Replies: 5 comments 8 replies
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So the problem only occured with the PJ75AL33SA? I have never had such an issue but I will try to measure it myself in the coming days. What track voltage are u using? Admittedly, the LDO is also a weak point in the design as it is subject to very high thermal loads, especially at high track voltages, the power loss is not insignificant. I am currently working on a revised design which is improved in this respect, among others. |
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Hello together, I made similar observations:
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Gude, unfortunatly, the MCP1799 is not that available for a quick fix, what do you think about the following one? This one has a higher quiecent current, but that should not matter that much in this application. |
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After making a lot of test with changed capacitance on input and output side, I come to the point that the huge overshoot is only related to the fast turn on edge of the voltage input. Which looks for me that LDO is not acc. to the datasheet to not call it bug.
@gab-k : please remove that part from your schematic. |
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I have changed the schematic, removing the previously used LDO, replacing it with an alternative part that should work better. Another alternative part can be found below the BOM in the wiki. |
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Hello, this is the first time I am using this project. I have some pieces of decoders. For programming, I use another open-source project (DCC-EX), and some of my decoders have died (RP2040 has a short circuit inside) due to the incorrect operation of the LDO. I measured the LDO voltage and observed a 7V peak during power-on. Currently, I have replaced the LDOs with MCP1799T-3302H/TT. It has the same package, and it has thermal and current protections. Now it seems the decoder is working properly. Have you experienced similar problems?
![IMG_4879](https://private-user-images.githubusercontent.com/8313379/291929327-3a1b0513-9fca-49ce-86dc-9e7bdcb5135e.jpeg?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.4STTNpMB9ipp_asIpzy17JHgvhFkuQdA27Qdzyww6UY)
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