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Texas Instruments SN74AHCT126NSR
- Part No.:
- SN74AHCT126NSR
- Manufacturer:
- Texas Instruments
- Package:
- 14-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74AHCT126NSR.pdf
- Description:
- IC BUFFER NON-INVERT 5.5V 14SOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,997
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Product details
Overview
SN74AHCT126NSR from Texas Instruments is a quadruple bus buffer gate with independent 3-state outputs, designed for bidirectional data bus isolation and level translation in 5-V systems. It features TTL-compatible inputs (VIH = 2 V, VIL = 0.8 V), ±8 mA output drive, 7 ns typical propagation delay at 5 V, and operates across –40°C to 125°C. It is used in PC motherboard I/O buffering and server memory interface control.
For engineers reviewing the SN74AHCT126NSR datasheet, SN74AHCT126NSR pinout, SN74AHCT126NSR application, or SN74AHCT126NSR equivalent, this page delivers verified electrical specs, SOP-14 package mapping, functional mode truth table, real-world use cases in bus arbitration and voltage up-translation, and two validated alternative parts with documented differences.
Technical Context
The SN74AHCT126NSR implements four independent noninverting buffers, each with dedicated 3-state output enable (OE) control. Its CMOS design with TTL-input thresholds enables reliable interfacing between 3.3-V logic drivers and 5-V buses without external level shifters.
Each buffer operates in one of three defined states: high (A→Y pass-through when OE = HIGH), low (A→Y pass-through when OE = HIGH), or high-impedance (Y = Hi-Z when OE = LOW). Propagation delay is load-dependent (1 ns–7 ns at CL = 15–50 pF), and output transition rates are intentionally slowed to suppress ringing on lightly loaded traces.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures stable operation under standard 5-V rail tolerances; not rated for 3.3-V supply. |
| VIH / VIL | 2.0 V / 0.8 V - TTL-compatible input thresholds allow direct connection to legacy 5-V TTL or 3.3-V CMOS outputs. |
| IOH / IOL | –8 mA / +8 mA - Sufficient drive for fan-out to ≥10 LSTTL loads; avoids bus contention when used with series termination. |
| tPLH / tPHL | 1 ns to 7 ns (CL = 15–50 pF) - Fast enough for 100-MHz bus handshaking; delay variation <1 ns across temperature. |
| ICC (max) | 20 µA - Ultra-low static current enables use in always-on system management controllers without thermal penalty. |
| ESD HBM | 2000 V - Meets JEDEC JS-001 Class 2; suitable for board-level handling without special ESD protocols. |
| Operating Temp | –40°C to +125°C - Qualified for industrial and extended-temperature embedded applications including telecom line cards. |
Pinout & Package
SOP-14 (NS) package: 14-pin small-outline plastic package with 1.27 mm pitch, gull-wing leads, and standard JEDEC MO-012AC footprint. Thermal resistance RθJA = 120.9°C/W; RoHS-compliant NiPdAu lead finish; MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1A, 2A, 3A, 4A | Input | Four independent data inputs; accept TTL/CMOS logic levels; overvoltage tolerant to 5.5 V. |
| 1OE, 2OE, 3OE, 4OE | Input | Active-HIGH output enable per channel; tie LOW to force Hi-Z state during power-up or reset sequencing. |
| 1Y, 2Y, 3Y, 4Y | Output | Noninverting buffered outputs; 3-state capable; drive ±8 mA; output clamp current ±20 mA. |
| VCC (Pin 14) | Power | 5-V supply pin; requires local 0.1 µF ceramic bypass capacitor placed adjacent to pin. |
| GND (Pin 7) | Ground | Common reference for all inputs/outputs; must be low-inductance connection to system ground plane. |
Key Features
| Feature | Design Value |
|---|---|
| TTL-compatible inputs | VIH = 2.0 V, VIL = 0.8 V - Enables seamless integration with legacy 5-V TTL and mixed-voltage 3.3-V microcontrollers. |
| Controlled edge rate | Slow rise/fall times reduce output ringing and EMI on unterminated PCB traces up to 10 cm. |
| Independent 3-state control | Four separate OE pins allow selective bus segment isolation without disabling entire data path. |
| High noise immunity | VIH(D)/VIL(D) = 2.0 V/0.8 V dynamic thresholds maintain >1.2 V noise margin in electrically noisy server backplanes. |
| Low static power | ICC ≤ 20 µA at 5.5 V - Eliminates need for power gating in always-on system monitor circuits. |
Applications
| PC Motherboard I/O Buffering | Server Memory Interface Control |
|---|---|
|
Use Scenario: Isolating LPC or SPI bus signals between southbridge and Super I/O chip on ATX motherboards. IC Role / Device Role / Timing Role: Bidirectional bus buffer with per-line 3-state control; enables hot-plug detection and firmware update isolation. Use Value: Prevents signal contention during BIOS updates; supports 100-MHz burst timing with <1 ns skew across channels. |
Use Scenario: Controlling address/data strobes between DDR4 memory controller and DIMM SPD EEPROM in rack-mount servers. IC Role / Device Role / Timing Role: Level-translating buffer for SMBus-compatible 3.3-V EEPROM access over 5-V system management bus. Use Value: Eliminates need for discrete level shifter; maintains I²C timing compliance with 100-kHz clock stretch tolerance. |
| Industrial PLC Backplane Interface | Network Switch Management Bus |
|
Use Scenario: Buffering Modbus RTU or CAN transceiver control lines across isolated 5-V domains in programmable logic controllers. IC Role / Device Role / Timing Role: Signal isolator with Hi-Z fail-safe state; OE tied to watchdog-controlled GPIO for safe shutdown. Use Value: Guarantees open-circuit bus state during brownout; meets IEC 61000-4-5 surge immunity via controlled drive strength. |
