i.MX502: How to use USB_H1_VBUS pin?

[norishinozaki]

Hello,

I read: "i.MX53 - How to connect the USB_H1_VBUS pin?"

https://community.freescale.com/message/273105

I got the same kind of question about i.MX502.

The datasheet says,

"These inputs are used by the i.MX50 to detect the presence and level of USB 5 V".

How can we know when it detects the voltage of USB?

These pins are also obsoleted in i.MX502?

Best regards,

N.Shinozaki

[Rita_Wang]

Hi N.Shinozaki,

About the USB_H1_VBUS pin, you can refer to the datasheet:

These inputs are used by the i.MX50 to detect the presence and level of USB 5 V. If either

VBUS input pin is connected to an external USB connector, there is a possibility that a fast 5

V edge rate during a cable attach could trigger the VBUS input ESD protection, which could

result in damage to the i.MX50 silicon. To prevent this, the system should use some circuitry

to prevent the 5 V edge rate from exceeding 5.25 V / 1 μs. Freescale recommends the use of

a low pass filter consisting of 100 Ω resistor in series and a 1 μF capacitor close to the i.MX50

pin.

It is not the same with i.mx53, and 5 V power need supply to it.

You need according to the datasheet. Different chip have different functions and pin definition.
Have a great day,
Dan

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[norishinozaki]

Hello Dan,

Thanks, I understood the protection of the device as written in the datasheet.

However I'd like to know the purpose of the USB_H1_VBUS pin.

In our case, i.MX50 works USB Host only.

USB host can detect USB device in D+ signals when connected.

From the i.MX50EVK schematics, I thought this pin can be used to trigger USB_H1_PWR to indicate PMIC to supply USB_5V_HOST to USB device.

But what is the reason why USB_H1_VBUS needs to be connected in 5V first of all?

Best regards,

Nori Shinozaki

[art]

5V voltage, applied to the USB_H1_VBUS pin, indicates the presence of the valid USB bus. So, please just follow the reference design.

Best Regards,

Artur

[norishinozaki]

Hello Artur,

In our board, the USB host function is working even without connecting USB_H1_VBUS pin to 5V.

We need to know whether the pin is connected to 5V or not.

Is there a register or way to know that?

Best regards,

N.Shinozaki

[art]

There is no way of doing that for the Host only core, only the VBUS Valid bit is available for the OTG core.

Best Regards,

Artur

[art]

The answer, given in the thread you're referring to:

https://community.freescale.com/message/273105

is wrong.

The VBUS pins of both i.MX50 and i.MX53 series processors are not obsolete and they must be connected to the VBUS voltage of the corresponding USB port.

Have a great day,
Artur

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[norishinozaki]

Artur,

Thanks, then how can we know the detection of the USB voltages?

The datasheet says:

"These inputs are used by the i.MX50 to detect the presence and level of USB 5 V".

I can't find any registers which indicate detection of the USB voltage.

Is it used by i.MX50 internally?

Best regards,

N.Shinozaki