i.MX Processorsのトピックi.mx6dl VDDUSB_CAP issue

i.mx6dl VDDUSB_CAP issue

zhongweihe — Fri, 15 Nov 2019 02:29:50 GMT

Hi Team:

Could you please tell me VDDUSB_CAP if can support 3.4V? the spec request is 3.0V output , but why

the registor can be programmed VDDUSB_CAP up to 3.4V? if VDDUSB_CAP is programmed to 3.4V , the USB

function can be influence ?

Re: i.mx6dl VDDUSB_CAP issue

jimmychan — Fri, 15 Nov 2019 08:58:10 GMT

This is a good question.
PMU_REG_3P0n provides power for USB PHY, and it supports 3 different voltage output, 2.625V, 3.0V and 3.4V.
BUT i.MX6 serial processors require it's USB PHY should work on less than 3.3V voltage. So we configure the USB LDO output 3.0V to supply USB PHY in BSP.

If you set the USB LDO to output 3.4V, it can't damage USB PHY, too. But probably several years later, this will cause performance of CPU down.
So we strongly suggest that USB PHY's input voltage should be 3.0V.

Re: i.mx6dl VDDUSB_CAP issue

zhongweihe — Fri, 15 Nov 2019 10:51:35 GMT

Hi Jimmy:
Thanks your great support , but about USB I still have one question , please help to analysis and give us a good suggestion ,thanks .

The qustion is that:

1. Our USB_OTG_DN/DP used as device signal not OTG fuction .

2. But Now we found that if usb device cable disconnected from computer , the usb_otg_vbus still has a 4.4V voltage .

Generally , if usb device disconnected from computer , the usb_otg_vbus should be 0V . so we feel very confuse that where the 4.4V voltage come from .

3. This circult theory is that when usb device connect to the computer , the Mosfet Q38 ON , so 5V supply to usb_otg_vbus. usb_otg_vbus not connect with any signal.

4. so please help to analysis togerther it .thanks very much.

Re: i.mx6dl VDDUSB_CAP issue

jimmychan — Mon, 18 Nov 2019 08:00:01 GMT

We checked this on our boards. We don't have this issue. Please double check your hardware board.