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Texas Instruments SN74BCT640NS
- Part No.:
- SN74BCT640NS
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74BCT640NS.pdf
- Description:
- IC TXRX INVERT 5.5V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,080
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Product details
Overview
SN74BCT640NS 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 two 8-bit buses in TTL-compatible systems. It operates from 4.5 V to 5.5 V, supports 0°C to 70°C ambient, delivers up to 64 mA low-level output current on B-port, and features undershoot-protection circuitry and power-up high-impedance state.
For engineers reviewing the SN74BCT640NS datasheet, SN74BCT640NS pinout, SN74BCT640NS application, or SN74BCT640NS equivalent, key selection considerations include its BiCMOS architecture for reduced standby current, 20-pin SOP (NS) package with 12.0 ns max propagation delay (A→B), and isolation capability when OE is high - critical for bus contention avoidance in industrial control backplanes and legacy system upgrades.
Technical Context
The SN74BCT640NS implements a dual-bus transceiver topology with separate A and B 8-bit I/O ports, controlled by DIR (determines data flow direction) and OE (enables/disables all outputs). Its BiCMOS design combines bipolar input stages for TTL-level compatibility and CMOS output drivers for high sink/source capability.
Electrical behavior is defined across two operating modes: bidirectional data pass-through (OE = L, DIR = L/H) and three-state isolation (OE = H). Propagation delays are asymmetric - tPLH/tPHL from A→B range 0.5–6.5 ns, while OE-controlled enable/disable times (tPZL/tPHZ) reach up to 12.3 ns, requiring timing margining in synchronous bus arbitration logic.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - ensures compatibility with standard 5 V TTL and mixed-voltage backplane designs. |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade industrial and computing applications, not extended/military range. |
| B-port Low-Level Output Current | 64 mA - enables direct driving of multiple TTL loads without external buffers in legacy bus interfaces. |
| Max Propagation Delay (A→B) | 6.5 ns at VCC = 4.5 V - supports high-speed data handshaking in real-time control subsystems. |
| Input Clamp Current | −18 mA - provides robust protection against transient overvoltage on control inputs during hot-swap or ESD events. |
| Standby ICCZ Current | 4–11 mA - BiCMOS architecture reduces quiescent power vs. pure bipolar equivalents, easing thermal management. |
| ESD Protection | >2000 V per MIL-STD-883C Method 3015 - meets baseline reliability requirements for board-level assembly and field service. |
Pinout & Package
SN74BCT640NS is housed in a 20-pin plastic small-outline package (SOP-20, package code NS), 7.6 mm × 12.6 mm body size, 1.27 mm lead pitch, and 2.65 mm maximum height - compatible with standard SOIC footprint layouts and automated SMT placement.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | A-port data inputs/outputs | Bi-directional TTL-compatible I/O pins connected to source bus; high-impedance when OE = H. |
| 9 | GND | Power ground reference for all internal logic and output drivers. |
| 10 | VCC | Positive supply rail (4.5–5.5 V); decoupling capacitor required within 10 mm. |
| 11 | OE | Active-low output enable - drives all A/B ports into high-Z when high, isolating buses. |
| 12, 13, 14, 15, 16, 17, 18, 19 | B-port data inputs/outputs | Bi-directional TTL-compatible I/O pins connected to destination bus; direction set by DIR. |
| 20 | DIR | Direction control - L routes B→A, H routes A→B; latched internally, no external pull-up needed. |
Key Features
| Feature | Design Value |
|---|---|
| Undershoot-protection circuitry | Prevents negative voltage excursions below −0.5 V on I/O pins during fast edge transitions, eliminating need for external clamping diodes. |
| Power-up high-impedance state | Guarantees all outputs remain in three-state until VCC stabilizes and control inputs settle - prevents bus contention at power-on. |
| Buffered control inputs | Reduces DC loading on DIR and OE lines to ≤0.1 µA, enabling direct connection to microcontroller GPIO without level-shifting or current-limiting resistors. |
| State-of-the-art BiCMOS design | Combines TTL input thresholds with CMOS output drive strength, achieving 64 mA sink capability while limiting ICCZ to 11 mA. |
Applications
| Industrial Backplane Interface | Legacy System Bus Extension |
|---|---|
Use Scenario: Interfacing a modern microcontroller-based module to an aging 8-bit ISA-style backplane with separate address/data buses. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing data flow between CPU and peripheral cards under software-controlled DIR and hardware handshake-driven OE. Use Value: Enables drop-in replacement of obsolete 74LS245 while maintaining signal integrity and timing margins due to sub-7 ns propagation delay and 64 mA drive strength. | Use Scenario: Adding isolated memory-mapped I/O expansion to a PLC mainboard using shared address/data bus architecture. IC Role / Device Role / Timing Role: Isolates local I/O bus from main system bus during configuration writes via OE control, preventing unintended register access. Use Value: Eliminates need for discrete bus switches or FPGA glue logic - single IC provides direction control, isolation, and TTL-level compatibility. |
| Test Equipment Data Path Switching | Automated Test Fixture Signal Routing |
Use Scenario: Routing DUT signals between multiple instrument channels (e.g., DMM, SMU, pattern generator) in a modular ATE rack. IC Role / Device Role / Timing Role: Configurable bidirectional path selector controlled by test sequencer GPIO, with DIR selecting source/sink and OE enabling/disabling paths. Use Value: Supports simultaneous multi-point measurements with guaranteed bus isolation during reconfiguration - no signal leakage or latch-up risk. | Use Scenario: Reconfiguring signal paths between DUT pins and test head connectors in production ICT fixtures with limited PCB real estate. IC Role / Device Role / Timing Role: Compact 20-pin SOP solution replacing discrete logic arrays for dynamic bus routing under fixture controller command. Use Value: Reduces fixture PCB layer count and component count versus discrete AND/OR gate solutions while preserving timing predictability. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ABT245N | Higher drive (100 mA), lower propagation delay (3.2 ns), but requires 4.5–5.5 V and lacks undershoot protection. | Preferred for new designs demanding higher speed and drive; not drop-in due to different pinout and lack of built-in undershoot clamp. | Select SN74ABT245N only if layout revision accommodates new pin assignment and system ESD environment is controlled. |
| 74ACT245SC | CMOS-based, 5 V tolerant, 24 mA output drive, no BiCMOS power advantage - ICCZ ≈ 20 µA vs. SN74BCT640NS's 4–11 mA. | Suitable for low-power, noise-sensitive analog-digital hybrid boards where standby current matters more than drive strength. | Choose 74ACT245SC when interfacing with mixed-voltage ASICs or when thermal budget prohibits BiCMOS dissipation. |
Compared with SN74ABT245N and 74ACT245SC, the SN74BCT640NS uniquely balances legacy TTL compatibility, robust undershoot protection, and moderate drive capability in a pin-compatible SOP-20 footprint - making it optimal for repair, retrofit, and cost-sensitive industrial upgrades where reliability under electrical stress is prioritized over raw speed.
