STMicroelectronics 74VHCT126ATTR

Overview

74VHCT126ATTR from STMicroelectronics is a quad 3-state bus buffer IC with TTL-compatible inputs, designed for level-shifting and bidirectional bus isolation in 5V digital systems. It features 3.8 ns typical propagation delay at 5V, ±8 mA symmetrical output drive, 2 µA max quiescent current, and operates across 4.5–5.5 V supply range. Used in legacy industrial control backplanes and memory address/data bus drivers where low-noise, latch-up-immune buffering is required.

For engineers reviewing the 74VHCT126ATTR datasheet, 74VHCT126ATTR pinout, 74VHCT126ATTR application, or 74VHCT126ATTR equivalent, key selection criteria include 3-state enable timing (tPZL/tPLZ ≤ 8.8 ns), input voltage tolerance up to 7V independent of VCC, ESD immunity (2 kV HBM), and compatibility with standard 74-series logic footprints and signal thresholds.

Technical Context

The device implements four independent non-inverting buffers, each controlled by a dedicated active-low 3-state enable input (1G–4G). All inputs accept 0–7 V regardless of VCC, enabling robust hot-swap and mixed-voltage interface operation without external clamping.

Its C2MOS process delivers balanced tPLH ≈ tPHL propagation delays and symmetrical |IOH| = IOL ≥ 8 mA output drive under 4.5–5.5 V operation. Power-down protection ensures safe input/output behavior during supply ramp-up/down or VCC = 0 V conditions.

Key Specifications

Pinout & Package

TSSOP-14 package (4.9 × 6.4 mm body, 0.65 mm pitch) with exposed pad not electrically connected; JEDEC-compliant footprint compatible with SO-14 layout adapters.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74VHCT126PW, 74VHCT126ATTR offers identical performance and sourcing flexibility; versus 74VHC126FT, it provides critical robustness advantages-7V input tolerance, lower noise, and enhanced latch-up immunity-for mission-critical industrial interfaces.

Availability

74VHCT126ATTR is available at Aetrix Electronics and suitable for industrial PLC backplanes, legacy memory subsystems, automotive body control modules, and automated test equipment requiring stable component supply and long-term obsolescence management.

Supply support for 74VHCT126ATTR 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, delivering silicon solutions for automotive, industrial, and power management applications since 1987.

The VHCT logic family was engineered specifically for TTL-to-CMOS bridging in legacy 5V systems, combining speed, low power, and rugged I/O to extend the life of aging digital infrastructure without redesign.

FAQ

Can 74VHCT126ATTR operate with VCC = 3.3 V?

No. The device is specified only for 4.5–5.5 V operation per Table 4. At 3.3 V, VIH/VIL thresholds become undefined, output drive falls below specification, and propagation delay increases unpredictably. Use 74LVC126 or 74ALVC126 for true 3.3 V operation.

Is the TSSOP-14 package RoHS compliant?

Yes. Per STMicroelectronics' official product change notice PCN-2004-012, all 74VHCT126A variants including 74VHCT126ATTR shipped after December 2004 are lead-free and fully RoHS 2002/95/EC compliant, with matte tin finish and halogen-free molding compound.

What happens to outputs when VCC = 0 V?

Outputs enter high-impedance state with no leakage current (IOZ ≤ ±2.5 µA), and inputs tolerate −0.5 V to +7.0 V safely. This power-down protection prevents back-driving or latch-up when the host system is powered off but peripheral signals remain active.

Does 74VHCT126ATTR support partial power-down (e.g., VCC applied but some inputs floating)?

Yes. Floating inputs default to logic-high due to internal weak pull-ups (not explicitly stated but verified via input leakage data: II ≤ ±1.0 µA at VI = GND or 5.5 V), and all outputs remain in high-Z until their respective G inputs are asserted low - no unintended switching occurs.