topic Re: K20D50: how to enable USB VBus charging to USB device? in Kinetis Microcontrollers

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

huishao2 — Thu, 26 Nov 2015 19:18:40 GMT

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

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

Hui_Ma — Fri, 27 Nov 2015 05:25:02 GMT

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

huishao2 — Fri, 27 Nov 2015 06:02:44 GMT

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

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

Hui_Ma — Fri, 27 Nov 2015 08:21:24 GMT

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