Texas Instruments SN74HC540DWRE4

Overview

SN74HC540DWRE4 from Texas Instruments is an octal inverting buffer/line driver with 3-state outputs, designed for bus interface and data routing in digital systems. It operates from 2 V to 6 V, delivers ±6 mA output drive at 5 V, exhibits typical propagation delay of 8 ns, and features low ICC (80 μA max), enabling high-density logic interfacing in industrial and embedded control applications.

For engineers reviewing the SN74HC540DWRE4 datasheet, SN74HC540DWRE4 pinout, SN74HC540DWRE4 application, or SN74HC540DWRE4 equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, application-specific implementation guidance, and two confirmed alternative parts with documented functional and layout implications.

Technical Context

The SN74HC540DWRE4 implements eight independent inverting buffers, each with a 2-input NOR-based 3-state enable (OE1/OE2): either OE input high forces all outputs into high-impedance. Its data flow-through pinout places all eight inputs on one side and all eight outputs on the opposite side of the TSSOP-20 package, simplifying PCB trace routing and reducing crosstalk.

It belongs to the 74HC logic family and is functionally identical to the 'HC240 series but with inverted output polarity. Electrical behavior is specified across −40°C to +85°C, with guaranteed switching performance at 50 pF load and supply voltages down to 2 V - supporting mixed-voltage system interfacing and low-power operation without sacrificing speed.

Key Specifications

Pinout & Package

TSSOP-20 package (PW), 6.50 mm × 4.40 mm body size, 1.2 mm max height, lead finish NIPDAU, MSL Level-1, RoHS compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC540DWRE4, SN74HCT540PWRE4 offers improved TTL-input compatibility at the cost of reduced low-voltage operability, while 74LVC541APW,118 trades inversion and optimized layout for higher speed and drive - making SN74HC540DWRE4 optimal for space-constrained, mixed-voltage, inverting bus isolation where layout efficiency is critical.

Availability

SN74HC540DWRE4 is available at Aetrix Electronics and suitable for industrial automation, embedded control, and test equipment applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for SN74HC540DWRE4 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, with over 90 years of innovation in logic, power management, and signal chain technologies.

The SN74HC540DWRE4 belongs to TI's 74HC high-speed CMOS logic family, engineered for reliable, low-power digital interfacing in industrial, automotive, and communications systems where noise immunity, wide supply range, and predictable timing are essential.

FAQ

What is the function of OE1 and OE2 on the SN74HC540DWRE4?

The SN74HC540DWRE4 uses a 2-input NOR gate to control its 3-state outputs: if either OE1 or OE2 is driven high, all eight outputs enter high-impedance mode. This dual-enable architecture allows flexible bus arbitration - for example, OE1 can serve as a global disable while OE2 enables local subsystem control. Both inputs must be low for normal inverted buffer operation.

Does the SN74HC540DWRE4 support 3.3 V-only operation?

Yes, the SN74HC540DWRE4 fully supports 3.3 V operation: its recommended VCC range is 2 V to 6 V, and electrical characteristics including VIH (min 2.0 V at VCC = 3.3 V), VOL (max 0.33 V), and tpd (typ. 13 ns) are explicitly specified at 3.3 V. It is widely used in 3.3 V FPGA and microcontroller interfaces without level translation.

What is the maximum capacitive load the SN74HC540DWRE4 can drive reliably?

The SN74HC540DWRE4 is characterized for CL = 50 pF and 150 pF loads in its switching specifications. At 50 pF, tpd is 8 ns (typ) and tt is 6 ns (typ) at 6 V. While not rated beyond 150 pF, practical use up to ~200 pF is feasible with increased propagation delay and potential edge degradation - for heavier loads, add series termination or consider a dedicated bus driver.

Is the SN74HC540DWRE4 pin-compatible with other 74HC540 variants?

Yes, the SN74HC540DWRE4 shares identical pinout and functionality with all 74HC540 variants in TSSOP-20 (PW) packaging, including SN74HC540PWR and SN74HC540PWRE4. Differences are limited to tape-and-reel packaging details and date-code marking - electrical, thermal, and mechanical specifications are identical across these orderables.

How should unused inputs be handled on the SN74HC540DWRE4?

All unused inputs on the SN74HC540DWRE4 must be terminated to a valid logic level - either VCC or GND - to prevent floating nodes that cause excessive ICC, oscillation, or ESD susceptibility. TI recommends tying unused A-inputs to GND (for logic low) or VCC (for logic high) using short traces; leaving them open violates recommended operating conditions and risks erratic behavior.