Why I cannot download firmware into my 52840? USB cable is the only power supply.

[ndc_bee]

I connect VBUS to VDDH, and use a USB cable for power supply(high voltage mode), but I cannot download firmware into the 52840.

Unless I power the 52840 from the VDD pin, why?

My cricuit as below:

[Øyvind]

Hello, 

Can you give me some more details? You can't download if powered by VDDH, but you can download if powered by VDD? How are you connecting to your device to download/program it?

Kind regards,
Øyvind

[ndc_bee]

I use  JLINK to download firmware,  connect VDD/VDDH , GND ,SWDIO, SWCLK to JLINK.

when I use  usb cable power the 52840 from the VDDH, I cannot download firmware.

but if I use 3.3V power the 52840 from the VDD, It works.