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Texas Instruments SN74BCT245NS
- Part No.:
- SN74BCT245NS
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74BCT245NS.pdf
- Description:
- PROTOTYPE
- Quantity:
- Payment:
- Shipping:
Inventory:4,705
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Product details
Overview
SN74BCT245NS from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in TTL-level systems. It features direction control (DIR), output enable (OE), 5 V supply operation, ±128 mA sink capability on B-port outputs, and ESD protection exceeding 2000-V HBM. It is commonly used to isolate or buffer memory address registers in industrial control backplanes.
For engineers reviewing the SN74BCT245NS datasheet, SN74BCT245NS pinout, SN74BCT245NS application, or SN74BCT245NS equivalent, key selection criteria include its 20-pin SOP-NS package, 3-state bus isolation behavior, 7 ns max propagation delay (A↔B), 64 mA B-port low-level drive, and compatibility with legacy 5 V TTL logic families.
Technical Context
The SN74BCT245NS implements dual 8-bit bidirectional data paths controlled by DIR and OE inputs. When OE is low, data flows either A→B (DIR = high) or B→A (DIR = low); when OE is high, all outputs enter high-impedance state, electrically isolating both buses. Its BCT (Bipolar-CMOS-TTL) process delivers TTL-compatible input thresholds and CMOS-level power efficiency.
It operates strictly within 4.5 V to 5.5 V supply range and supports full 5 V TTL signal levels at inputs and outputs. The device exhibits asymmetric drive strength: B-port sinks up to 64 mA (IOL), while A-port sinks only 24 mA - a design choice reflecting typical bus driver/receiver asymmetry in memory interface applications.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - ensures compatibility with standard 5 V TTL power rails and tolerance against rail droop. |
| B-port IOL (max) | 64 mA - enables direct driving of multiple TTL loads or termination-resistor networks without external buffers. |
| tPLH / tPHL (max) | 7 ns - supports reliable data transfer up to ~70 MHz in short-bus configurations with 50 pF load. |
| ESD Protection | ≥2000 V HBM - meets JEDEC JESD22-A114-A, reducing risk of handling damage in manufacturing environments. |
| Operating Temperature | 0°C to 70°C - rated for commercial-grade industrial equipment and embedded control systems. |
| Package Thermal Impedance | 60°C/W (θJA) - allows sustained operation at full drive strength without forced cooling in typical PCB layouts. |
| Input Clamp Current | –18 mA - limits transient overvoltage stress on control inputs during hot-swap or fault conditions. |
Pinout & Package
SOP-NS (Small Outline Package, Narrow, 20-pin) with 0.65 mm lead pitch, 7.4 mm × 5.3 mm body, and 2.0 mm max height. RoHS-compliant, NIPDAU lead finish, MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | DIR | Direction control input: high = A→B, low = B→A; TTL-compatible threshold (VIL ≤ 0.8 V, VIH ≥ 2 V). |
| 2–9 | A1–A8 | Input/output port A: bidirectional data lines connected to local subsystem (e.g., microcontroller address/data bus). |
| 10 | GND | Ground reference for all internal circuitry and I/O terminals. |
| 11 | VCC | +5 V supply input; decoupling capacitor required near pin for noise suppression. |
| 12 | OE | Output enable active-low: low = enabled, high = 3-state isolation; critical for bus arbitration and power sequencing. |
| 13–20 | B1–B8 | Input/output port B: bidirectional data lines connected to shared system bus (e.g., memory or peripheral expansion bus). |
Key Features
| Feature | Design Value |
|---|---|
| Asymmetric Output Drive | B-port sinks 64 mA vs. A-port's 24 mA - optimized for driving heavier-loaded system buses while minimizing local-side loading. |
| Fast 3-State Enable/Disable | tPZL/tPLZ ≤ 11.6 ns - minimizes bus contention window during direction or enable transitions in real-time systems. |
| TTL-Compatible Interface | VIH = 2 V, VIL = 0.8 V, VOH ≥ 2.4 V @ –15 mA - ensures seamless interoperability with legacy 74LS/74ALS logic without level shifters. |
| Low ICCZ Quiescent Current | 10–15 mA - reduces standby power in always-on bus isolation applications compared to standard TTL transceivers. |
| Robust Input Clamping | VIK = –1.2 V @ –18 mA - protects inputs from negative transients during hot-plug or cable discharge events. |
Applications
| Industrial Backplane Isolation | Memory Address Buffering |
|---|---|
|
Use Scenario: Isolating CPU address/data bus from modular I/O expansion slots in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional bus transceiver enabling dynamic read/write access while preventing signal contention during slot insertion/removal. Use Value: Enables hot-swap-capable backplane architecture using single SN74BCT245NS per 8-bit lane, eliminating need for discrete bus switches or FPGA glue logic. |
Use Scenario: Driving 8-bit segment of a 16-bit memory address bus from a microcontroller with limited drive strength. IC Role / Device Role / Timing Role: Unidirectional buffer (A→B mode) with 3-state disable, synchronized to memory access strobes. Use Value: Provides 64 mA B-port sink current to meet TTL fan-out requirements for multiple SRAM chips, reducing timing skew versus discrete transistor buffers. |
| Legacy System Bus Extension | Test Equipment Signal Routing |
|
Use Scenario: Extending a vintage 5 V TTL bus across a multi-board test fixture with impedance-matched trace lengths. IC Role / Device Role / Timing Role: Direction-controlled repeater operating in A↔B mode, with OE tied to system reset for safe power-up initialization. Use Value: Maintains signal integrity over 15 cm traces at 20 MHz due to 7 ns propagation delay and low output capacitance (Cio = 12 pF). |
