Kinetis K20, Flexbus, USB and ULPI interface question

[sherry_zahid]

Hi,

I have 2 questions regarding a Kinetis K20 based microcontroller (specifically MK20FN1M0VMD12).

The reference manual for k20 family states on page 154 that "When USB is not used it the application, it is recommended that the USB regulator "VREGIN" and "VOUT33" pins remain floating."

Now my issue is that I am not using USB OTG, but I am using ULPI (to connect to a USB transceiver (with ULPI interface)). The pins used are:-

ULPI_DATA[7:0]                                                          For data

ULPI_CLK, ULPI_DIR, ULPI_NXT, ULPI_STP             For control signals

I have left the pins "USB0_DP" and "USB0_DN" unconnected and floating.

Question1> Does the above mentioned rule from pg. 154 of the reference manual still hold true? (meaning with this setup do I NEED to leave "VREGIN" and "VOUT33" floating? whats the worst that can happen if I power VREGIN with 5V?)

Question2> Is it safe to have "USB0_DP" and "USB0_DN" pins floating and not connected?

Many thanks in advance

Sherry

[Hui_Ma]

1> MK20FN1M0VMD12 has two USB controller modules, one is USB full speed OTG controller, the other one is USB high speed OTG controller.

The USB0_DP and USB0_DN pins are belongs to USB full speed OTG controller.

For customer only use the USB High speed module, there is no problem to keep "VREGIN" and "VOUT33" floating.

2> Yes, it is also safe to keep "USB0_DP" and "USB0_DN" pins floating.

Wish it helps.
Have a great day,
Ma Hui

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[sherry_zahid]

Hi Ma Hui,

Thanks for your response, however I still need to know :-

I am using the following pins for ULPI USB interface

ULPI_DATA[7:0]                                                          For data

ULPI_CLK, ULPI_DIR, ULPI_NXT, ULPI_STP             For control signals

Q) I am using the above pins to connect to USB ULPI and I am not using OTG. So do I need to power VREGIN and VOUT33 or do I have to leave these 2 pins floating?

(Asking because of the note on pg. 153 of reference manual "When USB is not used it the application, it is recommended that the USB regulator "VREGIN" and "VOUT33" pins remain floating.")

Thanks

[Hui_Ma]

Hi,

Please check the USB FS Subsystem overview diagram:

For customer doesn't use USB FS controller, the VERGIN and VOUT33 pin can be left floating.

Wish it helps.

Have a great day,
Ma Hui

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Note: If this post answers your question, please click the Correct Answer button. Thank you!
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