The part number " SN74HC245NSR " is a product of Texas Instruments (TI), which is known for manufacturing a wide range of semiconductor products. It refers to an octal buffer with 3-state outputs, commonly used in digital circuit design for signal buffering and voltage level shifting.
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Part Number: SN74HC245NSR
Manufacturer: Texas Instruments Package Type: SOIC (Small Outline Integrated Circuit), typically 20-pin, surface-mount.
Pin Function Specifications
The SN74HC245 is an octal buffer with 3-state outputs. It is used to isolate different parts of a digital circuit, particularly useful for data transmission between buses or to isolate control lines.
Pinout for SN74HC245NSR (20-pin SOIC) Pin # Pin Name Function Description 1 A1 Input for data line 1 2 A2 Input for data line 2 3 A3 Input for data line 3 4 A4 Input for data line 4 5 A5 Input for data line 5 6 A6 Input for data line 6 7 A7 Input for data line 7 8 A8 Input for data line 8 9 GND Ground pin (0V) 10 LE (Latch Enable) Enables the latch to hold data 11 DIR (Direction) Sets the direction of data flow: input or output 12 O1 Output for data line 1 13 O2 Output for data line 2 14 O3 Output for data line 3 15 O4 Output for data line 4 16 O5 Output for data line 5 17 O6 Output for data line 6 18 O7 Output for data line 7 19 O8 Output for data line 8 20 VCC Power supply pin (typically 5V)Principle of Operation
The SN74HC245NSR operates as a bidirectional buffer with three-state outputs, meaning that the data lines can either drive output signals or be in a high-impedance state (not connected). It is used to facilitate the flow of data between two different parts of a circuit, such as between two bus systems, and helps isolate different sections of the circuit to avoid interference.
Latch Enable (LE): When LE is high, the data input (A1 to A8) is latched into the buffer, and the outputs (O1 to O8) reflect this data. Direction Pin (DIR): The direction pin determines if the buffer will act as an input or output. When DIR is high, data flows from the A pins to the O pins (output mode). When DIR is low, data flows from the O pins to the A pins (input mode). Three-State Output: In the off state, the outputs (O1 to O8) are in a high-impedance state, meaning they do not interfere with other components connected to the bus.Detailed FAQ on SN74HC245NSR
1. What is the function of the LE pin on SN74HC245NSR? The LE pin is the Latch Enable pin. When it is active (high), it allows data from the A pins to be latched into the buffer and output on the O pins. 2. What does the DIR pin do on the SN74HC245NSR? The DIR pin determines the direction of data flow. When DIR is high, the buffer drives data from A pins to O pins (output mode). When DIR is low, it receives data from O pins to A pins (input mode). 3. How many pins are in the SN74HC245NSR package? The SN74HC245NSR comes in a 20-pin package. 4. What is the function of the A pins (A1 to A8)? The A pins are data inputs that accept signals from other parts of the circuit. These inputs are latched into the buffer and output to the corresponding O pins when LE is active. 5. What is the significance of the VCC and GND pins? VCC is the power supply pin, typically connected to 5V. GND is the ground pin, typically connected to 0V. 6. What is a three-state output and how is it implemented in SN74HC245NSR? A three-state output means that the output can either drive a signal, be in a high-impedance state (effectively disconnected), or be driven low. The SN74HC245 uses this feature to isolate outputs when they are not needed. 7. What is the maximum operating voltage for SN74HC245NSR? The maximum operating voltage is typically 6V for the SN74HC245NSR. 8. Can I use SN74HC245NSR to connect multiple devices to a single bus? Yes, the SN74HC245NSR can be used for bus systems to isolate and buffer multiple devices to prevent interference. 9. What is the purpose of the high-impedance state in the SN74HC245NSR? The high-impedance state allows the outputs (O pins) to effectively become disconnected from the circuit, preventing interference with other components connected to the same bus. 10. How do I use the SN74HC245NSR to interface two microcontrollers? By using the direction control (DIR) and latch enable (LE) pins, you can configure the buffer to allow bidirectional data transfer between the two microcontrollers. 11. What are the current drive capabilities of the SN74HC245NSR? The SN74HC245 can typically drive currents of up to 6mA per pin, which is suitable for many logic-level interfacing applications. 12. What is the propagation delay of the SN74HC245NSR? The propagation delay is typically around 14ns, meaning it takes about 14 nanoseconds for a change at the input to affect the output. 13. Can the SN74HC245NSR be used with different logic levels? Yes, the device is compatible with both CMOS and TTL logic levels, typically operating at 5V logic. 14. Can the SN74HC245NSR drive LEDs directly? No, the current drive capability of the SN74HC245 is not suitable for directly driving LEDs. You should use current-limiting resistors or drivers when interfacing with LEDs. 15. What is the maximum input voltage for the A pins? The maximum input voltage is typically VCC + 0.5V. 16. Can I use the SN74HC245NSR to buffer analog signals? No, the SN74HC245NSR is designed for digital signals only and cannot be used to buffer analog signals. 17. Is the SN74HC245NSR compatible with TTL logic? Yes, it is fully compatible with TTL logic signals and voltage levels. 18. What happens when the DIR pin is tied low? When DIR is tied low, the SN74HC245NSR will operate in input mode, allowing data to flow from the O pins to the A pins. 19. What is the power consumption of SN74HC245NSR? The power consumption is typically low, with the device drawing minimal current except when driving outputs. 20. How should I handle unused pins on the SN74HC245NSR? Unused input pins should be tied to ground or VCC to avoid floating inputs, which may cause unpredictable behavior.Conclusion
The SN74HC245NSR is an essential device for buffering and isolating data in digital circuits. It has 20 pins, each with specific roles related to data transfer and control. The FAQs provide a detailed understanding of its operation, which will help engineers use the device effectively in various applications.