Use Scenario: Configurable signal path routing in automated test equipment where DUT interfaces must be dynamically isolated or looped. IC Role / Device Role / Timing Role: 3-state bus switch controlled by FPGA GPIOs; DIR selects signal direction, OE enables/disables path. Use Value: Achieves sub-12 ns path enable/disable latency and <0.5 V VOL under 48 mA load - critical for deterministic test cycle timing. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS245N | Lower drive (IOL = 24 mA), higher ICC (40 mA typ), slower (tPLH = 15 ns), PDIP-only packaging. | Legacy board replacements where speed and power are secondary to footprint compatibility. | Choose when retrofitting into existing LS-based designs with no layout change; avoid for new designs requiring >5 MHz operation. |
| SN74LVC245APW | 3.3 V only (1.65–3.6 V), higher speed (tPLH = 4.5 ns), lower power (ICCZ = 10 µA), TSSOP-20 package. | Modern low-voltage systems requiring level translation between 3.3 V and 5 V domains via external resistors. | Prefer for new 3.3 V designs needing lower static power and faster timing; requires voltage translation for 5 V bus interfacing. |
Compared with SN74LS245N, SN74BCT245NS offers 2× higher B-port drive and 2× faster propagation, enabling denser bus loading and higher clock rates; compared with SN74LVC245APW, it provides native 5 V tolerance and stronger drive but consumes more quiescent power and lacks 3.3 V compatibility.
Availability
SN74BCT245NS is available at Aetrix Electronics and suitable for industrial backplane isolation, memory address buffering, legacy system bus extension, and test equipment signal routing requiring stable component supply and long-term obsolescence management.
Supply support for SN74BCT245NS 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 50 years of innovation in industrial and automotive electronics.
The SN74BCT245NS belongs to TI's BCT-series logic family, engineered specifically for robust 5 V TTL bus interfacing in industrial control, instrumentation, and legacy system upgrades where reliability and drive strength outweigh ultra-low power requirements.
FAQ
What is the maximum capacitive load the SN74BCT245NS can drive while maintaining specified timing?
The SN74BCT245NS is characterized for CL = 50 pF in switching specifications, with tPLH/tPHL ≤ 7 ns under those conditions. At 100 pF, typical propagation delay increases to ~9 ns - still functional but outside guaranteed spec. For reliable 7 ns performance, keep total load (trace + stub + receiver input) ≤ 50 pF, using series termination if needed.
Can the SN74BCT245NS operate with a 3.3 V supply?
No. The SN74BCT245NS requires VCC between 4.5 V and 5.5 V per its recommended operating conditions. Applying 3.3 V will result in undefined logic levels, degraded noise margins, and potential failure to meet VOL/VOH specs. For 3.3 V systems, consider SN74LVC245A instead.
How should unused inputs be handled on the SN74BCT245NS?
All unused inputs - including DIR and OE - must be tied to VCC or GND. Floating control inputs cause increased ICC, erratic 3-state behavior, and possible latch-up. TI recommends tying OE to VCC (disabled state) and DIR to GND or VCC depending on default direction requirement, using 10 kΩ pull-up/down resistors if driven by open-collector sources.
Is the SN74BCT245NS pin-compatible with other packages in the same family?
Yes - all SN74BCT245 variants (NS, DW, DB, PW, N) share identical 20-pin functional pinout and logic behavior. However, mechanical dimensions, thermal performance (e.g., θJA = 60°C/W for NS vs. 58°C/W for DW), and reflow profiles differ. Layout changes are required when swapping packages due to footprint incompatibility.
Does the SN74BCT245NS support hot-swap operation?
The SN74BCT245NS has no built-in hot-swap protection, but its 3-state outputs and robust input clamping (VIK = –1.2 V) allow safe use in hot-plug scenarios when OE is held high until power stabilizes. TI recommends sequencing VCC before applying signals and using series resistors on A/B lines to limit inrush current during insertion.
SN74BCT245NS Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74BCT
- Package/Case:
- 20-SOIC (0.209", 5.30mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Logic Type:
- Transceiver, Non-Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 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
SN74BCT245NS FAQ
1.How can I place an order for SN74BCT245NS through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74BCT245NS 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 SN74BCT245NS reliable?
The price and inventory of SN74BCT245NS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74BCT245NS is usually 5 days.
3.What payment methods are accepted for SN74BCT245NS?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74BCT245NS transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74BCT245NS?
SN74BCT245NS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74BCT245NS 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 SN74BCT245NS?
For technical support, including SN74BCT245NS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74BCT245NS requirements.
6.How does Aetrix verify that SN74BCT245NS is sourced from the original manufacturer or authorized distributors?
All SN74BCT245NS 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 SN74BCT245NS meets industry standards.
7.What is the process for return or replacement of SN74BCT245NS?
All SN74BCT245NS units undergo pre-shipment inspection (PSI). If there is an issue with SN74BCT245NS, 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 SN74BCT245NS part is unused and in its original packaging.
Return procedure for SN74BCT245NS:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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