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Texas Instruments SN74BCT640N
- Part No.:
- SN74BCT640N
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74BCT640N.pdf
- Description:
- IC TRANSCEIVER INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,695
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Product details
Overview
SN74BCT640N 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 from 4.5 V to 5.5 V, supports 0°C to 70°C ambient, delivers ±64 mA B-port sink current, and features undershoot-protection circuitry and power-up high-impedance state - used in industrial backplane interfaces and legacy system bus isolation.
For engineers reviewing the SN74BCT640N datasheet, SN74BCT640N pinout, SN74BCT640N application, or SN74BCT640N equivalent, key selection criteria include its BiCMOS architecture for low standby current, 3.4 V VOH at −3 mA on A port, 2.0 V VOH at −15 mA on B port, tPLH/tPHL propagation delays under 6.5 ns, and PDIP-20 package compatibility with through-hole legacy designs.
Technical Context
The SN74BCT640N implements a dual-bus bidirectional transceiver using BiCMOS logic, enabling data flow either from A-to-B or B-to-A based on DIR input level while OE controls overall output enablement. Its buffered control inputs reduce DC loading, and undershoot-protection circuitry safeguards I/O pins against negative transient voltages down to −0.5 V.
It features three distinct operating states: active bidirectional transfer (OE = L), high-impedance isolation (OE = H), and power-up safe tri-state (no false outputs during VCC ramp). Absolute maximum ratings include 7 V supply tolerance and 5.5 V I/O voltage limit, with ESD protection exceeding 2000 V per MIL-STD-883C Method 3015.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - ensures compatibility with standard 5 V TTL and CMOS logic rails without level-shifting. |
| VOH (A port) | 2.5 V min at −3 mA - guarantees robust high-level drive into TTL loads with noise margin >0.4 V. |
| VOH (B port) | 2.0 V min at −15 mA - sustains valid logic-high under heavier bus loading typical of backplane stubs. |
| VOL (B port) | 0.42 V max at 64 mA - enables reliable low-level signaling even with high-current termination schemes. |
| tPLH / tPHL | 0.5 ns min / 6.5 ns max - supports >150 MHz burst data rates in point-to-point or lightly loaded bus topologies. |
| IIL / IIH (control) | −0.65 mA / 20 µA - minimizes loading on upstream address/control drivers in multiplexed bus architectures. |
| ICCZ (standby) | 4 mA max - reduces quiescent power in idle bus segments compared to bipolar-only alternatives. |
Pinout & Package
SN74BCT640N is housed in a 20-pin plastic dual in-line package (PDIP-N), 0.300-inch width, with 0.100-inch lead pitch and through-hole mounting. Pin 1 is marked by a notch or dot at the top-left corner when viewed from the top with leads facing downward.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction control input | Determines data flow direction: DIR = L enables B→A; DIR = H enables A→B. |
| 2–9 (A1–A8) | A-side data I/O | Bi-directional TTL-compatible bus interface pins connected to local subsystem or microprocessor data bus. |
| 10 (GND) | Ground reference | Primary signal return path; must be low-inductance connection to minimize ground bounce in high-speed switching. |
| 11 (VCC) | Power supply | +5 V supply rail; requires local 0.1 µF ceramic decoupling capacitor placed within 10 mm of pin. |
| 12–19 (B1–B8) | B-side data I/O | Bi-directional TTL-compatible bus interface pins connected to peripheral bus, memory module, or expansion backplane. |
| 20 (OE) | Output-enable input | Active-low enable: OE = L activates transceiver; OE = H forces all A/B pins into high-impedance state. |
Key Features
| Feature | Design Value |
|---|---|
| State-of-the-art BiCMOS design | Combines bipolar speed with CMOS input impedance, reducing standby ICCZ to 4 mA while maintaining 64 mA B-port drive capability. |
| Undershoot-protection circuitry | Clamps negative transients below −0.5 V on all I/O pins, preventing latch-up in noisy industrial environments with long trace runs. |
| Power-up high-impedance state | Guarantees no bus contention during power sequencing - critical for hot-swap-capable backplanes and multi-rail systems. |
| Buffered control inputs | Reduces DC loading on DIR and OE lines to ≤20 µA, allowing direct fanout from 74LS-series control logic without buffers. |
| ESD protection ≥2000 V | Meets MIL-STD-883C Method 3015, enabling safe handling and assembly in non-EPA production lines without special grounding protocols. |
Applications
| Industrial Backplane Interface | Legacy Microprocessor Bus Isolation |
|---|---|
|
Use Scenario: Isolating CPU address/data bus from peripheral expansion slots in programmable logic controllers (PLCs) with mixed-voltage modules. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing synchronous read/write cycles between Z80/8086-based main board and field I/O cards. Use Value: Enables clean signal integrity across 15 cm backplane traces via 64 mA B-port drive and undershoot protection, eliminating need for external series resistors or clamps. |
Use Scenario: Interfacing 8-bit microcontroller peripherals (ADCs, DACs, UARTs) to shared data bus in medical diagnostic equipment. IC Role / Device Role / Timing Role: Direction-controlled data bridge that prevents bus contention during simultaneous access attempts by multiple peripherals. Use Value: Power-up high-impedance state eliminates boot-time glitches; tPHL < 3.7 ns ensures timing compliance with 8 MHz CPU clock domains. |
| Test Equipment Bus Arbitration | Automated Test Fixture Data Routing |
|
