The "SN 74HC245D WR" is a component manufactured by Texas Instruments (TI). It is part of their HC (High-Speed CMOS) series. This specific part is an octal bus transceiver with 3-state outputs, designed for communication between two devices in different voltage domains. The DWR suffix indicates that this component comes in a SOIC-20 (Small Outline Integrated Circuit) package.
Below is a detai LED breakdown of the pin functions, specifications, and circuit principles of the SN74HC245DWR:
SN74HC245DWR Pin Function Specifications & Circuit Principle
Package Type: SOIC-20
Pin Count: 20 pins Description: The SN74HC245DWR comes in a 20-pin SOIC package and has 8 bidirectional data bus pins, along with additional control pins to manage the direction and enable states of the bus. Pin Function Table (All 20 Pins) Pin Number Pin Name Pin Type Description 1 A1 I/O Data bus input/output 1 2 A2 I/O Data bus input/output 2 3 A3 I/O Data bus input/output 3 4 A4 I/O Data bus input/output 4 5 A5 I/O Data bus input/output 5 6 A6 I/O Data bus input/output 6 7 A7 I/O Data bus input/output 7 8 A8 I/O Data bus input/output 8 9 GND - Ground connection 10 DIR Input Direction control pin (high for output, low for input) 11 OE Input Output enable (low enables the outputs, high disables them) 12 B1 I/O Data bus input/output 1 (opposite side of A1) 13 B2 I/O Data bus input/output 2 (opposite side of A2) 14 B3 I/O Data bus input/output 3 (opposite side of A3) 15 B4 I/O Data bus input/output 4 (opposite side of A4) 16 B5 I/O Data bus input/output 5 (opposite side of A5) 17 B6 I/O Data bus input/output 6 (opposite side of A6) 18 B7 I/O Data bus input/output 7 (opposite side of A7) 19 B8 I/O Data bus input/output 8 (opposite side of A8) 20 VCC - Positive supply voltage connectionPin Function Detailed Descriptions
A1-A8 (Pins 1-8): These pins serve as data input/output (I/O) terminals for the bus. They are bidirectional and can be used to either send or receive data depending on the direction control (DIR) pin.
B1-B8 (Pins 12-19): These pins are also bidirectional I/O terminals. The signals on these pins are the complementary counterparts of the A pins. When the device is in output mode, the data on A pins is sent to B pins, and vice versa when in input mode.
DIR (Pin 10): This pin determines the direction of data flow. When set to logic high, the A pins output data to the B pins. When set to logic low, the B pins output data to the A pins.
OE (Pin 11): The output enable pin controls whether the I/O pins are actively driving data or in a high-impedance (high-Z) state. When OE is low, the outputs are enabled. When OE is high, the outputs are disabled.
VCC (Pin 20): This is the power supply pin that provides the positive voltage to the device.
GND (Pin 9): The ground pin connects the device to the system ground.
Circuit Principle
The SN74HC245DWR is an octal bus transceiver that allows data to flow between two buses, typically within different voltage domains. The device can either transmit or receive data depending on the state of the DIR and OE pins. The key feature of the SN74HC245DWR is the ability to tri-state its outputs when necessary, enabling multiple devices to share the same bus lines without interfering with each other.
The DIR pin selects the direction of data flow, while the OE pin controls whether the outputs are enabled or in a high-impedance state, allowing for high flexibility in bus configurations.
20 Frequently Asked Questions (FAQs)
Q: What is the main function of the SN74HC245DWR? A: The SN74HC245DWR is an octal bus transceiver used for bidirectional data communication between two buses.
Q: How many pins does the SN74HC245DWR have? A: The SN74HC245DWR has 20 pins.
Q: What package type is the SN74HC245DWR available in? A: The SN74HC245DWR is available in an SOIC-20 package.
Q: What does the DIR pin control? A: The DIR pin controls the direction of data flow between the A and B pins. A high signal enables the A pins to output data, while a low signal enables the B pins to output data.
Q: What happens when the OE pin is set high? A: When the OE pin is set high, the outputs are disabled, putting the I/O pins in a high-impedance state.
Q: How do the A and B pins work? A: The A pins and B pins are bidirectional, and they work in pairs to transfer data between two buses.
Q: What is the voltage range for the SN74HC245DWR? A: The operating voltage range for the SN74HC245DWR is typically between 2V and 6V.
Q: Can the SN74HC245DWR be used in 3.3V systems? A: Yes, the SN74HC245DWR can operate in 3.3V systems, as it supports a wide voltage range.
Q: What is the function of the GND pin? A: The GND pin is the ground reference for the device and connects to the system ground.
Q: How can I control the direction of data flow between A and B pins? A: The direction of data flow is controlled by the DIR pin.
Q: What happens if both A and B pins are set as outputs? A: If both A and B pins are set as outputs, data will be driven onto the bus, and the data transfer will occur from the A side to the B side or vice versa, depending on the DIR pin state.
Q: Can I use multiple SN74HC245DWR devices on the same bus? A: Yes, multiple SN74HC245DWR devices can share the same bus, with each device having its own OE pin to enable or disable outputs as needed.
Q: What happens if the OE pin is set high when the device is powered? A: If the OE pin is high, the device will be in high-impedance mode, and no data will be driven to the bus.
Q: Is the SN74HC245DWR compatible with TTL logic levels? A: Yes, the SN74HC245DWR is compatible with TTL logic levels.
Q: What is the typical propagation delay for the SN74HC245DWR? A: The typical propagation delay for the SN74HC245DWR is around 12 ns (nanoseconds).
Q: How do I ensure correct operation of the bus transceiver? A: Ensure proper voltage levels at the VCC and GND pins, and control the DIR and OE pins to manage data flow and output enablement.
Q: What is the maximum current rating for the SN74HC245DWR's I/O pins? A: The maximum current per I/O pin is typically 25 mA.
Q: Can the SN74HC245DWR drive LEDs? A: The SN74HC245DWR is not designed to drive LEDs directly but can interface with a logic level circuit that drives LEDs.
Q: How do I disable the outputs on the SN74HC245DWR? A: Set the OE pin high to disable the outputs.
Q: Can the SN74HC245DWR be used in both 3.3V and 5V systems? A: Yes, the SN74HC245DWR can operate in both 3.3V and 5V systems.
This completes the detailed pin function specifications, circuit principle instructions, and FAQ for the SN74HC245DWR.