FTDI Community
General Category => Discussion - Hardware => Topic started by: mikes603 on January 05, 2021, 02:26:48 PM
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Hi Gents,
I had/have an issue where our FT230XS is supplying current into our MCU over the FT230XS's TX and RX lines. And keeping the MCU a bit alive across reboots. Some current limiting resistors seem to be needed on these two lines. But I'm curious if this is a common issue / known limitation. Are series resistors the suggested design? And what is going on with the FT230XS whereby it can supply current on TX/RX?
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Hello,
Can you please email your local support team and we can look into this issue further?
https://www.ftdichip.com/FTContact.htm (https://www.ftdichip.com/FTContact.htm)
Then you can post any resolution here to help other community users.
Best Regards,
FTDI Community
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It's a known phenomenon in electronics: unpowered chip gets powered trough its internal ESD protection diodes when its signals are driven high.
The right way to deal with it is to use buffers with so-called Ioff feature (e.g. TI SN74AUP1G34) or a dual-supply voltage translators (e.g. ON FXMA2102).
Using series high-value resistors is not ideal as it will make signal edges very slow.