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Electronics => Projects, Designs, and Technical Stuff => Topic started by: Pack34 on October 18, 2016, 08:19:48 pm

Title: On Semi: EMI2121 USB Filter Pinout
Post by: Pack34 on October 18, 2016, 08:19:48 pm

Does anyone here have experience with the On Semi EMI2121 EMI/ESD chip?
http://www.onsemi.com/pub_link/Collateral/EMI2121MT-D.PDF (http://www.onsemi.com/pub_link/Collateral/EMI2121MT-D.PDF)

I'm attempting to keep my USB circuit as compact as possible and I noticed that the positive and negative pins on the input of the chip do not line up with the actual data lines on a USB connector. IN_1+ and IN_1- should be switched.

USB Connector pinout:
https://en.wikipedia.org/wiki/USB#Pinouts (https://en.wikipedia.org/wiki/USB#Pinouts)

If the simplified schematic can be believed then having USB_DM connected to IN_1+ and USB_DP connected to IN_1- shouldn't matter. I just wanted to get some

Title: Re: On Semi: EMI2121 USB Filter Pinout
Post by: exmadscientist on October 19, 2016, 03:14:59 am

I haven't used that particular part, but a similar ST part (ECMF02-4CMX8) has the same pinout issue and swapping the pairs works just fine.

Just be sure to swap them an even number of times!

Title: Re: On Semi: EMI2121 USB Filter Pinout
Post by: technix on October 20, 2016, 04:28:33 am

As far as I see the two channels are completely symmetric and can be interchanged freely.

Title: Re: On Semi: EMI2121 USB Filter Pinout
Post by: Pack34 on November 22, 2016, 02:46:12 pm

I never mentioned the resolution for this. Swapping the pins worked out fine. I was concerned since the channels were specifically labeled as Data_Plus and Data_Minus but it didn't matter.