onsemi MM74HCT540N

Overview

MM74HCT540N from onsemi is an octal 3-state inverting buffer IC designed for high-speed TTL-to-CMOS bus interfacing. It features 12 ns typical propagation delay at 5 V, ±6 mA output drive capability, and TTL-compatible input thresholds (VIH = 2.0 V, VIL = 0.8 V), enabling direct replacement of LS-TTL devices in memory address/data bus drivers.

For engineers reviewing the MM74HCT540N datasheet, pinout, applications, or equivalent options, key selection criteria include its inverting logic function, dual 3-state enable (G1/G2 NOR gate), SOIC-20 package compatibility, and operation across −55 °C to +125 °C industrial temperature range.

Technical Context

The MM74HCT540N implements eight independent inverting buffers with a shared two-input NOR 3-state control (G1, G2), where either high input forces all outputs into high-impedance. Its silicon-gate CMOS process delivers LS-TTL speed with CMOS power efficiency - quiescent ICC ≤ 160 µA at 25 °C and 5 V.

Input protection diodes clamp to VCC and GND, supporting ESD robustness. The device achieves fanout of 15 LS-TTL loads and drives up to 150 pF bus capacitance with guaranteed 30 ns max propagation delay over full temperature range.

Key Specifications

Pinout & Package

MM74HCT540N is supplied in a 20-pin SOIC wide-body (Case 751D-05) package measuring 12.8 mm × 7.5 mm × 2.65 mm, with 1.27 mm pitch and gull-wing leads. Pin numbering follows JEDEC MS-013, with inputs on one side and outputs on the opposite side to simplify PCB routing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT540N and 74VHC540N, the MM74HCT540N offers optimal balance of proven industrial temperature performance, true TTL input compatibility, and lowest quiescent power - making it ideal for cost-sensitive, long-lifecycle industrial retrofits and bus-isolation applications.

Availability

MM74HCT540N is available at Aetrix Electronics and suitable for memory subsystems, microcontroller peripheral expansion, industrial PLC I/O modules, and legacy system upgrades requiring stable component supply and long-term obsolescence management.

Supply support for MM74HCT540N 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 supplier specializing in energy-efficient power management, analog, logic, and sensing solutions for automotive, industrial, and cloud infrastructure markets.

The MM74HCT540N belongs to the HCT logic family - engineered for seamless TTL-to-CMOS interoperability in high-reliability industrial control and instrumentation systems where signal integrity and thermal stability are critical.

FAQ

What logic function does the MM74HCT540N implement?

The MM74HCT540N implements eight independent inverting buffers with a shared dual-input NOR 3-state enable (G1/G2). When both enables are LOW, each input A1–A8 is inverted and appears at corresponding outputs Y1–Y8; if either G1 or G2 is HIGH, all outputs enter high-impedance state. This architecture supports precise bus arbitration in multi-master systems.

Is MM74HCT540N pin-compatible with 74LS540?

Yes, the MM74HCT540N is a direct pin-compatible and functionally equivalent replacement for 74LS540. It uses the same SOIC-20 package (Case 751D-05), identical pinout, and matches LS-TTL voltage thresholds (VIH = 2.0 V, VIL = 0.8 V), allowing drop-in substitution without PCB changes while reducing power consumption by >95%.

What is the maximum capacitive load the MM74HCT540N can drive reliably?

The MM74HCT540N is characterized to drive up to 150 pF load capacitance with guaranteed 30 ns maximum propagation delay across −55 °C to +125 °C. At 50 pF, typical delay is 12 ns. Output rise/fall times remain ≤18 ns under these conditions, ensuring signal integrity on heavily loaded backplanes or long traces.

Does MM74HCT540N support operation at 3.3 V supply?

No, the MM74HCT540N is specified only for 4.5 V to 5.5 V operation per its Recommended Operating Conditions. Its TTL-compatible inputs require VIH ≥ 2.0 V, and output drive strength degrades below 4.5 V. For 3.3 V systems, consider 74LVC540A or 74ALVC540, which are explicitly rated for 3.3 V operation.

How is 3-state control implemented on the MM74HCT540N?

The MM74HCT540N uses a two-input NOR gate for 3-state control: pins 1 (G1) and 19 (G2) form the enable inputs. If either G1 or G2 is HIGH, all eight outputs (Y1–Y8) go high-impedance regardless of input states. Only when both G1 and G2 are LOW do the inverting buffer functions activate - this design allows flexible enable sourcing from multiple controllers or fault-safety logic.