FTDI Community

General Category => Discussion - Hardware => Topic started by: mikes603 on January 05, 2021, 02:26:48 PM

Title: FT230XS
Post by: mikes603 on January 05, 2021, 02:26:48 PM

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?

Title: Re: FT230XS
Post by: FTDI Community on January 06, 2021, 04:47:15 PM

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

Title: Re: FT230XS
Post by: cioma on January 09, 2021, 10:37:59 AM

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.