onsemi MC74LCX540DTG

Overview

MC74LCX540DTG from onsemi is an inverting octal 3-state buffer with flow-through pinout, operating from 2.3 V to 3.6 V supply. It features 5 V-tolerant inputs/outputs, ±24 mA output drive at 3.0–3.6 V, 7.5 ns max propagation delay, and IOFF protection enabling live insertion. It serves as a level-shifting bus driver in memory address and TTL-level data bus applications.

For engineers reviewing the MC74LCX540DTG datasheet, pinout, applications, or equivalent options, key selection criteria include 5 V tolerance, flow-through layout for PCB routing efficiency, 24 mA sink/source capability, low ICC (10 µA), and TSSOP-20 package compatibility with high-density layouts.

Technical Context

The MC74LCX540DTG implements dual independent output enable controls (OE1, OE2) that place all eight outputs in high-impedance state when asserted HIGH. Its inverting logic function and flow-through architecture-inputs on one side (pins 1–8, 19–20), outputs on the opposite side (pins 11–18)-minimize trace crossovers in bus interface designs.

It supports mixed-voltage system interfacing via 5.5 V absolute maximum input voltage rating and guaranteed operation down to 2.3 V VCC. The IOFF specification ensures <10 µA leakage when VCC = 0 V, enabling hot-swap capability without damaging backdrive currents.

Key Specifications

Pinout & Package

TSSOP-20 (Case 948E), 0.65 mm pitch, 6.5 mm × 4.4 mm body, 1.1 mm max height, Pb-free, RoHS compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC541APWR and 74LCX540MTCX, the MC74LCX540DTG uniquely combines inverting logic, flow-through pinout, and TSSOP-20 packaging-enabling compact, low-skew bus routing in space-constrained embedded designs without added inversion logic.

Availability

MC74LCX540DTG is available at Aetrix Electronics and suitable for memory address driving, TTL-level bus transceiver, and hot-swappable I/O module applications requiring stable component supply and long-term industrial availability.

Supply support for MC74LCX540DTG 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

onsemi (formerly ON Semiconductor) is a global semiconductor manufacturer specializing in energy-efficient silicon solutions for automotive, industrial, cloud, medical, and IoT applications.

The MC74LCX540DTG belongs to the LCX low-voltage CMOS logic family, designed specifically for mixed-voltage system interfacing where 3.3 V logic must reliably communicate with 5 V legacy components.

FAQ

What is the maximum input voltage rating for MC74LCX540DTG?

The MC74LCX540DTG supports a maximum DC input voltage of 5.5 V, independent of VCC level. This 5 V tolerance allows direct connection to 5 V TTL outputs without external protection circuitry. The specification is validated across the full operating temperature range (−40°C to +85°C) and applies to all input pins including OE1, OE2, and D0–D7. This rating is confirmed in the Absolute Maximum Ratings table of the official onsemi datasheet (Rev. 9, October 2024).

Does MC74LCX540DTG support live insertion when VCC is unpowered?

Yes, the MC74LCX540DTG supports live insertion via its IOFF specification: when VCC = 0 V, input and output leakage current is limited to 10 µA maximum even with 5.5 V applied to any pin. This prevents backdrive current from damaging the device or disturbing other powered components on the bus. The feature is explicitly guaranteed in the DC Electrical Characteristics table and is a defined design requirement for hot-swap applications per the datasheet.

What is the propagation delay of MC74LCX540DTG at 3.3 V supply?

At VCC = 3.3 V, the MC74LCX540DTG exhibits a maximum propagation delay (tPLH/tPHL) of 6.5 ns under standard AC test conditions (CL = 50 pF, RL = 500 Ω, tR/tF = 2.5 ns). This value is specified in the AC Characteristics table for the 3.0–3.6 V VCC range. The typical delay is lower, but design margins should use the 6.5 ns max value for timing closure in synchronous bus interfaces.

Is MC74LCX540DTG pin-compatible with other octal buffers in TSSOP-20 package?

The MC74LCX540DTG uses a flow-through pinout unique to the LCX540 family: inputs on left/right edges (pins 1–8, 19–20), outputs on top/bottom (pins 11–18). It is not pin-compatible with non-flow-through octal buffers like SN74LVC541APWR (which places inputs and outputs on same side). Pin compatibility must be verified per exact pin function mapping-not just package outline or pin count.

What is the output drive strength of MC74LCX540DTG at 2.7 V supply?

At VCC = 2.7 V, the MC74LCX540DTG provides ±12 mA output drive (IOL = 12 mA, IOH = −12 mA), as specified in the Recommended Operating Conditions table. This reduced drive versus 24 mA at 3.0–3.6 V reflects process-voltage scaling but remains sufficient for driving LVTTL loads or short PCB traces. The value is measured under defined load conditions and is guaranteed across temperature.