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Texas Instruments SN74BCT640DWR

Name: SN74BCT640DWR
Brand: Texas Instruments
SKU: SN74BCT640DWR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74BCT640DWR

Manufacturer:: Texas Instruments

Category:: Buffers, Drivers, Receivers, Transceivers

Package:: 20-SOIC (0.295", 7.50mm Width)

Datasheet:: SN74BCT640DWR.pdf

Description:: IC TXRX INVERT 5.5V 20SOIC

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Product details

Overview

SN74BCT640DWR 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 industrial temperature range, delivers ±64 mA B-port low-level output current, and features undershoot-protection circuitry for robust signal integrity in backplane or board-level interconnect applications.

For engineers reviewing the SN74BCT640DWR datasheet, SN74BCT640DWR pinout, SN74BCT640DWR application, or SN74BCT640DWR equivalent, key selection criteria include its BiCMOS architecture enabling low standby current, power-up high-impedance state for hot-swap safety, buffered control inputs reducing DC loading, and SOIC-20 (DW) package compatibility with standard surface-mount assembly processes.

Technical Context

The SN74BCT640DWR implements a dual-bus transceiver architecture with independent DIR and OE controls, enabling configurable unidirectional data flow (A→B or B→A) or full bus isolation. Its BiCMOS design integrates bipolar switching transistors for high drive strength and CMOS logic for low static power consumption.

Each of the eight A/B I/O channels supports TTL-level input thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2 V) and provides rail-to-rail output swing with VOH ≥ 2.4 V at IOH = −3 mA (A port) and ≥ 2.0 V at IOH = −15 mA (B port), ensuring reliable interfacing with legacy TTL and mixed-voltage logic systems.

Key Specifications

Parameter	Value and Actual Design Meaning
Supply Voltage	4.5 V to 5.5 V - Ensures stable operation across standard 5 V ±10% power rails without regulation overhead.
Operating Temperature	0°C to 70°C - Qualified for commercial/industrial ambient environments, excluding extended or military ranges.
B-Port Low-Level Output Current	64 mA - Enables direct driving of multiple TTL loads or termination resistors on high-capacitance buses.
Propagation Delay (t_PHL)	3.7 ns max - Supports high-speed bus handshaking up to ~135 MHz clock-equivalent timing in synchronous interfaces.
Input Clamp Current	−18 mA - Protects against transient overvoltage events on control inputs without external clamping diodes.
Standby ICCZ Current	11 mA max - BiCMOS optimization reduces quiescent power during bus isolation versus pure bipolar alternatives.
ESD Protection	>2000 V per MIL-STD-883C Method 3015 - Provides handling robustness during PCB assembly and field service.

Pinout & Package

SN74BCT640DWR is housed in a 20-pin SOIC (DW) package measuring 12.83 mm × 7.5 mm × 2.65 mm, with 1.27 mm pitch, RoHS-compliant NiPdAu lead finish, and JEDEC MS-013 compliant footprint.

Pin/Terminal	Circuit Role	Design Meaning
1	DIR	Direction control input: LOW enables B→A data flow; HIGH enables A→B data flow.
2–9	A1–A8	Bus A I/O terminals - Bidirectional data lines connected to first system bus segment.
10	GND	Ground reference for all internal circuitry and I/O voltage levels.
11–18	B1–B8	Bus B I/O terminals - Bidirectional data lines connected to second system bus segment.
19	OE	Output-enable input: LOW activates transceiver; HIGH places all A/B pins in high-impedance state.
20	VCC	Positive supply terminal - Must be decoupled locally to suppress switching noise on shared 5 V rail.

Key Features

Feature	Design Value
BiCMOS process technology	Combines bipolar drive strength (64 mA B-port sink) with CMOS low standby current (ICCZ ≤ 11 mA).
Undershoot-protection circuitry	Prevents negative voltage excursions below GND on I/O pins during fast edge transitions, eliminating need for external Schottky clamps.
Power-up high-impedance state	Guarantees all A/B pins float at power-on reset, preventing bus contention during system initialization.
Buffered control inputs	Reduces DC loading on DIR and OE lines to ≤0.1 µA, enabling direct connection to microcontroller GPIO without pull-up/down burden.
TTL-compatible voltage thresholds	V_IL ≤ 0.8 V and V_IH ≥ 2 V ensure interoperability with legacy 74LS, 74F, and microprocessor address/data buses.

