Texas Instruments SN74AHCT125RGYR

Overview

SN74AHCT125RGYR from Texas Instruments is a quadruple 3-state bus buffer gate IC with independent output-enable control per channel, TTL-compatible inputs (VIH = 2 V, VIL = 0.8 V), ±8 mA drive strength at 5 V, and VQFN-14 (RGY) package. It enables signal isolation in digital data paths, such as microcontroller GPIO expansion or bidirectional bus control in industrial I/O modules.

For engineers reviewing the SN74AHCT125RGYR datasheet, SN74AHCT125RGYR pinout, SN74AHCT125RGYR application, or SN74AHCT125RGYR equivalent, key selection criteria include 3-state output timing (tPLH/tPHL ≤ 6.5 ns @ 15 pF), input voltage compatibility with legacy TTL logic, thermal performance (θJA = 87.1 °C/W), and VQFN-14 footprint suitability for space-constrained PCB layouts.

Technical Context

The SN74AHCT125RGYR implements four independent CMOS buffer gates, each with dedicated active-low output-enable (OE) control. Each gate passes A→Y when OE is low; outputs enter high-impedance state when OE is high-enabling bus sharing without contention.

It operates strictly within 4.5–5.5 V supply range, supports 50 pF capacitive load per output, and features TTL-level input thresholds (VIH = 2 V min, VIL = 0.8 V max) while maintaining CMOS output swing (VOH ≥ 3.8 V @ –8 mA, VOL ≤ 0.44 V @ 8 mA).

Key Specifications

Pinout & Package

VQFN-14 (RGY) package: 3.5 mm × 3.5 mm body, 0.5 mm pitch, exposed thermal pad, leadless construction optimized for thermal performance and PCB area efficiency.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bus buffer applications.

Compared with SN74AHCT125DR and SN74LVC125APWR, SN74AHCT125RGYR uniquely balances 5 V TTL compatibility, compact VQFN thermal performance, and production-ready tape-and-reel packaging-making it optimal for volume-manufactured industrial controllers requiring robust 5 V signal integrity.

Availability

SN74AHCT125RGYR is available at Aetrix Electronics and suitable for industrial I/O modules, PLC input cards, and microcontroller peripheral expansion requiring stable component supply, RoHS-compliant packaging, and long-term lifecycle support.

Supply support for SN74AHCT125RGYR 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 SN74AHCT125RGYR belongs to TI's AHCT logic family, designed specifically for 5 V systems requiring TTL-compatible inputs, 3-state bus control, and robust noise immunity in harsh industrial environments.

FAQ

What is the recommended power supply decoupling for SN74AHCT125RGYR?

TI specifies a 0.1 µF ceramic bypass capacitor placed as close as possible to the VCC pin of SN74AHCT125RGYR, with low-inductance connection to the ground plane. This suppresses high-frequency supply noise generated during output switching. For systems with heavy simultaneous switching, paralleling a 1 µF capacitor is acceptable to improve low-frequency regulation. The exposed thermal pad must be soldered to a thermal land connected to GND for optimal thermal and electrical performance.

Can SN74AHCT125RGYR drive a 50 pF load while meeting timing specifications?

Yes - SN74AHCT125RGYR switching characteristics (tPLH, tPHL, tPZH, etc.) are fully characterized at CL = 15 pF and CL = 50 pF. At 50 pF, tPLH/tPHL ≤ 8.5 ns and tPZH/tPLZ ≤ 8 ns under VCC = 5 V and TA = 25°C. Driving beyond 50 pF is possible but degrades timing margins and increases dynamic power; TI explicitly recommends limiting total load capacitance to ≤50 pF for guaranteed specification compliance.

How should unused inputs be handled on SN74AHCT125RGYR?

All unused inputs on SN74AHCT125RGYR - including A and OE pins - must be terminated to either VCC or GND to prevent floating states that cause excessive ICC, oscillation, or ESD susceptibility. TI recommends using 10 kΩ pull-up or pull-down resistors for unused OE pins to ensure defined high-impedance default state at power-up. Direct connection is acceptable for permanently unused inputs, provided routing avoids noise coupling.

Is SN74AHCT125RGYR pin-compatible with other SN74AHCT125 package variants?

Yes - SN74AHCT125RGYR shares identical pin functions and logic behavior with all SN74AHCT125 variants (e.g., DR, DBR, DGVR), though physical pin numbering differs between VQFN (RGY) and SOIC/SSOP packages. Pin mapping is preserved functionally: 1OE, 1A, 1Y, 2OE, 2A, 2Y, GND, VCC, 4OE, 4A, 4Y, 3OE, 3A, 3Y appear in the same logical sequence across packages, confirmed in TI's Figure 4-2 and Table 4-1.

What is the maximum operating temperature for SN74AHCT125RGYR?

SN74AHCT125RGYR is rated for commercial operation from –40°C to +85°C ambient temperature, as specified in TI's Recommended Operating Conditions. Its VQFN-14 package delivers θJA = 87.1 °C/W, allowing up to ~150 mW of continuous power dissipation before reaching the absolute maximum junction temperature of 150°C. Derating is required above 70°C ambient per TI's thermal guidelines.