74545 8-Bit TRI-STATE High-Speed Transceiver

Overview

The 74545 is an 8-bit, TRI-STATE, high-speed bidirectional transceiver designed for bus-oriented microprocessor and digital communication systems. This component features straight-through bidirectional data flow with different drive capabilities on its A and B ports, making it ideal for interfacing between systems with varying voltage and current requirements. The device offers enhanced ESD protection and simplified control logic through its Transmit/Receive (T/R) and Output Enable (OE) functions.

Key Features

• 8-bit bidirectional data flow reduces system package count
• TRI-STATE inputs/outputs for bus-oriented system interfacing
• 24 mA (20 mA Military) bus drive capability on A ports
• 64 mA (48 mA Military) bus drive capability on B ports
• Transmit/Receive and Output Enable simplify control logic
• Guaranteed 4000V minimum ESD protection
• Pin-for-pin compatible with Intel 8286
• Available in commercial and military grade packages

Applications

• Microprocessor bus interfacing
• Data communication systems
• Bidirectional data transfer between systems with different drive requirements
• Bus isolation and buffering
• Military and aerospace electronics (54F series)

Electrical Characteristics

Absolute Maximum Ratings

• Supply Voltage (Vcc): -0.5V to +7.0V
• Input Voltage: -0.5V to Vcc +0.5V
• Output Voltage: -0.5V to Vcc +0.5V
• Operating Temperature Range:
  • Commercial: 0°C to +70°C
  • Military: -55°C to +125°C
• Storage Temperature Range: -65°C to +150°C

DC Characteristics

• Input HIGH Voltage (VIH): 2.0V min
• Input LOW Voltage (VIL): 0.8V max
• Output HIGH Voltage (VOH):
  • A Port: 2.4V min @ IOH = -3mA
  • B Port: 2.4V min @ IOH = -15mA
• Output LOW Voltage (VOL):
  • A Port: 0.5V max @ IOL = 24mA
  • B Port: 0.5V max @ IOL = 64mA
• Input Leakage Current: ±1μA max
• TRI-STATE Output Leakage Current: ±10μA max

AC Characteristics

• Propagation Delay (A to B): 6ns max
• Propagation Delay (B to A): 6ns max
• Output Enable Time: 8ns max
• Output Disable Time: 8ns max

Package Information

Available Packages

• 74F545PC (N20A): 20-Lead (0.300" Wide) Molded Dual-In-Line
• 54F545DM (J20A): 20-Lead Ceramic Dual-In-Line (Military)
• 74F545SC (M20B): 20-Lead (0.300" Wide) Molded Small Outline, JEDEC
• 74F545SJ (M20D): 20-Lead (0.300" Wide) Molded Small Outline, EIAJ
• 54F545FM (W20A): 20-Lead Cerpack (Military)
• 54F545LM (E20A): 20-Lead Ceramic Leadless Chip Carrier, Type C (Military)

Package Notes

• Commercial devices (74F prefix) available in 13" reel packaging (suffix SCX and SJX)
• Military grade devices (54F prefix) include environmental and burn-in processing (suffix DMQB, FMQB, and LMQB)

Functional Description

The 74545 features two 8-bit bidirectional buses (A0-A7 and B0-B7) with different drive capabilities. The direction of data flow is controlled by the Transmit/Receive (T/R) input, while the Output Enable (OE) input controls the TRI-STATE outputs. When OE is active LOW, the device is enabled, and data flows from A to B when T/R is HIGH, or from B to A when T/R is LOW. When OE is HIGH, both buses are in high-impedance state.

Truth Table

Unit Loading and Fan Out

• OE (Output Enable): 1.0/2.0 U.L. (Input HIGH/LOW)
• T/R (Transmit/Receive): 1.0/2.0 U.L. (Input HIGH/LOW)
• A0-A7 Ports: 3.5/1.083 U.L. (Input HIGH/LOW), 150/40 (33.3) mA output drive
• B0-B7 Ports: 3.5/1.083 U.L. (Input HIGH/LOW), 600/106.6 (80) mA output drive

Design Considerations

When implementing the 74545 in system designs, consider the following:

• The asymmetric drive capability makes the device ideal for interfacing between systems with different current requirements
• Proper decoupling (0.1μF ceramic capacitor) should be placed near the Vcc pin
• Unused inputs should be tied to Vcc or ground through a resistor
• For military applications, the 54F series should be used for extended temperature range and reliability
• The TRI-STATE outputs allow for bus sharing among multiple devices

Conclusion

The 74545 8-bit bidirectional transceiver provides a robust solution for bus-oriented systems requiring different drive capabilities on each bus. With its high-speed operation, TRI-STATE outputs, and military-grade options, it serves a wide range of applications from commercial computing to harsh-environment military systems. The device's compatibility with industry-standard parts and multiple packaging options make it a versatile choice for system designers.