BadRequest
- Oct 28, 2022
- 4
- Joined
- Oct 28, 2022
- Messages
- 4
I'm wanting to do a multiplexed LED project, maybe using the TM1681 LED driver. The datasheet has a confusing suggestion and I was hoping someone could tell me whether they think it makes sense. https://html.alldatasheet.com/html-pdf/1133642/TITAN/TM1681/713/4/TM1681.html
The datasheet is in Chinese but on page 4 it says that the row source current is 7 mA while the com sink current 350 mA. On the second half of page 11, it suggests that we might want to use transistors to power the LEDs but why does it put them on the com pins? At 7 mA per row, even if all 32 rows are on, that's 224 mA which is still below the 350 mA capacity of each com pin. Is there any point in that configuration?
In the other examples it has transistors on both rows and com pins but this particular one seemed pointless to me, offering no increase in current over direct drive. I will probably use transistors on the rows and the columns.
Edit: I just noticed, in the examples where transistors are used on both the rows and the columns, for some reason they swap the row and column pins around so the rows are controling the sinking of current through transistors and the coms are controling the source of current through transistors. What did they do that for?
The datasheet is in Chinese but on page 4 it says that the row source current is 7 mA while the com sink current 350 mA. On the second half of page 11, it suggests that we might want to use transistors to power the LEDs but why does it put them on the com pins? At 7 mA per row, even if all 32 rows are on, that's 224 mA which is still below the 350 mA capacity of each com pin. Is there any point in that configuration?
In the other examples it has transistors on both rows and com pins but this particular one seemed pointless to me, offering no increase in current over direct drive. I will probably use transistors on the rows and the columns.
Edit: I just noticed, in the examples where transistors are used on both the rows and the columns, for some reason they swap the row and column pins around so the rows are controling the sinking of current through transistors and the coms are controling the source of current through transistors. What did they do that for?
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