onsemi 74VHCT245AN

Overview

74VHCT245AN from onsemi is an octal bus transceiver with 3-STATE outputs, designed for bidirectional asynchronous data bus communication between 3 V and 5 V systems. It features 5.4 ns typical propagation delay at 5 V, ±8 mA output drive, and operates across −40°C to +85°C. Its T/R control pin determines data direction, while OE enables/disables all outputs for bus isolation.

For engineers reviewing the 74VHCT245AN datasheet, pinout, applications, or equivalent options, key selection criteria include bidirectional 3-state timing, 5 V CMOS-compatible logic levels, input/output overvoltage tolerance up to 5.5 V, and compatibility with legacy 74HCT245 layouts in mixed-voltage interfacing.

Technical Context

The 74VHCT245AN implements dual 8-bit bidirectional data paths controlled by independent OE (active-low output enable) and T/R (transmit/receive) inputs. Its silicon gate CMOS process delivers TTL-compatible speed with CMOS power efficiency, achieving tPLH/tPHL ≤ 8.5 ns (max) at CL = 15 pF and VCC = 5.0 V.

Input and output protection circuits allow safe operation with 0 V to 5.5 V applied to pins regardless of VCC, enabling robust level-shifting between 3 V and 5 V domains without external components. The device supports power-down states with IOZ ≤ ±2.5 µA and IIN ≤ ±1.0 µA under worst-case conditions.

Key Specifications

Pinout & Package

74VHCT245AN is housed in a 20-pin TSSOP package (Case 948AQ, 4.4 mm × 6.5 mm), with 0.65 mm pitch and JEDEC MO-153 compliance. Pin 1 is marked with a dot or notch orientation indicator.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal bus transceiver applications.

Compared with 74VHCT245AMTCX, the 74VHCT245AN offers identical performance but differs in packaging marking and shipping format; versus SN74LVC245A, it provides essential 5 V tolerance and higher drive strength for legacy system integration, making it irreplaceable in mixed-voltage bus bridging.

Availability

74VHCT245AN is available at Aetrix Electronics and suitable for industrial PLC backplanes, automotive body control modules, and embedded test equipment requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for 74VHCT245AN 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 focused on energy-efficient technologies for automotive, industrial, cloud, and IoT applications.

The 74VHCT245AN belongs to the VHCT logic family, engineered specifically for high-speed, low-power bidirectional bus interfacing in mixed-voltage systems where reliability and pin compatibility with legacy TTL/HCT designs are critical.

FAQ

What is the maximum operating temperature range for the 74VHCT245AN?

The 74VHCT245AN is rated for continuous operation from −40°C to +85°C. This industrial temperature range ensures reliable performance in demanding environments such as factory automation controllers and automotive under-hood modules. All DC and AC electrical characteristics in the datasheet are guaranteed across this full range, including propagation delay, output drive, and leakage current specifications.

Can the 74VHCT245AN safely interface a 3.3 V microcontroller with a 5 V peripheral bus?

Yes, the 74VHCT245AN supports this exact use case. Its inputs and outputs tolerate 0 V to 5.5 V regardless of VCC, allowing direct connection of 3.3 V logic signals to its A or B ports while powered from 5 V. No external level shifters or pull-up resistors are needed, preserving signal integrity and reducing board space. The 74VHCT245AN maintains valid logic thresholds (VIH = 2.0 V, VIL = 0.8 V) under these conditions.

Is the 74VHCT245AN pin-compatible with the older 74HCT245?

Yes, the 74VHCT245AN is pin- and function-compatible with the 74HCT245. Both share identical 20-pin DIP and TSSOP footprints, identical pin assignments (including OE, T/R, A0–A7, B0–B7), and matching truth table behavior. This allows direct substitution in existing designs to gain improved speed (5.4 ns vs. ~10 ns typical) and lower power consumption without PCB changes.

What is the typical propagation delay of the 74VHCT245AN at 5 V supply?

The 74VHCT245AN has a typical propagation delay (tPD) of 5.4 ns at VCC = 5.0 V with CL = 50 pF load. This value applies to both tPLH and tPHL transitions and reflects real-world performance under standard test conditions. Maximum delay is specified as 9.5 ns across temperature and voltage extremes, supporting reliable timing closure in 20–25 MHz bus systems.

Does the 74VHCT245AN require external pull-up or pull-down resistors on its control pins?

No, the 74VHCT245AN does not require external pull-up or pull-down resistors on OE or T/R inputs. Its CMOS inputs have negligible leakage (IIN ≤ ±1.0 µA), and unused inputs must be tied to VCC or GND per datasheet guidance. However, for robust noise immunity in noisy industrial environments, weak pull-ups (e.g., 10 kΩ to VCC) on OE are recommended when driven by open-drain or high-impedance sources - but this is a system-level design choice, not a device requirement.