The following is the pinout and functional circuit diagram of the 74LS48, a commonly used seven-segment decoder driver. This chip is widely applied in digital circuits and display systems within microcontroller-based projects.
The 74LS48 is designed to drive seven-segment displays, converting binary-coded decimal (BCD) inputs into signals that light up specific segments of the display. It has several control pins that allow for additional functionality, such as lamp testing, blanking, and ripple blanking.
Here is the pin function table for the 74LS48:
| Decimal Number or Function | LT | RBI | DCBA | BI/RBO | a | b | c | d | e | f | g | Remarks |
|-----------------------------|----|-----|------|--------|---|---|---|---|---|---|---|---------|
| 0 | H | H | 0000 | H | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 |
| 1 | H | x | 0001 | H | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 2 |
| 2 | H | x | 0010 | H | 1 | 1 | 0 | 1 | 1 | 0 | 1 | 3 |
| 3 | H | x | 0011 | H | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 4 |
| 4 | H | x | 0100 | H | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 5 |
| 5 | H | x | 0101 | H | 1 | 0 | 1 | 1 | 0 | 1 | 1 | 6 |
| 6 | H | x | 0110 | H | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 7 |
| 7 | H | x | 0111 | H | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 8 |
| 8 | H | x | 1000 | H | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9 |
| 9 | H | x | 1001 | H | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 10 |
| 10 | H | x | 1010 | H | 0 | 0 | 0 | 1 | 1 | 0 | 1 | 11 |
| 11 | H | x | 1011 | H | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 12 |
| 12 | H | x | 1100 | H | 0 | 1 | 0 | 0 | 0 | 1 | 1 | 13 |
| 13 | H | x | 1101 | H | 1 | 0 | 0 | 1 | 0 | 1 | 1 | 14 |
| 14 | H | x | 1110 | H | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 15 |
| 15 | H | x | 1111 | H | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 16 |
| BI | x | x | XXXX | L | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 17 |
| RBI | H | L | 0000 | L | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 18 |
| LT | L | x | XXXX | H | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 19 |
The 74LS48 includes several key functions:
- **LT (Lamp Test)**: When set to low, it turns on all segments, allowing you to test the display.
- **RBI (Ripple Blanking Input)**: Used to blank the display when certain conditions are met, typically during cascading operations.
- **BI/RBO (Blanking Input/Output)**: Controls whether the output is active or blanked. When low, it disables the output.
This chip is ideal for applications where a seven-segment display needs to show numbers from 0 to 9, and even some letters in certain configurations. Its reliability and simplicity make it a popular choice in many electronic projects.
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