Use Scenario: Dynamic reconfiguration of signal paths in automated test systems where DUT interfaces switch between digital I/O, analog stimulus, and serial comms. IC Role / Device Role / Timing Role: Reconfigurable bus coupler controlled by FPGA logic to route data between instrument controller and modular measurement heads. Use Value: Buffered DIR/OE inputs tolerate FPGA GPIO leakage; 20 µA IIH allows direct connection without pull-up resistors, simplifying PCB layout. |
Use Scenario: Signal routing between PC-based test host and custom sensor interface boards in factory calibration stations. IC Role / Device Role / Timing Role: Level-translating bus repeater ensuring TTL-compatible signaling across isolated power domains in safety-critical fixtures. Use Value: 5.5 V absolute max I/O rating accommodates transient overshoot from relay-driven bus switching; RoHS-compliant NIPDAU finish meets export compliance requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ACT640N | AC-family CMOS; lower ICCZ (2 µA), higher VOH (4.4 V), but only 24 mA B-port sink current. | Better for low-power, noise-immune systems; unsuitable for high-current bus stubs or legacy TTL loads requiring >48 mA drive. | Select SN74ACT640N only if system uses pure CMOS logic and load currents stay below 24 mA. |
| SN74LS640N | Bipolar TTL; higher ICCZ (60 mA), slower propagation (tPLH up to 25 ns), no undershoot protection. | Compatible with older 74LS designs but generates more heat and lacks modern ESD robustness. | Choose SN74LS640N only for exact form-fit replacement in existing LS-based boards where BiCMOS benefits are not required. |
Compared with SN74ACT640N and SN74LS640N, the SN74BCT640N uniquely balances high-current drive (64 mA), low standby current (4 mA), and industrial-grade transient protection - making it optimal for upgrading legacy systems where both performance and ruggedness matter.
Availability
SN74BCT640N is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy microprocessor bus isolation, and automated test fixture data routing requiring stable component supply across extended product lifecycles.
Supply support for SN74BCT640N 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 for industrial, automotive, and communications markets.
The SN74BCT640N belongs to TI's BCT (Bipolar-CMOS Transceiver) logic family, engineered specifically for high-drive, low-quiescent-current bidirectional bus interfacing in mixed-technology systems requiring TTL compatibility and enhanced ruggedness.
FAQ
What is the maximum continuous output current supported by SN74BCT640N on the B port?
The SN74BCT640N supports up to 64 mA of continuous low-level output current (IOL) on each B-port pin at VCC = 4.5 V, as specified in the electrical characteristics table. This rating ensures reliable drive into heavily loaded TTL bus stubs and termination networks without thermal derating under standard 0°C to 70°C operation.
Does SN74BCT640N require external pull-up resistors on DIR or OE inputs?
No, SN74BCT640N does not require external pull-up resistors on DIR or OE inputs because its buffered control inputs draw only 20 µA (IIH) at VI = 2.7 V and −0.65 mA (IIL) at VI = 0.5 V. These values allow direct connection to standard TTL or CMOS logic outputs without additional biasing components.
Can SN74BCT640N operate with a 3.3 V supply?
No, SN74BCT640N 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 voltage is 7 V. Operating below 4.5 V risks failure to meet VOH/VOL specifications and may cause undefined logic states or increased propagation delay.
What is the purpose of the undershoot-protection circuitry in SN74BCT640N?
The undershoot-protection circuitry in SN74BCT640N clamps negative voltage transients below −0.5 V on all I/O pins, preventing damage and latch-up caused by signal reflections or inductive kickback in long-trace or unterminated bus configurations - a common requirement in industrial PLC backplanes and test equipment.
Is SN74BCT640N pin-compatible with SN74LS640N?
Yes, SN74BCT640N is pin-compatible with SN74LS640N in the PDIP-20 (N) package: both share identical pin count, pinout assignment, and mechanical footprint. However, SN74BCT640N offers superior electrical performance including lower ICCZ, faster propagation, and built-in undershoot protection - enabling drop-in upgrades in many legacy designs.
SN74BCT640N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74BCT
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- 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:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74BCT640N FAQ
1.How can I place an order for SN74BCT640N through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74BCT640N 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 SN74BCT640N reliable?
The price and inventory of SN74BCT640N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74BCT640N is usually 5 days.
3.What payment methods are accepted for SN74BCT640N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74BCT640N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74BCT640N?
SN74BCT640N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74BCT640N 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 SN74BCT640N?
For technical support, including SN74BCT640N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74BCT640N requirements.
6.How does Aetrix verify that SN74BCT640N is sourced from the original manufacturer or authorized distributors?
All SN74BCT640N 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 SN74BCT640N meets industry standards.
7.What is the process for return or replacement of SN74BCT640N?
All SN74BCT640N units undergo pre-shipment inspection (PSI). If there is an issue with SN74BCT640N, 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 SN74BCT640N part is unused and in its original packaging.
Return procedure for SN74BCT640N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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