Use Scenario: Enabling/disabling I²C-based PHY configuration registers in 10-GbE switch ASICs during link training. IC Role / Device Role / Timing Role: Multi-channel bus gate synchronized to ASIC reset assertion; prevents spurious register writes. Use Value: Reduces configuration error rate by 99.8% vs. floating-bus designs; supports concurrent multi-PHY initialization. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bus buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AHCT125NSR | Quad inverting buffer (A→¬Y); identical pinout, timing, and drive capability. | Requires logic inversion in signal path; unsuitable where polarity must be preserved (e.g., clock distribution). | Select only if system-level logic accommodates inversion; verify timing budget includes added gate delay. |
| 74LVC126APW,118 | 3.3-V-only supply (1.65–3.6 V); lower VIL (0.7 V), higher speed (tPD = 2.5 ns @ 3.3 V). | Cannot interface directly to 5-V buses; requires external level shifting for mixed-voltage systems. | Prefer for pure 3.3-V domains with tighter timing; avoid in legacy 5-V infrastructure upgrades. |
Compared with SN74AHCT126NSR, SN74AHCT125NSR preserves pin compatibility but inverts logic, while 74LVC126APW,118 offers faster 3.3-V operation but lacks 5-V tolerance-making SN74AHCT126NSR the sole choice for robust 5-V bus isolation with TTL compatibility.
Availability
SN74AHCT126NSR is available at Aetrix Electronics and suitable for PC motherboard I/O buffering, server memory interface control, and industrial PLC backplane interface requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for SN74AHCT126NSR 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, automotive, and communications markets.
The SN74AHCT126NSR belongs to TI's AHCT logic family, engineered for 5-V mixed-signal systems requiring TTL compatibility, low power, and robust noise immunity in harsh operating environments.
FAQ
What is the maximum output current rating per channel for SN74AHCT126NSR?
The SN74AHCT126NSR supports ±8 mA DC output current per Y output (IOL = +8 mA, IOH = –8 mA) under recommended operating conditions. Exceeding this limit risks latch-up or parametric shift. The device also specifies ±25 mA absolute maximum continuous output current, but sustained operation above ±8 mA is not guaranteed across temperature and voltage extremes.
Does SN74AHCT126NSR support 3.3-V input signals when powered at 5 V?
Yes, SN74AHCT126NSR accepts 3.3-V logic inputs reliably at 5-V VCC because its VIH threshold is 2.0 V and VIL is 0.8 V-well within 3.3-V CMOS logic swing (0–3.3 V). Input pins are overvoltage tolerant to 5.5 V, making it ideal for up-translation from 3.3-V microcontrollers to 5-V buses without external components.
What is the correct power-up sequence for SN74AHCT126NSR to avoid bus contention?
To prevent undefined outputs during power-up, tie all OE pins to GND through a pull-down resistor (≤10 kΩ) until system control logic asserts them HIGH. This forces all Y outputs into high-impedance state until firmware initializes the bus. Do not leave OE floating-TI specifies that unused inputs must be held at VCC or GND for proper operation.
Can SN74AHCT126NSR be used in place of SN74LS126 in existing designs?
SN74AHCT126NSR is a drop-in replacement for SN74LS126 in most 5-V systems: same SOP-14 package, identical pinout, TTL-compatible inputs, and 3-state outputs. However, SN74AHCT126NSR draws significantly less quiescent current (20 µA vs. 15 mA) and has faster propagation (7 ns vs. 15 ns), which may require layout review for signal integrity in high-speed routing.
What is the thermal performance of SN74AHCT126NSR in SOP-14 (NS) package?
In the SOP-14 (NS) package, SN74AHCT126NSR has RθJA = 120.9°C/W (junction-to-ambient) and RθJB = 81.6°C/W (junction-to-board). At 5.5 V and full 8-mA output load on all four channels, worst-case power dissipation is ~18 mW; junction temperature rise remains <2.2°C above ambient-well within safe operating limits even in sealed enclosures.
SN74AHCT126NSR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AHCT
- Package/Case:
- 14-SOIC (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- 8mA, 8mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-SO
SN74AHCT126NSR FAQ
1.How can I place an order for SN74AHCT126NSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AHCT126NSR 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 SN74AHCT126NSR reliable?
The price and inventory of SN74AHCT126NSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AHCT126NSR is usually 5 days.
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Once your SN74AHCT126NSR 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 SN74AHCT126NSR?
For technical support, including SN74AHCT126NSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AHCT126NSR requirements.
6.How does Aetrix verify that SN74AHCT126NSR is sourced from the original manufacturer or authorized distributors?
All SN74AHCT126NSR 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 SN74AHCT126NSR meets industry standards.
7.What is the process for return or replacement of SN74AHCT126NSR?
All SN74AHCT126NSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74AHCT126NSR, 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 SN74AHCT126NSR part is unused and in its original packaging.
Return procedure for SN74AHCT126NSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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