Overview
The SN74HC245DBRG4, produced by Texas Instruments, is an octal bus transceiver with 3-state outputs. This device is designed for asynchronous two-way communication between data buses, making it versatile for various digital circuit applications. The SN74HC245 allows data transmission from the A bus to the B bus or from the B bus to the A bus, controlled by the direction-control (DIR) input. Additionally, the output-enable (OE) input can be used to disable the device, effectively isolating the buses.
Key Specifications
| Parameter | Test Conditions | Unit | Min | Max | |
|---|---|---|---|---|---|
| VCC Supply Voltage | - | V | 2 | 5 | 6 |
| VIH High-Level Input Voltage | VCC = 2 V | V | 1.5 | - | 1.5 |
| VIH High-Level Input Voltage | VCC = 4.5 V | V | 3.15 | - | 3.15 |
| VIH High-Level Input Voltage | VCC = 6 V | V | 4.2 | - | 4.2 |
| VIL Low-Level Input Voltage | VCC = 2 V | V | 0.5 | - | 0.5 |
| VIL Low-Level Input Voltage | VCC = 4.5 V | V | 1.35 | - | 1.35 |
| VIL Low-Level Input Voltage | VCC = 6 V | V | 1.8 | - | 1.8 |
| VOH High-Level Output Voltage | IOH = -20 µA | V | 1.9 | - | 1.9 |
| TA Operating Free-Air Temperature | - | °C | -40 | - | 85 |
| tpd Propagation Delay (A or B to B or A) | VCC = 2 V, CL = 50 pF | ns | 40 | - | 160 |
| tpd Propagation Delay (A or B to B or A) | VCC = 4.5 V, CL = 50 pF | ns | 15 | - | 32 |
| tpd Propagation Delay (A or B to B or A) | VCC = 6 V, CL = 50 pF | ns | 12 | - | 27 |
Key Features
- Wide Operating Voltage Range: The device operates over a wide voltage range from 2 V to 6 V, making it versatile for different system designs.
- High-Current 3-State Outputs: The outputs can drive bus lines directly or up to 15 LSTTL loads, and they can be placed in a high-impedance state.
- Asynchronous Two-Way Communication: Data can be transmitted from the A bus to the B bus or from the B bus to the A bus, controlled by the DIR input.
- Output Enable (OE) Input: The OE input allows the device to be disabled, effectively isolating the buses.
- Low Drive and Slow Edge Rates: These characteristics minimize output ringing, overshoot, and undershoot, making the device suitable for applications where signal integrity is crucial.
Applications
The SN74HC245 is suitable for a variety of bus interface applications, including:
- Microcontroller Interfaces: Connecting microcontrollers to other system components or peripherals.
- Bus Communication Systems: Enabling data transfer between different segments of a bus system.
- Industrial Control Systems: Used in industrial automation for reliable data communication between different modules.
- Embedded Systems: Integrating into embedded systems where asynchronous two-way communication is necessary.
Q & A
- What is the operating voltage range of the SN74HC245?
The SN74HC245 operates over a voltage range from 2 V to 6 V.
- How does the direction-control (DIR) input work?
The DIR input controls the direction of data transmission between the A and B buses. When DIR is low, data is transmitted from the B bus to the A bus, and when DIR is high, data is transmitted from the A bus to the B bus.
- What is the purpose of the output-enable (OE) input?
The OE input can be used to disable the device, placing the outputs in a high-impedance state and effectively isolating the buses.
- What are the typical propagation delays for the SN74HC245?
The propagation delays vary with voltage and load capacitance but are typically around 12-160 ns depending on the conditions.
- Can the SN74HC245 drive multiple LSTTL loads?
- What is the significance of the low drive and slow edge rates in the SN74HC245?
The low drive and slow edge rates minimize output ringing, overshoot, and undershoot, ensuring better signal integrity.
- What are the thermal characteristics of the SN74HC245?
The device has various thermal metrics such as junction-to-ambient thermal resistance, which varies depending on the package type.
- How should unused inputs be handled to ensure proper device operation?
All unused inputs must be held at VCC or GND to ensure proper device operation.
- What are some common applications of the SN74HC245?
- What are the available package options for the SN74HC245?
