K20D50: how to enable USB VBus charging to USB device?

[huishao2]

Hi-

I am using MK20DX128VFM5 and trying to build up a USB CDC host board to drive the enumeration and charging of a CDC device. My custom board is receiving +12V DC from power source and I expect the charging current to be around 400mA.

Question is, how can I make VBus of K20 to output current above for charging purpose? I see from user manual there is a USB Voltage Regulator inside k20, but its output is only 120mA.

Is there a reference design available for such case?

thanks!

Hui

[Hui_Ma]

Hi,

Please check below DC-DC circuit for 12V transfer to 5V:

The USB VBUS can use this 5V source.

Wish it helps.

Have a great day,
Ma Hui

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[huishao2]

Hi Hui,

Thank you so much for the detailed circuitry design. One more question regarding this design, can I short 5V_EXT directly to my K20's VBUS? Will it reversely charge my USB host?

Thanks!

Hui

[Hui_Ma]

Hi,

You can directly connect 5V_EXT to USB VBUS to power external USB device.

It also can provide power to the USB host (K20) board.

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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