74245 Octal Bus Transceiver Technical Summary

Overview

The M54/74HC245, HC640, and HC643 are high-speed octal bus transceivers designed for bidirectional communication between data buses. These devices utilize advanced silicon-gate CMOS technology to achieve high-speed operation while maintaining low power consumption. The 74245 is part of the 74HC family, which is known for its compatibility with both CMOS and TTL logic levels, making it versatile for mixed-voltage systems.

The 74245 is an 8-bit transceiver with non-inverting outputs, featuring separate input and output ports for bidirectional data flow. It is commonly used in applications requiring data buffering, bus isolation, or voltage level translation. The device is available in multiple package options, including DIP, SOIC, and TSSOP, to accommodate various PCB layouts and space constraints.

Features

• High-Speed Operation: Typical propagation delay of 8 ns at 5V, making it suitable for high-performance systems.
• Wide Operating Voltage Range: 2V to 6V, compatible with both 3.3V and 5V logic systems.
• Low Power Consumption: CMOS technology ensures minimal static and dynamic power dissipation.
• Bidirectional Data Flow: Direction control pin (DIR) determines the direction of data transmission.
• 3-State Outputs: Allows multiple devices to share a common bus without interference.
• High Noise Immunity: CMOS design provides robust performance in noisy environments.
• TTL-Compatible Inputs: Can interface directly with TTL logic levels.
• ESD Protection: Built-in protection against electrostatic discharge, enhancing reliability.

Applications

The 74245 octal bus transceiver is widely used in various digital systems, including:

• Data Bus Buffering: Isolates and drives data buses in microprocessors and microcontrollers.
• Level Shifting: Bridges 3.3V and 5V logic systems in mixed-voltage designs.
• Memory Interfacing: Facilitates communication between CPUs and memory modules.
• Industrial Control Systems: Provides robust data transmission in harsh environments.
• Automotive Electronics: Used in vehicle control units and infotainment systems.
• Communication Equipment: Enables bidirectional data flow in networking hardware.

Electrical Characteristics

Absolute Maximum Ratings

• Supply Voltage (V_CC): -0.5V to +7V
• Input Voltage (V_IN): -0.5V to V_CC + 0.5V
• Output Voltage (V_OUT): -0.5V to V_CC + 0.5V
• Operating Temperature Range: -40°C to +85°C (industrial grade)
• Storage Temperature Range: -65°C to +150°C

Recommended Operating Conditions

• Supply Voltage (V_CC): 2V to 6V
• Input High Voltage (V_IH): 3.15V (min) at V_CC = 4.5V
• Input Low Voltage (V_IL): 1.35V (max) at V_CC = 4.5V
• Output High Current (I_OH): -4 mA (max) at V_CC = 4.5V
• Output Low Current (I_OL): 4 mA (max) at V_CC = 4.5V

Dynamic Characteristics

• Propagation Delay (t_PD): 8 ns (typical) at V_CC = 5V
• Output Transition Time (t_THL, t_TLH): 6 ns (typical) at V_CC = 5V
• Input Capacitance (C_IN): 3.5 pF (typical)
• Power Dissipation (P_D): 500 mW (max)

Package Information

The 74245 is available in several industry-standard packages, each offering distinct advantages for different applications:

20-Pin DIP (Dual Inline Package)

• Package Code: DIP-20
• Dimensions: 25.4 mm x 6.35 mm
• Pin Spacing: 2.54 mm
• Mounting: Through-hole
• Typical Use: Prototyping, breadboarding, and legacy systems.

20-Pin SOIC (Small Outline Integrated Circuit)

• Package Code: SOIC-20
• Dimensions: 12.8 mm x 7.5 mm
• Pin Spacing: 1.27 mm
• Mounting: Surface-mount
• Typical Use: Compact PCB designs, consumer electronics.

20-Pin TSSOP (Thin Shrink Small Outline Package)

• Package Code: TSSOP-20
• Dimensions: 6.5 mm x 4.4 mm
• Pin Spacing: 0.65 mm
• Mounting: Surface-mount
• Typical Use: High-density PCB layouts, portable devices.

Conclusion

The 74245 octal bus transceiver is a versatile and reliable component for bidirectional data communication in digital systems. Its high-speed operation, low power consumption, and compatibility with both CMOS and TTL logic levels make it a preferred choice for designers working on mixed-voltage and high-performance applications. With multiple package options, the 74245 can be easily integrated into a wide range of electronic systems, from industrial controls to consumer electronics.