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Texas Instruments SN74AHCT125D
- Part No.:
- SN74AHCT125D
- Manufacturer:
- Texas Instruments
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74AHCT125D.pdf
- Description:
- IC BUF NON-INVERT 5.5V 14SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,014
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Product details
Overview
SN74AHCT125D from Texas Instruments is a quadruple 3-state bus buffer gate IC used for digital signal routing, isolation, and level translation in 5-V logic systems. It features four independent channels, TTL-compatible inputs (VIH = 2 V, VIL = 0.8 V), ±8 mA output drive, and operates across –40°C to +85°C. It enables selective data path control in microcontroller GPIO expansion and bus arbitration applications.
For engineers reviewing the SN74AHCT125D datasheet, SN74AHCT125D pinout, SN74AHCT125D application, or SN74AHCT125D equivalent, key selection criteria include 3-state output timing (tPLH/tPHL ≤ 6.5 ns @ 5 V, CL = 15 pF), SOIC-14 package compatibility, input voltage tolerance up to 5.5 V, and commercial-grade temperature range suitability for industrial control and embedded interface designs.
Technical Context
The SN74AHCT125D implements four identical non-inverting buffer gates, each with dedicated active-low output-enable (OE) control. Each channel passes A→Y when OE is low and presents high-impedance (Z) when OE is high - enabling bidirectional bus sharing without contention.
Its TTL-voltage-compatible inputs accept 0.8 V/2.0 V thresholds while operating from a 4.5–5.5 V supply, ensuring interoperability with legacy 5-V TTL and CMOS logic. The device exhibits latch-up immunity exceeding 250 mA per JESD 17 and supports capacitive loads up to 50 pF while maintaining specified switching performance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - ensures stable operation across standard 5-V rail tolerances and brown-out resilience. |
| Input Thresholds | VIH = 2.0 V, VIL = 0.8 V - guarantees reliable recognition of TTL-level signals without external level shifters. |
| Output Drive | ±8 mA - sufficient to drive multiple 74-series loads or moderate PCB traces without buffering. |
| Propagation Delay | tPLH/tPHL ≤ 6.5 ns @ 5 V, CL = 15 pF - supports >100 MHz data rates in short-path digital interfaces. |
| 3-State Enable Time | tPZH/tPZL ≤ 6 ns @ 5 V, CL = 15 pF - enables fast bus turnaround for time-critical multiplexing. |
| Power Consumption | ICC ≤ 20 µA @ 25°C - ultra-low static current ideal for always-on control logic sections. |
| Input Capacitance | Ci = 10 pF - minimizes loading on upstream drivers and preserves signal edge integrity. |
Pinout & Package
SN74AHCT125D uses a 14-pin SOIC (Small Outline Integrated Circuit) package with 1.27 mm pitch, JEDEC MS-012AC compliant, and 8.65 mm × 3.91 mm body dimensions. Pin numbering follows standard D-package top-view orientation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 4, 10, 13 | OE1–OE4 (active-low) | Independent 3-state enable controls per channel; tie together for synchronous gating. |
| 2, 5, 9, 12 | A1–A4 | Buffer input terminals; accept TTL/CMOS logic levels with 10 pF input capacitance. |
| 3, 6, 8, 11 | Y1–Y4 | Non-inverting buffered outputs; high-impedance when corresponding OE is high. |
| 7 | GND | Ground reference for all logic and power domains; must be low-impedance for noise immunity. |
| 14 | VCC | Positive supply terminal; requires local 0.1 µF bypass capacitor placed adjacent to pin. |
Key Features
| Feature | Design Value |
|---|---|
| TTL-voltage compatible inputs | Accepts 0.8 V/2.0 V thresholds at 4.5–5.5 V supply - eliminates need for external level translators with legacy TTL sources. |
| Independent 3-state control per channel | Four separate OE pins allow granular bus segment isolation - critical for multi-master arbitration and GPIO multiplexing. |
| Latch-up immunity ≥250 mA | Meets JESD 17 Class II requirements - ensures robustness against transient ground bounce or ESD-induced latch-up in industrial environments. |
| Low dynamic power dissipation | Cpd = 14 pF - reduces switching current and thermal rise in high-frequency enable/disable cycling. |
| No internal pull-ups on OE pins | OE pins are true CMOS inputs requiring external pull-up if high-impedance state is required during power-up - prevents unintended output activation. |
Applications
| Microcontroller GPIO Expansion | Industrial Bus Arbitration |
|---|---|
|
Use Scenario: A microcontroller with limited GPIO pins routes multiple peripheral signals (SPI, UART, I²C) through shared PCB traces. IC Role / Device Role / Timing Role: SN74AHCT125D acts as a programmable signal router - individual OE pins select active peripherals while isolating inactive ones from the bus. Use Value: Enables single MCU to manage 4 independent data paths using only 8 GPIOs (4 inputs + 4 OEs), reducing PCB layer count and BOM cost. |
Use Scenario: Two PLC modules share a common RS-485 transceiver; only one may drive the bus at a time. IC Role / Device Role / Timing Role: SN74AHCT125D provides hardware-enforced bus direction control - OE signals synchronized with transceiver DE/RE pins ensure no bus contention. Use Value: Eliminates risk of simultaneous drive damage by guaranteeing <10 ns dead-time between driver disable and enable transitions. |
| LED Indicator Control | Switch Debounce Interface |
|
Use Scenario: Industrial HMI panel uses discrete LEDs to indicate status of 4 sensor inputs (e.g., limit switches, flow sensors). IC Role / Device Role / Timing Role: SN74AHCT125D buffers and drives LEDs directly - Y outputs sink up to 8 mA per channel with TTL-compatible input thresholds. Use Value: Removes need for discrete transistors or current-limiting resistors on MCU side; simplifies layout and improves LED brightness consistency. |
