i.MX28 USB bus powered device with no power switch

[george]

Dear all,

We have planned USB bus powered device using i.MX28.

The product does not have a power switch.

Since it connected with USB-HOST, it begins boot.

Though we are going to design according to "VDD5V source only" of AN4199, it is not known how we should do a PSWITCH pin.

Is what is necessary just to tied to VDD3V3 or GND?

Best Regards,

George

[francescoluccon]

Hi guys,

I'm working on a custom i.mx28 board powered just by external 5v of USB bus. After several bootup starts of u-boot-2011.12 I found out that the system hangs on mx28_power_setup_5v_detect() function. Have you applied different tunings during spl code of u-boot? Could you give me any tips?

Regards,

Francesco

[Yuri · Accepted solution]

  There is no need for a POWER button in a 5V only configuration. If a

5V source is present on the VDD5V pin, the i.MX device will automatically

power up. In such case the PSWITCH should be pulled down.

Have a great day,
Yuri

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[george]

Dear Yuri,

Thnaks.

BR,

George