onsemi 74LVQ240SCX

Overview

74LVQ240SCX from Fairchild Semiconductor is an inverting octal buffer/line driver with dual 3-STATE output enables, operating at 2.0–3.6 V supply, featuring 8.4 ns max propagation delay (VCC = 2.7 V), ±12 mA output drive, and guaranteed incident-wave switching into 75 Ω transmission lines-used in memory address buffering and clock distribution on dense PCBs.

For engineers reviewing the 74LVQ240SCX datasheet, pinout, applications, or equivalent options, key selection considerations include simultaneous switching noise control, ESD immunity (≥4 kV), low-voltage 3.3 V compatibility, and JEDEC SOIC-20 (M20B) package mapping for board space-constrained designs.

Technical Context

The 74LVQ240SCX implements a dual-enable, inverting octal buffer architecture with independent OE1 (pins 12,14,16,18) and OE2 (pins 3,5,7,9) controlling four outputs each. It uses patented EMI reduction circuitry to suppress simultaneous switching noise during high-speed transitions.

It guarantees dynamic threshold performance and incident-wave switching into 75 Ω loads across −40°C to +85°C, with input edge rate tolerance ≥125 mV/ns (VCC = 3.0 V) and latch-up immunity compliant with ±300 mA DC stress limits.

Key Specifications

Pinout & Package

74LVQ240SCX is packaged in 20-lead SOIC (JEDEC MS-013, 0.300" wide, Package Number M20B), with gull-wing leads, 1.27 mm pitch, and standard surface-mount footprint.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal buffer/line driver applications.

Compared with 74LVQ240SCX, the 74LVC240PW,118 offers faster timing but requires redesign for polarity; the SN74LV240APWR adds 5 V tolerance and stronger drive but omits the incident-wave guarantee critical for impedance-controlled backplanes.

Availability

74LVQ240SCX is available at Aetrix Electronics and suitable for memory address buffering, clock distribution networks, and industrial bus transceiver interfaces requiring stable component supply, long-term lifecycle support, and consistent SOIC-20 (M20B) packaging.

Supply support for 74LVQ240SCX 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

Fairchild Semiconductor was a U.S.-based analog and power IC manufacturer acquired by ON Semiconductor in 2016; known for high-reliability logic, interface, and power management solutions.

The LVQ logic family-including 74LVQ240SCX-was engineered for low-noise, low-power 3.3 V digital systems where EMI control, transmission-line integrity, and PCB density are critical constraints.

FAQ

What is the recommended operating voltage range for the 74LVQ240SCX?

The 74LVQ240SCX is specified for operation from 2.0 V to 3.6 V. Its DC and AC parameters-including propagation delay, output drive, and input thresholds-are fully guaranteed across this range. Operation below 2.0 V may result in undefined logic states or increased propagation delay; above 3.6 V risks exceeding absolute maximum ratings and voiding reliability guarantees. The 74LVQ240SCX performs optimally at 3.3 V ±0.3 V in commercial and industrial environments.

Does the 74LVQ240SCX support true 3-STATE operation with independent enable controls?

Yes, the 74LVQ240SCX features two independent 3-STATE output enable inputs: OE1 (pins 12,14,16,18) controls outputs O4–O7, and OE2 (pins 3,5,7,9) controls outputs O0–O3. When either OE is HIGH, its associated four outputs enter high-impedance state regardless of input levels. This allows selective bus partitioning and avoids contention in multi-driver systems. The 74LVQ240SCX does not require external pull-ups to maintain defined states during 3-STATE.

What is the significance of "guaranteed incident wave switching into 75 Ω" for the 74LVQ240SCX?

This specification means the 74LVQ240SCX has been characterized to cleanly launch signals onto 75 Ω transmission lines without requiring source-series termination-critical for video, RF front-end, or high-speed digital interconnects. It ensures the output waveform remains monotonic during initial edge propagation, minimizing reflections and ringing. The 74LVQ240SCX achieves this via controlled output impedance and edge-rate tuning, validated across −40°C to +85°C and full VCC range.

Can the 74LVQ240SCX be used in mixed-voltage systems with both 3.3 V and 5 V logic?

No-the 74LVQ240SCX is not 5 V tolerant. Its absolute maximum input voltage is VCC + 0.5 V, and VCC must remain ≤3.6 V. Applying 5 V signals to any input (including OE pins) exceeds absolute maximum ratings and risks permanent damage. For mixed-voltage interfacing, level translators or 5 V–tolerant alternatives like SN74LV240APWR must be used. The 74LVQ240SCX is strictly a 3.3 V domain device.

How does the patented EMI reduction circuitry in the 74LVQ240SCX function?

The EMI reduction circuitry in the 74LVQ240SCX employs staggered internal output stage activation and optimized gate drive timing to minimize simultaneous current surges during parallel output transitions. This reduces peak di/dt and associated magnetic-field emissions without degrading propagation delay. Measured results show >10 dB reduction in radiated emissions at 30–300 MHz versus standard LV logic. This feature is intrinsic to the 74LVQ240SCX silicon design and requires no external components or layout changes.