Use Scenario: Mechanical pushbutton on factory equipment generates noisy, slow-rising edges that cause false interrupts in MCU. IC Role / Device Role / Timing Role: SN74AHCT125D conditions the switch signal - its Schmitt-trigger-like input behavior (due to TTL thresholds + hysteresis in CMOS structure) cleans slow edges before reaching MCU. Use Value: Reduces firmware debounce overhead by >70% and eliminates missed or spurious edge detections in vibration-prone environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bus buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AHCT125DR | Same die, SOIC-14 tape-and-reel packaging (2500 pcs/reel); identical electrical specs and pinout. | Designed for automated SMT assembly; same footprint and thermal profile as SN74AHCT125D. | Select SN74AHCT125DR for volume production; SN74AHCT125D is obsolete but available for legacy rework or prototyping. |
| SN74LVC125A | Lower VCC range (1.65–3.6 V), higher speed (tPD ≤ 3.7 ns), but not TTL-input compatible (VIH = 2 V only at VCC ≥ 3 V). | Suitable for 3.3-V systems with tighter timing budgets; requires level-shifting for TTL source interfacing. | Choose SN74LVC125A only when migrating to 3.3-V logic; retain SN74AHCT125D for mixed 5-V/TTL environments. |
Compared with SN74AHCT125DR, SN74AHCT125D shares identical functionality but lacks modern tape-and-reel support; versus SN74LVC125A, it delivers guaranteed TTL compatibility at 5 V - a decisive advantage in legacy industrial backplanes where signal integrity depends on VIH/VIL margins.
Availability
SN74AHCT125D is available at Aetrix Electronics and suitable for industrial control panels, embedded test equipment, and legacy 5-V communication interfaces requiring stable component supply and long-term obsolescence management.
Supply support for SN74AHCT125D 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 SN74AHCT125D belongs to TI's AHCT logic family - engineered for seamless 5-V TTL-to-CMOS interfacing with robust noise immunity and latch-up protection, targeting industrial control, instrumentation, and legacy system upgrades.
FAQ
What is the maximum capacitive load SN74AHCT125D can drive while meeting all datasheet specifications?
The SN74AHCT125D is characterized and guaranteed to meet all timing and voltage specifications with a load capacitance of up to 50 pF. Driving larger capacitive loads is possible but may degrade propagation delay, increase power consumption, and reduce noise margins. For designs exceeding 50 pF, SN74AHCT125D should be paired with a dedicated line driver or buffer stage to maintain signal integrity.
Can SN74AHCT125D operate reliably with a 3.3-V supply voltage?
No - SN74AHCT125D is specified only for 4.5 V to 5.5 V operation. At 3.3 V, its TTL-compatible input thresholds (VIH = 2.0 V, VIL = 0.8 V) cannot be met reliably, and output drive strength falls outside specification. For 3.3-V systems, use SN74LVC125A instead, which is designed for 1.65–3.6 V operation and maintains full functionality at 3.3 V.
How should unused input pins be terminated on SN74AHCT125D?
All unused inputs on SN74AHCT125D must be tied to either VCC or GND to prevent floating states that cause increased ICC, oscillation, or EMI. A 10-kΩ pull-up or pull-down resistor is recommended for flexibility; direct connection is acceptable if the input will never be used. Leaving inputs unconnected violates the Recommended Operating Conditions and risks functional instability.
Is SN74AHCT125D pin-compatible with SN74HC125?
No - although both are quadruple 3-state buffers, SN74AHCT125D has TTL-compatible inputs (VIH = 2.0 V), while SN74HC125 has CMOS inputs (VIH = 0.7×VCC). At 5 V, SN74HC125 requires ~3.5 V for VIH, making it incompatible with standard TTL outputs. Substituting SN74HC125 for SN74AHCT125D risks logic misreads and system failure in mixed-signal environments.
What is the recommended bypass capacitor for SN74AHCT125D?
A 0.1 µF ceramic capacitor is recommended for SN74AHCT125D, placed as close as possible to the VCC (pin 14) and GND (pin 7) pins. This minimizes high-frequency supply noise and stabilizes transient current demands during output switching. For enhanced noise suppression, a parallel 1 µF capacitor may be added, but the 0.1 µF unit remains mandatory per TI layout guidelines.
SN74AHCT125D Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AHCT
- 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:
- 8mA, 8mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-SOIC
SN74AHCT125D FAQ
1.How can I place an order for SN74AHCT125D through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AHCT125D 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 SN74AHCT125D reliable?
The price and inventory of SN74AHCT125D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AHCT125D is usually 5 days.
3.What payment methods are accepted for SN74AHCT125D?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AHCT125D transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AHCT125D?
SN74AHCT125D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AHCT125D 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 SN74AHCT125D?
For technical support, including SN74AHCT125D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AHCT125D requirements.
6.How does Aetrix verify that SN74AHCT125D is sourced from the original manufacturer or authorized distributors?
All SN74AHCT125D 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 SN74AHCT125D meets industry standards.
7.What is the process for return or replacement of SN74AHCT125D?
All SN74AHCT125D units undergo pre-shipment inspection (PSI). If there is an issue with SN74AHCT125D, 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 SN74AHCT125D part is unused and in its original packaging.
Return procedure for SN74AHCT125D:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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