT640DW is functionally and pinout-compatible with SN74BCT640N (PDIP-20) and SN74BCT640NSR (SOP-20), sharing identical pin numbering, signal assignments, and electrical behavior. All variants implement the same logic function, timing, and DC specs - differing only in package type, thermal performance, and moisture sensitivity level.
SN74BCT640DW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74BCT
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- Logic Type:
- Transceiver, Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 3mA, 24mA; 15mA, 64mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
SN74BCT640DW FAQ
1.How can I place an order for SN74BCT640DW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74BCT640DW 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 SN74BCT640DW reliable?
The price and inventory of SN74BCT640DW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74BCT640DW is usually 5 days.
3.What payment methods are accepted for SN74BCT640DW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74BCT640DW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74BCT640DW?
SN74BCT640DW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74BCT640DW 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 SN74BCT640DW?
For technical support, including SN74BCT640DW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74BCT640DW requirements.
6.How does Aetrix verify that SN74BCT640DW is sourced from the original manufacturer or authorized distributors?
All SN74BCT640DW 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 SN74BCT640DW meets industry standards.
7.What is the process for return or replacement of SN74BCT640DW?
All SN74BCT640DW units undergo pre-shipment inspection (PSI). If there is an issue with SN74BCT640DW, 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 SN74BCT640DW part is unused and in its original packaging.
Return procedure for SN74BCT640DW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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