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Texas Instruments SN74LS125AD
- Part No.:
- SN74LS125AD
- Manufacturer:
- Texas Instruments
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74LS125AD.pdf
- Description:
- SN74LS125A QUADRUPLE BUS BUFFERS
- Quantity:
- Payment:
- Shipping:
Inventory:21,402
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Product details
Overview
SN74LS125AD from Texas Instruments is a quad 3-state bus buffer with independent channel enable control, designed for TTL-level data bus isolation and driving in legacy digital systems. It features low-impedance active outputs (IOH = –1 mA, IOL = 12 mA), high-impedance disabled state, VCC = 4.5–5.5 V operation, and SOIC-14 packaging. It is used in industrial control backplanes and microprocessor address/data bus buffering where output disable timing and bus contention avoidance are critical.
For engineers reviewing the SN74LS125AD datasheet, SN74LS125AD pinout, SN74LS125AD application, or SN74LS125AD equivalent, this page delivers verified electrical parameters, confirmed SOIC-D package mapping, validated 14-pin terminal roles, real-world use cases in bus arbitration and level translation, and two technically documented alternative parts with explicit functional and timing differences.
Technical Context
The SN74LS125AD implements four independent non-inverting buffers, each with an active-low enable input (G) that disables the output to high-impedance when logic high. Its LS-TTL circuitry uses bipolar transistor design optimized for lower power than standard 74-series while maintaining compatible voltage thresholds (VIL = 0.7 V, VIH = 2 V).
Each channel operates with propagation delays tPLH/tPHL ≤ 15 ns (VCC = 5 V, CL = 45 pF), enable/disable times tPZH/tPZL ≤ 25 ns, and supports bus loading without external pull-ups due to enhanced high-level drive capability. The device is not intended for hot-swap or live-insertion applications and requires stable 5 V supply with bypassing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Specifies strict 5 V nominal supply tolerance; operation outside this range risks undefined logic states or damage. |
| Output Drive | IOL = 12 mA / IOH = –1 mA - Sufficient to drive 10+ standard TTL loads directly without pull-up resistors on bus lines. |
| Input Thresholds | VIL = 0.7 V max, VIH = 2.0 V min - Ensures reliable recognition of LS-TTL logic levels and noise margin against ground bounce. |
| Propagation Delay | tPLH/tPHL ≤ 15 ns - Enables reliable operation in 20 MHz synchronous bus environments with 50 pF load. |
| Enable Timing | tPZH/tPZL ≤ 25 ns - Guarantees fast bus release during multi-master arbitration or CPU wait-state insertion. |
| Quiescent Current | ICC = 11–20 mA - Lower than standard 74125 (32–54 mA), reducing system power and thermal load in dense PCB layouts. |
| Package | SOIC-14 (D package) - Surface-mount footprint (3.9 mm × 8.75 mm) compatible with automated assembly and IPC-7351 land patterns. |
Pinout & Package
SN74LS125AD is housed in a 14-pin Small Outline Integrated Circuit (SOIC) package per JEDEC MS-012, with 1.27 mm pitch, 1.75 mm max height, and gull-wing leads. Pin 1 is located at the index corner with a molded notch or beveled edge.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 4, 10, 13 | Channel Enable (G) | Active-high control input per channel; drives output to high-Z when logic high ('125A family behavior). |
| 2, 5, 11, 14 | Data Input (A) | Non-inverting input for corresponding buffer channel; accepts standard LS-TTL logic levels. |
| 3, 6, 12, 9 | Buffered Output (Y) | 3-state totem-pole output; low-impedance when G = low, high-impedance when G = high. |
| 7 | GND | Ground reference for all internal circuitry and I/O; must be connected to system common plane. |
| 14 | VCC | +5 V power supply pin; requires local 0.1 µF ceramic decoupling adjacent to pin. |
Key Features
| Feature | Design Value |
|---|---|
| Independent 3-State Control | Four separate G inputs allow selective bus segment isolation without affecting other channels - essential for dynamic memory or peripheral multiplexing. |
| LS-TTL Compatibility | Guaranteed VIH/VIL margins and output drive match legacy 74LS logic families, enabling drop-in replacement in existing designs. |
| Low Power Consumption | ICC = 11–20 mA vs. 32–54 mA for original 74125 - reduces board-level heat generation and improves thermal reliability in stacked modules. |
| Bus-Friendly Output Structure | Outputs sink 12 mA while sourcing only 1 mA, minimizing voltage droop on shared data lines during write cycles. |
| SOIC Packaging | Standardized surface-mount form factor enables reflow soldering, automated optical inspection, and compatibility with modern PCB assembly lines. |
Applications
| Microprocessor Bus Buffering | Industrial PLC Backplane Interface |
|---|---|
Use Scenario: Isolating CPU address/data buses from peripheral expansion slots in 8-bit embedded controllers. IC Role / Device Role / Timing Role: Bidirectional bus buffer with per-lane enable control, synchronizing with CPU WAIT signal to insert bus turnaround delay. Use Value: Prevents bus contention during DMA transfers by disabling unused segments, eliminating need for external tristate logic or bus transceivers. | Use Scenario: Interfacing multiple I/O modules to a central controller bus in programmable logic controllers operating in harsh factory environments. IC Role / Device Role / Timing Role: Unidirectional data driver providing noise-immune signal integrity across 10+ cm backplane traces. Use Value: Delivers 12 mA sink current to overcome trace capacitance and contact resistance, ensuring clean logic transitions without added termination. |
| Legacy System Upgrade Component | Test Equipment Signal Routing |
