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74HC245D

Octal bus transceiver, 3-state, 2-6V, 7ns, SOIC-20, bidirectional

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Manufacturer Part：

74HC245D

Package：

SOIC-20 (12.8 x 7.5 x 2.65 mm)

Description

Product Overview

The 74HC245D from Nexperia (formerly NXP/Philips) is an octal bus transceiver with 3-state outputs in a 20-pin SOIC package. With 2V to 6V supply range, 7ns propagation delay at 5V, and bidirectional data flow controlled by DIR and OE inputs, it is the industry-standard bus interface for microprocessor and digital systems.

Key Specifications

Logic Type	Octal Bus Transceiver, 3-State
Channels	8 (bidirectional)
Supply Voltage	2.0V to 6.0V
Propagation Delay	7 ns (typ @ 5V)
Output Drive	+/-6 mA @ 4.5V
Output Type	3-State (non-inverting)
ESD Protection	HBM >2000V, CDM >1000V
Operating Temperature	-40 to +125 C
Package	SOIC-20 (7.5mm width)

Features

8-bit bidirectional bus transceiver
Non-inverting 3-state outputs
Output Enable (OE) and Direction (DIR) control
2V to 6V wide supply voltage range
7ns propagation delay at 5V
CMOS low power dissipation
High noise immunity
Input clamp diodes for overvoltage protection
ESD protection: HBM >2000V
Pin compatible with 74HCT245 (TTL input levels)

Applications

Microprocessor bus interface buffering
Memory bank switching
Level translation between logic domains
Board-to-board communication isolation

Product Introduction:74HC245D Product Introduction

The 74HC245D from Nexperia is an octal bus transceiver with 3-state non-inverting outputs in a 20-pin SOIC package. The D suffix denotes the SOIC-20 package with 7.5mm body width. As the industry-standard 8-bit bus transceiver, it provides bidirectional data transfer between two buses using a Direction (DIR) pin for flow control and an Output Enable (OE) pin for bus isolation. With 2V to 6V supply range and 7ns propagation delay at 5V, it serves as a universal bus buffer in microprocessor systems, memory interfaces, and board-to-board communication links. The 3-state outputs allow multiple devices to share a common bus without contention. The 74HCT245D variant provides TTL-compatible input thresholds.

Working Principle:74HC245D Working Principle

The 74HC245D operates through three subsystems: (1) Bidirectional Data Path: Eight identical non-inverting data channels connect the A bus (A0-A7) to the B bus (B0-B7). Each channel can carry data in either direction, but only one direction at a time. (2) Direction Control: The DIR pin determines data flow direction. When DIR is HIGH, data flows from A to B (A inputs, B outputs). When DIR is LOW, data flows from B to A (B inputs, A outputs). This allows a single control line to manage bidirectional bus communication. (3) Bus Isolation: The active-low OE (Output Enable) pin controls the 3-state outputs. When OE is LOW, the outputs are enabled according to the DIR setting. When OE is HIGH, all outputs are forced to a high-impedance state, effectively disconnecting the device from both buses. This allows multiple 74HC245 devices to share the same bus through time-division multiplexing. Input clamp diodes on all inputs allow interfacing to voltages exceeding VCC when current-limiting resistors are used.

Pin Description:74HC245D Pin Definition and Functions

Pin	Name	Type	Description
1	DIR	Input	Direction control (HIGH=A-to-B, LOW=B-to-A)
2-9	A0-A7	I/O	Bus A data lines
10	GND	Power	Ground
11-18	B7-B0	I/O	Bus B data lines (reversed pin order)
19	OE	Input	Output enable (active LOW)
20	VCC	Power	Supply voltage (2-6V)

Application Scenarios:In which products and applications is74HC245D used

Microprocessor 8-bit data bus buffering with OE control for bus isolation during DMA cycles
Memory bank switching with DIR pin selecting read/write direction and OE enabling specific banks
Board-to-board communication with 3-state outputs allowing multiple boards on a shared bus
Level translation between 3.3V and 5V logic domains using input clamp diodes with series resistors

Alternative Models:What chips are recommended as replacements for 74HC245D

Model	Manufacturer	Input Level	Package	Notes
74HCT245D	Nexperia	TTL	SOIC-20	TTL-compatible inputs
74LVC245APW	Nexperia	CMOS	TSSOP-20	3.3V, smaller package
SN74HC245DW	TI	CMOS	SOIC-20	Pin-compatible alternative
MC74HC245DWG	onsemi	CMOS	SOIC-20	Pin-compatible alternative