Internal 3P0-LDO for USB

[slw]

Hi,

We have a custom board (SVF512R3K1) where only USB0 is connected and USB1 is not used.

After enabling the internal 3P0-LDO the software hangs, cause there is a loop which waits until the flag OK_VDD3P0 in reg ANADIG_REG_3P0 is set, which never happens.

I have done some tests with different settings (ENABLE_ILIMIT, ENABLE_BO, REG_3P0_VBUS_SEL, ..) in this register without success.

I have done some tests using the TWR-Board and I only get a working 3P0-LDO when USB1_VBUS is connected to 5V and either USB0_VBUS_DETECT or USB1_VBUS_DETECT

is also connected to 5V. It seems that the 3P0-LDO can only be supplied by USB1_VBUS and not by USB0_VBUS.

Can anybody confirm this ?

Regards

Sebastian

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[richard_stulens]

Hi Sebastian,

Sorry for the delay in replying.

There are a few threads about this. Please take a look at this thread:

Vybrid USBx_VBUS, USBx_VBUS_DETECT, USBx_VBUS_EN and USBx_VBUS_OC pins

In short, you can use any USBx_VBUS pin to supply the LDO and at least one of the VBUS_DETECT pins must see 5V.

ENABLE_LINREG must be set for OK_VDD3P0 to turn on

Best regards,

Richard

[slw]

Hi Richard,

Thanks for answering.

On the TWR-Board it seems that the LDO only works if USB1_VBUS is connected to 5V (using Jumper J21 1-2).

When only USB0_VBUS is connected to 5V (J21 no jumper ; J20 1-2 set), the LDO doesn't work, and I get the BO-flag,

regardless the setting for REG_3P0_VBUS_SEL.

Regards

Sebastian

[jiri-b36968]

Hi Sebastian,

As Richard say: at least one VBUS_DETECT have to be powered (5V).

And VBUS have to be powered. Tested on TWR-VF65 rev.H:

• When J21 is open (USB1_VBUS is not powered) and also J20 is open (USB0_VBUS is not powered) then USB0 does not work.
• But when just J20 is inserted, J21 is open, then everything works fine - USB0_VBUS_DETECT is powered from USB0_VBUS which goes directly from J8. Please check J19 - it have to be inserted between 2-3 if you power from J8.

/Jiri