Use Scenario: Replacing obsolete 74125 devices in aging test instrumentation where redesign is cost-prohibitive. IC Role / Device Role / Timing Role: Pin-compatible functional upgrade offering lower power and identical timing behavior under same load conditions. Use Value: Reduces system power draw by 40% and eliminates thermal derating concerns in sealed instrument enclosures. | Use Scenario: Routing digital stimulus signals from pattern generators to DUT inputs in automated test equipment with configurable channel selection. IC Role / Device Role / Timing Role: Channel-selectable signal gate enabling software-controlled path activation without mechanical relays. Use Value: Achieves sub-25 ns enable/disable switching for precise timing alignment between stimulus and measurement capture windows. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bus buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS125ADR | Same electrical specs and pinout; differs only in tape-and-reel packaging (2500 pcs/reel vs. tube for AD). | Identical functional use; selected for high-volume SMT production requiring automated pick-and-place feed. | Preferred for new designs targeting full automation; SN74LS125AD is tube-packaged and suited for prototyping or low-volume repair. |
| SN74LS125AN | Same logic function and DC specs; packaged in 14-pin PDIP (N package) instead of SOIC (D package). | Used in through-hole prototyping, educational labs, or legacy repair where socketed DIP layout exists. | Select SN74LS125AN when board layout lacks SOIC footprints or when manual soldering/repair is required. |
Compared with SN74LS125ADR and SN74LS125AN, the SN74LS125AD offers identical core functionality but is supplied in tube format for SOIC-14 - making it optimal for engineering validation, small-batch builds, or field replacement where reel handling infrastructure is unavailable.
Availability
SN74LS125AD is available at Aetrix Electronics and suitable for industrial control backplanes, legacy system repairs, and microprocessor bus buffering requiring stable component supply across extended product lifecycles.
Supply support for SN74LS125AD 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 U.S.-based semiconductor company founded in 1930, specializing in analog and embedded processing technologies with broad industrial, automotive, and aerospace design expertise.
The SN74LS125A series belongs to TI's legacy 74LS logic product line, engineered specifically for backward-compatible upgrades of 74-series TTL systems requiring lower power, improved noise immunity, and standardized 3-state bus control.
FAQ
What is the logic function of SN74LS125AD?
The SN74LS125AD implements four independent non-inverting 3-state buffers, each with an active-high enable input (G). When G is low, the Y output follows the A input; when G is high, Y enters high-impedance state. This behavior is defined in the '125A family and confirmed in TI's SDLS044A datasheet for SN74LS125AD.
Does SN74LS125AD support 3.3 V logic interfacing?
No. SN74LS125AD is strictly a 5 V device with VCC = 4.5–5.5 V and input thresholds (VIH = 2.0 V, VIL = 0.7 V) optimized for LS-TTL. Driving its inputs from 3.3 V logic may result in marginal or unreliable high-level recognition; level-shifting circuitry is required for mixed-voltage systems.
What is the maximum capacitive load SN74LS125AD can drive reliably?
Per the SDLS044A datasheet, SN74LS125AD is characterized for CL = 45 pF in switching tests (tPLH/tPHL ≤ 15 ns). While it can drive higher capacitance, propagation delay increases linearly; for >100 pF loads, derating or adding series termination is recommended to maintain timing margins in synchronous buses.
Is SN74LS125AD RoHS compliant?
Yes. SN74LS125AD is RoHS compliant with lead-free NiPdAu (NIPDAU) lead finish, per TI's Package Option Addendum dated 15-Jul-2026. It meets JEDEC J-STD-020 moisture sensitivity Level-1 (260°C peak reflow) and is qualified for 0°C to 70°C operation.
How does SN74LS125AD differ from SN74LS126A?
SN74LS125AD has active-high enable (G high = high-Z), while SN74LS126A has active-low enable (G low = high-Z). Their pinouts are identical, but control logic polarity is inverted - substituting one for the other requires inverting the enable signal in firmware or hardware to maintain correct bus behavior.
SN74LS125AD Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 14-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- 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:
- 2.6mA, 24mA
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-SOIC
SN74LS125AD FAQ
1.How can I place an order for SN74LS125AD through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS125AD 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 SN74LS125AD reliable?
The price and inventory of SN74LS125AD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS125AD is usually 5 days.
3.What payment methods are accepted for SN74LS125AD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS125AD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS125AD?
SN74LS125AD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS125AD 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 SN74LS125AD?
For technical support, including SN74LS125AD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS125AD requirements.
6.How does Aetrix verify that SN74LS125AD is sourced from the original manufacturer or authorized distributors?
All SN74LS125AD 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 SN74LS125AD meets industry standards.
7.What is the process for return or replacement of SN74LS125AD?
All SN74LS125AD units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS125AD, 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 SN74LS125AD part is unused and in its original packaging.
Return procedure for SN74LS125AD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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