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Texas Instruments SN74BCT125AD
- Part No.:
- SN74BCT125AD
- Manufacturer:
- Texas Instruments
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74BCT125AD.pdf
- Description:
- IC BUF NON-INVERT 5.5V 14SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,446
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Product details
Overview
SN74BCT125AD from Texas Instruments is a quadruple bus buffer gate with 3-state outputs, designed for bidirectional data bus isolation and memory address register buffering in 5-V TTL-compatible systems. It operates from 4.5 V to 5.5 V, delivers 128 mA low-level output current per channel, and features BiCMOS logic for reduced ICCZ quiescent current. Used in industrial control backplanes and legacy computing address latching.
For engineers reviewing the SN74BCT125AD datasheet, SN74BCT125AD pinout, SN74BCT125AD application, or SN74BCT125AD equivalent, key selection criteria include 3-state enable timing (tPZH = 3.4 ns min), output drive strength (IOL = 64 mA), thermal resistance (θJA = 86°C/W), and SOIC-14 package compatibility with legacy PCB layouts.
Technical Context
The SN74BCT125AD implements four independent non-inverting buffers, each with dedicated active-low output-enable (OE) control. Its BiCMOS architecture combines bipolar input stages for TTL-level compatibility and CMOS output stages for high-current drive and low standby power.
Each channel supports true 3-state operation: output is high (VOH ≥ 2.4 V at IOH = –12 mA), low (VOL ≤ 0.55 V at IOL = 64 mA), or high-impedance (IOZH ≤ 50 µA, IOZL ≥ –50 µA) based on OE state. Propagation delays range from tPLH = 1.6 ns to tPHL = 2.7 ns under 5-V/50-pF conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - Ensures robust operation across industrial 5-V rail tolerances. |
| Output Drive (IOL) | 64 mA - Sufficient to drive 50-pF bus loads with <7.7 ns tPHL delay. |
| 3-State Leakage | ±50 µA - Minimizes bus contention current when outputs are disabled. |
| Propagation Delay | 1.6–6.9 ns - Measured A→Y and OE→Y transitions define timing margins for synchronous bus handshaking. |
| Input Thresholds | VIL = 0.8 V, VIH = 2.0 V - Matches standard TTL logic levels for seamless interface with legacy controllers. |
| Thermal Resistance | θJA = 86°C/W - SOIC-14 package requires minimal heatsinking in ambient ≤70°C environments. |
| Operating Temperature | 0°C to 70°C - Qualified for commercial-grade embedded systems and instrumentation. |
Pinout & Package
SN74BCT125AD uses a 14-pin SOIC (D) package with 1.27-mm pitch, 8.75 mm × 3.9 mm body, and 1.75 mm max height. Pin 1 is marked by a beveled corner or dot; device orientation follows JEDEC MS-012AB standard.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 4, 10, 13 | Output Enable (1OE, 2OE, 3OE, 4OE) | Active-low control: high = high-Z output; tied to VCC via pullup for power-up safety. |
| 2, 5, 11, 14 | Input (1A, 2A, 3A, 4A) | TTL-compatible inputs accepting 0.8 V/2.0 V thresholds; must be terminated to VCC or GND if unused. |
| 3, 6, 12, 9 | Output (1Y, 2Y, 3Y, 4Y) | Non-inverting buffered outputs capable of sourcing –12 mA or sinking 64 mA into 50-pF loads. |
| 7 | GND | Ground reference for all logic and output stages; requires low-inductance connection to system ground plane. |
| 14 | VCC | Positive supply (4.5–5.5 V); bypass capacitor (0.1 µF ceramic) required adjacent to pin. |
Key Features
| Feature | Design Value |
|---|---|
| BiCMOS process technology | Reduces ICCZ to 6–14 mA versus 19–49 mA in pure bipolar equivalents, lowering system power in idle states. |
| Independent 3-state controls | Four separate OE pins allow selective bus segment isolation without gating entire data paths. |
| TTL-input / CMOS-output compatibility | Accepts standard TTL voltage thresholds while delivering CMOS-level drive strength and noise margin. |
| High-speed enable/disable timing | tPZH = 3.4 ns min and tPLZ = 2.8 ns min ensure rapid bus arbitration in multiplexed memory systems. |
| Robust absolute ratings | Withstands –0.5 V to 7 V on inputs/outputs and –55°C to 150°C storage, supporting rework and harsh environment handling. |
Applications
| Memory Address Buffering | Industrial Backplane Isolation |
|---|---|
Use Scenario: Latching CPU address lines to multiple peripheral decoders in a modular PLC rack. IC Role / Device Role / Timing Role: Non-inverting buffer with per-channel 3-state control isolates address bus segments during DMA cycles. Use Value: 64 mA drive ensures clean signal integrity across 20-cm backplane traces; tPHL < 7.7 ns meets 12-MHz bus timing budgets. | Use Scenario: Preventing signal contention between hot-swappable I/O modules sharing a common data bus. IC Role / Device Role / Timing Role: Bus buffer enabling/disabling module-specific data lanes via independent OE signals. Use Value: ±50 µA 3-state leakage avoids cumulative bus loading; SOIC-14 footprint fits dense Eurocard layouts. |
| Legacy System Bus Expansion | Test Equipment Signal Routing |
Use Scenario: Extending ISA or VMEbus address/data paths in retro-computing hardware restoration. IC Role / Device Role / Timing Role: Level-shifting and fanout buffer matching TTL logic families across mixed-vendor boards. Use Value: VIH/VIL thresholds align precisely with 74LS/74ALS families; 128 mA sink capability drives multiple TTL inputs. | Use Scenario: Multiplexing DUT signals to measurement instruments in automated test fixtures. IC Role / Device Role / Timing Role: Controlled signal path selector using OE pins as digital switches for channel routing. Use Value: Sub-10 ns enable/disable transitions support 100-MHz switching rates; low ICCZ reduces fixture self-heating. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bus buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS125N | Lower drive (IOL = 24 mA), higher ICC (46 mA), slower tPHL (15 ns), PDIP-only packaging. | Suitable only for low-speed, low-fanout TTL systems; lacks BiCMOS power efficiency. | Select when cost-sensitive, low-frequency designs require pin-compatible drop-in replacement with no layout change. |
