Texas Instruments SN74HC125DR

Overview

SN74HC125DR from Texas Instruments is a quadruple 3-state buffer IC used for digital signal enablement and bus isolation in CMOS logic systems. It operates across 2 V–6 V supply, supports –40°C to +85°C ambient, delivers propagation delay as low as 11 ns at 6 V, and drives up to 10 LSTTL loads. It is commonly deployed in bidirectional data bus control and microcontroller peripheral interfacing.

For engineers reviewing the SN74HC125DR datasheet, SN74HC125DR pinout, SN74HC125DR application, or SN74HC125DR equivalent, key selection considerations include its 14-pin SOIC package, active-low 3-state enable per channel, rail-to-rail output swing, low quiescent current (≤80 µA), and compatibility with standard CMOS input thresholds.

Technical Context

This device implements four independent non-inverting buffers, each with an active-low 3-state output enable (OE). Each channel performs Y = A in positive logic, with no internal inversion or logic combination. The outputs are balanced CMOS, capable of sourcing and sinking comparable currents (±6 mA typical at 4.5 V).

Input structure uses standard CMOS gates with ≤10 pF input capacitance and ±1 µA leakage at 6 V. Output switching is characterized under 50 pF and 150 pF loads, with disable delay (tdis) as low as 15 ns and transition time (tt) down to 6 ns at 6 V - enabling reliable operation in medium-speed digital interfaces up to ~20 MHz.

Key Specifications

Pinout & Package

SN74HC125DR is housed in a 14-pin SOIC (D) package measuring 8.70 mm × 3.90 mm, with standard 1.27 mm pitch and gull-wing leads compatible with automated SMT assembly.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad 3-state buffer applications.

Compared with SN74HC125DR, SN74HCT125DR offers guaranteed TTL-input compatibility at 5 V while retaining identical functionality, whereas 74LVC125AD delivers superior speed and voltage flexibility at the cost of pinout and thermal profile differences - making SN74HC125DR the optimal choice for industrial 2–6 V mixed-signal bus control where proven reliability and SOIC manufacturability are prioritized.

Availability

SN74HC125DR is available at Aetrix Electronics and suitable for industrial control panels, test equipment interfaces, and embedded microcontroller peripheral expansion requiring stable component supply, long-term lifecycle support, and RoHS-compliant SOIC packaging.

Supply support for SN74HC125DR 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 decades of experience in high-reliability industrial and automotive-grade components.

The SN74HC125DR belongs to TI's 74HC logic family, designed specifically for low-power, high-noise-immunity digital interfacing in industrial, instrumentation, and computing applications where consistent timing and wide supply tolerance are critical.

FAQ

What is the maximum capacitive load SN74HC125DR can reliably drive?

SN74HC125DR is characterized for loads up to 150 pF, but optimal performance (meeting all timing specs) is guaranteed at ≤70 pF. Driving >150 pF risks exceeding absolute max output current (±35 mA) and degrading tpd/ten/tdis. For heavier loads, add a series resistor to limit peak current per the Absolute Maximum Ratings table in the SN74HC125DR datasheet.

Can SN74HC125DR operate with a 3.3 V supply and interface directly with 5 V logic?

Yes - SN74HC125DR supports 3.3 V VCC and produces rail-to-rail outputs (0 V to 3.3 V). Its inputs tolerate up to VCC, so it safely accepts 3.3 V signals. However, to drive 5 V logic, use SN74HCT125DR instead, as SN74HC125DR's VIH threshold at 3.3 V is ~2.3 V - insufficient for reliable recognition of 5 V inputs without external level shifting.

How should unused inputs and outputs be handled on SN74HC125DR?

Unused inputs on SN74HC125DR must be terminated to VCC or GND - floating inputs cause excessive current draw and potential oscillation. Unused outputs may be left unconnected (floating) since they enter high-Z state when OE is HIGH. Do not tie outputs directly to VCC or GND, as this violates the Absolute Maximum Ratings for output current.

Does SN74HC125DR require decoupling capacitors, and if so, what value?

Yes - SN74HC125DR requires a 0.1 µF ceramic decoupling capacitor placed as close as possible between VCC (pin 14) and GND (pin 7). This suppresses supply noise induced by fast output transitions. For noisy environments, paralleling with a 1 µF capacitor improves low-frequency filtering, as recommended in the SN74HC125DR application guidelines.

Is SN74HC125DR pin-compatible with other packages in the same family?

Yes - SN74HC125DR (SOIC-14) shares identical pin configuration and function with SN74HC125DBR (SSOP-14), SN74HC125PW (TSSOP-14), and SN74HC125N (PDIP-14). All variants implement the same 14-pin functional map shown in Figure 5-1 of the SN74HC125DR datasheet, enabling footprint interchangeability where package height and thermal constraints allow.