Applications

Industrial Backplane Interconnect	Legacy Microprocessor Bus Extension
Use Scenario: Isolating and extending parallel address/data buses between CPU module and peripheral carrier board in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing A→B or B→A data routing under microcontroller DIR/OE control during memory-mapped I/O cycles. Use Value: 64 mA B-port drive capability sustains signal integrity across 15 cm backplane traces with 30 pF/ft capacitance and 50 Ω terminations.	Use Scenario: Adding external RAM or EPROM to Z80 or 8085-based embedded systems where address/data bus loading exceeds native driver capacity. IC Role / Device Role / Timing Role: Level-shifting and buffering interface between microprocessor's multiplexed AD bus and separate address/data lines of memory devices. Use Value: 3.7 ns max t_PHL ensures setup/hold timing margins are preserved at 4 MHz CPU clock with 2-cycle memory access.
Test Equipment Signal Routing	Automated Test Fixture Interface
Use Scenario: Dynamically reconfiguring signal paths between DUT connector and instrument I/O ports in boundary-scan test systems. IC Role / Device Role / Timing Role: Controlled bus switch enabling one-shot data capture or stimulus injection via DIR/OE sequencing during JTAG scan operations. Use Value: Power-up high-Z state prevents false triggering on instrument ports before firmware initializes control lines.	Use Scenario: Isolating production test adapters from host controller during fixture calibration or fault injection sequences. IC Role / Device Role / Timing Role: Bus gate enforcing strict directional control between tester logic and DUT pins to prevent feedback-induced latch-up. Use Value: Undershoot protection eliminates need for discrete clamping diodes on 20+ channel test head cabling, reducing BOM count and layout area.

Industrial Backplane Interconnect

Legacy Microprocessor Bus Extension

Use Scenario: Isolating and extending parallel address/data buses between CPU module and peripheral carrier board in programmable logic controllers.

IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing A→B or B→A data routing under microcontroller DIR/OE control during memory-mapped I/O cycles.

Use Value: 64 mA B-port drive capability sustains signal integrity across 15 cm backplane traces with 30 pF/ft capacitance and 50 Ω terminations.

Use Scenario: Adding external RAM or EPROM to Z80 or 8085-based embedded systems where address/data bus loading exceeds native driver capacity.

IC Role / Device Role / Timing Role: Level-shifting and buffering interface between microprocessor's multiplexed AD bus and separate address/data lines of memory devices.

Use Value: 3.7 ns max t_PHL ensures setup/hold timing margins are preserved at 4 MHz CPU clock with 2-cycle memory access.

Test Equipment Signal Routing

Automated Test Fixture Interface

Use Scenario: Dynamically reconfiguring signal paths between DUT connector and instrument I/O ports in boundary-scan test systems.

IC Role / Device Role / Timing Role: Controlled bus switch enabling one-shot data capture or stimulus injection via DIR/OE sequencing during JTAG scan operations.

Use Value: Power-up high-Z state prevents false triggering on instrument ports before firmware initializes control lines.

Use Scenario: Isolating production test adapters from host controller during fixture calibration or fault injection sequences.

IC Role / Device Role / Timing Role: Bus gate enforcing strict directional control between tester logic and DUT pins to prevent feedback-induced latch-up.

Use Value: Undershoot protection eliminates need for discrete clamping diodes on 20+ channel test head cabling, reducing BOM count and layout area.

Equivalent & Alternatives

The following parts are listed as comparable options for similar bus transceiver applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74ABT640DWR	Higher drive (100 mA B-port sink), lower propagation delay (2.8 ns), ABT series with improved noise immunity.	Preferred for new designs requiring higher speed or fanout; not drop-in due to different AC characteristics and tighter V_OH spec.	Select SN74ABT640DWR when upgrading from SN74BCT640DWR for >5 MHz bus rates or stricter EMI requirements.
74ACT640SO20	CMOS-based (not BiCMOS), 24 mA B-port sink, wider V_CC range (4.5–5.5 V), no undershoot protection.	Suitable for low-power, low-noise applications but lacks robustness for noisy industrial backplanes.	Choose 74ACT640SO20 only if system-level ESD/clamp protection is already implemented externally and drive strength <64 mA suffices.