| SN74ACT125DR | Higher speed (tPHL = 2.5 ns), wider VCC range (4.5–5.5 V), lower VOL (0.35 V), but higher ICCZ (20 µA). | Better for high-noise environments requiring tighter VOH/VOL margins; not drop-in due to different input thresholds. | Choose for new designs needing faster edge rates and improved noise immunity, accepting minor schematic updates. |
Compared with SN74BCT125AD, SN74LS125N trades performance for cost and legacy compatibility, while SN74ACT125DR improves speed and noise margin at the expense of slightly higher 3-state leakage-making SN74BCT125AD optimal for balanced 5-V bus isolation where power, speed, and TTL interoperability are jointly critical.
Availability
SN74BCT125AD is available at Aetrix Electronics and suitable for industrial control backplanes, legacy computing address latching, and test equipment signal routing requiring stable component supply and long-term obsolescence management.
Supply support for SN74BCT125AD 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 SN74BCT125AD belongs to TI's legacy BCT logic family, engineered specifically for high-drive, low-power 5-V bus interfacing in industrial and computing infrastructure where TTL compatibility and reliability are mandatory.
FAQ
What is the maximum operating temperature range for the SN74BCT125AD?
The SN74BCT125AD is rated for operation from 0°C to 70°C, meeting commercial-grade specifications. Its absolute maximum storage temperature is –65°C to 150°C, and it withstands transient supply voltages up to 7 V. This range supports deployment in enclosed industrial enclosures and office-based test equipment without forced cooling.
How does the SN74BCT125AD handle unused input pins?
All unused inputs on the SN74BCT125AD must be held at a valid logic level-either tied to VCC or GND-to prevent floating nodes that could cause excessive ICC or erratic output behavior. TI's application report SCBA004 explicitly mandates this practice for reliable operation, as uncontrolled inputs may trigger internal shoot-through currents in the BiCMOS structure.
Can the SN74BCT125AD be used in place of the SN74LS125 in existing designs?
Yes, the SN74BCT125AD is pin-compatible and functionally equivalent to the SN74LS125, but offers superior performance: 64 mA vs. 24 mA output drive, 1.6 ns vs. 15 ns propagation delay, and 6 mA vs. 46 mA ICC. No PCB changes are required, though decoupling and layout best practices for higher-speed operation should be verified.
What is the recommended pull-up resistor value for the OE pins on the SN74BCT125AD?
The minimum pull-up resistor value for SN74BCT125AD OE pins is determined by the driver's current-sinking capability. With IIL = –20 µA max at VI = 0.5 V, a 10-kΩ resistor to VCC ensures OE remains solidly high during power-up while limiting current to <0.5 mA. TI recommends values between 4.7 kΩ and 10 kΩ for robust noise immunity and fast disable timing.
Does the SN74BCT125AD support hot-swap or live-insertion applications?
The SN74BCT125AD is not characterized for hot-swap operation. Its absolute maximum ratings permit –0.5 V to 5.5 V on outputs in the disabled state, but no controlled slew-rate or bus-fault protection is integrated. For live-insertion, external series resistors and TVS diodes are required; TI recommends evaluating SN74CBT125C or dedicated hot-swap controllers instead.
SN74BCT125AD Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74BCT
- Package/Case:
- 14-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Logic Type:
- Buffer, Non-Inverting
- Number of Elements:
- 4
- Number of Bits per Element:
- 1
- 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:
- 14-SOIC
SN74BCT125AD FAQ
1.How can I place an order for SN74BCT125AD through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74BCT125AD 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 SN74BCT125AD reliable?
The price and inventory of SN74BCT125AD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74BCT125AD is usually 5 days.
3.What payment methods are accepted for SN74BCT125AD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74BCT125AD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74BCT125AD?
SN74BCT125AD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74BCT125AD 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 SN74BCT125AD?
For technical support, including SN74BCT125AD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74BCT125AD requirements.
6.How does Aetrix verify that SN74BCT125AD is sourced from the original manufacturer or authorized distributors?
All SN74BCT125AD 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 SN74BCT125AD meets industry standards.
7.What is the process for return or replacement of SN74BCT125AD?
All SN74BCT125AD units undergo pre-shipment inspection (PSI). If there is an issue with SN74BCT125AD, 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 SN74BCT125AD part is unused and in its original packaging.
Return procedure for SN74BCT125AD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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