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LED display 1/4 scan circuit analysis
- Jan 09, 2018 -


circuit analysis:

1.this circuit is the line selection circuit, the role is to select and drive the corresponding line. 4953 chip play a role in amplification.

2.the circuit is 1/4 scan circuit. It can be seen that the A, B, C and D signals coming out of the HC245 chip are not directly connected to the 4953 chip through the 3-8 decoder, indicating that there is no 3-8 decoder in the whole circuit. The circuit uses A, B, C , D total of 4 signal lines to do the line selection. When A signal is valid, 4 lines will be selected. Similarly, available B, C, D signal is valid, will be selected 4 lines. Scan 4 times to complete a cycle, so the 1/4 scan. From a different perspective to understand the circuit scan mode, the circuit control a total of 16 lines, a total of 4 signal lines to choose from, so 4/16 = 1/4. So for the 4 scan circuit.

3.the circuit shows that to achieve the scan mode does not have to use 3-8 decoder. Nor is it as many data said as long as the interface definition A, B, C, D signal is 16 scan mode. Judgment is what scan mode, see A, B, C, D signal at the same time, depends on whether there is 3-8 decoder. If there are A, B, C signals, a 3-8 decoder, then 1/8 scan mode. If there are A, B, C, D signals, there are 2 3-8 decoders at the same time, it is 1/16 scan.

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