Availability
SN74BCT640NS is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus extensions, test equipment data path switching, automated test fixture signal routing, and PLC I/O expansion requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74BCT640NS 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 specializing in analog, embedded processing, and logic technologies, with decades of heritage in industry-standard logic families.
The SN74BCT640NS belongs to TI's BCT (Bipolar-CMOS Transceiver) logic series, engineered specifically for high-drive, noise-immune bidirectional bus interfacing in industrial and computing systems where TTL compatibility and electrical ruggedness are mandatory.
FAQ
What is the maximum operating temperature range for the SN74BCT640NS?
The SN74BCT640NS is characterized for operation from 0°C to 70°C - this commercial-grade temperature rating is confirmed in the absolute maximum ratings and recommended operating conditions tables of the SCBS025C datasheet. It is not rated for extended industrial (−40°C to 85°C) or military (−55°C to 125°C) ranges; those apply only to SN54BCT640 variants in ceramic packages. Thermal derating is not specified beyond this range.
Does the SN74BCT640NS support hot-swap or live-insertion into a powered bus?
The SN74BCT640NS incorporates undershoot-protection circuitry and input clamp current rating of −18 mA, which improves resilience during transient events, but it does not feature full hot-swap enablement such as power sequencing control or slew-rate-limited I/O. The device enters high-impedance state at power-up, reducing risk, yet TI documentation does not validate or guarantee safe live insertion - external current-limiting or bus isolation remains recommended for true hot-swap applications involving the SN74BCT640NS.
Can the SN74BCT640NS be used with 3.3 V logic systems?
No - the SN74BCT640NS requires a minimum supply voltage of 4.5 V and is not 3.3 V tolerant. Its input thresholds (VIH = 2 V min, VIL = 0.8 V max) and output voltage levels (VOH ≥ 2.4 V at IOH = −3 mA) are specified only for 4.5–5.5 V operation. Connecting it directly to 3.3 V controllers or buses risks undervoltage lockout, incorrect logic interpretation, or damage due to VI/O exceeding −0.5 V to 5.5 V limits. Level translation is required when interfacing with 3.3 V systems.
What is the pin 1 marking and orientation for the SN74BCT640NS in tape-and-reel packaging?
The SN74BCT640NS uses SOP-20 (NS) packaging with pin 1 located in quadrant Q1 of the carrier tape, as documented in TI's PACKAGE MATERIALS INFORMATION (10-Aug-2026). The device marking on the top surface reads "BCT640", and the physical pin 1 identifier is a beveled corner or notch on the package body - consistent with JEDEC MS-013 standard for SOIC outlines. Reel orientation follows standard clockwise feed direction with sprocket holes aligned per IPC-7351 guidelines.
How does the SN74BCT640NS handle bus contention when both DIR and OE are floating?
The SN74BCT640NS has buffered control inputs with specified IIH/IIL leakage (±0.1 µA at VCC = 5.5 V), but no internal pull-up or pull-down resistors on DIR or OE. If left floating, these inputs may assume indeterminate logic states, potentially causing partial or unstable bus driver activation and contention. TI's datasheet explicitly requires externally establishing valid logic levels - OE must be held low (to enable) or high (to isolate), and DIR must be actively driven to define direction. Floating controls are not a supported operating condition for the SN74BCT640NS.
SN74BCT640NS Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74BCT
- Package/Case:
- 20-SOIC (0.209", 5.30mm 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-SO
SN74BCT640NS FAQ
1.How can I place an order for SN74BCT640NS through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74BCT640NS 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 SN74BCT640NS reliable?
The price and inventory of SN74BCT640NS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74BCT640NS is usually 5 days.
3.What payment methods are accepted for SN74BCT640NS?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74BCT640NS transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74BCT640NS?
SN74BCT640NS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74BCT640NS 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 SN74BCT640NS?
For technical support, including SN74BCT640NS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74BCT640NS requirements.
6.How does Aetrix verify that SN74BCT640NS is sourced from the original manufacturer or authorized distributors?
All SN74BCT640NS 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 SN74BCT640NS meets industry standards.
7.What is the process for return or replacement of SN74BCT640NS?
All SN74BCT640NS units undergo pre-shipment inspection (PSI). If there is an issue with SN74BCT640NS, 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 SN74BCT640NS part is unused and in its original packaging.
Return procedure for SN74BCT640NS:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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