Texas Instruments SN74HCS125BQAR

Overview

SN74HCS125BQAR from Texas Instruments is a quadruple non-inverting buffer IC with 3-state outputs and Schmitt-trigger inputs, operating across 2V–6V supply. It delivers ±7.8mA output drive at 6V, features typical ICC of 100nA, and supports –40°C to +125°C ambient operation. It enables signal routing control in bus-hold or noise-immune digital interfaces.

For engineers reviewing the SN74HCS125BQAR datasheet, SN74HCS125BQAR pinout, SN74HCS125BQAR application, or SN74HCS125BQAR equivalent, key selection criteria include Schmitt-trigger hysteresis (ΔVT ≥ 0.55V at 2V), 3-state enable timing (ten ≤ 24ns at 2V), thermal performance in WQFN (RθJA = 109.7°C/W), and compatibility with 50pF capacitive loads.

Technical Context

This device implements four independent Y = A positive-logic buffers, each with active-low 3-state output enable (OE). The Schmitt-trigger inputs provide hysteresis (ΔVT = 0.55–1.49V depending on VCC) to reject slow edges and noise up to ±0.745V peak-to-peak at 6V.

Each channel operates as a CMOS push-pull driver with balanced sourcing/sinking capability. Output states are fully defined: logic HIGH (VOH ≥ VCC − 0.1V), logic LOW (VOL ≤ 0.1V), or high-impedance (Hi-Z) when OE is high - enabling bus sharing without contention.

Key Specifications

Pinout & Package

The SN74HCS125BQAR uses a 14-pin WQFN (BQA) package measuring 3.00mm × 2.50mm with an exposed thermal pad. Pin 1 is marked by a dot; the thermal pad may be connected to GND or left floating - no connection to other signals or supplies.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCS125DR and SN74LVC125AQPWRQ1, the SN74HCS125BQAR uniquely combines ultra-low quiescent current (100nA), extended temperature support (–40°C to +125°C), and compact WQFN packaging - making it optimal for space- and power-constrained industrial edge nodes.

Availability

SN74HCS125BQAR is available at Aetrix Electronics and suitable for industrial sensor interfaces, automotive body control modules, and programmable logic expansion requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for SN74HCS125BQAR 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 delivering analog and embedded processing solutions for industrial, automotive, and personal electronics markets.

The SN74HCS125BQAR belongs to TI's HCS logic family, designed specifically for robust, low-power digital interfacing in harsh environments - emphasizing noise immunity, wide voltage operation, and extended temperature reliability.

FAQ

What is the function of the OE pins on the SN74HCS125BQAR?

Each OE pin (1OE–4OE) is an active-low output enable control for its respective buffer channel. When OE is low, the corresponding Y output follows the A input (Y = A); when OE is high, the output enters high-impedance (Hi-Z) state. This allows individual channel gating without affecting other buffers - essential for bus arbitration and signal multiplexing in the SN74HCS125BQAR.

Does the SN74HCS125BQAR require external pull-up or pull-down resistors on unused inputs?

Unused inputs on the SN74HCS125BQAR must be terminated to either VCC or GND to prevent floating states that cause undefined logic behavior and increased power consumption. While Schmitt-trigger inputs tolerate slow transitions, they do not eliminate the need for proper DC biasing - so a 10kΩ pull-up or pull-down resistor is recommended for any unconnected A or OE pin in the SN74HCS125BQAR design.

Can the SN74HCS125BQAR drive a 50pF capacitive load while meeting timing specifications?

Yes - the SN74HCS125BQAR is characterized to meet all switching specifications (including tpd ≤ 24ns at 2V) with a total capacitive load of up to 50pF. Exceeding this value increases propagation delay and transition time; therefore, layout must limit trace length and receiver input capacitance to stay within the 50pF limit specified for guaranteed timing performance of the SN74HCS125BQAR.

What is the significance of the thermal pad on the SN74HCS125BQAR WQFN package?

The exposed thermal pad on the SN74HCS125BQAR improves heat dissipation, lowering junction-to-board thermal resistance to 77.9°C/W. It may be connected to GND for both thermal and electrical benefit, or left floating - but must never connect to any signal or supply net other than GND. Proper solder stencil design and pad coverage are critical to realize the full thermal advantage of the SN74HCS125BQAR.

How does the Schmitt-trigger input architecture improve noise immunity in the SN74HCS125BQAR?

The SN74HCS125BQAR Schmitt-trigger inputs provide hysteresis (ΔVT = 0.55–1.49V) between rising and falling thresholds, creating a noise margin that prevents multiple toggles from a single noisy edge. For example, at 6V supply, input noise up to ±0.745V peak-to-peak is rejected - ensuring clean, chatter-free logic transitions even in electrically noisy industrial or automotive environments for the SN74HCS125BQAR.