Compared with SN74BCT640DWR, SN74ABT640DWR offers superior speed and drive for next-generation upgrades, while 74ACT640SO20 trades off ruggedness for lower static power-neither is pin-compatible without layout revision, and both require validation of timing closure and noise margin in target systems.

Availability

SN74BCT640DWR is available at Aetrix Electronics and suitable for industrial backplane interconnect, legacy microprocessor bus extension, test equipment signal routing, and automated test fixture interface applications requiring stable component supply across long-lifecycle programs.

Supply support for SN74BCT640DWR 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 solutions, with over 90 years of innovation in industrial, automotive, and communications markets.

The SN74BCT640DWR belongs to TI's BCT logic family, engineered specifically for high-drive, TTL-compatible bidirectional bus interfacing in noise-sensitive industrial control and instrumentation systems.

FAQ

What is the maximum operating temperature range for the SN74BCT640DWR?

The SN74BCT640DWR is characterized for operation from 0°C to 70°C, matching the commercial temperature grade. It is not rated for extended industrial (−40°C to 85°C) or military (−55°C to 125°C) ranges-those require SN54BCT640 variants in ceramic packages. Always verify ambient and junction temperature limits using the device's thermal resistance and power dissipation in your PCB layout.

Does the SN74BCT640DWR support hot-swap insertion into a live bus system?

Yes, the SN74BCT640DWR features a power-up high-impedance state that guarantees all A/B I/O pins remain in tri-state until V_CC stabilizes and control inputs settle, preventing bus contention during hot-plug events. This behavior is inherent to its BiCMOS design and requires no external reset sequencing-critical for modular backplane architectures using the SN74BCT640DWR.

Can the SN74BCT640DWR drive standard 50 Ω transmission lines directly?

The SN74BCT640DWR can drive 50 Ω loads in short-run configurations: its B-port delivers 64 mA sink current, supporting ≤10 cm traces with proper termination. However, for longer runs or multi-drop topologies, external series resistors (e.g., 33 Ω) are recommended to damp reflections-TI's application notes confirm this practice for SN74BCT640DWR in backplane designs.

What is the purpose of the undershoot-protection circuitry in the SN74BCT640DWR?

The undershoot-protection circuitry in the SN74BCT640DWR actively clamps negative voltage excursions below GND on I/O pins during fast edge transitions, preventing damage to downstream receivers and eliminating the need for external Schottky diodes. This feature is confirmed in the SCBS025C datasheet and directly enhances reliability in electrically noisy industrial environments where the SN74BCT640DWR is commonly deployed.

Is the SN74BCT640DWR pin-compatible with other 20-pin bus transceivers like the 74LS640?

No, the SN74BCT640DWR is not pin-compatible with 74LS640. While both are 20-pin bus transceivers, their pin assignments differ: SN74BCT640DWR places DIR on Pin 1 and OE on Pin 19, whereas 74LS640 uses Pin 1 for OE and Pin 19 for GND. Layout reuse requires verification against each device's official pinout diagram-TI's DW package drawing confirms SN74BCT640DWR's unique mapping.

SN74BCT640DWR Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74BCT

Package/Case:: 20-SOIC (0.295", 7.50mm Width)

Packaging:: Tape & Reel (TR)

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:: 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

SN74BCT640DWR FAQ

1.How can I place an order for SN74BCT640DWR through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74BCT640DWR 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 SN74BCT640DWR reliable?

The price and inventory of SN74BCT640DWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74BCT640DWR is usually 5 days.

3.What payment methods are accepted for SN74BCT640DWR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74BCT640DWR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74BCT640DWR?

SN74BCT640DWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74BCT640DWR 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 SN74BCT640DWR?

For technical support, including SN74BCT640DWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74BCT640DWR requirements.

6.How does Aetrix verify that SN74BCT640DWR is sourced from the original manufacturer or authorized distributors?

All SN74BCT640DWR 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 SN74BCT640DWR meets industry standards.

7.What is the process for return or replacement of SN74BCT640DWR?

All SN74BCT640DWR units undergo pre-shipment inspection (PSI). If there is an issue with SN74BCT640DWR, 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 SN74BCT640DWR part is unused and in its original packaging.

Return procedure for SN74BCT640DWR:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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